By the end of this lesson you will have learned:
- about primary and secondary building elements (an introduction)
- about each element of a traditionally constructed building, including:
- the methods and materials used
- the kinds of defects which may be associated with each element
The elements included here are:
- Joinery fittings
- Other joinery
- Electricity supply
- Gas supply
- Dampness and condensation (defects which may relate to various elements)
- Outside areas
Note: This lesson is based on the material in Unison section 2 (as introduced in Lesson 3.1)
This is a long lesson, so if you are not familiar with this material, do take your time.
However, it is more likely that you know much of this material already and can read through quickly to check that your knowledge is complete.
Within the sections below, text concerning problems and issues is highlighted with a green background.
Responsibility for repairing and maintaining dwellings differs depending on ownership patterns. Some homes are privately owned, some are the responsibility of social landlords, and some may now be in “part let, part buy” schemes. Whoever is responsible for these buildings needs a detailed knowledge of their construction and procedures relating to their repair and maintenance. Such knowledge is also required when developing long term plans for robust energy efficient retrofit.
As you go through the sections below, jot down on paper which features relate to your own house (or a project you are working on) and identify any unknowns.
For example, do you know which kind of foundations your building has?
After each element, note any issues that you have encountered.
If your own house (or the projects you are working on) are of non-traditional construction, note any features here that are relevant, but focus on the activity in Lesson 3.3
Primary Building Elements
The primary building elements are all related to the basic structure / shell of the building: the foundations, walls, floors, roofing timbers and the roof covering. When a house is being constructed these are usually the first elements to be constructed.
Secondary Building Elements
The secondary elements relate to aspects such as wiring, plumbing, internal joinery (such as doors, architraves, windows), plaster and painting.
The type and construction of each building element varies between, and even within the same dwellings, depending on when a property was constructed, and/or converted or modernised. As shown in Lesson 3.1, in this century alone, huge changes have been made in the particular construction techniques employed.
For social landlords, it is therefore essential to maintain records showing the differing construction of each dwelling and employing specialist staff or advisors capable of diagnosing constructional problems as they occur, and who are capable of correcting those problems. (Sadly, private homeowners may not have easy access to this kind of information when they retrofit a house.)
Another good way to understand dwellings is to look at changes over time in the way that buildings were built, focusing on the gradual evolution of the principal elements of construction:
2. External walls
3. Ground Floors
4. Upper Floors
5. Roof Structure
The author of ‘Evolution of Building Elements’ published online from the University of The West of England has done just this. Suggested reading 1: http://fet.uwe.ac.uk/conweb/house_ages/elements/print.htm
We recommend reading sections 1-6 and have added prompts throughout this section at the appropriate if you wish to refer to this resource.
Once a decision to construct a building has been made and all of the approvals have been obtained, the first task is to determine the “quality” of the ground on which it is to be built. This is done by drilling or excavating a number of small trial holes on the site to establish the solidity, or otherwise, of the ground below the immediate surface. This ensures that the appropriate foundations for the building can be correctly specified.
The purpose of foundations
You can probably think of various buildings or structures which do not have solid foundations (the leaning Tower of Pisa, and others closer to home).
Most of the weight of a building is in the walls and roof and this is transmitted to the ground via the walls. Foundations can therefore help to spread the load of a building more evenly over the ground. Foundations then exist to support the whole building by providing a firm base to prevent its movement and to spread the weight more evenly.
Recommended reading 1: Foundations http://fet.uwe.ac.uk/conweb/house_ages/elements/print.htm
Types of foundations
The type of foundation used will depend upon the nature of the ground on which building is to take place. Put simply, the “weaker” or more variable the sub-soil, the bigger the foundations required. A site survey may be necessary to establish the exact nature of the sub-soil.
Nowadays all foundations are made from concrete and can take one of three basic forms:
Probably the most common form of modern foundation, this is created by digging a trench to the pattern of the load-bearing walls of the building and then pouring concrete into the bottom of the trench. Frequently, the concrete is reinforced by laying steel bars or mesh into the wet concrete. Once the concrete has dried the walls are then constructed, using the foundation as a base.
A variation of the strip foundation is the system known as “trench-fill” which is similar, but the concrete is poured much deeper and actually fills the trench up to ground level.
(b) Raft foundations
Where the soil is “weak” or where subsidence may occur, a raft foundation may be constructed. This lies near ground level under the entire building and, just like a raft, provides a single, solid, plate upon which the whole house rests.
This raft foundation approach has been enthusiastically adopted by many of the early adopters of Passivhaus construction as it allows simplified detailing for thermal bridge free construction.
To support very heavy buildings, such as flats, or if the sub-soil is very poor, then a much deeper foundation is needed. In such cases deep holes are sunk at the corners of the building. These are filled with concrete to form deep “legs” upon which a reinforced strip foundation is then laid.
In some dwellings built at the turn of the century, or even earlier, the foundations may consist entirely of bricks, but this practice, known as “Providing brick-footings”, has subsequently been discontinued.
Problems with foundations
It is unlikely that people directly notice defective foundations. They are more likely to see some other problem with their house, which could then be attributed to problems with the foundations.
The most likely is observing cracks in the walls. Wall cracking, as we will see later, can have a number of causes but one of the causes can be defective foundations.
Areas in Great Britain have suffered from exceptionally dry summers leading to the water content of the soil falling. This has caused the ground to dry out and shrink. One of the results has been that dwellings have subsided if the foundations have not been deep enough. As the ground shrinks then the building may move, causing the cracking which is often the first sign of any problem.
Of course newer houses should not suffer from this problem because the building regulations now impose much more stringent requirements for foundation design.
Note: If climate change brings hotter, drier summers – as is predicted – ground shrinkage could increase.
Another cause of cracking could be heave: where the ground is very porous, it can expand and contract depending on the amount of water in the soil. If the original foundations were not designed with this in mind then the ground may swell and “push” the building upwards. A common cause of heave is when trees growing near to buildings are removed. As they are no longer taking water from the earth, the water content causes the ground to swell and to affect the stability of the building.
