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WINDOW & DOOR COMPLIANCE — UPDATED 2026
FENSA — building-control sign-off for new windows & doors.
When you replace a window or external door in England or Wales, the new unit must comply with Building Regulations Part L (energy efficiency) and Part B (fire). FENSA-registered installers self-certify the work; their certificate is the document conveyancers ask for at sale.
Building Regulations 2010Enforced by Local Authority Building Control
Statutory refBuilding Regulations 2010, Approved Documents L1B + B + Q
Enforcement bodyLocal Authority Building Control (LABC)
Fee range£0 with FENSA installer · £200–£450 retroactive LABC
ValidityCertificate is permanent — kept with title deeds
FENSA
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QUICK ANSWER
What is a FENSA certificate and do I need one?
FENSA (Fenestration Self-Assessment Scheme) is the competent-person scheme for replacement windows and external doors in England and Wales. A FENSA-registered installer issues a certificate within 30 days of finishing work — confirming the new units meet Part L (U-value ≤ 1.4 W/m²K) and Part B (egress + fire). At sale, your conveyancer will ask for the FENSA certificate for any windows replaced since 2002.
2002FENSA scheme launch
Replacement windows since 1 April 2002 must be FENSA / Certass / LABC-certified.
1.4Max U-value (W/m²K)
Part L1B 2022 thermal performance ceiling for replacement windows in dwellings.
£500+Sale-time penalty
Typical price drop where replacement windows have no certificate.
GLOSSARY
FENSA — the terms that matter
Plain-English definitions for the 5 terms you'll see in any quote, certificate or enforcement notice for FENSA Window Replacement.
- Fenestration Self-Assessment SchemeFENSA
- A government-authorised competent-person scheme operated by GGFi for the replacement window, door and roof-window industry in England and Wales. Established 1 April 2002.
- Approved Document L1BAD L1B
- Building Regulations 2010 statutory guidance on conservation of fuel and power in existing dwellings — sets the U-value ceiling for replacement windows.
- Approved Document BAD B
- Building Regulations guidance on fire safety — sets minimum egress dimensions for upper-floor windows in habitable rooms.
- U-valueU-val
- Thermal-transmittance coefficient measured in W/m²K. Lower is better. Replacement windows must achieve ≤ 1.4; new-build is tighter at ≤ 1.2.
- Window Energy RatingWER
- BFRC industry rating from G (worst) to A++ (best). Sales-side proxy for U-value; FENSA installers list it on quotations.
HOW IT WORKS
How to replace windows and stay Part L compliant
Five steps from instruction to certificate. Total time: 3w.
01
Pick FENSA / Certass installer
Day 0
FENSA, Certass, or BSI Kitemark KM 567778 are the three main competent-person schemes. Verify the registration number on the body's public register before signing the quote.
02
Confirm spec
Day 1–3
Quotation must state U-value ≤ 1.4 W/m²K, BFRC WER, glass spec (low-E coating, argon fill), egress hinge for upper-floor habitable rooms, and trickle vents (mandatory since 2022).
03
Install + commissioning
Day 7–14
Install typically takes 1 day per window. Installer fits new sealed unit, weatherproof seals, and tests opening / locking. Defective panes can be swapped within 30 days at no cost.
04
Certificate issued
≤30 days
FENSA posts certificate to homeowner and council within 30 days of completion. Building Regulations Compliance Certificate covers Parts L + B + Q + F.
05
Store with deeds
Forever
File the FENSA certificate with title deeds. Conveyancers will request it at sale; no certificate = price negotiation or retroactive LABC fee.
WHY FENSA MATTERS
FENSA Window Replacement. Done compliant.
Every TradeMatch-listed tradesperson covering FENSA Window Replacement carries the relevant scheme registration. Verified at onboarding, re-verified annually, certificates posted to you within 30 days of any notifiable work.
2002FENSA scheme launch
1.4Max U-value (W/m²K)
£500+Sale-time penalty
COMPLIANT vs NOT
FENSA installer vs unregistered fitter — what changes for you
Side-by-side comparison of the compliant route versus the unregistered shortcut. Most rows trace a straight line from regulation to financial exposure.
| Factor | FENSA / Certass installer | Unregistered fitter |
|---|---|---|
| COMPLIANT — RECOMMENDEDBuilding-control sign-off | Self-certified — certificate within 30 days | You must notify LABC before work + pay £200–£450 fee |
| Insurance-backed warranty | 10-year IBG via FENSA / Certass mandatory | Optional — depends on individual fitter; rarely insurance-backed |
| Sale-time disclosure | FENSA certificate satisfies conveyancer | Buyer's solicitor flags as risk; price negotiation typical |
| Spec verification | Body audits sample of jobs annually | No external audit — quality varies |
| Cost | £400–£1,500 per window installed | Sometimes 10–20% cheaper, but retro LABC clawback closes the gap |
| Mortgage lender stance | Standard — no extra question | Underwriter increasingly asks for proof of compliance |
Source: FENSA Public Register, Certass Public Register, GOV.UK competent-person scheme directory.
FAQ
The questions homeowners ask before they commit.
Do I need a FENSA certificate for every replacement window?
In England and Wales, replacement windows installed since 1 April 2002 must be certified — FENSA, Certass, BSI Kitemark KM 567778, or LABC. New-build first-fit windows are covered by the new-build Building Regulations Compliance Certificate, not a separate FENSA. Repairs and like-for-like sealed-unit swaps in an existing frame are not notifiable.
How much does a FENSA-certified window installation cost?
A standard uPVC casement window runs £400–£700 installed; a triple-glazed sash £900–£1,500; a larger bay or sliding patio door £2,000–£3,500. London adds 20–30%. The FENSA registration premium is typically nil — most replacement-window businesses are FENSA-registered as standard.
What if windows were replaced without a FENSA certificate?
You can apply retroactively to the local council for a Regularisation Certificate — typically £200–£450 plus an inspection that may force remediation if specs don't meet Part L. At sale, the buyer's side may either demand the regularisation upfront or negotiate £500+ off the asking price. Indemnity insurance is sometimes accepted as a cheaper alternative for solicitors.
How long does a FENSA certificate last?
A FENSA certificate is permanent — it certifies the installation complied on the day. It does not expire. The 10-year insurance-backed guarantee that FENSA installers must provide is separate and runs from completion date.
Is FENSA the same as Certass?
Both are government-authorised competent-person schemes for the same Building Regulations Part L compliance. FENSA (operated by GGFi) is the larger of the two; Certass is the alternative. Either certificate is equally valid at sale.
Do I need FENSA for windows in Scotland or Northern Ireland?
No. Scotland follows the Building (Scotland) Regulations 2004 — replacement windows need a Completion Certificate from the local council or via a SAPS (Scottish Approved Person Scheme) installer. Northern Ireland follows Building Regulations (NI) 2012 with broadly equivalent thermal requirements.
RELATED GUIDES
Going deeper.
READY WHEN YOU ARE
New windows, fully certified.
TradeMatch window fitters are FENSA / Certass registered with 10-year insurance-backed guarantees. Certificate posted to you within 30 days of install.