Trades master copy
Last reviewed: March 2026
What Part Q is
Part Q is the forced-entry/security bit of Building Regulations. It sets minimum standards for doors and windows in new dwellings so an opportunist burglar can't just lever them open quietly.
The aim is: new homes (and dwellings formed by change of use) have external doors, windows and rooflights that are robust enough, with the right locks and glazing, to resist basic physical attack.
This guide is a summary to make Part Q easier to use on site. It does NOT replace Approved Document Q: Security - Dwellings (current edition).
You must read and follow the full Approved Document Q plus the test/third-party certificates for the door and window systems you fit.
This guide is written for England. Wales, Scotland and Northern Ireland have their own versions of building regulations - the principles are similar but the documents and approval routes differ, so check local requirements if you're working outside England.
Where it applies on your jobs
Part Q applies when:
- You build new houses or flats.
- You form new dwellings by change of use (offices to flats, barns to houses, etc.).
- You create new flats within a building and there are common entrances/corridors.
It covers "easily accessible" doors, windows and rooflights, typically:
- Ground-floor doors and windows.
- Basement doors/windows.
- Anything reachable from a flat roof, balcony, verandah, external stairs, or nearby structure.
It does not normally apply to like-for-like window replacements in existing houses unless local policy/planning adds something extra.
Key "trigger points" - what matters on site
Easily accessible doors
Doors giving access to:
- The dwelling from outside.
- Common parts leading to flats.
- A garage that has a connecting door into the dwelling.
These doorsets must be proven to meet an approved security standard - most commonly:
- PAS 24 (e.g. PAS 24:2016) tested doorsets, or
- Other standards listed in AD Q (e.g. STS 201, LPS 1175 SR1) that are acceptable equivalents.
Easily accessible windows and rooflights
- Ground-floor and easily accessible upper-floor windows/rooflights must also resist physical attack by a casual burglar.
- Again, you're usually aiming for complete windows tested to PAS 24 or another recognised standard, not "any old frame with a beefy lock".
Glazing security
- In some cases, especially where window locks are non-key-locking or glass is close to door locks, Part Q expects laminated glass that meets BS EN 356 (e.g. minimum P1A) to stop a burglar quietly lifting the glass out.
- The idea is: either they give up or they have to break the glass, which is noisy and messy - that's good from a security point of view.
Whole-product testing - not just components
- Part Q is about tested doorsets/windows, not mixing and matching uncertified frames, hardware and glazing.
- A compliant doorset/window has been tested as a system - frame, sash, glass, hinges, locking, keeps, fixings - to an approved security standard.
- You can't claim compliance by just saying "we fitted a PAS 24 lock" to an untested door leaf.
Quick reference table - common jobs
New-build house with front and back doors + patio doors
- Front, back and any side/patio doors must be Part Q-compliant doorsets - usually PAS 24 with evidence from the manufacturer.
- Ground-floor and easily accessible windows/patios must be Part Q-compliant too.
- Keep manufacturer's certification and spec; don't swap to non-compliant doors/windows mid-job.
Office-to-flat conversion
- All new flats created are "new dwellings" - Part Q applies to flat entrance doors, common entrance doors and easily accessible windows.
- Many planners also layer on Secured by Design (SBD) - that usually means PAS 24 doors/windows as a base level.
House with integral garage
- External garage door is in scope if there is a connecting door from garage into dwelling - someone can break into house via the garage.
- You either use a Part Q-compliant garage door or treat the internal connecting door as the secure line and specify that door to Part Q/PAS 24.
New block of flats over a podium
- Main entrance doors to the building, flat entrance doors off common corridors, and any easily accessible windows/rooflights all need to meet Part Q.
- Often combined with SBD requirements, so you're into specific certified ranges of windows and doors.
Routes to compliance for trades
Use doors and windows that are sold as Part Q/PAS 24 compliant
Tell your suppliers up front: "We need full doorsets/windows that comply with AD Q - PAS 24 or equivalent, with documentation."
Get and keep certification, test reports or declarations that show:
- Standard (PAS 24, STS 201, LPS 1175 etc.).
- Scope (door type, opening size, hardware).
- Any installation conditions (fixing, packers, substrates).
Install them as tested
Follow the manufacturer's fixing and packer layouts, frame fixings, and glass type.
Don't reduce screw numbers, change keeps, or swap handles/locks "because we had these on the van"; that can invalidate the test basis.
Know the difference between Part Q, PAS 24 and Secured by Design
- Part Q = legal minimum for new dwellings.
- PAS 24 = test standard for door/window resistance; often used to show Part Q compliance.
- Secured by Design (SBD) = police-backed scheme that normally requires PAS 24 and sometimes higher specs; often a planning or housing association requirement.
Who is responsible for what
On a typical domestic/new-build job:
- The designer is responsible for identifying which doors/windows are in scope for Part Q and specifying compliant products.
- The builder/main contractor is responsible for actually ordering Part Q-compliant systems, not cheaper "similar-looking" products, and for installing them as per the certification.
- The window/door supplier and installer are responsible for providing evidence of compliance (certificates/test reports) and fitting hardware and glazing as tested.
- The client/developer lives with the security risk and mortgage/insurance/Building Control queries if Part Q is ignored.
Blunt version:
If you swap the specified PAS 24 doors/windows for cheaper kit that "looks the same", you've just undone Part Q. When Building Control, SBD or a housing association ask for certificates - or when there's a break-in - that decision lands straight back on you.
Simple rule to drum into your team
If it's a new dwelling and the door or window is at ground level or otherwise easily reached, treat it as a Part Q item. Only fit products with proper security certification, installed exactly as the system was tested.
This guide was last reviewed March 2026. SiteKiln does not provide legal, financial or tax advice. All content is for general information purposes only. Always seek professional advice for your specific situation.
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Working in Wales? The building rules are different. See our Working in Wales guides.
Working in Scotland? Building standards work differently. See our Working in Scotland guides.
Working in Northern Ireland? The system uses Technical Booklets. See our Working in Northern Ireland guides.
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