House extension prices - what affects them?

Many house extension builders and designers often quote an average price per square metre for costing out a house extension.  Regretfully there are many factors that will affect a house extension price.  These are:-

Location of the property - upmarket areas will cost more than ex-council house extensions for example.  House extensions in the south east of the UK will cost more than a house extension north of Watford simply due to living costs & the local economy.

Complexity of the house extension - simple 'bolt ons' (horrible phrase) will cost less than a complicated design of extension with extensive internal remodelling of the layout.

Who you employ for your design and planning services - Cheap plans will produce cheaper builders estimates at the beginning of the job but you will pay for the deficiencies later on at the end of the job.  Professionally prepared and well detailed plans and specifications will provide a more accurate and correct price for the house extension right from the start.

So, how do you estimate a budget cost for your house extension and what price should you be allowing? Use the advise of an experienced and professional home extension designer or architect.  Get them in for an informal chat right from the start and interview several.  Listen to what they say and record all estimated costs.  Then average them out for an idea of what to expect.

It is not an exact science as that is why formal plans and specifications are required in order for the builder to see the extent of your house extension scheme and price the works on the known and approved design.

Regretfully, all homeowners are in a 'chicken and egg' situation where they will have to spend out on fees and time to have a house extension scheme prepared on paper before the builder can price it correctly.

House extension design work is never really wasted provided you have obtained formal Planning Permission.  This is called planning gain where you have formal approval to add additional floor space that is now confirmed and this does have an influence on the current house value and can make it far more appealing to a wider market should you decide to abort the scheme and sell up to move on rather than building the house extension.