Conservatory roof building regulations, planning & FENSA
Replacing a glass or polycarbonate roof with a solid one almost always needs building control approval — but not planning permission, and never FENSA. Here's exactly what's required in 2026.
Does a new roof need building regulations approval?
For a solid or tiled roof: yes, almost always. Under the Building Regulations 2010, swapping a translucent roof for an insulated solid one is a “material alteration” — it changes the building's thermal envelope and adds significant structural load — so it needs building control approval and a completion certificate. A like-for-like glass or polycarbonate swap normally doesn't.
When is a conservatory exempt (and why a solid roof ends that)?
A conservatory is usually exempt from building regs only if it:
- is built at ground level and under 30 m² internal floor area;
- is separated from the house by external-quality walls, windows or doors;
- has its own independent heating controls; and
- has at least 75% of the roof and 50% of the walls glazed or translucent.
Fitting a solid roof breaks that last “75% translucent roof” rule, so the structure loses its exemption and comes under building control — which is why structural calculations and an inspection are required.
The FENSA myth
A FENSA certificate cannot sign off a solid conservatory roof. FENSA is a Competent Person Scheme for replacement windows, doors and rooflights only — it has no authority over conservatory roof conversions. The work must go through a Building Notice or Full Plans application with Local Authority Building Control or an approved private inspector (such as JHAI). Relying on a FENSA document can cause legal complications and delay a future sale.
Planning permission
For most homes a replacement roof is Permitted Development (no planning application), provided:
- it's no higher than the highest point of the existing house roof;
- all extensions together cover no more than 50% of the land around the original house; and
- it isn't forward of the principal or side elevation facing a highway.
Exceptions: listed buildings need Listed Building Consent, and homes in Conservation Areas or AONBs may have Permitted Development rights removed by an Article 4 Direction — so always check before you commit.
England, Wales & Scotland — the rules differ
| Requirement | England | Wales | Scotland |
|---|---|---|---|
| Target U-value | 0.15–0.16 | 0.15 | 0.12 (strictest) |
| Approval type | Building Notice / Full Plans | Building Notice / Full Plans | Building Warrant (before work starts) |
| Daylight rule | SAP calcs if open-plan | Mandatory photo evidence | Can't block light to adjoining rooms |
| FENSA self-cert? | No | No | No |
Guarantees & protection to insist on
A properly protected installation has three layers of guarantee:
- Manufacturer / system warranty — covers the roof components (typically 10–40 years).
- Installer workmanship guarantee — covers fitting, sealing and flashing (10 years is standard).
- Building Control completion certificate — the legal proof it's compliant and safe. Solicitors ask for this when you sell.
Crucially, a workmanship guarantee is only worth anything if the installer stays in business — so insist on an Insurance-Backed Guarantee (IBG) that honours it for up to 10 years even if they cease trading, plus deposit protection. Look for accreditations such as TrustMark, the Consumer Protection Association (CPA), GGF, DGCOS, NFRC and Certass.
One myth to avoid
“If it's Permitted Development, I can ignore building regs.” False. Planning and building regulations are separate legal frameworks — planning governs size and appearance; building regs govern structural safety and energy efficiency. A solid roof almost always needs building regs even when no planning permission is required.
Related: roof options & systems · replacement costs · the complete guide.
Building regs & planning — FAQs
›Do I need building regulations to replace a conservatory roof?
For a solid or tiled roof, almost always yes. Swapping a translucent roof for an insulated solid one is a 'material alteration' that changes the thermal envelope and structural loading, so it needs building control approval and a completion certificate. A like-for-like glass or polycarbonate swap usually does not.
›Do I need planning permission?
Usually no — a replacement roof is normally Permitted Development, provided it isn't higher than the existing house roof, doesn't extend forward of the principal elevation, and your extensions don't cover more than 50% of the garden. Listed buildings and conservation areas (Article 4) are exceptions and may need permission.
›Can a solid conservatory roof be FENSA certified?
No. This is a common and costly misconception. FENSA only certifies replacement windows, doors and rooflights — it has no authority over solid roof conversions. A solid roof must be signed off by Local Authority Building Control or an approved inspector (e.g. JHAI), not FENSA.
›Will I need the paperwork when I sell my house?
Yes. Buyers' solicitors routinely ask for the Building Control completion certificate for a solid roof conversion. Without it, a sale can be delayed or fall through, so keep it safe — and never accept a FENSA certificate as a substitute.
›What insulation standard does the roof have to meet?
It varies by nation: England requires a U-value of about 0.15–0.16, Wales 0.15, and Scotland the strictest at 0.12. A reputable installer designs the system to hit your nation's target and proves it to building control.
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