In areas with porous soil, it may be necessary to consider a raft foundation. If there is movement the whole of the raft will move, but the walls will remain at right angles to the foundations.
(c) Tree roots
Tree roots may not only take up moisture and cause subsidence; they may also push away the foundations, damaging their structural integrity.
(d) Defective construction
If the foundations have been badly designed or constructed, then they may not be suitable for the ground conditions in the area. The result may be the structural cracking.
How to recognise foundation failure
The most obvious symptom of a foundation failure is a movement of the walls. Whilst the actual movement is not apparent to the eye, cracked brickwork or lines of failed mortar are usually an indication that part of the wall has moved. This movement is often most apparent around window and door openings.
Unfortunately, it is not easy to see any failure in the actual foundation as this is below ground level and, to be checked, must be excavated.
If walls have moved out of the perpendicular then they may be shored up or buttressed using external props. Alternatively, the unsound wall can be “tied” to a structurally sound wall or joist using metal rods.
More drastic remedies include demolition of either the whole building or of just the defective wall and rebuilding. If partial demolition is chosen, then the foundations must be excavated and repaired. This is normally achieved by underpinning – actually propping up the foundation and wall from underneath.
Walls are normally constructed of brick but other materials may be used to either supplement or replace traditional brickwork. Stone, reconstructed stone, breeze blocks, cast concrete or even wood can be used.
The choice of material for the walls will depend on a number of factors – appearance, strength, etc. – and different materials may be used for different parts of the dwelling. The external surface of the wall may also be rendered to provide a smooth finish. This is especially common in Scotland.
(b) The purpose of walls
Walls serve a number of purposes: they delineate boundaries; support roofs and floors; prevent water entering the dwelling; keep warmth in and cold out; prevent the spread of fire, etc. Some walls will be required to have all of these properties whilst others may only be required to fulfil some of these functions. Obviously a wall has failed if it can no longer fulfil all of the purposes for which it was constructed or if it becomes unsafe in its own right.
(c) Types of walls
Walls can be split into four basic types for the purpose of this lesson:
- load bearing;
- non-load bearing.
All walls fall into two of these basic types. Normally external walls are load bearing whilst only a few internal walls are load bearing – but it is not always immediately apparent which is which! However, the construction of internal walls is often a very accurate clue as to whether or not they are load-bearing.
(a) Solid walls
External walls built in the 100 years or so before 1930 were always at least 9” thick: they were constructed using two or more thicknesses of brick/stone. These are referred to as solid walls.
(b) Cavity walls
After 1930, the tendency has been to construct walls consisting of two “skins” of brick with a space or cavity between them, thus the wall is about 11” thick (2” x 4.5” wide bricks with a 2” space between the two). More recently builders have used breeze block to create the inner part of the cavity wall because blocks are bigger and cheaper than brick and, as they are not visible, their unattractive appearance is hidden from view. They may also have improved thermal properties.
To determine whether a wall is a solid or cavity wall one may either measure its thickness – through a window or door opening, for example – or look at the outside. If the ends of the bricks are visible, this will normally indicate that the bricks are laid across two courses of brickwork and the wall is therefore solid.
SOLID (English bond) CAVITY (Stretcher bond)
Bricks which are laid lengthways (looking at the wall) are known as stretchers whilst those laid “endways” are called headers.
(d ) Ties
When cavity walls are constructed, the inner and outer skins of brickwork are “tied” together using either metal or plastic “wall ties” which are laid across the cavity into the mortar between layers of bricks, approximately six layers of bricks apart vertically and 900mm horizontally.
At various places within the walls it is necessary to leave spaces for windows and doors. Above these, to support the brickwork above, are laid lintels usually made of pre-cast and reinforced concrete or steel. In older properties, they will be made of wood.
This, then, is the structure of an external and load-bearing wall, although some internal load-bearing walls may dispense with two lines of brickwork and, instead, consist of only a 4.5” wall.
The external wall must, however, fulfil other functions than that of supporting loads such as floors and roofs. It must also prevent cold and moisture from entering the house.
The cavity in between the two skins of brickwork acts as an insulator, the air in between the bricks keeping both the moisture out and helping to lessen the effects of the extremes of outside temperature. Nowadays, many cavity walls are actually filled with some insulating material to retain the heat within the building, but the material must be carefully chosen and inserted to prevent it from acting as a moisture conductor, allowing water to get away from the outer layer of brickwork to the inner.
The material used to join bricks is called mortar. This is a mixture of sand, cement and/or lime, and water.
The properties of a good mortar are:
(i) it should be easily workable;
(ii) it should stiffen quickly after laying to enable bricklaying to proceed without delay;
(iii) it should develop sufficient strength for the job on which it is used;
(iv) it should bond to the bricks to give a tight joint through which rain will not penetrate;
(v) it must be durable.
With age, mortar will loosen and gaps will appear between the bricks. The property will need replacement of the mortar, called “repointing”.
(g) Damp penetration
A cavity wall fails to function properly if it allows in moisture, which may permeate into the dwelling by several means:
(i) By being carried across by dirt or other material (mortar stuck to a wall tie, extraneous material in the cavity wall insulation, etc.).
(ii) By following lintels, sills, etc., which are actually fixed across both “skins” of brick.
(iii) By getting into the bottom of the wall or foundation and working up through the brickwork – rising damp!
To prevent moisture rising up through the wall or penetrating across lintels, etc., a number of damp proof courses (dpc) must be laid when the wall is constructed. Nowadays, a strong plastic sheeting is used to form the dpc, but in old properties the dpc may be made of lead, slates, asphalt or copper. Normally a dpc will be laid on top of the second brick above ground level, below every sill, above every lintel and below the floor. Of course, if the dpc is torn when laid then it will fail to prevent the passage of moisture.
