Can you put a solid roof on any conservatory?

Most conservatories can take a lightweight solid roof, but not automatically. A roof is only as good as what holds it up: the window frames have to carry the load down to the base, the base has to sit on sound ground, and the house wall the roof fixes to has to be in good condition.

LABC, which represents council building control teams in England and Wales, says “most existing conservatories will be able to support the increased loads”. The pitfalls it names are foundations that move and crack away from the house, and window and door frames that are not strong enough to take the roof. This guide covers how both are checked and what happens if yours fall short.

Can a conservatory have a solid roof?

Yes. Lightweight solid roof systems are made for Victorian, Edwardian, lean-to, gable-fronted and P-shaped conservatories, and they sit on the existing frames and base. The conditions are that the frames are steel reinforced, the foundations are adequate and the roof gets building regulations approval. Where frames are unreinforced, LABC says new windows or extra structural posts may be needed.

Shape rarely rules a conservatory out on its own. Pitch can matter more, especially on a lean-to. Ultraframe says its LivinRoof suits pitches from 5° to 40.9°, Britmet says its lightweight tiles go down to 5°, and Guardian’s brochure gives 15° as the minimum pitch for its roof windows. If your roof is very shallow, ask which systems and tiles suit it.

What the survey has to establish

Before a solid roof is designed, the installer’s surveyor (or a structural engineer) should check these points. They are the same things building control will look at.

1. Frame reinforcement. The upright frames must contain steel to carry the roof down to the floor slab. LABC says door supports should contain steel inserts for the same reason.
2. The base and foundations. They must be adequate for the new load, with no sign of settlement.
3. Signs of movement. Cracks in walls, at the vertical joints with the house or around the flashing are a warning that the structure is already moving.
4. The house wall. Ultraframe’s LivinRoof guide asks fitters to check the host wall’s condition and whether it is plumb. Guardian’s guide advises checking it for existing damp.
5. Dwarf walls. They should be level all round. SupaLite also recommends air bricks in dwarf walls.
6. Openings and spans. Doors under a gable, bi-folds and wide openings may need extra support.

Leka’s installer guide puts it bluntly: “It is the sole responsibility of the installer to establish the structural suitability of the existing conservatory wall system.” That is why the survey matters more than the brochure.

How much heavier is a solid roof?

Not much heavier than glass. Lightweight systems are designed to be close to the weight of a glass roof, and LABC puts the extra load at typically less than 10% over a glazed roof. These are the published figures, from the makers where they give one and from comparison sites where they do not.

System	Stated weight	Who says so
Ultraframe LivinRoof	31kg per m², including plasterboard	Ultraframe
Ultraframe Ultraroof	38kg per m²	Ultraframe
Leka	About 34kg per m²; Leka itself says “similar weight, or lighter than a glass roof”	A comparison site; Leka installer guide
SupaLite tiled roof	Under 46kg per m² (varies by style); 40 to 49kg quoted elsewhere	SupaLite; an installer and comparison sites
Guardian Warm Roof	About 55kg per m²; Guardian publishes no figure	A comparison site
Eurocell Equinox	67kg per m², the heaviest in that site’s comparison; Eurocell publishes no figure	A comparison site

LABC’s technical guidance puts the load in structural terms: a glazed roof (not polycarbonate) typically loads the frames at under 10kN/m, and a lightweight composite solid roof “is only likely to add an additional 0.5kN/m”, or less than 10% more.

The comparison in those figures is with glass. Frames that were only ever meant to carry polycarbonate are the ones LABC singles out as possibly lacking the reinforcement for anything heavier. LABC and SupaLite also caution that a traditional tiled roof, or a new roof built over the old one, can add more load than the structure was designed for. Our guide to lightweight roof tiles explains the tiles these systems use.

How to tell if your frames are reinforced

LABC suggests two simple site tests: drill small pilot holes, or hold a magnet against the frame to find a steel core. Inspectors check that the steel runs the full length of the mullions (the upright frame members).

If the reinforcement is there, LABC’s guidance says building control cannot require new windows. If it is not, “new window frames may be needed … or additional reinforcement installed abutting the existing frames”, which in practice means structural posts fitted alongside the old frames.

