Building Regulations
Building Regulations for Supply-Only Sash Windows
Since April 2002, replacing sash windows in England, Wales, Scotland, and Northern Ireland has been subject to Building Regulations. If you purchase sash windows from us on a supply-only basis, you (or your installer) are responsible for ensuring the work meets the latest legal requirements.
What Do Building Regulations Cover for Sash Windows?
Building Regulations set minimum standards for safety, energy efficiency, and comfort. For sash windows, the key areas are:
Thermal performance – Approved Document L
Safety glazing in critical locations – Approved Document K
Ventilation – Approved Document F
Fire safety & escape routes – Approved Document B
Access for cleaning and maintenance – Approved Document K (where relevant)
Key Building Regulation Requirements for Sash Windows
Replacement sash windows must meet the following:
Maintain or improve existing compliance – do not make safety or performance worse.
U-value limits for energy efficiency:
England & Wales: Max 1.4 W/m²K
Scotland: Max 1.4 W/m²K
Northern Ireland: Max 1.6 W/m²K
Provide background ventilation with trickle vents (Approved Document F).
Meet means of escape requirements in certain rooms – minimum clear opening area 0.33 m² with both height and width at least 450mm.
Include safety glass in critical locations (e.g., glazing below 800mm from the floor).
Who Is Responsible for Compliance?
When you arrange your own installation, compliance with Building Regulations is your responsibility. There are two main routes to achieving compliance:
1. Using a FENSA/ CERTASS -Registered Installer
The installer self-certifies the work.
FENSA registers the installation with your local authority and sends you a Building Regulations Compliance Certificate.
2. Using a Non-FENSA/ CERTASS Installer or DIY Fitting
You must notify your local authority building control before work begins.
The installation will be inspected for compliance.
If approved, you’ll receive a compliance certificate from the local authority.
New-Build or Major Renovations
For new builds, extensions, or significant alterations, sash windows must fully comply with all relevant Approved Documents. You can access these via the Government Planning Portal: https://www.planningportal.co.uk
Key Building Regulation Requirements for Sash Windows
Replacement sash windows must meet the following:
Maintain or improve existing compliance – do not make safety or performance worse.
U-value limits for energy efficiency:
England & Wales: Max 1.4 W/m²K
Scotland: Max 1.4 W/m²K
Northern Ireland: Max 1.6 W/m²K
Provide background ventilation with trickle vents (Approved Document F).
Meet means of escape requirements in certain rooms – minimum clear opening area 0.33 m² with both height and width at least 450mm.
Include safety glass in critical locations (e.g., glazing below 800mm from the floor).
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