Building a Home Extension

Building a Home Extension

An extension can often seem like the perfect solution for a cramped house, hut one very important thing to consider when planning an extension is exactly what you arc going to use the extra space for. If you need an extra bedroom then its function will be clear, but, surprisingly, misunderstandings about an extension’s purpose between couples, and within families, can remain until well into the construction stage. Is it going to be a play room? A study? Or a larger lounge? Or has someone else in the household got their eye on it for some entirely different function, like table-tennis or sewing? It is best to get these things ironed out before you move in the furniture, or you could find yourself playing ping-pong while someone tries to make a dress down at the other end of the table.

One unexpected advantage of extensions is that they can sometimes dramatically free up other areas of the house. Something like a large kitchen extension, for instance, with a portable television in it, can suddenly act as a magnet for younger, noisier and perhaps more fridge-oriented members of the household, who then free up the formerly overcrowded lounge for their parents perhaps a final armistice in the battle for the remote.


Building Regulations

Extensions almost always require Building Regulations approval, particularly brick-built ones with habitable rooms like the one that most people plan: so prepare to have your wilder ideas curtailed. You will have to apply for approval from your local authority.


Planning permission

This is usually required if you have used up your permitted development allowance — the volume by which you are permitted to increase the original house.

As long as it falls within the permitted allowance, the extension will not need planning permission if it complies with the following additional conditions:

• it must not project above the original roof line of the house, nor in front of any house wall facing a highway

• it must not exceed 4m (13ft) in overall height if it will be built within 2 m (6ft, 6 in) of a boundary

• it must not result in more than half the site being built on.

If the allowance has been used, permission may still be granted if a good case can be made that your proposals fit within the planning guidelines. Local architects who are familiar with the local requirements — and the tastes of individual planning officers — may be able to assist in getting a sympathetic addition approved, particularly if a precedent has been set nearby.

Note that if the extension is built to provide facilities such as a self-contained granny flat or a home office, planning permission may be needed to cover the change of use, even if the extension itself comes within the permitted development rules. Check this out at an early stage.

Remember, too, that there may be circumstances in which your permitted development rights have been removed: for example, as a condition of a previous planning consent, such as that granted when the house was first built.

The most common problems

• Matching the extension to the original design of the house

In some areas, it may be compulsory to use local stone.

A problem with houses built with imperial 9 in bricks used up to around the mid-1970s is that bricks are now standardised at 225mm, which is ever so slightly smaller. It’s the small (1.7mm) difference in height that is the main problem. This soon adds up, so that the add-on is always noticeable, particularly to obsessive brick-watchers, of whom there are surprisingly many — as extension owners tend to discover. You have three choices: make the mortar course thicker so that the brick courses line up; ignore the problem; or use second-hand (reclaimed) bricks, which may also have the advantage that they are already weathered and match the existing bricks. there is a huge choice of bricks available —you can find brick ‘libraries’ on the Internet — and you should be able to get something suitable. Well-chosen bricks ‘weather in’ and become indistinguishable from the main house over a period of several years. Alternatively you could deliberately choose to have your extension in a contrasting colour — though this approach may not be possible if you live in a listed building or Conservation Area, in which case you may only be allowed to use certain brick bonding patterns and types of lintels and plinths.

• Siting the extension

You need to find a good place on the outside of the building that will match your internal requirements and which fits with the requirements for planning permission. If your house is of a fairly common type in the area, it will be well worth touring your neighbourhood to look at other extensions. If one really catches your eye, then the person who commissioned it will almost certainly be pleased to talk to you about it and perhaps hand you the details of both the architect and the builders who built it.

• Getting the roof right

If you are adding to the gable end of a house, try to follow the slope of the existing roof and match the tiles or slates. A pitched roof with good-quality slates, for instance, often accounts for a significant proportion of the cost of the extension. But if your existing house adopts this style, then something like a flat felt roof would be a false economy, drawing attention to the add-on and making it look like a prefabricated hut. You may be able to pitch the new roof at right angles to the existing one — and get away with using man-made slates, some of which are very realistic. Man-made slates are much lighter than traditional ones and are significantly less expensive.

• Windows

It is important to try to match the style and height of the windows used in the extension to those used on the adjacent elevation of the house. Keeping the windows’ head and sill levels the same will go a long way towards unifying the appearance of the old and new buildings. This applies particularly to older houses, in which modern casement windows would look completely incongruous next to original sash windows. If you cannot find an off-the-shelf match, consider having your new windows made to measure.


The biggest problem: good design

Apart from the problem of getting planning permission, which can range from being straightforward to very awkward indeed, extensions can suffer from access problems between the old and the new sections of the house, and create traffic-flow problems elsewhere if they are poorly designed. The new room might become extremely popular and create demands on passageways or thoroughfares which were not there before, but which now need to be accommodated. You can also make an existing room significantly darker if an existing window is used to create a doorway into the extension. Your design will be controlled in terms of access routes, fire risk, lighting, power and ventilation but no one in Building Control will stop you from proceeding with something which may turn out to be impractical. An architect will be skilled at anticipating potential problems.


The sequence of events

1. The site is cleared

This could range from demolishing an existing structure to simply tidying up the lawn. Decisions about storing materials and tools have to be made and the area of the foundations marked out.

2. Digging commences

Extensions generally require deep foundations and extra drainage, including that for the extra water coming off the roof— all of which generally means that a lot of mud has to be dug up and transported out of the garden.

3. The walls go up

Block or brick walls are labour-intensive to construct, but this can be one of the most dramatic and rewarding stages of any job to withess. In a timber-frame construction, the inner walls appear as if by magic.

4. Upper-floor joists are built in

5. The roof is added

Waterproofing the structure is a time-consuming but highly significant stage, at the end of which it all starts to look like a real house again — only bigger.

6. Wiring, plumbing and heating are put in place

Supplying these services is usually straightforward. You should be able to run new socket outlets off the existing ring circuit, provided the total area served by the whole ring is not more than 100sq m, but a new kitchen extension should have its own new socket outlet circuit. Existing lighting circuits can usually be extended too, and most boilers have the capacity to support extra radiators.

7. Plastering is carried out — the last of the really messy processes.

8. Skirtings and decorating are completed

These are tasks which many people like to tackle themselves, to save money and to take possession of the project at the earliest possible moment.

Timescale: Usually eight to twelve months from planning to completion. It can be a longer process.


The case for using a specialist

Employing an architect and/or builder who specialises in extensions and who knows the ropes in a given area can offer significant benefits. People in sensitive planning areas can be over-cautious and apply for a construction hardly bigger than a porch. A specialist will know exactly what is permissible, who to approach, and how to keep the Building Control Officer happy. A specialist will also be more skilled in that vital art — making the extension look as though it is part of the original house.

The relationship with your contractor can be smoother if you employ someone who has been through all the stages of the job with a large number of customers. Large-scale building work in the home is quite an upheaval: a specialist will be able to anticipate at which stages the customer is likely to get stressed and upset, and is more likely to handle matters sensitively. If the builder is encountering problems and getting flustered himself, he may pass that on to the client, which makes for a less pleasant job.


Finding an extension specialist

The Federation of Master Builders (FMB) will be able to provide you with a list of builders who specialise in or have a lot of experience of building extensions, perhaps of the type you require (such as kitchen or garage extensions).

If you are commissioning a two- or three-storey structure, it is important to make sure that the builder has some experience in this area.


22. May 2011 by admin
Categories: Building Regulations/Planning Permission, Construction | Tags: , | Comments Off on Building a Home Extension


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