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House Extension Cost

Most builders apply a certain formula to give you a guide price on how much your house extension will cost. They usually vary between £1000 and £1200 per square metre. Remember that this does not include interior design works, planning applications if they are necessary or if you would like an architect involved in the design aspect of your extension.

You can expect to pay around £500 - £1650 per metre square for a single storey extension.

A double storey extension can cost between £500 - £1500 per meter square.

Planning costs can cost between £1000 - £27000, although the average price is around £5100.

Basic conservatories cost around £500 per square metre to supply and fit. If the ground needs levelling this price will increase. Luxurious conservatories can vary between £750 and £1000 a square metre.

The average cost of a loft conversion varies depending on the size of the conversion and the location of the property.  Average costs for a brick dormer extension are around £150 per cubic metre.  This figure could reduce depending on the materials used. Additional charges would apply if you had a sloping roof or required double glazing windows to be fitted. 

These prices are a rough guideline to what you can expect to pay. A range of different factors will affect the final quote.

It is very difficult to give an exact price of what you should expect to pay for an extension on your home. Prices can vary dramatically depending on a number of factors. Where you live needs to be taken into consideration, for example if you live in London where overheads and labour costs more, then you can expect your extension prices to reflect this. The size and shape of your extension will affect your costs a lot.

It may be necessary to have additional beams or columns and thicker walls, which would obviously increase your spend. In general a simple floor plan of square or rectangular shape will be more economical to build than some highly complex scheme of interlocking octagons with an equally complicated roof!

Despite expecting to pay little difference between a one story extension and a two or three storey, there are certain regulations that apply the higher you build, which will lead to additional costs that you may not have considered. Fire regulations on a two or three story extension will be harder to comply with than if you were only building a one storey extension.

Sound proofing, insulation, plumbing, extra windows and additional door frames will also need to be thought about and will influence the price. The quality of the building materials and interior design works will inevitably have an impact on what you can expect to pay. If you are having a new bathroom installed, this will cost more than converting extra space into a living area. The same applies to where you are extending.

A room that already exists such as a cellar or loft will be cheaper to build than an extension to the side of the house where more foundations and structures will need to be added. We have given you a rough idea of what you should expect to pay for various extensions, but remember to take all of the above factors into consideration.

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