Older houses are usually solid-walled, with no cavity to drain, so they rely on drying out through their own surface. A hard cement render stops that happening, trapping moisture that then pushes the render off and shows inside as damp. The most common rendering problem on an older house is not a worn-out render — it is the wrong kind of render, applied decades ago.
- Solid walls need a breathable system. Dense cement render on one is a specification error, not just an ageing finish.
- Hollow render and internal damp on the same wall usually share a cause: moisture trapped behind an impermeable coating.
- Lime renders look like they are failing when they are doing their job — they are meant to be the sacrificial layer.
- Before re-rendering an older property, establish what the wall is built of. It changes the whole specification.
- Solid walls behave differently, and that is the whole story
- The problems we see most on period property
- Lime render, and why it looks worse than it is
- Why a cement patch does more harm than no patch
- Getting the specification right on an older wall
- Breathable options that work on solid walls
- Planning and permission on older property
- What this work costs
Solid walls behave differently, and that is the whole story
Most Coventry housing built before roughly the 1930s has solid masonry walls, typically a brick and a half thick, with no cavity. A cavity wall deals with driving rain by letting the outer leaf get wet and allowing the water to run down inside the cavity and out again. A solid wall has nowhere for that water to go, so it absorbs it and then releases it back out through the surface when the weather improves.
That cycle is not a defect. It is how the wall was designed to work, and it worked for a hundred years before anyone rendered it.
The problem arrives when somebody applies a modern dense cement render, or a plastic masonry paint, or both. Water still gets in — through a crack, over the top, around a window — because no coating is perfect. It then cannot get back out. Moisture builds up in the wall and behind the render, and two symptoms appear at once: damp inside, and render that sounds hollow when you tap it.
The problems we see most on period property
| Problem | Why it happens on older houses | What it usually needs |
|---|---|---|
| Widespread blown render | Moisture trapped behind an impermeable system on a solid wall | Remove and replace with a breathable build-up |
| Damp inside with no obvious leak | The wall can no longer dry through its surface | Breathable system; check ground levels and DPC |
| Render bridging the damp-proof course | Later render carried down past the original DPC line | Cut back above the DPC, fit a bellcast bead |
| Spalling brick behind the render | Frost acting on brick kept permanently wet | Cut out and replace bricks; fix the moisture source |
| Cracking along a straight line | Movement at a lintel or a change of material | Investigate the lintel, then reinforce and repair |
| Patchy repairs in different materials | Decades of well-meant cement patching on lime render | Remove incompatible patches, re-render to a break |
| Render over an original feature | String courses, plinths and reveals covered flat | A conservation decision before a technical one |
Lime render, and why it looks worse than it is
Older properties were originally rendered in lime, and a fair amount of original lime render survives. It behaves nothing like cement and it is routinely condemned by people who expect it to.
Lime is deliberately weaker than the masonry behind it. It is soft, slightly porous, and it carries a degree of movement and salt crystallisation in itself rather than passing it on to the brick. A lime render that is crumbling slightly at the surface, has fine crazing, or shows some erosion in an exposed corner is often doing exactly what it was designed to do: sacrificing itself so the wall underneath does not.
The right response is usually repair in like material rather than replacement in cement. Patching lime render with a cement mix is one of the most common and most damaging things done to period property: the hard patch survives, and the brickwork and the softer render around its edge take the damage instead.
Why a cement patch does more harm than no patch
This deserves spelling out because it is counter-intuitive and because it is still done constantly.
The principle in traditional construction is that each layer should be weaker and more permeable than the one behind it. Mortar weaker than brick; render weaker than mortar. When something has to give, it gives in the layer that is cheapest and easiest to replace.
A cement patch inverts that. It is harder and less permeable than everything around it. Water that would have evaporated through the render now travels sideways to the nearest permeable material and leaves through there, concentrating salts and frost damage at the edges of the patch. Within a few years you have a sound patch surrounded by a halo of failed render and spalled brick — which usually gets patched again, in cement, and the halo grows.
Getting the specification right on an older wall
There is no single correct answer, but the decision follows a fairly short set of questions.
Is the wall solid or cavity?
Measure the thickness at a window reveal. A solid wall is typically around 225mm plus finishes; a cavity wall is noticeably thicker. This single fact drives most of what follows, and it is worth establishing before anyone quotes.
Is there a damp-proof course, and where?