Categories of DPC. A damp proof course (DPC) is – in its most effective form – a barrier of impervious material built into a wall or pier. It’s job is to prevent moisture (and carried dissolved hygroscopic salts) from the ground moving through porous materials via capillary action (‘rising or penetrating damp’) to other parts of the building. This is to protect vulnerable adjacent or embedded materials, typically structural timber and decorative finishes. The ‘ground’ moisture source may be related to humid, damp or saturated soils or adjacent materials, standing or running water or rain splash-back.
Where DPCs are not of the 100% continuous mechanical type and when adding insulation and draught proofing measures, a degree of ‘residual’ moisture movement past the existing or new DPC should be expected. Surface water management and lowering the water table locally close to wall bases and floors can in some situations achieve a similar result. (If this method is being used in preference to a retrofitted DPC please use the free text fields in the CLR certification forms to explain how this is an adequately robust measure.)
Types of DPC:
- Bitumen based (Hot laid, mastic asphalt, sheet, felt)
- Metal Sheet
- Over burnt or dense brick course(s)
- Stone or Slate
- Plastic, Chemical injection (into bricks only)
- Chemical injection (into mortar joint only)
Internal, non-load bearing walls
(a) If an internal wall is constructed simply to form the wall of a room and is not required to carry any weight, then it will frequently, nowadays, be built of wood and plasterboard; the wood forming a frame onto which is nailed plasterboard or a similar proprietary board. These walls are known as panel or stud-panelled partition walls.
(b) Older houses will often have 4.5” thick brick walls even though they are not required to support weight. Breeze block is also used fairly frequently.
(c) Obviously, it is important to determine whether a wall is “load-bearing” before removing all or part of it. If the wall does support the floor above or a wall on upper floors, then the gap to be left must be supported by a steel girder or a concrete lintel.
(d) Covering the walls.
Occasionally people will leave the surface of an internal wall as bare brick for decorative purposes but this does require an inner skin of decorative brick. It is more usual for internal wall surfaces to be finished by either covering with plaster or plasterboard. Both finishes provide a smooth, even and resistant surface which can be subsequently decorated by the householder.
Problems with walls
A large housing association kept a log over a number of weeks of the problems relating to walls that were reported. This was the list:
- Cracking to both internal and external walls
- Damp patches appearing on internal walls.
- Black mould on the walls.
- Water penetration.
- Cracking at the joint between ceilings and walls.
- Mortar falling out of brickwork.
- Bricks disintegrating.
- Walls bulging.
(a) Cracking to both internal and external walls. Cracking at the joint between ceilings and walls.
We have already looked in the last section at the problem of foundation failure; cracking to walls could be an indicator that there are problems with the foundations. Some cracking however may simply be due to new building work drying out and cracks appearing as part of this process. These cracks can usually be filled with a proprietary filler and they will not recur.
(b) Damp patches appearing on internal walls. Black mould on the walls. Water penetration.
These may have a number of causes. The most likely problem is condensation where the warm humid air inside a dwelling hits the relatively colder wall and causes moisture to form. If this is not wiped away, black mould can form. We will be looking at condensation in more detail later in this lesson. It is typically countered by:
(i) increasing both the heating and the ventilation in the building, to reduce the amount of water vapour in the air;
(ii) avoiding activities which increase water vapour, such as drying clothes on radiators or cooking without having the kitchen well ventilated.
Moisture penetration could however occur, as we have seen, if the wall cavity is bridged, or in the case of a solid wall, if water has worked its way through the brickwork. In the event of the cavity being bridged it will be necessary to clean up the cavity to avoid the problem and this can be a costly exercise.
A further cause could be rising damp where water rises up the wall from ground level. A damp proof membrane is normally in place to avoid this happening, but if there is no damp proof membrane, or it is faulty, rising damp may be the cause of the complaint. Another cause of rising damp is where the ground outside has been allowed to be raised above the damp proof course level, allowing moisture to travel unhindered up a wall.
(c) Mortar falling out of brickwork. Bricks disintegrating.
These problems are often due to defective construction. If the mortar is falling out of the joints this means that moisture can penetrate the brickwork more easily. To remedy this situation it will be necessary to repoint the brickwork, by “raking” out the defective mortar and replacing it.
In certain circumstances, mortar can fail and bricks begin to “spall” or disintegrate because of frost attack. If water gets into the joints or into the brick and then freezes it will expand and may crack the mortar or brick.
(d) Walls bulging
This may be due to the failure, or omission, of wall ties which hold the internal and external walls together. This type of structural defect will need to have expert attention to remedy it.
(e) Remedial work
The most frequent failing is of the damp proof course, which makes a total replacement necessary. In some cases it may be necessary to take out parts of the wall to tackle the source of the problem. The problems of dampness and condensation are examined later in this section. In cases of severe structural failure it becomes necessary to rebuild the wall.
Plasterwork finishes which “fail” are usually removed and either replaced or plastered over, often based on the recommendations of a ‘damp proofing’ contractor.
Although flats often have floors of pre-cast, or cast in-situ concrete, floors in traditional two or three storey dwellings are either:
- solid floors, or
- suspended timber floors.
The ground floor may be of either construction whilst the upper floor will be suspended.
The construction of both is best explained by referring to the following two figures.
Suspended timber floors may be supported in other ways than by using a “sleeper wall”, as is shown above. Obviously floors higher than the ground floor must be held up in other ways. The two alternative methods are: build the end of the joists into the wall itself, or hang steel shoes or hangers onto the wall into which the joist will fit.
Problems with solid floors
A major problem with solid floors is dampness coming up through the floor which will be caused by the DPC failing, or by the fact that the membrane below the concrete floor is not connected with the DPC running through the inner leaf of brick work.
Solid floors may also bulge or crack when laid on certain types of shale hard cores which, when water reacts with the sulphate in the shale, expands and forces up the floor itself.
In both cases the floor will probably have to be dug up to carry out the necessary repair, to replace the dpc or clear all the shale, before a new floor is re-laid. This can be expensive and inevitably causes disruption to residents.