Other points that change the answer:

• Age and condition. Anglian, an installer, says frames that are 10 to 15 years old or damaged may not be strong enough. That is a seller’s claim, but it is worth asking how old your frames are.
• Full-height glass. Guardian says its roof can go on full-height frames, or on conservatories with plastic panels, if they are fully reinforced and the certified installer verifies the structure.
• Bi-folding doors. The LivinRoof LABC certificate says bi-folds under the roof must be bottom supported, not top hung.
• Doors under a gable and wide spans. Ultraframe offers bolster bars, reinforced box gutters and eaves beam reinforcement, and says doors under a gable frame need additional structural support.
• Tie bars. Ultraframe says tie bars stop the ridge deflecting and the frames spreading outwards under snow, and that if they are specified they must be fitted.

Will the foundations need work?

Not usually. LABC’s guidance says trial holes may be dug to check the existing foundations and that “in most cases a 150mm thick concrete strip foundation or reinforced concrete slab which bears onto original ground will be adequate”. Where the load increase is small, typically under 15%, trial holes may not be needed at all, depending on local conditions.

Foundations that pass over drains, sit near tree roots or rest on filled ground “may require further consideration”. And if the structure shows no signs of distress, LABC says no additional requirements should be imposed on foundation depths. For roofs with an LABC Registered Detail, the guidance expects a trial hole to be dug where possible and photographed.

If new or deeper foundations are needed close to a neighbour’s building in England or Wales, the Party Wall etc. Act 1996 may require you to give notice at least one month before digging.

Do solid conservatory roofs need building regs?

Yes. Replacing a glass or polycarbonate roof with a solid one takes the conservatory out of its building regulations exemption, so you need an application and, at the end, a completion certificate. LABC says the new roof must meet current standards, including a U-value of 0.15 in England, while the existing walls and floor must be no worse than before.

Systems with an LABC Registered Detail or a private “type approval” speed this up but do not replace it. The LivinRoof certificate says it is “designed to fast-track, not remove, the requirement to obtain Building Regulation Approval”. The roof target is tighter in Wales (0.13), and Scotland needs a building warrant with a 0.12 target. Our building regulations guide covers the process, and the rules in Scotland, Wales and Northern Ireland differ in the details.

LABC’s guidance also sets limits on what building control can ask for on a roof-only job. It says inspectors should not require you to upgrade the walls and floor, fit cavity trays retrospectively or remove existing heating, and there is no limit on the amount of glazing kept in the walls. The conservatory must stay thermally separated from the house by external-quality doors.

What can turn up once the old roof is off

Some problems only show once the old roof is stripped. The installation guides and LABC name these, with the usual remedy.

Found on the day	Usual remedy
House wall out of plumb	Ridge and starter bars packed out with aluminium shims (LivinRoof guide)
No steel in the frames	New windows or structural posts (LABC)
Box gutter projects too far for gallows brackets	Steel uprights, with a structural engineer’s assessment (Leka guide)
Foundations over drains, near trees or on fill	Further checks by building control (LABC)
Damp where the roof meets the house	Investigate; take building control advice on cavity trays (Guardian guide)

How these extras are priced varies by installer. Citizens Advice recommends a written contract that sets out what you are paying for, and warns that an estimate, unlike a fixed quote, can leave you liable for extra charges.

Other reasons a solid roof may not suit

• Escape windows above. The Planning Portal advises against conservatories that block ladder access to upstairs windows needed for escape in a fire. Scotland’s technical handbook says a roof below an escape window should be designed for the load of people lowering themselves onto it.
• Light in the rooms behind. A solid roof cuts daylight, and rooms that borrow light through the conservatory can become noticeably darker. Our guide to skylights and lighting covers the fixes.
• Height. Raising the roof can take it outside permitted development: in England a single-storey extension must not exceed 4m, and eaves within 2m of a boundary must not exceed 3m.
• Opening windows under a box gutter. Guardian notes that its box gutter insulation sits 82mm below the aluminium, so clearance for opening sashes and doors has to be allowed for.
• Snow. One installer notes that snow stays longer on an insulated roof than on glass. Ultraframe says its roofs are designed for the postcode where they will be fitted.

Before you commit

If your conservatory is sound, a lightweight tiled roof on a medium conservatory typically costs £7,400 to £12,100 fitted, about £9,600 typical; our tiled roof cost page breaks that down. What changes the price is structural work. Price guides put steel reinforcement or structural upgrades at £800 to £4,000 when needed (ExpertSure, MyJobQuote), a structural engineer’s inspection at £200 to £500, and replacing the side frames and dwarf wall at £2,000 to £4,000 (Taskino). So when you get quotes, ask each installer:

• How they checked your frames for steel, and what they found.
• Whether a trial hole is planned, and who pays if the foundations need work.
• Whether structural posts, tie bars, box gutter supports or new windows are included.
• Which building control body will sign the roof off, and when you will receive the completion certificate.