The short answer
A solid conservatory roof can have a plastered ceiling, a boarded and taped one, or timber lining, all fixed beneath the insulated roof structure. Plaster gives a house-like finish and takes recessed lights, but the build-up must get insulation, vapour control and airflow right to avoid condensation. The roof needs a Building Regulations application, so the ceiling make-up is part of what is inspected.
Ceiling finishes that suit a solid roof
The common choice is plasterboard screwed under the rafters, skimmed with plaster and painted. It reads like the ceiling in the rest of the house and hides the roof structure. Boarded and taped finishes are quicker but show more joints. Tongue-and-groove timber lining gives a warmer, more rustic feel and can follow a sloping or faceted ceiling with less filling.
The shape matters. A flat ceiling hides the roof space and leaves a void above for cables, but it costs you height. A sloping ceiling that follows the rafters keeps the volume and sits well with a roof window. Our guide to solid and tiled conservatory roofs for Stroud homes covers how the roof itself is built; this page deals with what you see from inside.
Where insulation and the vapour layer sit
Behind the ceiling lies the insulation. Part L 2021 Table 4.2 sets a U-value of 0.15 for a new roof element, and that figure decides how much insulation is needed in the depth between and under the rafters. Low conservatory roofs often leave little depth, so the build-up is settled at the survey, before anyone picks up a saw.
A vapour control layer sits on the room side of the insulation and keeps damp air away from colder timber. Its joints must be taped, because every gap lets moisture through. A zero rate of VAT covers the insulation itself until 31 March 2027; boards, plaster and other roofing work are charged at 20%. Advice on mixed jobs is outside what we give.
The depth question catches many owners out. Filling the gap between rafters with insulation board is straightforward, but if the rafters are shallow the layer may have to continue beneath them, which lowers the ceiling by a few centimetres. Measure the room height at the door before you settle on a design, because the lining always costs a little headroom, and check where roof windows and any beams will sit once the lining is up.
Lighting set into a plastered ceiling
One of the quiet gains of a plastered ceiling is that it can hold lighting. Recessed downlights, wall washers and a central pendant all become possible where a glazed roof offered nothing to fix to. Think about where you sit, eat or work, and whether you want dimmable circuits, before the ceiling is closed.
Recessed fittings cut through the ceiling can leak warm air into the roof if they are not sealed, so choose units made for insulated ceilings and ask the electrician to keep to the maker's clearance from the insulation. Cables go in before the boards. If you want daylight to remain, a glazed panel or roof window can sit within the ceiling; see can a solid conservatory roof have roof windows.
Condensation behind and beneath the plaster
Condensation is moisture from warm room air landing on something cold. In a conservatory that can mean the glazing, the frame or the underside of a badly built roof. A sealed, well-insulated ceiling keeps its plaster face warm, which is one reason a solid roof makes a room feel less clammy in winter than old polycarbonate did.
BS 5250 guidance, published by Marley, expects a cold roof void to be ventilated, with extra high-level ventilation where a roof is a single slope. Whether yours is a cold or warm design depends on the build-up that is specified. Day to day, open windows, run an extractor if there is a kitchen or laundry nearby and keep washing off the radiators in the room. A conservatory used as a utility room needs more attention than one used as a lounge.
Inspection, sequence and who does what
Building Regulations apply to a solid conservatory roof because it alters the structure, so a building control application is needed (Homebuilding and Renovating, 2023). The inspector looks at the structure, insulation and ventilation before they are covered, which is why the ceiling goes up last. We talk through consent during the visit and file the notification wherever the rules call for one.
Plastering and decorating are often separate trades, and some owners choose to finish the inside themselves. If that appeals, read can I replace my conservatory roof myself before deciding which parts to take on. Our quote covers the boards, the plaster and any lighting preparation. The full service is described on our conservatory roof replacement page.
Drying times, painting and living with the new ceiling
New plaster needs time to dry before it is painted, and a ceiling in a room that changes temperature quickly can craze if it is rushed. A mist coat of thinned emulsion followed by a normal coat is the usual route. Leave windows and vents open while it dries so the moisture leaves the room and does not settle on the glazing.
Choose a paint suited to a bright room. Sun through the glazed walls shows every brush mark on a ceiling, so a matt finish hides flaws better than a sheen. In the first winter, watch for hairline cracks where plaster meets the frame and the wall; small movement there is normal while the building settles, and a flexible filler or caulk dealt with at the first redecoration is the usual cure.