Part Q Building Regulations Explained
What is Part Q?
Part Q deals with security in dwellings.
Its purpose is straightforward: certain windows and doors must provide reasonable resistance to unauthorised access.
For window and door contractors, this means security cannot simply be judged by looking at the lock.
Compliance relates to the complete tested product.
The Most Important Thing to Understand
Part Q does not apply to every replacement window in every house.
Requirement Q1 applies to new dwellings and relevant parts of buildings where access can be gained to a flat.
That distinction matters.
A builder saying:
“Every replacement window legally needs PAS 24.”
is oversimplifying the regulation.
Other contractual, planning, insurance or Secured by Design requirements may still call for PAS 24, but that is different from saying Part Q itself applies universally.
What Does Part Q Require?
Reasonable provision must be made to prevent unauthorised access.
The Approved Document addresses windows and doors that could provide access to the dwelling and expects suitable resistance to physical attack.
One of the principal routes used by the industry to demonstrate this is PAS 24.
What Is PAS 24?
PAS 24 is an enhanced security performance standard for doorsets and windows.
Testing assesses the ability of the product to resist specified methods of attack.
The critical word is product.
PAS 24 isn’t simply:
- A multipoint lock
- A security handle
- Laminated glass
- A certain cylinder
- Security hinges
A window or doorset is assessed as a complete configuration.
Don’t Build Your Own “PAS 24” Product
This is a serious specification mistake.
Suppose a builder orders:
- An aluminium door
- A good multipoint lock
- A 3-star cylinder
- Laminated glass
and concludes:
“That’s PAS 24.”
Not necessarily.
The configuration needs to fall within valid test evidence and permitted variations for that system.
Changing components can take the product outside the evidence.
Which Windows Matter?
The focus is on windows that are accessible to potential intruders.
Ground-floor windows are obvious examples, but accessibility can also arise through:
- Flat roofs
- Balconies
- Adjacent structures
- Easily reached upper levels
Don’t assume “first floor” automatically means security requirements are irrelevant.
Doors
Relevant doors may include:
- Front entrance doors
- Back doors
- French doors
- Sliding doors
- Other accessible external doorsets
Again, compliance is based on the complete doorset and appropriate evidence.
What About Bifold Doors?
Bifolds can be specified to enhanced security standards, but don’t assume every bifold from a particular system is automatically PAS 24 compliant.
Check:
- Tested configuration
- Maximum/minimum sizes
- Hardware
- Glazing
- Threshold
- Locking
- Opening arrangement
This is especially important with unusually large doors.
What About Sliding Patio Doors?
The same principle applies.
Ask the supplier:
“Does this exact configuration fall within your PAS 24 evidence?”
That is a much better question than:
“Is this system PAS 24?”
Glazing
Where security glazing is required as part of a tested configuration, the correct glass specification matters.
Do not substitute glass after manufacture without confirming compatibility with the certification.
PAS 24 vs Secured by Design
They are related, but they are not the same thing.
PAS 24 is a product security performance standard.
Secured by Design is a police-backed initiative covering broader security principles and accredited products.
A project specification may demand Secured by Design even where basic Building Regulations compliance is the starting point.
Read the specification carefully.
Replacement Windows
Part Q is commonly misunderstood here.
Normal replacement windows in an existing dwelling are not automatically brought within Requirement Q1 simply because they are being replaced.
However, enhanced security remains sensible, and PAS 24 may still be required because of:
- Contract specification
- Client requirements
- Insurance
- Planning conditions
- Secured by Design requirements
- Other project-specific obligations
Common Part Q Mistakes
“It has multipoint locking, so it’s PAS 24.”
Wrong.
“The profile system is PAS 24, therefore every window is.”
Not necessarily.
“It’s laminated glass, so it complies.”
Again, not necessarily.
“Part Q applies to every replacement window.”
No.
“If the standard window passes, any size passes.”
Dangerous assumption.
Test evidence and permitted product variations matter.
Real-World Example
A developer requires PAS 24 aluminium entrance doors.
The contractor chooses a reputable aluminium system but then requests a different lock and oversized door leaf.
The supplier cannot provide evidence covering that exact configuration.
The fact that the base system has previously passed PAS 24 does not automatically make the altered doorset compliant.
The correct approach is to check the proposed configuration against the manufacturer’s or fabricator’s evidence before ordering.
Documentation to Request
For projects requiring Part Q/PAS 24 compliance, request suitable evidence demonstrating that the proposed product is covered.
Keep this with the project file.
It may be required by:
- Building Control
- Main contractor
- Architect
- Client
- Warranty provider
Trade Tech’s Practical Advice
Tell your supplier before quotation that PAS 24 is required.
Don’t wait until the products have been manufactured.
Provide:
- Sizes
- Configurations
- Opening directions
- Hardware requirements
- Glass specification
- Threshold requirements
- Project specification
That allows compliance to be checked before money is committed.
Frequently Asked Questions
Does Part Q apply to new houses?
Yes. Requirement Q1 applies to new dwellings.
Does Part Q automatically apply when replacing windows?
No.
Is PAS 24 the same as Part Q?
No. PAS 24 is an important method of demonstrating enhanced security performance used in connection with Part Q.
Does multipoint locking mean PAS 24 compliant?
No.
Does laminated glass automatically make a window PAS 24?
No.
Can aluminium windows achieve PAS 24?
Yes, where the particular product and configuration are covered by appropriate evidence.
Can bifold doors achieve PAS 24?
Yes, but the exact configuration must be covered.
Can sliding doors achieve PAS 24?
Yes, subject to the tested system and configuration.
Related Guides
- PAS 24 Explained
- Secured by Design Explained
- TS 007 Cylinders
- Laminated Glass Explained
- New-Build Window Regulations
- Building Control Checklist
Need PAS 24 Windows or Doors?
Send Trade Tech your drawings and specification before ordering.
We can help establish which window and door configurations need enhanced security and identify suitable compliant products.
Important: This guide provides general guidance for projects in England. Always check the current Approved Document Q, project specification and applicable product certification.