Problems with suspended floors
Most of the faults in suspended floors relate to the wetness or dryness of the area below. Lack of DPC or a faulty DPC will allow moisture into the joists which, unlike concrete, will slowly rot away. Many older houses will have no “oversite” concrete and under the floor one may find bare earth. In many cases this can also be a source of dampness. Older houses were frequently built with joists running right into the walls which also led to problems of wet and rotting wood.
It is also important to ensure that the space below the floor is ventilated as a lack of fresh air into this area will encourage the growth of the DRY ROT FUNGUS which, once established, will rapidly spread throughout the wood which forms the floor and joists.
The roof itself must be capable of providing protection against all forms of weather.
There are three main types of roof, as shown below:
It is important to note that flat roofs are never completely flat and if the slope of the roof is less than 10 degrees then the roof is referred to as a “flat roof”.
Pitched or mono-pitched roofs
Pitched roofs are normally covered by clay or cement tiles which overlap each other. Older houses may have slates. Both slates and tiles are nailed to wooden battens which are laid across the roof.
The battens are nailed to the rafters which run up and down the roof, see diagram above.
The triangular frames of the pitched roof are constructed in the factory and arrive at the building site ready made. Older houses will have been built in-situ. Normally the pre-constructed triangular frame will be braced with a “W” shape of bracing timbers, as in the diagram below.
Each triangular frame, consisting of rafters, a ceiling joist and truss ties, will normally come pre-formed. A series of these are placed on top of the wall and are then “tied” to each other by fixing binders which run the length of the roof.
The edge of the roof is sealed by nailing a sofit board below the rafter so as to fill the gap between the overhang of the roof and the external face of the wall.
Special ridge and hip tiles are used to cover the joints at the roof’s highest points. However, in the valleys which occur (as in Figure 17) where two roofs meet, or at the sides of chimneys or dormer windows which project through the roof, it is necessary to line the area with metal sheeting – often lead on older buildings. This is known as flashing which is inserted into the brickwork and overlaps the surrounding tiles or slates.
Flashings are necessary to prevent rainwater entering the roof space where there is a break in the roof. At chimneys, the roof is broken as the chimney protrudes through the roof and flashings are placed at this junction to stop rainwater finding its way into the roof through the gap. The image above demonstrates this principle very clearly.
Problem: poorly maintained flashing and masonry chimney stack.
In addition, the stepped brickwork and unfilled perpends in the face of the brickwork of the chimney (facing towards the prevailing wind) is acting to allow wind-driven moisture to enter the brickwork, bypass the flashing with water tracking down into the attic room where it is visible as damp patches. On other chimneys in the same small property where the flashing has been (expensively) repaired, the stepped sections have had concrete flaunching applied to help drain rain off the steps, but perpends were left unfilled allowing rain to bypass the renewed flashing – all four chimneys in the attic bedroom are showing damp patches. The flashing work itself is adequate, but the weatherisation of the chimney stack as a whole is defective.
During retrofit planning, the removal of redundant chimneys to below the airtightness and insulation layers should be considered at an early stage, as these represent thermal bridges, air leakage routes and of course an on-going maintenance cost.
(b) Problems with pitched roofs
(i) Structural problems
- The joints between rafters, joists and/or ties may fail, leaving the weight of the roof pushing downwards and forcing the triangle of the roof to spread.
- The wood itself may become wet and rot.
(ii) Roof covering
- The ridge tile which “seals” the peak of the roof comes loose or falls off, allowing water into the roof.
- Tiles or slates break and fall off.
- The roofing felt or “sarking” tears.
- The nails holding slates/tiles perish, allowing the roof covering to fall off.
- The flashing fails.
- The slates/tiles are not overlapped sufficiently, or the slope of the roof is too shallow, so wind and rain enters through the roof.
- Rain enters the top of the wall because no dpc exists and dampness works down through the wall.
Flat roofs are simpler to construct, but more liable to become defective. They are constructed like floors, normally from wood although some dwellings will have a pre-cast concrete slab roof.
Flat roofs should not be totally flat as this will not encourage water to drain off and will allow pools to form and stand on the surface. Normally a fall of between 1 in 40 and 1 in 80 is expected.
The surface laid on top of the concrete or wood is critical. Usually it consists of asphalt or multiple layers of roofing felt. Often stone chippings are used to coat the surface to prevent extremes of temperature affecting the roof surface.
(b) Problems with flat roofs
Many of the faults found in flat roofs are the same as those found in pitched roofs but, in addition, the roof covering may split or crack or the joints may become unsealed. Strong sunshine may melt a bitumen (tar-based) material causing blistering. If the blister bursts this will leave a hole in the roof covering.
Unfortunately, when leaks occur in flat roofs the fault often does not lie immediately above the damp patch seen on the ceiling. This is because moisture works its way through the gaps, joints and lines of least resistance, making it possible for water which enters a gap in the roof covering to exit through the ceiling at the other side of the dwelling. Tracing the problem is thus difficult and perhaps the only reliable remedy for a leaking flat roof is to totally replace or recover it.
As we have seen in the last section, all roofs must have a fall to dispose of rainwater. Roofs normally project a little beyond the external walls so as to prevent water running down or into the brickwork, with gutters attached to collect the water which runs off the roof and then channel it away.
In older houses, the guttering will possibly be fixed directly to the joist ends, but on most buildings the fascia board will support the guttering. Older gutters may be of cast iron or wood; asbestos cement was used from about the 1940s. Plastic and aluminium are now the most common materials.
The gutter itself must be fixed at a slight angle to the horizontal to allow the water to flow down to its outlet pipe for eventual discharge.
(b) Problems with guttering
Some guttering materials are more likely to be affected than others: iron may rust if not properly maintained, asbestos cement may crack and wood will rot! In addition, the actual fixing may fail because nails or screws have rusted away or the fascia board itself has rotted.
Other problems include:
(i) No “fall”, or gutter slopes in the wrong direction. This can be caused by incorrect fixing, by screws loosening or by light plastic materials sagging. As a result, the water collects at one end or at the centre of the gutter and overflows instead of running down into the pipe.
