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What does cracked or hollow render mean?

Cracked or hollow render can let rain into the wall behind it. That is penetrating damp, not automatically rising damp. On an old solid wall, a hard cement coat can also trap moisture that used to escape. A survey can look and tap. It does not remove the render, and it does not price the scaffolding.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless a source says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

How does cracked render become damp inside?

Render is a coat. When it cracks or loses its key, water runs through the crack and down the face of the wall it was meant to protect. Inside, that shows as staining under the same patch, often worse after rain. That pattern is penetrating damp. It is repaired by keeping the rain out, which may mean the render, the sill, or the gutter that is soaking the top of the wall. It is not repaired by injecting a damp-proof course at the bottom.

What does hollow render tell you?

A hollow sound means the coat has left the wall in that spot. It can fall, and it can hold a pocket of water. The surveyor taps where they can reach. They do not tap the whole house from a scaffold they do not have. “Hollow in places at low level” is not “the entire elevation has failed”. Ask how far they think it goes, and whether they could only reach the ground floor.

Ask whether the cracks are only in the coat or also in the bricks.
Ask whether ground levels or a path are bridging the bottom of the wall.
Ask whether the wall behind is solid or cavity, because the repair differs.

Why do surveyors worry about cement on old walls?

Solid walls built with lime mortars were meant to get wet and dry. A hard cement render does not move or breathe in the same way. Moisture that gets in at a crack, or from inside the house, can be slower to leave, and the coat can trap it against the masonry. The survey is not telling you to strip every rendered house. It is telling you not to specify a new hard coat on a wall that needed a softer one, without someone who understands that wall.

When is the crack the wall rather than the render?

When the same line runs through the masonry, or the wall is bowed, or openings are distorted. Then read the pages on cracks, lintels and bowing, and treat the render as the surface that showed the movement. Recoating a moving wall hides the evidence and fails again. GOV.UK’s damp guidance is about health in rented homes, not a specification for render. It is a reason to take internal mould seriously while you find the rain path.

Common questions

Will masonry paint solve cracked render?

Paint covers a sound coat. It does not bridge a crack that moves, and it does not stick a hollow patch back. If the survey says the coat has failed, a decorator’s quote is the wrong document.

Does one hollow patch mean the whole house must be re-rendered?

Not on this page’s say-so. Ask how widespread the failure is, within what the surveyor could reach. Local repair is sometimes honest. A whole-elevation specification is for when the coat has generally left the wall. Get that distinction in the quote.

Is pebbledash the same issue?

It is still a coat that can crack, trap water, or hide the bricks. It is also harder to patch invisibly. The survey should say whether it is cracked or hollow, not merely that it is pebbledash. The finish is not a defect.

Can render bridge a cavity?

Render taken down over the damp-proof course, or across a gap it should have stopped at, can carry water to places the cavity was meant to drain. Ask the surveyor if they saw the coat buried in a path or covering a vent. That detail changes the repair.

There is no stain inside. Can you leave the cracks?

If the surveyor says the coat is still stuck and the cracks are hairline, they may call it maintenance. If they say it is hollow, the risk is that it falls or lets water in later. “No stain today” is not a survey of next winter. Read their recommendation.

What does re-rendering cost per square metre?

No official national rate is cited here. Access, the type of coat, whether the wall is lime or cement, and whether masonry needs repair underneath all change the price. A figure without those words is not a quote for the report you have.

Is scaffolding included in a render quote?

Ask. Upper walls are not repaired from a stepladder in any specification this page will invent. A quote that is silent on access is not finished.

The contractor says cracked render proves rising damp. Does it?

No. Cracks at low level are often splashback, a path that is too high, or a failed coat. Rising damp is a particular mechanism. Do not accept an injection specification because the bottom of the render looks tired.

Sources

Key facts

Rain path: Cracks and hollow patches are routes for water. The stain inside may start here.
Old walls: A dense modern render on a solid wall built to breathe can hold moisture in. The survey should say what the wall is made of, if it can tell.
Movement: A crack through render that continues in the masonry may be the wall, not the coat. Read both.
Limit: The survey does not hack off render to inspect. Hollow means hollow where they tapped.