Building Regulations for Replacement Windows

Building regulations for replacement windows concern how the new installation performs and is fitted. Planning permission concerns whether a proposed change is allowed. Permission from a landlord or freeholder concerns whether you may alter the property at all. One document does not automatically answer all three questions, so check each route before ordering.

This guide explains the paperwork for ordinary uPVC and aluminium replacement windows in England, how FENSA and Certass fit into the process, and what to do if an older certificate is missing. Verify the chosen installer’s scheme registration and the certification route for your specific installation before agreeing the work.

When building regulations apply

Planning Portal guidance explains that replacing the whole fixed frame and opening parts of a window normally requires compliance with building regulations. Relevant considerations include thermal performance, ventilation, safety glazing and, where applicable, escape arrangements. The specification needs to suit the actual opening and room rather than simply copy a brochure illustration.

A glass-only repair is not necessarily the same job as replacing a complete frame. Describe the intended work accurately when seeking advice from building control or an installer. Ask how the existing ventilation and opening arrangements will be addressed, particularly where a new window is intended to be more airtight than the old one.

The competent-person route and building control

GOV.UK explains that a tradesperson registered with an appropriate competent-person scheme can self-certify eligible work. The scheme route can include notifying the local authority and providing evidence that the installation complies. The registration must cover the work being undertaken; the existence of a company name on a search result is not sufficient by itself.

If the installation is not being self-certified through an applicable scheme, discuss the building-control approval route before work starts. Ask who makes the application, which inspections or information are required and who obtains the final record. Agree these responsibilities in writing so completion paperwork is not left to assumption.

Certass vs FENSA: what to compare

FENSA and Certass are separate organisations with their own installer and certificate systems. For a householder, the important questions are whether the installer is registered for the relevant work, whether your job will be notified and how you will receive the resulting certificate. A badge should lead to a verifiable record, not replace checking.

When comparing FENSA installers with installers using another approval route, compare the proposed window specification and the certification arrangements together. Do not treat scheme membership as planning permission or landlord consent. Ask the installer to identify the route that applies to your property and keep the answer with the written quote.

Do I need planning permission for new windows?

For many ordinary houses, replacement windows may fall within permitted development, but the property and proposed change must be checked. Flats do not share all the permitted-development rights of houses.

Use your local planning authority’s guidance for the address and proposed design. Changing material, colour, opening pattern or glazing bars may need a closer check than a straightforward replacement. Planning advice and building-control advice are distinct: receiving one does not settle the other.

Leaseholder and tenant consent

For a flat, read the lease to establish who owns or maintains the frames and whether alterations need the freeholder’s written consent. A managing agent may also need to approve the appearance, contractor access and use of shared spaces. Building-regulations compliance does not override a restriction in a lease.

Tenants should ask the landlord before arranging replacement work. Keep written consent and any agreed conditions with the installation documents. If work affects shared elevations or several flats, establish who is coordinating it and how the specification is kept consistent before ordering individual windows.

Finding a replacement FENSA certificate

If an installation was registered with FENSA, use its official certificate search and ordering service. Check the address and installation details carefully. A missing search result does not by itself prove that the work was unlawful: it may have used another scheme or the building-control route, or the record may need further investigation.

For Certass-registered work, use its replacement-certificate portal or contact the scheme if an expected certificate never arrived. If neither scheme can find the installation, speak to the original installer and the local authority building-control service about existing records. A replacement-copy service cannot simply turn an unregistered installation into a registered one.

Keep a complete window paperwork folder

Keep the survey, written specification, quote, ownership consent where required, any planning decision and the building-regulations completion record together. Record which openings were replaced and which were repaired, because later enquiries may relate only to part of the property.

When selling, the buyer’s solicitor may ask for the installation paperwork. Resolving missing records early is more practical than assuming the documents can be reconstructed immediately during a sale. For new work, ask at quotation stage when and how each document will be supplied.

Sources and current guidance

• GOV.UK: competent-person schemes
• Planning Portal: window building regulations
• Planning Portal: window planning permission
• FENSA: find a certificate
• Certass: replacement certificates
• Council example: leaseholder alterations

Questions people ask