FENSA vs CERTASS: Which Window Competent Person Scheme Should I Join?

Summary

Any installer replacing windows, doors, or roof windows in existing UK dwellings needs a route to Building Regulations compliance. Since a replacement window or door is "controlled fitments" work under Part L of the Building Regulations, every job is technically notifiable — meaning either you notify building control directly and pay for an inspection, or you register with a competent person scheme (CPS) and self-certify. FENSA (Fenestration Self-Assessment Scheme) and CERTASS are the two schemes that dominate this market, and for the vast majority of installers, choosing between them is really a business decision, not a technical one.

Both schemes were authorised under Section 11A of the Building Act 1984 and Regulation 20 of the Building Regulations 2010, and both notify the relevant local authority building control body on your behalf after each job, issuing the homeowner a compliance certificate. A common misconception is that FENSA is somehow the "official" scheme and CERTASS a lesser alternative — this isn't correct. Both appear on the government's published list of authorised competent person scheme operators, and a CERTASS certificate is accepted by conveyancing solicitors, mortgage lenders, and local authorities exactly the same way a FENSA certificate is. The practical differences are commercial: pricing structure, portal usability, additional certification scopes on offer, and brand recognition among homeowners who've heard of one but not the other.

Getting this decision right matters because switching schemes mid-year involves re-registration, a new assessment, and — if you're not careful about timing — a gap in cover where you'd need building control notification for any job completed outside a valid registration. It's worth comparing properly once, rather than picking whichever scheme a supplier or sales rep happens to recommend.

Key Facts

• Both schemes cover the same scope of work — replacement windows, external doors, and roof windows in existing dwellings, assessed against Part L1B (existing dwellings, energy efficiency) thermal performance requirements (Window Energy Rating band or U-value)
• Neither scheme covers new openings — cutting a new hole in a wall for a window that didn't exist before is a structural/Part A matter requiring building control, regardless of glazing certification
• FENSA pricing (2026) — approximately £280 ex VAT one-off application fee, £172 ex VAT annual registration fee, plus £2.05 ex VAT per job notification
• CERTASS pricing — flat monthly subscription of £24.95 (approximately £300/year), which for many installers simplifies budgeting versus FENSA's fee-plus-per-job structure — ****
• FENSA market share — FENSA is the larger and longer-established of the two schemes and is the name most UK homeowners and conveyancing solicitors recognise on a compliance certificate
• CERTASS additional scopes — CERTASS more readily bundles TrustMark registration and PAS 2030 (retrofit/insulation) certification alongside glazing, which suits installers who also do wider retrofit work
• Both require insurance-backed warranty provision — a TrustMark requirement for domestic work, provided through the scheme or a nominated third-party warranty provider
• Assessment process is broadly similar — an initial assessment of competence (paperwork review, sometimes a site visit or sample inspection), followed by periodic reassessment; exact frequency varies by installer volume and scheme
• Portal and job logging — both operate an online portal where you log each completed job for notification to building control; workflow and interface differ, and installers who've used one sometimes cite portal preference as a deciding factor
• No technical difference in certificate legal standing — a FENSA certificate and a CERTASS certificate carry identical legal weight for Part L self-certification; neither is a "backup" to the other
• Switching schemes — requires a new registration and assessment with the new scheme; there is no formal transfer process, so time any switch to avoid a coverage gap between deregistering from one and being live on the other
• You must be registered before starting notifiable work — retrospective registration does not cover jobs completed while unregistered; those jobs need separate building control regularisation
• FENSA and CERTASS certificates are checked in conveyancing — missing or absent certificates for known replacement glazing are one of the most common queries solicitors raise during a property sale, regardless of which scheme was used

Quick Reference Table

Detailed Guidance

Working out which scheme is cheaper for your job volume

The two schemes' pricing models cross over at different points depending on how many notifiable jobs you complete per year, which is why "which is cheaper" doesn't have one universal answer.

FENSA's structure — £172/year plus £2.05 per job — means your annual cost scales with volume: a fitter completing around 40 replacement jobs a year would pay roughly £172 + (40 × £2.05) = £254 in fees, on top of the one-off £280 joining cost in year one. A fitter doing 100+ jobs a year pays proportionally more in per-job fees but is also generating far more revenue per job, so the marginal cost per installation stays low.

CERTASS's flat £24.95/month (~£300/year) model means cost doesn't move with volume at all. For a low-volume or seasonal installer — someone doing occasional replacement glazing alongside other carpentry or building work — this can work out more expensive than FENSA's usage-based model if job count is genuinely low. For a mid-volume installer doing enough jobs that FENSA's per-job fees start adding up, CERTASS's flat rate can end up cheaper. Run the actual numbers against your last 12 months of completed notifiable jobs before deciding — don't assume either scheme is "the cheap one" without doing the sums for your business specifically.

**** — subscription and any additional per-job charges are worth confirming directly with CERTASS, as scheme pricing is reviewed periodically and the flat-fee-only model described here may have changed.

Brand recognition and the conveyancing conversation

FENSA is, in practice, the name most UK homeowners have heard of when it comes to window compliance certificates — it's often the first thing raised (or asked about) during a property sale by an estate agent or solicitor. This doesn't make a CERTASS certificate less valid, but it can occasionally mean an extra sentence of reassurance to a customer who's only ever heard of FENSA and is surprised to see a different scheme name on their paperwork.

