Home extension estimated costs 

It is important that you establish in your own mind what your available budget is for your home extension right from the start as your wish list may be unachievable for the budget or finance you have.

Therefore you need to have some idea of the estimated costs based upon your requirements. This can be combined with interviewing a number of home extension designers or architects for some initial advice. Each one should be able to give you an idea of the home extension cost based upon your verbal description of the intended works.

Another route to obtaining an idea of estimated costs is to consult with a few builders but many are reluctant to offer a home owner budget costs estimates for a home extension as they do not know the full extent of your intended works.

Homeowners often forget that any extension work will involve some degree of repairs, making good, remodelling of the existing house layout or other overlapping works that can be hard to identify at the very start.  Most builders like to price from the detailed building regulations construction level drawings and specifications rather than some verbal description.

Therefore, do not be surprised if the site visiting builder is unresponsive or reluctant to discuss costs and those that do will usually get it wrong by a considerable margin.  One way around this is to just ask the builder to estimate the build costs purely for the new built frame of the extension and exclude client selected items like bathrooms, en-suites, kitchens and other internal remodelling.  That way the site visiting builder should be able to get a better handle on the those costs.  You can then add in the extra costs you think relevant for the home owner selected items.

Some professional bodies (RICS) will publish estimated building costs on per square metre basis for various types of new build work.  These can be difficult to use or locate the correct information but this is another tool for you to pool all three sets of estimated build costs in order o obtain a possible average, minimum or maximum cost of your home extension.