Summary
- Part Q applies only to new dwellings (including those created by material change of use) — not to extensions or replacement windows in an existing house.
- Easily accessible doors and windows in new dwellings must resist physical attack: in practice, doorsets and windows tested to PAS 24 (or an equivalent standard listed in AD Q Appendix B).
- The evidence is product certification: keep the PAS 24 test/certification reference per doorset and window on the schedule — 'secure by design' language without test evidence does not comply.
What the Building Safety Act requires for Part Q on non-HRB jobs
Requirement Q1 requires that easily accessible doors and windows in new dwellings resist physical attack by a casual or opportunist burglar. 'Easily accessible' means ground floor openings and anything reachable from a flat roof, balcony or similar climbing aid — which on tight urban plots catches more first-floor windows than designers expect.
Compliance is product-led: doorsets manufactured to a design shown by test to PAS 24:2016 (or the equivalents in Appendix B), windows likewise, and letter plates to TS 008 where fitted. Bespoke timber doors can comply via the construction specification in AD Q Appendix A, but the joiner must actually follow it and you should record that they did.
For the Principal Designer (BSA), Part Q is a procurement-discipline test: the certification lives with the product, so if the contractor substitutes a cheaper window system, the compliance evidence disappears with the original spec. A schedule that states 'PAS 24 certified, certificate to be provided' per opening keeps the trail intact through substitution requests — and flat conversions (material change of use) are fully in scope, which surprises many practices.
Key design risks and evidence needed (RIBA Stages 2–4)
- Stage 2: identify which openings are 'easily accessible' — including those reachable from flat roofs, porches, bin stores and boundary walls.
- Stage 3: coordinate security with escape (Part B egress windows must still open easily from inside), ventilation (Part F night vents) and overheating (Part O night purge) — the same window serves four masters.
- Stage 4: window and door schedule stating PAS 24 certification per item; letter plate to TS 008; bespoke doors detailed to AD Q Appendix A with a compliance statement from the joiner.
Standards and references you should be citing
- PAS 24:2016 — enhanced security performance for doorsets and windows (the core Part Q benchmark).
- STS 201/202, LPS 1175 (SR1/SR2), LPS 2081 — alternative standards accepted in AD Q Appendix B.
- TS 008 — letter plate security specification.
- Secured by Design 'Homes' guidance — the police-preferred specification that exceeds Part Q, often invoked by planning condition.
Part Q applicability check
| Project | Part Q applies? | What to log |
|---|---|---|
| New-build house or flat | Yes | PAS 24 certification per accessible opening |
| Flat conversion (material change of use) | Yes | As above — commonly missed |
| Extension to existing dwelling | No | Tracker entry: 'not applicable — extension' |
| Replacement windows, existing house | No (Parts L/F apply instead) | Tracker entry with reasoning |
Common pitfalls that catch out sole practitioners
- Missing Part Q entirely on barn conversions and office-to-residential jobs — material change of use creating a dwelling is squarely in scope.
- A first-floor window above a single-storey flat roof treated as inaccessible — it is 'easily accessible' and needs PAS 24.
- Contractor substitution of certified windows for an uncertified system with 'equivalent locks' — locks alone are not a PAS 24 test.
- Secured by Design planning conditions conflated with Part Q; SBD requirements can exceed AD Q and both trails need evidencing separately.
Frequently asked questions
Does Part Q apply to replacement windows or extensions?
No. Part Q applies only to new dwellings, including dwellings created by change of use. Extensions and replacement windows in an existing house fall under Parts L and F instead — though fitting PAS 24 products remains good advice, it is not a regulatory requirement there.
What counts as an 'easily accessible' window under Part Q?
A window within 2 m vertically of an accessible level surface — ground level, a flat roof, a balcony, or any feature that can reasonably be climbed. On constrained sites this frequently includes first-floor windows over ground-floor projections; map them at design stage.
Track this natively instead of in Word templates
PD Pathway gives small practices an automated Parts A–T relevant-requirements tracker, stage-by-stage Principal Designer checklists and one-click compliance documents — built strictly for non-HRB projects. First project free, then from £10 per project or £99/yr unlimited.