A flat roof extension is a great way to add extra space to your home without splashing out on the costs of a pitched roof extension. Often exempt from planning permission rules, you can build a flat roof extension up to 3 metres in height as long as it's not visible from a road. But how much do they cost in CO2?

A flat roof extension ranges from the cheapest of £21,200 (Ace Locksmith based in CO3) to the dearest of £21,688 (Open Plan Renovation based in CO4), but these are just estimates. While they give you an idea of who will be better value, the best way to compare costs is to get real quotes. 

Find out how much your flat roof extension will cost in CO2 by posting a job with HaMuch. We'll send it to extension builders in CO2.