Building a home extension

Building Company at work

The vast majority of homeowners can extend their home in various ways, and in some cases quite extensively, without requiring planning permission thanks to the amended ‘Permitted Development’ regulations introduced by the Government in 2008.

As a result a more extensive range of out buildings, extensions and alterations can now be built without the need for formal planning permission, including homes that are located in the normally very restricted areas of Green Belt and Flood Plain areas, for example.

Among the raft of changes to the planning rules announced by the government is a temporary relaxation of laws surrounding domestic extensions in England. The full detail will be in a consultation document, expected to be published next week, but here we look at the current rules and how they might change.

What can I currently build?

You can apply for planning permission to build anything you like, although it may very well not be granted, or if you want to make more minor changes without planning permission you can opt for a permitted development. It is the rules around what this constitutes which the government wants to relax.

What currently counts as a permitted development?

It depends where you live: conservation areas and listed buildings have different rules, but broadly speaking extensions, loft conversions and conservatories can all be permitted developments. There are, however, restrictions. When it comes to extensions the main ones are:

• all extensions and other buildings must not exceed 50% of the total area around the house as it stood on 1 July 1948, or the day it was built if later.

• the extension is not on the side of the house that faces the road.

• on a detached house a single storey extension can be up to 4m long and side extensions can only be a single storey.

• on a terraced or semi-detached house a single storey extension can only be 3m long.

• the building must not be clad in any outlandish material – if you want to do something that doesn’t match the exterior of your house you will need to get the council’s permission.

• single storey extensions must not exceed 4m in height.

• two-storey extensions can only be 3m long.

The government’s planning portal has guides and details on common projects including permitted developments.

What about my loft?

You can do a lot to a loft without planning permission – most conversions are permitted developments. However, you will need permission if you want to add a dormer to the front of a house or raise the roof level in any way. You will also be restricted to creating space equal to 40 cubic metres in a terraced house and 50 cubic metres in a semi-detached property.

• on a detached house a single storey extension can be up to 8m long.

• on a terraced or semi-detached house a single storey extension can be 6m long.

Rules on height, materials and so on are expected to remain unchanged.

Great, anything I need to know before I start building?

Only that the rules are not quite as hard-and-fast as they sound. Chris Wojtulewski, director of planning consultancy Parker Dann, says the rules around permitted developments are “intensely complicated” and councils have a 49-page guide to applying them. “There are subtle variations between local authorities – inevitably people are going to have different interpretations of the rules.”

Wojtulewski suggests homeowners who are in any doubt about whether their proposed build is or isn’t permitted should contact their local council for clarification at the beginning of the process.

You also need to be aware of building regulations: if an extension doesn’t meet them a council can ask for it to be taken down. If you are employing a builder to do your work make sure you confirm they are taking responsibility for meeting the rules.

Can my neighbours complain?

When a homeowner applies for planning permission the council sends out letters to neighbours asking if they have any objections. These are taken into account when a planning officer makes a decision, although the fact a neighbour has complained does not necessarily mean a scheme will be rejected.

This process doesn’t occur if you are building a permitted development, but you will still need to notify your next-door neighbours if you are building near to your boundary. Once you start building, any neighbour who believes you are breaking the permitted development rules can contact the council, which will send round an enforcement officer.

Demolition and foundations

Sometimes, building a small extension can be done very cheaply if the new extension can make use of three existing walls. You might not need Planning Permission, but you must apply for Building Control by submitting a Building Notice and pay the required fee. Note: if you submit the Building Notice but you do not pay the fee – the Building Notice is ignored by the Council.

Because there are already three existing walls, the old property and the neighbour’s extension wall, in this case we have an U – shaped site. After getting the neighbour to sign the Party Wall Agreement, the wall can be used as part of the new extension.


Experts can lay bricks or blocks, quickly and well. Amateurs can usually do one or the other, but not both.
It you are content to work slowly, and if necessary to knock down a piece of wall and start again (if you do it before the mortar is dry you can brush off the bricks and all you have wasted is a few shovelsful of mortar), there’s no reason why a householder shouldn’t be his own bricklayer.

Once you’ve begun to master the technique a whole range of jobs becomes possible, from making dwarf walls for the base of a greenhouse or garden shed to building a garage or a house extension. Start with a garden wall – if the results are a little irregular, you can always claim that the rustic look was intended.

Most tools needed can be hired or bought: brick trowel, pointing trowel, bricklayer’s spirit level (a yard long with two bubbles so it can be used horizontally and vertically), club hammer, bolster chisel, bricklayer’s line, a rule.

To cut a brick, chip a groove in it with hammer and bolster and tap unwanted side sharply. When a bricklayer does it the brick falls neatly in half; amateurs can use a lot of bricks before they master the knack (though a brick which hasn’t broken cleanly can still be used provided the face side is the right length). An easy way round this is to use a brick saw, a handsaw with hardened teeth set into the blade, and simply saw the bricks to size.

Wear working or gardening gloves; the mortar is hard on the hands. For a garden wall, mark out and dig a foundation twice the width of the wall; take out topsoil until you reach a firm base, the deeper the footing is, the better. Drive in pegs and level them, using a line or a straight-edged board and spirit level, so peg heads are about 7cm below ground level. Now fill trench with concrete (1 part cement, 6 of all-in ballast) to the top of the pegs and leave it to harden.

Bonds are the patterns in which bricks are laid – English bond, stretcher , Flemish bond. Their purpose, apart from appearance, is to ensure that, for the sake of strength, no vertical joint comes directly above another. With foundations laid, stretch a line to mark where the face of the wall is to be, put a pile of bricks near each end.

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