(b) If, for similar reasons, the fall is too great then water may overshoot the discharge outlet and create a waterfall at the end of the gutter.
(c) Gutters often become blocked because of leaves, moss (even bird nests!) and other debris and need fairly regular clearing. This means that gutter clearing should be included as part of every home owner’s / housing organisation’s planned maintenance programme.
Copings, parapet walls, abutments
1. In a traditional 2 storey building are the upper floors likely to be solid or suspended?
2. What is needed in the space below a suspended timber floor to prevent dry rot?
3. What are the three main types of roof?
4. What prevents rain-water penetration to the roof space where a chimney breaks through the roof?
5. What part of the roof supports guttering on newer dwellings?
6. What are the main problems of pitched roofs likely to be reported to a housing office?
2. Adequate ventilation.
3. Pitched, flat and mono pitched.
5. Fascia board.
6. The main problems are likely to be:
– rainwater coming through the roof;
– tiles/slates missing;
– tiles/slates slipped;
– ridge tiles missing or slipped.
6. Joinery Fittings
Doors and windows
In older houses, both are made of wood, although metal window frames were introduced during the 1930s, and nowadays aluminium and UPVC (plastic) are more popular materials for window frames.
Building Regulations require doors to withstand fire for specific periods of time, and more thought is being given to the security aspect of both doors and windows.
External doors will normally be heavier and more solid than internal doors because they have been constructed to fulfil different purposes.
The traditional exterior door will consist of a timber frame containing a number of glass or wooden panels.
In many older houses, panelled doors have also been used internally. In some cases these have been subsequently “flushed” by nailing onto the door a sheet of hardboard.
Flush doors are now commonly used internally. As they do not have to withstand the weather they can be made thinner and lighter and, consequently, cheaper.
Most flush doors are built as in the diagram above; some will have a middle rail running across the door instead of the lock block. The core material will vary dependent upon the quality of the door; often the interior is filled with an “egg box” – like material which acts as an insulator.
External doors are normally finished by attaching to the bottom, a strip of wood known as a weatherboard which is sloped to deflect water away from the gap at the bottom of the door. In addition the bottom of the door frame is finished with a threshold which also acts to prevent water running into the building.
Where dwellings are built to a mobility standard which means that the threshold must be flush with the footpath outside, this can cause problems in preventing water coming into the building and careful attention to detail is required.
Note: Under both weatherboard and threshold is a small groove. This is called a DRIP or THROAT and is cut into the bottom of the overhang to prevent water trickling back into the house along the underside of the material.
(ii) Problems with doors
The most common faults are those relating to the “fit” of the door: if too loose it allows in rain and draughts; if too tight then it is impossible to open or close. Unfortunately, doors made of wood naturally expand and contract unless they have been made of properly seasoned and treated wood and kept in good condition. A door which swells and jams in the winter and is subsequently “eased” by shaving off a little wood may, when it dries and contracts in the summer, allow rain in easily from any summer showers.
Unless well maintained, all woodwork will perish, with joints and hinges the most likely to go first. In addition, any movement of the house or foundations may vary the “fit” of the door because of the movement of the frame.
Windows frames tended to be made of wood but other materials have become more commonplace. In particular, UPVC windows are popular because they avoid the need for regular repainting. Some windows open whilst others are fixed, and all are constructed of glass set into a frame of wood or other material. The frame is screwed or nailed into the surrounding wall.
The various components of a window are shown below.
The glass is held into the surrounding frame by a combination of putty and small nails or by putty, and a thin beading, nailed to the frame. Where the frame is not wood, different systems may be made.
Various types of windows and window opening systems exist, the commonest shown below.
Below the window there is normally a sill which is constructed in similar fashion to the threshold.
(ii) Problems with windows
Wooden windows suffer the same problems as wooden doors, but windows also contain glass which is more liable to create condensation in the interior. Therefore, windows may be more likely to suffer problems of rot than doors. In addition, the putty used for retaining the glass may crack or drop out, and needs regular checking.
(c) Problems of all woodwork
Normally wood is given two coats of primer before being assembled as, once in place, only the exposed parts can be painted. This would mean that any water which seeps into the joints between the frame and the brickwork is likely to permeate both the wood and the wall. Paint, properly applied, forms a waterproof coating to the woodwork but does not last forever, so it is normal for all external woodwork to be repainted at regular intervals.
The result of untreated faults is that the entire door, frame or window has to be replaced. It is, therefore, important to act quickly upon any sign of deterioration.
Obvious signs of deterioration include:
- Staining at the joints.
- Depressions or soft patches in the woodwork.
- Crumbling, loose or missing putty.
- Flaking or peeling paintwork.
7. Other joinery
Staircases are described by their general shape e.g. Straight Flush, Quarter Turn (where they turn through 90 degrees) or Half Turn (a 180 degree turn). Some common types are illustrated in Figure 28.
Each step (a tread and a riser) is fitted to the strings (side panels) and sometimes rests on a central carriage or bearer which runs from top to bottom.
A stair stringer (also called ‘string’ or ‘stringer board’) is the housing on either side of a flight of stairs, into which the treads and risers are fixed. A staircase will have two stringers, one on either side of the steps. If one edge of the flight sits flush against an adjacent wall, the stringer that connects the treads and risers to the wall is referred to as a ‘wall stringer’.
Modern staircases are usually prefabricated and are made of timber. In flats, the staircases may be concrete, in which case they are cast on site.
Points to keep in mind when applying insulation and airtightness to staircases:
Stairs over unheated basements:
If retaining basement access via an underwater doorway, the underside and areas of adjoining walls will have to be insulated and made airtight with an insulated and airtight door.
If this (or any) staircase is against an external or party wall, consideration needs to be given to dealing with the thermal bridge and airtightness routes associated with the stair stringer.
Where internal wall insulation is used above and/or below the stringer, any impact from rising damp and rain wetting loads should be mitigated. Ideally, space could be found between the stringer and the masonry for moisture mitigation, airtightness and thermal measures.
