How this site is written and checked
The rules behind every planning page, cost figure and extension guide here, and what to do if you think one of them is wrong.
Feasibility before sales
Most extension sites answer “what does it cost and who can build it”. This one starts a step earlier, with “are you allowed to build it, and is it the right thing for your house”, because that is what more than half the people who come to us are still working out. So our pages are written to be read before you have appointed anyone — and they are meant to be just as useful if the honest answer turns out to be that you should not build at all.
Sourced, not remembered
Every statement about planning rules, permitted development limits or Building Regulations is checked against the current text on the Planning Portal or GOV.UK before it is published, and the page says which regime it describes. Permitted development in particular varies between England, Wales and Scotland and is narrower in conservation areas, on listed buildings and in some London boroughs; where a rule has exceptions, we name them rather than rounding them off.
Nothing here is a substitute for a written decision from your local planning authority. We say that on the pages where it matters, and we mean it.
Where the numbers come from
Cost figures are drawn from the regional cost model maintained on BestBuilders.co.uk, which is run by the same company as this site. We say so wherever we cite it, because a figure from a sister site is not independent corroboration and should not be dressed up as one. Our own demand figures — how many people were still researching, how many had no drawings, which extension type was most asked about — come from the enquiries submitted through our quote tool, and are described as such.
Money and independence
The site is funded by a fee from a lead-generation partner when you submit an enquiry, as set out on how we get paid. That fee does not change what we write, which pages exist, or whether a page tells you that your project is unlikely to get permission. No builder, architect, product or lender has paid to appear here, and none is recommended by name.
Corrections
If a rule has changed, a figure looks wrong or a link is dead, tell us through the contact form. Every report is checked, and material corrections are made on the page itself. Pages carry the date they were last updated; regulatory pages are re-checked whenever the guidance changes and at least annually.