The costs of building your extension, or renovating and refurbishing your home, can be huge. If you are getting builders in, then it’s a great idea to have an indication of what the costs are likely to be and if you are planning to Do It Yourself, then that knowledge is just as important. So, how do you get an estimate of the likely build costs? The books below will give you a great guide and there is some great on-line help available also. You can start off though with some rule of thumb calculations, to give an estimate based on the size of house you wish to build. If you haven’t got a plot yet, or haven’t got a house design in mind, then you may have to be a little more inventive, perhaps use the dimensions of your current abode to give an idea.
During 2008 the average build cost of a house was in the region of £90 - £95 per square foot, for a reasonable standard specification. The square foot measure is for internal dimensions of total floor area and do not include a detached garage. If a garage is built in and includes cavity work, then include it.
You can check this figure with a local architect – contacting an architect at an early stage would be a good idea. Although material prices may be fairly standard throughout the UK, the labour rates do vary according to location and this may affect the price per square foot figure - an architect may be able to help here.
Now we are into 2009, it may be prudent to use a figure of £100 per square foot for a reasonable standard specification. For a high specification house this figure may rise to £130-£140 per square foot. But now you are asking “what is a reasonable standard specification?” We will answer that by identifying just some of the features that will bump up the cost:
- Bespoke kitchen furniture and worktops – buying from a company that will tailor-make to your requirements will add many thousands of pounds to the good quality kitchens that can be obtained from high street outlets. You may get a uniquely designed kitchen with units made from solid wood instead of melamine or veneered particle board. Marble worktops, luxury hob and oven or Aga style cookers.
- Top of the range sanitary ware, wall tiles and floor tiles – for example, walk-in shower enclosures, Jacuzzis, marble tiles
- Hardwood stairs, internal doors, architrave, skirting board - wood such as Oak and Ash (slightly cheaper than Oak but still good looking)
- Hardwood flooring – you will need to determine which floors will be hardwood, but at least the cost will be easier to estimate by checking prices at the many suppliers available throughout the country
- Real fireplace with chimney – the materials and work required to build a chimney breast and the stack will add at least a couple of thousand pounds
- Balconies – if built above other rooms, these will add a few thousand pounds due to the extra labour and materials required to prevent water from penetrating to the rooms below
- Retaining walls – for a substantial wall you may have to pay in excess of £50,000 – but this is for a really large retaining wall. Smaller walls may still cost a few thousand pounds, however.
If you wish to delve into more specific costs for materials, remember that the prices you can get by having an account at a builders merchant will be much lower than those that they display in their premises, and lower than the prices at DIY stores.
Check out these books for assistance in estimating costs: