The FENSA / CERTASS certificate — what it proves and what to do without one

The short answer: certificates turn "I think the work was bad" into "the work skipped its legal compliance step". Check the official register for the tradesperson, order replacements where possible, and treat a missing certificate as evidence in your dispute.

REVIEWED BY: Sean McNamara on 2026-09-03

Replacement windows and doors need building-regulations certification — FENSA or CERTASS provide it. Buyers' solicitors ask for this certificate at sale; a missing one can be ordered retrospectively (or indemnity-insured). In a dispute, a missing glazing certificate is evidence the work skipped compliance — see checking a builder.

Check the register

FENSA / CERTASS certificate — official register (verified 2026-09-03).

In a dispute

Attach certificates (or note their absence) in your letter before action and witness statement. At sale time, missing certificates cost real money — that diminution is claimable: schedule of loss.

Independent information directory — not legal advice.

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This page is general information, not legal advice.

Reviewed by Sean McNamara · 2026-09-03 · Independent information directory — not legal advice.