Changing a polycarbonate conservatory roof for another sheet roof is a repair job in the eyes of most councils. Swapping it for a roof of tiles, slate or insulated panels is something else. Once the roof is solid, the conservatory has stopped being a light glazed structure and has become a room with a real roof over it, heavier, warmer and held up by a frame that was not necessarily designed for it. That is why the Building Regulations take an interest. This guide explains why a solid roof needs an application, what the building control body checks, which parts of the regulations bear on it, and what to do in Bath, where B&NES Council deals with both building control and the consent questions for older houses. It is general guidance and not legal advice. For your own house, the final word belongs to your building control body.
Why a solid roof needs an application
Published building guidance is clear on this point. Trade guidance treats a new solid roof on a conservatory as a material alteration, and an application to building control follows from that. The reasoning is straightforward. Glass and sheet weigh little and let heat straight out. A solid roof puts more weight on the frame and alters how the room keeps its warmth, so the building control body wants evidence that the frame will cope and that the new roof is insulated to a proper standard.
It is worth separating this from the planning question. Planning permission deals with what you build and where. Building Regulations deal with how it is built. A project can need either, both or neither, and a yes under one is no guarantee under the other. The planning side has its own page, the planning permission answer.
Treat the application as part of the job and not a hurdle in front of it. A roof built with no application behind it tends to cause trouble on resale, when the buyer's side asks to see the paperwork. Approval in hand from day one avoids that and leaves you a record of what went on.
Who you apply to in Bath
There are two routes. The first is the local authority. For a Bath address that means B&NES itself, whose building control officers deal with applications across the city and the district around it. The alternative is a registered building control approver, a private firm entered on the register run by the Building Safety Regulator. The register opened to firms on 6 April 2024 and took the place of the older approved inspector system. Both routes aim at one outcome: a certificate showing the finished work meets the regulations.
Live outside B&NES and the council in charge changes. Chippenham and Corsham sit with Wiltshire Council, Keynsham with B&NES and Bristol with Bristol City Council, and we confirm which applies at the survey. The B&NES team, based in Manvers Street in Bath, lists its phone number (01225 477517) on its website, and the team can say what it wants to see.
Which route is better depends on the job and on your preference. Each route sends someone to inspect the work on site. Where they differ is in fee, pace and how much of the handling you want to leave to others, and once you have picked a roof we will talk you through the options.
What building control looks at
An application is judged against a handful of questions. The first is structure. The inspector wants proof that frame, walls and foundations can take the extra load. Approved Document A governs this, and under the re-roofing rules the rules for re-roofing class a covering that makes the whole roof 15 per cent heavier or more as work needing approval, with the structure checked. In a conservatory the difference between glass and a tiled roof is far larger than that, so the check is not a formality. We prepare the information the inspector needs from what we see at the survey, and a structural engineer's calculation is brought in where the frame calls for it.
The second matter is thermal performance. Approved Document L covers new fabric in existing dwellings. For the roof element, Table 4.2 in that document sets 0.15 W/m²K. Paragraph 4.8 adds that a replacement should do no worse than what came out and should meet the table. That is a lower figure than a thin sheet can reach, which is why a solid roof carries real insulation. Glazing let into the new roof is judged separately: for a roof window the table gives 1.4 W/m²K, with a Band B window energy rating as an alternative route, and for a rooflight it gives 2.2 W/m²K.
The third matter is the joint with the house and the weathering of the roof. Rain must not find a way in where roof meets wall, so the application describes the flashings, the gutter and the drainage. A roofer sees this junction as the weakest point of any conservatory roof, which is why the lead is dressed into the brickwork or stone and not simply sealed with mastic. Ventilation and the way the room relates to the rest of the house may also come up. Which of these applies is the inspector's call, and the application shows how each point is met.
The checks follow the roof: heavier means a structural check, warmer means a thermal check, and an opening in the roof means a window check.
The documents and the site visits
A building control application is a set of papers and a series of visits. On the paper side, you will usually need drawings of the existing conservatory and the new roof, a description of the build-up with its insulation, a plan showing how the roof is supported, and details of the junction with the house wall. If the frame needs strengthening, the proposal for it goes in too. We prepare what is needed from our survey, so you are not left to draw it yourself.
Once the application is accepted, the inspector comes to look at the work as it goes. These visits are timed to the stages at which something would be covered up and could not be checked afterwards, such as the structure before the insulation and lining go over it. When the work is finished, a final visit leads to the completion certificate. File that certificate with the house papers, because a later buyer will want it.
The one rule that keeps the process smooth is simple: do not start before the application is in. A date for the work is best fixed only once the approval route has been settled, and it is worth telling the scaffolders and the plasterer that the dates may move. Starting early can mean opening up finished work for inspection, and that costs time and money. To see where the application falls in the programme, read the answer on timescales.
Listed houses and the Bath conservation area
Building Regulations approval is one thing. Consent for changes to a protected building is another. A conservatory attached to a listed house may fall within the listing, and B&NES, as local planning authority, grants the consent. The council's own advice is to contact it before touching a listed building, and it stresses that the two kinds of permission differ. Where consent is needed and not obtained, the owner commits a criminal offence.
An unlisted house inside Bath's conservation area (about half the city lies within it) raises a different question: does the change need planning permission, and does it affect the character of the area? World Heritage status applies to the whole city. Some roads are subject to Article 4 directions, which take away particular permitted development, and B&NES keeps a map that shows which. On a listed property we match materials to the main house and settle the consent position in writing before anything is ordered. More detail sits in the guide to listed-house conservatories.
On consent, our part is to say which questions to put to the council and to gather the drawings and photographs it will want.
What happens if the work is done without approval
Some owners put in a solid roof without an application, either because a fitter said it was not needed or because they did not know. The consequences usually arrive later. A buyer's solicitor notices that the roof is not on the council's records. Dealing with the work after the event may mean opening up the structure so the hidden parts can be seen. In the worst case the work has to be altered to meet the regulations, and by then the roof is finished and the money spent.
Two things make the position safer. Ask any fitter, in writing, who is making the application and when. And keep the paper trail: the approval, the inspector's visit notes and the completion certificate. If you are buying a house with a solid conservatory roof, ask for them. If they are missing, the building control body can tell you what options exist, and Does a solid conservatory roof add value shows why the paperwork counts at sale.
How we handle the paperwork
Part of our job on a solid conservatory roof is to explain consent and handle the Building Regulations side. At the survey, which costs nothing, we take photographs of the roof and frame, measure the span and judge what the structure can carry. Each roof option then goes to you with the application it would need. Once you choose, we assemble the papers building control asks for and write the fixed price down. File the completion certificate with the deeds once it arrives, since a conveyancer acting for any future purchaser will want to see it.
If you are still deciding between a glazed roof and a solid one, the guide to conservatory roof options compares them on comfort, light, cost and approvals, and the solid roof guide shows the build the inspector will be assessing. For general guidance on the process, the Planning Portal is a reliable starting point. To make a start, see conservatory roof replacement in Bath or call 01225 285181.