The short answer
Most conservatory dwarf walls can stay when the roof is replaced. They are rebuilt only if they are cracked, damp, moving, or too weak to carry a heavier roof. A light replacement such as new polycarbonate or glass often asks little of the walls. A solid tiled roof asks more, so the walls, the frame on top of them and the ground beneath are checked before anything is ordered.
What the dwarf wall actually does
The dwarf wall is the low brick or block wall that runs round the base of most conservatories, usually up to about window sill height. The uPVC or timber frame sits on top of it. That makes it the link between the conservatory and the ground, and every load in the roof reaches the ground through it, one way or another.
The load travels from the roof into the frame, from the frame into the wall, and from the wall down to its foundation. Whatever is weakest in that path will be the first thing to complain when a heavier roof arrives. A cracked wall under a light roof may be a cosmetic worry for years. The same crack under a much heavier roof can open further, because the wall now has more to carry.
That is why the question is not really whether the wall is old. It is whether the wall is sound, and whether it is strong enough for the roof you are choosing. A wall built well and left alone can carry a replacement roof without any work to it at all.
Signs the wall needs work before a new roof
When we survey a conservatory we look at the wall before we look at the roof, because it decides what the roof can be. These are the things that point towards repairs or a rebuild.
- Stepped or diagonal cracks. Cracks that follow the mortar joints in a staircase pattern, or that are wider at one end, suggest the wall has moved. A fine hairline crack is a different matter and is often old shrinkage.
- Damp at the base. Dark patches, salt marks or crumbling mortar low down can mean the damp proof course has failed or been bridged by soil or paving. A damp proof course is the waterproof layer in the wall that stops ground moisture rising.
- Gaps between the frame and the wall. Daylight, or a sealant line that keeps splitting, can mean the frame has shifted on its base.
- Bulging or leaning brickwork. A wall that is no longer straight is not a safe base for added weight.
- Loose or hollow-sounding brick. Spalled faces and perished mortar need repair whatever the roof is.
None of these automatically means a rebuild. Repointing, a new damp proof course or a few replaced bricks may be enough. The point is to find out first, because it is far cheaper to correct a wall before the new roof goes on than after.
Why a solid roof changes the question
Many conservatories were built with a polycarbonate or glass roof, which is light. A solid roof, tiled or lightweight, is a warm roof with insulation, plasterboard and a weathering layer, and it weighs more. Once the new covering is at least 15 per cent heavier than the old, the regulations want approval plus an engineer-style look at the structure. A solid replacement is also classed as material alteration work, which means a building control application whatever the weight.
The structural check looks at the whole chain. That means the frame, which may need strengthening or a steel section hidden in it, the dwarf wall beneath, and the foundation under that. Older conservatories often sit on shallow foundations designed for a light roof, and the ground can matter. Clay that shrinks and swells with the seasons is less forgiving than firm ground, and nearby trees add to that.
If the walls are sound and the base is adequate, they stay. If the check shows a weakness, the fix is usually targeted, such as a stronger beam above the wall to spread the load, rather than demolition. We would rather tell you that after looking at your own conservatory than guess from the outside. For the structural side, read structural checks before a solid conservatory roof.
When a rebuild is the right call
A full rebuild of a dwarf wall is the exception. It makes sense in a few situations.
The first is a wall that has clearly moved and is still moving. Rebuilding on top of continuing movement only repeats the problem, so the cause, whether drainage, tree roots or poor ground, has to be dealt with as well. The second is a wall with a failed damp proof course and heavy damp damage, where repair would cost nearly as much as starting again. The third is a wall that was built without proper foundations at all, which happens on some older additions.
There is also a practical reason to open up the base. If you are fitting a different style of frame or changing the size of the conservatory, the wall may have to change with it. That is a decision about the whole design, and it belongs with the choice of roof.
Where a rebuild is needed, matching brick or block to the house keeps the finish looking as if it belongs. We explain the options at the survey and write the work into the fixed price, so the cost of the wall is not a surprise halfway through.
What happens to the frame on top
The frame and the wall are judged together, because the frame is fixed down to the wall and the roof is fixed to the frame. If the wall is repaired, the frame is checked for square, for failed seals and for how well it is fixed down. In many cases the frame can be kept, and whether you can keep your uPVC frames with a new roof has its own answer.
If only the sheets need swapping, the job is simpler, and a separate page covers how to replace polycarbonate sheets.
Our survey costs nothing, and the photographs it produces show your own walls, base and frame as we saw them. Look in them for cracks running from the corners of the frame down into the brickwork, which point to movement in the wall rather than a fault in the roof. Anywhere within 30 road miles of Bath, ring 01225 285181, use WhatsApp, or complete the enquiry form on this site. The full job is described on our conservatory roof replacement page.
