Does a solid conservatory roof need new foundations?

A glazed or polycarbonate roof is light. A solid roof is not. Timber rafters, insulation, battens and a tile or slate covering put a heavier and steadier load on the frame, and the frame passes it down through the walls to the base. That chain, from the ridge to the ground, is what has to hold. The foundation is only the last link in it.

Most conservatories were designed around a roof that weighs very little. Nobody drew the base with a tiled roof in mind. That does not mean it will fail, only that it cannot be assumed to cope. Some bases carry the extra weight without any trouble. Others already show movement, with cracks at the corners, a door that sticks or a floor that has dropped, and those need looking at before more weight goes on. Our page on solid conservatory roofs explains the roof types themselves.

The survey starts at the top and works down. We look at the frame for bowing, loose joints and rot, then at the low brick or block walls it stands on, then at the floor and the way the base meets the house. Cracks, gaps at the wall junction and uneven door and window gaps tell us where movement has happened and whether it has stopped.

Pictures of each of those points come with the quote, giving you the same view we had on the day. If the base looks sound and the frame is straight, a solid roof can usually go on with the existing structure kept as it is. If something looks doubtful, you hear it before any price is given, because a roof built on a moving base will crack its own finishes within a season or two. A structural engineer's opinion is the safe route for anything unclear, and we would rather you had one than guessed.

It also helps to know the history. Was the conservatory built with proper foundations, or sat on a slab? Has the ground nearby been dug up, planted with a large tree or flooded? Those answers change how closely the base needs reading, and any paperwork from the original build is worth finding.

New foundations are the exception, not the rule. They come into the conversation when the base is shallow, cracked or clearly moving, when the new roof is much heavier than the old one, or when the plan is to change the walls as well. Then the job is no longer a roof job. It is a structural repair with a roof on top, and it needs a designer and an inspector.

There are lighter ways to go. Lightweight tile systems and carefully chosen insulated panels cut the load, and on a marginal base that can be the difference between strengthening and leaving it alone. The point is to match the roof to the base you have, not to push a heavier roof onto it and then fix the damage.

Strengthening, where it is needed, is usually done by an engineer's design: underpinning, a new ring beam or extra support under the frame. Each carries its own cost and its own inspection, so it is better to know before the roof is chosen than after the old one has come off and the room is open to the weather.

Planning Portal guidance puts a replacement conservatory roof under the Building Regulations, so a solid roof's frame loads are examined as part of the approval. Your council's building control team, or a registered building control approver, looks at the design and inspects while the work is under way.

We explain what is needed and deal with the Building Regulations notification where the work is notifiable, sparing you the form-filling. Our guide to solid conservatory roof regulations sets out the steps. Expect the inspector to ask about the frame, the base and the fixings, which is one more reason to keep the survey pictures to hand. If an engineer has been involved, their drawings and calculations go to building control too, and the inspector will want to see the work built as drawn.

Photographs of the conservatory, inside and out, are the best way to begin, along with a line on how the current roof is built. We book a survey, look at the frame and base, and give you a plain verdict: the roof can go on as the structure stands, it needs strengthening first, or a lighter option suits better. The written quote then follows, at one total price.

If the base needs work, the quote spells it out before anything starts, and the decision is yours with the full picture. Cracks, movement or damp near the floor are worth mentioning when you get in touch, because they tell us where to look first. You can also read about the frame and tiled roof weight or return to our conservatory roof replacement service.