If a significant share of your customer base is likely to sell their property within a few years of the installation (which, realistically, is most domestic customers over a long enough timeline), it's worth being ready to explain — briefly and confidently — that CERTASS carries identical legal standing to FENSA. Some installers keep a short, plain-English note in their customer pack for exactly this purpose.

If you also do wider retrofit or insulation work

CERTASS's closer integration with TrustMark and PAS 2030 certification is a genuine practical advantage for installers whose work spans beyond pure glazing replacement — for example, businesses doing external wall insulation, cavity wall insulation, or broader retrofit packages alongside window and door replacement. Bundling certification scopes under one scheme membership can simplify admin and reduce the number of separate bodies you're dealing with. FENSA-registered installers who also want PAS 2030 scope typically need a separate certification route for that work.

If your business is purely glazing installation with no plans to expand into wider retrofit work, this consideration doesn't apply and shouldn't influence the decision.

The registration and switching process

Both schemes follow a broadly similar path to registration: submit an application with evidence of trading history, insurance (public liability as a minimum), and — depending on the scheme and your assessment route — a sample of recent installations or references. An assessor reviews the application and may carry out a site visit before confirming registration. Once registered, you can begin self-certifying notifiable work immediately.

If you're switching from one scheme to the other (common reasons include cost, dissatisfaction with the portal, or a change in the type of work you do), there is no formal "transfer" — you need to complete a new registration with the receiving scheme before deregistering from the original. Time this carefully: any notifiable job completed after deregistering from your old scheme and before your new registration is confirmed leaves you without a self-certification route for that job, meaning it would need separate building control notification.

What neither scheme covers

Neither FENSA nor CERTASS registration extends to structural alterations, new window or door openings, or work on listed buildings and buildings in conservation areas where planning consent (not just Part L compliance) is the controlling issue. Creating a new opening in a load-bearing wall is Part A structural work requiring a building notice or full plans application regardless of your glazing scheme membership, and window replacement in a listed building may need Listed Building Consent before either scheme's self-certification is relevant at all. Always separate the planning/conservation question from the Part L compliance question — they're assessed differently and by different bodies.

Frequently Asked Questions

Can I be registered with both FENSA and CERTASS at the same time?

There's no regulatory barrier to holding dual membership, but in practice almost no installer does — the ongoing cost of maintaining two separate scheme registrations, each with its own annual fee and assessment cycle, rarely makes commercial sense for a business doing one type of work. Dual registration is more commonly seen where a business has multiple trading entities or operates across regions with different scheme relationships, which is an edge case rather than the norm.

Does the customer care which scheme I use?

Most customers care that the work is certified and that they'll receive paperwork proving compliance for future resale — the specific scheme name matters far less than making sure the certificate actually gets issued and the customer receives it. Where it can matter is at the point of sale years later, when a solicitor unfamiliar with CERTASS may ask a clarifying question that a FENSA certificate wouldn't prompt. Neither issue affects the validity of the work.

What happens if I let my registration lapse without noticing?

Any notifiable job completed while your registration has lapsed is not self-certified and technically requires separate building control notification. If this happens, the fix is either retrospective building control regularisation for the affected job(s) (involving an inspection fee, and possible remedial work if the installation doesn't meet Part L standards) or, in some cases, re-registering promptly and discussing the gap with the scheme — policies on this vary, so contact the scheme directly if you discover a lapse. The safest approach is to diarise renewal dates well ahead of expiry rather than relying on the scheme's own renewal reminder.

Is one scheme's assessment stricter than the other's?

Both schemes are required to meet the same government authorisation standard for assessing installer competence, so neither is officially "stricter" as a matter of regulation. Anecdotally, individual installers sometimes report a smoother or more thorough experience with one scheme over the other, but this varies by assessor and region rather than being a structural feature of either scheme. Don't choose based on a reputation for being "easier" — both are assessing the same competence standard, and a lax assessment from either scheme doesn't reduce your legal responsibility for the compliance of your work.

Regulations & Standards

• Building Act 1984, Section 11A — statutory basis empowering the Secretary of State to authorise competent person self-certification schemes

• Building Regulations 2010, Regulation 20 — mechanism allowing authorised scheme members to self-certify compliance

• Approved Document Part L1B (Conservation of fuel and power — existing dwellings) — sets the thermal performance requirements (Window Energy Rating band or U-value) that replacement glazing must meet

• Planning (Listed Buildings and Conservation Areas) Act 1990 — governs consent requirements for glazing work on listed buildings, separate from and in addition to Part L self-certification

• TrustMark scheme requirements — sets the insurance-backed warranty standard that both FENSA and CERTASS registration must provide for domestic consumer protection

• GOV.UK — Competent person schemes: current schemes and how schemes are authorised

• GOV.UK — Building regulations approval: Use a competent person scheme

• FENSA — Installer benefits and fees

• CERTASS — Competent Person Scheme

• TrustMark — Consumer protection standards

• Planning Portal — Competent person self-certification schemes

• competent person — full competent person scheme directory across all trades, including FENSA and CERTASS pricing detail

• competent person schemes list — complete list of authorised scheme operators

• part p notifications — comparable self-certification process for electrical work, useful as a cross-trade reference

• glazing regs — Part L thermal performance requirements that FENSA/CERTASS certification confirms compliance with