Many pre-1900 properties have none, or have one that has been bridged by later ground levels, paving or render. A breathable system on a wall with no DPC is manageable; an impermeable one is not.
What is already on it?
Original lime, later cement, masonry paint, or layers of all three. Incompatible layers usually have to come off, and that removal is often the largest single item in the job.
Does the appearance matter?
On a property in a conservation area, or one where the original detailing is intact, the specification may be constrained by more than performance. Listed buildings and Article 4 areas need permission before the finish is changed at all.
Breathable options that work on solid walls
- Lime render — the traditional answer and still the most sympathetic on period property. Slow to apply and slow to cure, and it needs someone who has worked with it.
- Vapour-permeable silicone systems — a modern thin-coat topcoat over a suitable breathable basecoat. Through-coloured, low maintenance, and permeable enough for most solid walls. Check the manufacturer's stated vapour permeability rather than assuming all silicone systems are equal.
- Insulated render using mineral wool — where warmth is also the goal. Mineral wool is considerably more vapour-open than the common expanded polystyrene boards, which matters on a solid wall.
- Leaving it bare — worth saying. Sound, well-pointed solid brickwork in reasonable exposure often performs better unrendered than it would under the wrong render. Repointing in lime is sometimes the whole job.
Planning and permission on older property
Re-rendering a house is usually permitted development, but older property is exactly where the exceptions bite. Listed buildings need consent for any change to the external finish. Conservation areas restrict changes to the appearance, and an Article 4 direction can remove permitted development rights that would otherwise apply.
There is also a practical point that is not a legal one: on a terrace or a pair of semis, rendering one and not the other changes the appearance of both. It is worth a conversation with the neighbour before the scaffold arrives rather than after.
What this work costs
Work on older property is more variable than on modern housing, because the amount of removal and making good is only really known once the first area is opened up. For context, these are the rendering figures published across this site:
| Job | Typical Coventry guide price | Notes |
|---|---|---|
| Rendering | £40–£70 per m² | System & access dependent |
| Three-bed semi | £2,500–£5,000 | Full elevation render |
| Detached house | £9,000–£12,000 | Larger area & scaffolding |
| External wall insulation | £90–£140 per m² | Insulated render system |
Removing failed cement render from a solid wall, and repairing the brickwork underneath, is additional to those figures and is priced after survey. We would rather quote that honestly than discover it with the scaffold up.
We establish what the wall is built of before recommending a system, and we will tell you when the right answer is lime rather than anything modern.
Frequently asked questions
Can you render a Victorian house?
Yes, and many already are. What matters is the system: a solid wall needs a vapour-permeable build-up, either lime-based or a breathable silicone system over a suitable basecoat, so the wall can still dry through its surface. A dense cement render on a solid wall tends to create the damp problem it was meant to solve.
How do I know if my wall is solid or cavity?
Measure the wall thickness at a window or door reveal. A solid brick wall is usually around 225mm plus internal finishes; a cavity wall is noticeably thicker, typically 275mm or more. The brick bond helps too — a pattern with regular short header bricks showing suggests solid construction, while a wall of all stretchers suggests a cavity.
Is lime render better than cement on an old house?
For breathability and compatibility, generally yes, and on a listed or conservation-area property it may be required. The trade-offs are honest ones: lime costs more in labour, cures slowly, needs protecting from frost and rain while it sets, and wants someone experienced. A good breathable silicone system is a reasonable middle path on many unlisted solid-wall houses.
Should I remove old cement render from a solid wall?
If it is causing damp and large areas sound hollow, usually yes — it is doing active harm. If it is sound, well detailed and the inside is dry, removing it is a big job with no immediate payback and can damage the brick face. The deciding factors are how much is debonded and whether there is damp inside.
Why does my render keep failing in the same place?
Because the cause has not been dealt with. Repeat failure in one spot almost always marks a persistent water source — a gutter, a sill, a bridged damp-proof course, a missing drip detail — or an incompatible repair material concentrating stress at its edges. The render is the symptom; something is keeping that patch of wall wet.
Do I need permission to render a period property?
For most unlisted houses outside a conservation area, no — re-rendering is normally permitted development. Listed buildings need consent for any external finish change, conservation areas restrict appearance changes, and an Article 4 direction can remove the usual rights. Check the property status with the council before the work is booked.
Older property needs a different conversation
We establish the wall construction, check the damp-proof course and ground levels, and specify a system the wall can live with. Free survey, fixed written quote, honest advice about leaving well alone.