Turning a Conservatory Into a Usable Room
In practice this is one job with a legal consequence attached: the roof comes off and the structure stops being an exempt building. Nobody publishes a price for “conversion” as a job, so the figure below is assembled from the roof and fee rows that do exist, each carrying its own source. Start with which roof covering you have, then what a solid roof costs on the frames you already own.
Solid roof · existing 3m × 3m conservatory · installed inc VAT
£6,000 to £11,000 plus £200 to £800 building control
Well evidencedFour UK publishers agree within 1.05x on the floor, typical £8,075. The building control fee is Reasonably evidenced and conflicted, two publishers 2.0x apart. No source anywhere prices the conversion as a single job. Checked 20 August 2026.
What does it cost to convert a conservatory to a room?
£6,000 to £11,000 for the solid roof on a 3m by 3m conservatory, installed and including VAT, plus £200 to £800 in building control fees. Two conditional lines sit behind that, an engineer's report and frame reinforcement, and neither is known until somebody has surveyed the frames.
| Component | Low | Typical | High | Evidence | Sources and dates |
|---|---|---|---|---|---|
| Tiled or solid roof, 3m × 3m | £6,000 | £8,075 | £11,000 | Well | Four UK publishers |
| Tiled or solid roof, 4m × 4m | £8,000 | £10,700 | £14,400 | Well | The same four UK publishers |
| Building control fee | £200 | not published | £800 | Reasonably | Two publishers, Mar 2026 and 2026, conflicted |
| Structural reinforcement, conditional only | £800 | not published | £4,000 | Reasonably | Two publishers, May 2026 and 2026, conflicted |
| Structural engineer's report | £300 | not published | £500 | Thin | Google AI Overview synthesis, publisher not attributed |
The two roof rows are the strongest in our register: four independent publishers land inside 1.05x on the 3m by 3m floor and inside 1.20x at both ends on 4m by 4m, and both typicals are the median of the sourced point estimates rather than a midpoint. The fee and reinforcement rows are two publishers apart by 2.0x and 3.75x respectively and we publish both ends. The engineer's report is a figure Google's own AI Overview synthesises and attributes to nobody; we could not trace it and say so. Checked 20 August 2026, next check due 20 November 2026.
No register row prices this as a job. All 222 rows in our register price roofs, bases, materials, insulation and ancillaries. Not one prices “converting a conservatory to a room”, and neither does any mainstream UK cost publisher we could find: the nearest thing to a whole-job figure anywhere is a national trades directory's single line for rebuilding a conservatory as a full extension, £15,000 to £25,000, May 2024, which we hold as UNVERIFIED as at 20 August 2026 because we could not confirm it and it prices demolition and rebuild rather than a new roof on the frames you own. So the total below is our arithmetic, and we show it rather than assert it.
Derived, 3m by 3m, arithmetic shown. Roof £6,000 to £11,000, plus the fee at £200 to £800, gives £6,200 to £11,800 for the ordinary case. Where the survey finds no steel in the mullions, add the engineer's report at £300 to £500 and reinforcement at £800 to £4,000, and the ceiling becomes £16,300. That is addition on the sourced rows above, checked 20 August 2026, and not a published figure. The two conditional lines stay conditional: nobody publishes how often they apply, so we attach no probability to them. see what a new roof would cost you for the same rows applied to your own size band.
It stops being exempt
A conservatory under 30 m², at ground level, single storey, separated from the house by external-quality walls, doors or windows and with its own heating controls, is an exempt building under Building Regulations 2010 Schedule 2 Class 7. That exemption is the thing a conversion spends.
Regulation 9(1)(b) keeps the exemption only while the structure is still the kind of building Schedule 2 describes, and the 2013 DCLG circular says it may no longer apply where the glazing to the walls or roof is significantly reduced. Put an opaque roof on and that test is engaged. The work becomes a material alteration under regulation 3(c); regulation 23(2) is triggered because more than half the surface area of a thermal element is being replaced; and the new roof has to reach 0.15 W/m²K, the single roof row in Approved Document L Volume 1 2021 Table 4.2. All verified against legislation.gov.uk and the Approved Documents on 20 August 2026, and set out in full on building regulations for a conservatory.
It is also notifiable under regulation 12, by building notice or by an application for building control approval with full plans. It goes to Local Authority Building Control or a Registered Building Control Approver, and no competent person scheme covers it, which means neither FENSA nor CERTASS can sign it off: who has to inspect it explains what each scheme can and cannot certify, and why the certificate you are offered may not be the one a buyer's solicitor asks for.
The quiet one: heating. One of the five conditions in Approved Document L para 0.14 is that the dwelling's heating system is not extended into the conservatory. Running a radiator off the house system is how an exempt conservatory stops being exempt without anybody deciding to convert anything, and installers do it routinely. Verified against Approved Document L Vol 1 2021 with 2023 amendments and Schedule 2 Class 7, 20 August 2026.
The roof is the job
Strip the language back and a conversion is a roof replacement with paperwork. The walls, the frames and the base usually stay; what changes is what is over your head. The structural question follows from that, and it is not the foundations: LABC puts the added load of a lightweight composite solid roof at approximately 0.5 kN/m, less than 10 per cent over a typical translucent roof, and says the real risk is whether the existing mullions contain steel. Only pilot holes or a magnet test settle it, which is why the reinforcement line above is conditional rather than certain.
Everything about that job, from the size bands either side of 3m by 3m to what happens on site day by day, sits on having a conservatory roof replaced. This page is the reason to do it; that one is the job.
Insulating it instead, and what that does not fix
If the goal is a room that is usable in February rather than a room that is legally a room, insulating the roof you already own is the cheaper path and it does not engage any of the regulation above, because the structure stays substantially glazed. It also does not get you to 0.15 W/m²K, and it does not change what a survey or a sale will call the space. The methods and what each one costs are on conservatory insulation cost.
Going the other way, if the plan involves brick piers, a flat perimeter roof and a lantern rather than a full solid roof, that is a different product with a different price, and it is set out on conservatory to orangery conversion.
Price the roof, then the paperwork
Six questions, about sixty seconds, and an estimate built from the rows above with every source shown.
The estimate is banded by size rather than multiplied out of a flat rate per square metre, because the published per-m² rate falls by roughly 35 per cent from the smallest band to the largest. Use conservatory cost for the whole-structure figures, or conservatory roof quote when you want a real number against your own frames.
Check what your roof will cost
Or get quotes for your roof from local installers. We are paid when one of them quotes you, which is why every figure here carries a source, a date and a grade rather than a headline.
Questions people ask first
How much does it cost to convert a conservatory into a room?
Do I need building regulations approval to do it?
Do I need planning permission as well?
Can I put a radiator in once it is converted?
Sources: four UK cost publishers, dated 2026, July 2026, a table updated December 2024 and one undated, for the roof rows; two of them, March 2026 and 2026, for the fee; two of them, May 2026 and 2026, for reinforcement; one unattributed Google AI Overview synthesis for the engineer's report; Building Regulations 2010 Schedule 2 Class 7 and regulations 3(c), 9(1)(b), 12, 13, 14 and 23(2); the 2013 DCLG circular; Approved Document L Vol 1 2021 with 2023 amendments, Table 4.2 and para 0.14; GPDO 2015 Schedule 2 Part 1 Class C; LABC, Solid roofs to conservatories addendum, May 2018. The full list is on sources we use. Checked 20 August 2026, next check due 20 November 2026.
Find out what yours costs
Six questions, about sixty seconds, and an estimate built from published UK figures with every source shown. Then up to four local installers can quote you, if you want them to.