Why it matters more here

Loft conversions get scrutinised at sale more than any other alteration. A buyer's solicitor will ask for the certificate and the trade certificates. Without them, the deal stalls.

What is checked at final

Fire doors and seals, alarm coverage, escape windows, insulation evidence, structural details signed off, and the trade certificates for electrics, heating and any glazing.

Chasing it

Do not assume your builder will chase the certificate. Ask, in writing, before final payment. The leverage disappears the day the snagging cheque clears.