If under stair access to basements is not being retained, airtightness and insulation measures can be carried below the staircase construction, in the plane of the floor. Therefore an airtightness membrane is likely to have to be inserted under the stringers & bottom riser.
Note: the following sections give a historical overview of the most common plumbing and heating options in the UK housing stock. Module 7 of this course goes into more technical detail, chiefly focusing on the building services options available and suitable for retrofit.
This Section is concerned with the supply and heating of water; the fittings for making use of hot or cold water; and the means of disposing of waste water.
Cold water supply and distribution
Normally water is piped into every house from a public source. The incoming supply pipe is often found in the kitchen and is known as the rising main. At its lowest point, where the pipe enters the house, is usually found a valve which can shut off the supply to the whole house. This valve is known as the stoptap or stopcock. From this point the pipe will normally lead upwards with a spur leading off to the kitchen sink. Further spurs lead off to provide cold water to baths and basins and to the WC cistern before the pipe terminates at a storage tank, usually placed as high up in the building as is possible. All drinking water supplies will be provided direct from the rising main whilst the WC, shower, etc. may be fed from the storage tank.
Other stop taps may be inserted into the pipework to allow parts of the system to be shut down.
The pipework may be of iron or lead in older houses, although copper and plastic are common materials nowadays.
Traditionally, houses had storage tanks and the rising main terminated in a ball valve which controlled the flow of water into the storage tank. The tank itself will normally hold between 30 to 50 gallons of water and is usually situated in either the roof space or high on the first floor of the dwelling.
The ball valve automatically allows water to flow into the tank from the rising main to compensate for water drawn off from the tank. The storage tank will always have an overflow pipe leading directly through the exterior wall. This is there to prevent the tank overflowing and flooding the house in the event of a ball valve jamming open.
Water to be used for WC flushing will be controlled by a ball valve similar to that used to control the supply to the storage tank.
Hot water systems
Whilst there are a number of appliances, such as the Ascot water heaters, which heat water adjacent to a sink or bath, the commonest methods of heating water are those which involve the water being heated at one point and then being piped to all the fittings where hot water is required.
Heated water is often stored so that it is ready when required. Most dwellings will include a copper water cylinder which is usually sited in or near the bathroom, often within a cupboard which utilises the heat from the water contained in the cylinder to dry or air linen.
The two most common systems of water heating are:
(a) The immersion heater: an electrical element which is fitted into the cylinder to heat the water, in just the same way as an electric kettle works.
(b) The boiler: forms part of the house heating system, as a “back boiler” behind the fire, or an independent boiler which also provides a supply of hot water to central heating radiators. The water heated in this way may be used directly or may be piped, in a “coil” shape, through the copper cylinder to warm the water there.
The hot water taken from the cylinder is drawn off from the top and replaced by cold water which flows down, because of gravity, from the higher storage tank to fill up the space left in the hot water cylinder.
Note: Traditional boilers are increasingly being replaced by gas combi boilers in houses of all ages. Modern boiler systems are detailed in Module 7.
Disposal of waste and water
The appliances which use water – baths, showers, WCs, sinks and wash basins – are all connected to piping which will carry away the waste semi-automatically.
Sinks, baths and wash basins have a bottom which slopes slightly towards a waste outlet, which is fitted with a plug.
Appliances are also normally fitted with an additional outlet in the shape of an overflow, to prevent the receptacle from overflowing. The pipe from the overflow is itself connected into the waste pipe.
All these appliances rely on gravity to drain them; the WC suite or lavatory pan is emptied by extra water being flushed into the basin to push out the original contents.
In every case the pipe carrying out the waste or water contains a bend immediately below the appliance. This bend exists to retain water which forms a seal in the pipe. This is referred to as the trap. Under sinks and basins this “bend” will be a U shape.
Under the WC suite the shape of the waste pipe (called soil pipes in the case of WCs) will be one of the following shown in Figure 35.
The “trap” is there to prevent smells working back from the drains and into the building. Waste from the sink, basin and bath may discharge into an open gully outside the dwelling in a similar position to the downpipe on a guttering system. The WC will always discharge directly to the main drainage system. The overall waste disposal system is shown below.
The traditional form of heating was by logs or coal/coke being burnt on an open fire. Older houses will have one or more open fireplaces, but direct warmth from the fire is only available in the areas around the lit fire.
Houses built later than 1960 usually have a central heating system installed which provides heating throughout the dwelling. Older houses which have been modernised also normally contain a whole house heating system.
Main types of heating systems
(a) Radiation and convection
Dwellings can be heated by either radiated or convected heat, or by a combination of both. A radiant heater is one which heats by direct radiation, the rays of the sun being a good example. Radiant heat is normally given off from a heat source which is readily visible: for example, an open coal fire, the flames from a gas fire or by the elements or bars of an electric fire.
Whole house heating can be provided by the provision of radiant appliances in each room but, as each burns independently of the others, this can be both inefficient and expensive.
(b) Central heating
The normal systems of providing heating to the whole house is by the production of heat from a single central point, such as a boiler, which feeds outlets elsewhere. The following are the most common systems.
(i) Hot water radiators: the water being heated in a boiler which is itself heated by coal, coke, electricity, gas or oil.
(ii) Ducted warm air: air is “blown” around the dwelling through a series of ducts after being heated by electricity, gas or oil.
(iii) District heating: in which radiators in every dwelling on an estate are heated by hot water piped throughout the estate from a central boiler house serving the whole estate.
Probably the most popular and frequently used system is the hot water radiator system which can be installed in both new and existing houses relatively easily. The water is heated in either a fire back boiler (coal, coke or gas); a free-standing boiler (all fuels) or a wall-mounted unit (gas or electric). The system operates by water being pumped round the system of radiators before returning to the boiler for re-heating. Individual radiators can be switched off if not required, and many systems incorporate an adjustable thermostat at each radiator allowing automatic control to the temperature selected by the occupier.
