Ten things you need to know about... buiding an extension ¦ Property Guides on Times Online

1. Decide on your budget. Working out the cost of a house extension or loft conversion yourself is difficult because each one is different and costs often relate to the size of the project. A good source of costing is the Building Cost Information Service of the Royal Institution of Chartered Surveyors which publishes The Property Makeover Price Guide, or you could get some idea from www.whatprice.co.uk or try the free estimator on www.growyourhome.com When you are working out the cost of extending your house, most advisers suggest building in a contingency of, say 10%, in case your budget overruns. And don’t forget the fixtures and fittings which can add to the cost considerably.

2. Consider how you are going to cover the cost of extending your house. If you need to borrow the money you will normally have the choice of either increasing your mortgage or taking out a personal loan. You will pay a lower rate interest for a further advance on your mortgage but bear in mind that if you spread your repayments over the rest of your mortgage term you will probably end up paying more interest overall than with a short term loan. Make sure to shop around for the best loan deal or if you do decide to increase your mortgage, consider re-mortgaging (see www.moneyfacts.co.uk for the cheapest loan and mortgage deals). You may be able to get a cheaper mortgage deal, which will help to cover the cost of the increased loan.

3. Speak to your neighbours about your plans, you may need their agreement. The Party Wall Act 1996 covers work involving party walls, boundary walls and excavations near neighbouring walls. You may need your neighbours written consent for the work, otherwise they could go to court to stop you proceeding.

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4. Speak to your local authority to find out whether you need planning permission for your extension or conversion and whether it will need building regulation approval:

*Conservatories or porches built at ground level which are less than 30 square metres in floor area are exempt from building regulations but may need planning permission.

*House extensions will normally require planning permission and building regulations will also apply.

*Loft conversions only require planning permission if they alter the size or external appearance of your property, such as through the installation of dormer windows. However, they always need to comply with building regulations and if a loft conversion has not been approved you will not be allowed to use it for living accommodation or to describe it as such.

*Basement conversions which involve changing the structure of the building will also need to be approved under building regulations.

5. If you do need planning permission, decide whether you are going to employ an architect or surveyor to draw up your plans, find a builder and oversee the project, or whether you just want a professional to provide the plans and intend to do the rest yourself. Naturally, doing it yourself is the cheaper option, but if you don’t have a lot of time on your hands, having someone to supervise will spare you considerable hassle.

6. If you have to apply for planning permission, the fee is around £135. It will generally take around eight weeks to get a reply from your local planning department. Check with your builders that they are dealing with building regulations compliance, otherwise you will have to submit an application and arrange for an inspector to carry out the required inspections. You will also have to pay a fee for these visits which will depend on the size of the project. Check with your local authority.

7. If you are appointing the builders yourself, get three itemised quotes in writing – not estimates. (A quote is a fixed price, an estimate is only an approximate price.) Ask friends for recommendations. Ask for your builders’ address and landline telephone number, don’t rely on mobile numbers. Choose traders who belong to professional organisations such as the Federation of Master Builders which have dispute resolution procedures. Look out for those using the Government-backed TrustMark logo which means they are obliged to meet certain standards. Don’t choose traders because they can do the job immediately. Bear in mind that good builders are likely to be busy so be realistic about time scales.

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