Other control systems may include:
- A timer or programmer, which allows the occupier to pre- select the times that heat and/or hot water is wanted.
- A boiler thermostat, which can be adjusted so that the heating source is switched off when the water in the boiler reaches the selected temperature.
- Room thermostats, which control the heating system so that a fixed temperature is maintained.
A ducted system is normally installed at the time a dwelling is constructed. The system operates by fresh air being drawn into the system and drawn over a heating element by an electric fan. The warmed air is then passed along ducts and emitted through grills set at a low level in each room. Both timer/programmers and room thermostats may be used to control the system.
Other types of heating systems
(a) Open coal fires
Open coal fires are simple and easy to understand, but fuel has to be stored and is dirty. Coal storage is not always convenient and, of course, it is not possible to programme a traditional open fire to switch on and off!
Common faults are:
(i) Burnt-out grates usually caused by a failure to clear the ash from below the grate.
(ii) Poor burning, perhaps caused by lack of ventilation either to the room or because the space below the grate is filled. Chimneys must be cleaned regularly to provide an effective flue to carry away smoke and also to “draw” the fire.
(iii) Smoking back, which may be caused by a poorly drawing chimney; by a fireplace opening being too high (in which case a cowl might help), or because the chimney is “shaded” by a higher building, in which case the chimney may need heightening or a special cowl might be used.
(b) Individual electric convector heating
These are usually night storage heaters utilising cheap tariff electricity. This is relatively simple, but not always fully understood by home-owners / tenants and, if run incorrectly, can be extremely expensive.
The system works by taking electricity at night to store heat to be discharged the following day. A special tariff can be taken from the electricity company and a special meter is required. Electricity is purchased at a specially cheap rate at night BUT electricity taken during the day may be considerably more expensive! Faults are likely to be few, but the system may be inconvenient as the heaters must be “switched on” the day before heat is required and, once charged, the heat must be used.
(c) Electric underfloor heating
Heating cables are set into the floor when the dwelling is constructed. They operate on a similar “storage” system to (b) above. The biggest drawback of underfloor heating is repairing it! In many cases, faults can only be repaired by opening up the floor and many housing organisations now provide storage radiators to replace a broken underfloor system.
(d) Ceiling heat
This is similar to underfloor heating but cheaper to install and repair, using thinner, and easier to reach, heating elements. The system is rarely popular, contradicting, as it does, the common requirement of “cool head, warm feet”.
The image above shows a heat reflector below the heating cables and screed. In some cases of underfloor heating, there may be little or no insulation, making the system expensive to run. A modern installation should include a good layer of floor insulation below the heating cables and screed.
10. Electricity Supply
Meters and fuses
In older housing and in rural areas, many properties receive their supply of electricity by way of overhead cables but it is common in towns for the electricity to be supplied from the main under the street by an underground cable which rises through the ground floor.
At a convenient point close to the cable entering the house, the electricity company fixes a meter. The meter, the cable and supply to it remains the property of the electricity company, while the wiring from the meter is the responsibility of the owner or occupier.
Nowadays it is common for the meter to be situated on an external wall so that it can be read by the electricity company’s employees from outside. Older housing will have a meter inside, perhaps in the kitchen, hall, under the stairs, etc., where access is needed.
Service entry with internal meter cupboard
The incoming service cable is fused before reaching the meter. This fuse is sealed and remains the electricity company’s property. The purpose of the fuse is to cut off the supply to the circuit whenever an overload (or fault) occurs. The fuse must be the weakest link in the circuit. Thus it is essential that the correct size of fuse is used.
The incoming supply is then “metered” before passing though the fuse box or consumer unit. This box normally contains a mains switch which allows the occupier to shut down the whole supply of electricity, as well as individual fuses to protect the various circuits within the house. Newer housing will now use circuit breakers instead of fuses.
11. Gas supply
Gas is supplied through an underground pipe from the main in the road. The supply pipe is usually carried under the floor of the house and rises to the meter located in a convenient position such as a purpose-built cupboard or the space under the stairs.
The main gas cock to turn off the supply is on the pipe next to the meter. Where houses are converted into separate flats there may be a second isolating valve in the street outside. Homes in rural areas may not be supplied with a mains gas supply. In such locations, gas is supplied in “bottles” e.g. propane gas or Calor gas, or from a large tank in the garden.
Gas is distributed in the older house by iron pipes with threaded joints and fittings and, in modern houses, by copper pipes with compression joints. The pipes are carried under floorboards, clipped to joists and fitted with sleeves to protect them against damage when they pass through the walls.
All gas fittings such as boilers and fires have individual gas taps so they can be isolated from the supply for servicing, adjustment or repair. Some cooker connection points end in a bayonet-type fitting with tap. A flexible armoured hose is fitted to the cooker, and can be plugged into the bayonet fitting. This allows the cooker to be moved for cleaning.
Natural gas can cause death by suffocation and is explosive. It is therefore imperative to know the location of the main gas cock. It must be turned off at the first scent of a leak and the gas supply authority must be informed immediately.
12. Dampness and Condensation
One of the major problems which may occur in dwellings of all ages is that of dampness, which can create an unpleasant and unhealthy atmosphere within the house.
The major causes of dampness are:
- rising damp;
- penetrating damp;
As the name implies, rising damp may gain access at a low level and work its way up through the brickwork (the walls) as the problem continues.
Almost all building materials are porous and are capable of absorbing moisture. Earth is also very absorbent, and moisture in the ground can be transmitted into the structure of the dwelling if the damp proofing is inadequate.
Rising damp manifests itself in a damp patch reaching up the wall from ground level. In some cases it may be in a single patch, in others it may form a line almost horizontally across the wall.
At some point up the wall the amount of water in the brickwork (and plaster) will be low enough to evaporate and will leave a “tide mark” between an area of dry wall and, below it, a dark and damp area.
In order to prevent rising damp, there needs to be a barrier in the wall to prevent it rising – this barrier is provided in the form of a damp proof course laid horizontally across the brickwork. If a solid floor is created at ground level, then this must “sit on” a continuous damp proof membrane which continues into the surrounding wall.
Should rising damp occur, the likeliest causes are:
(a) No damp proof course.
(b) If there is a solid floor there may be no damp proof membrane.
(c) Either the damp proof course (dpc) or damp proof membrane is faulty.
(d) Earth has been built up outside the house to a higher level than the dpc (this normally only occurs in solid walls). See diagrams above.
(e) The bottom of the cavity, in a cavity wall, is full of debris or mortar which extends above the dpc and allows a “bridge” to cross the cavity. See diagrams above.
The only cures are to replace a faulty dpc or dpm or, if the fault is of the dpc being “bridged”, to remove the offending material – which is relatively straightforward if it is simply a build-up of external material, but involves opening up the cavity if the fault is actually within the wall. It is also probable that the woodwork around the area will have rotted and need replacing, as will the internal plasterwork.
Penetrating damp occurs at any point where moisture passes from the outside face of the wall to the interior. In solid walls this can happen quite often, but can only affect a cavity wall if the cavity is “bridged” in some way.
In the case of a solid 9” wall, once the brick or mortar has absorbed water it will simply work through into the house, and in some cases the remedy has been to cover the interior of the wall with a damp proof membrane and fasten a thin partition onto the face of the wall. This does not rid the wall of dampness but, if the dpm is not breached, provides a barrier between the wall and the new, inner, surface. (This technique is often called “dry-lining”.)
Cavity walls are, of course, constructed to prevent water from outside getting into the dwelling. Unfortunately, careless construction can provide a number of routes by which moisture can cross the cavity.
These “routes” across a cavity wall include:
(a) Debris wedged in the cavity.
(b) A wall tie, which is designed not to allow moisture to cross it, being coated with mortar when the wall is built.
(c) Pipework which extends through the wall.
(d) Window, door frames and lintels which have been poorly fitted with damp proof courses.
Often the only solution is to open up the wall and repair the defect.
In every house a number of pipes run through walls, under floors and through ceiling. Leaks usually are self-evident, with large amounts of water coming through ceilings, appearing under the floor, or wet patches on the wall or floor in the driest of weather.
Burst pipes are usually the easiest to find. Small leaks may not be as evident. As leaks and bursts are easier to correct than penetrating damp, the possibility of such a fault should be investigated before any other possibility is checked.
Should there be no obvious signs of a leaking pipe, then cutting off the incoming water at the stopcock and draining the hot water system (by turning all the taps on) will quickly empty the pipework and dripping water should cease. Leaks which are more difficult to trace are ones in storage tanks, cylinders and waste pipes, but are still relatively simple to correct.
Other leaks which may affect the house are faulty roofs and broken or badly fitted gutters, which may soak an external wall sufficiently to allow moisture to pass through a solid wall or find a possible “bridge” in a cavity wall.
Condensation creates a damp atmosphere, ruins furniture and decorations, increases heating costs and, like other forms of dampness, can lead to unpleasant mould growth and affect the health of the occupants of the dwelling.
Dampness which lies only on the surface of a wall is almost certainly condensation, but dampness which is deeper and recurs during cold or changeable weather rather than when the weather is wet, is also likely to be interstitial condensation.
Typically people try to prevent condensation occurring by:
- reducing the amount of water vapour in the building; and
- increasing the temperature of the building.
Reducing the amount of water vapour can be undertaken by:
(i) Increasing ventilation to clear away the water vapour filled air. This can be partially achieved by fitting extractor fans in the wettest rooms and opening windows and door – but it must be recognised that the air that is being cleared away is the air which has already been warmed and the replacement air will be cool, so the occupant will have to pay for its re-warming.
(ii) Trying to reduce the causes of evaporation which fill the air with water vapour. Washing-up, washing and clothes drying all put a substantial amount of moisture into the atmosphere. Whilst all these are necessary parts of life, the problems of condensation may be reduced by confining these activities to well-ventilated rooms which are closed off from the rest of the house.
(iii) By not drying clothes indoors, in front of fires or hung on radiators, which produces a great deal of water vapour.
(iv) Avoid using paraffin or calor gas heaters which provide cheap heating but emit approximately one and a quarter pints of water into the atmosphere for every one pint of fuel used. The result could be a very warm and wet house!
To increase the temperature of the building:
(i) Turn up the heating system and/or burn more fuel, which may reduce the incidence of condensation but at considerable financial and environmental cost. It is not normally realistic to suggest this, although “background” heating in each room may prevent sudden temperature changes.
Even so, certain cold spots may persist as some materials are less able to retain heat than others: for example the concrete lintel which supports the brickwork above windows and doors.
13. Outside areas
Paths and drives
The layout of paths should, as far as possible, avoid steps or steep slopes. Paths should follow the natural line of pedestrians, otherwise short-cuts will be taken and tracks appear across the corner of grassed areas. Paths should have proper drainage falls and, if they cross depressions, gullies will be needed.
…Where against house walls, they should fall away from the building, and should be at least 150mm below damp-course levels, to avoid the problem of rising damp.
Garages, stores and sheds
External garages, stores and sheds are normally built on concrete slabs (rafts) and may be brick, prefabricated concrete panels or asbestos panels on a steel frame, prefabricated timber panels, or purpose-built from timber based materials.
Roofs may be pitched or flat, and covered with felt, corrugated asbestos cement, pvc or tiles in traditional manner. Roof drainage is normally by gutter and downpipe, which sometimes discharges into a rainwater butt or more usually to a soakaway.
The walls of outbuildings are built to lower insulation standards than houses and are often single skin brickwork with strengthening piers.
This lesson has summarised each element of a traditionally constructed building, including:
- the methods and materials used
- the kinds of defects which may be associated with each element
- Evolution of ‘Building Elements – published online from the University of The West of England: http://fet.uwe.ac.uk/conweb/house_ages/elements/print.htm