Damp and moisture meters

If rain is coming through cracked render, has the damp-proof course failed?

Not on that evidence. Rain through cracked render is water from the outside face, which is penetrating damp. Rising damp, where it exists, is discussed at the base of the wall from the ground. A cracked coat does not show that the damp-proof course has failed, even if the inside face is then wet.

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

What is the fuller explanation?

Render is a coat on the wall, not the wall's damp-proof course. When it cracks, rain can track through the crack, along the back of the coat, and out on the plaster inside. The stain often sits under the cracked panel, sometimes well above the floor, and it worsens after wet weather. That pattern is the opposite of a diagnosis that starts from groundwater. A surveyor can see the crack and the internal stain. They cannot see every path behind the render.

A home survey does not water-test the elevation and does not guarantee concealed parts of the wall. The honest comment names the cracked render and where the inside was damp. Treating the base of the wall with an injected course leaves the crack in place, so the next wet spell can wet the same plaster. Ask for the outside defect to be described before anyone renames it as a failure of the course.

What should you ask your surveyor?

Does the internal damp line up with the cracked render outside?
Is the staining above skirting height, or only at the floor?
Did you see hollow or detached render, or only a hairline crack?

What are the typical next steps?

Photograph the cracks and the inside stain after rain, as two linked pictures.
Do not buy an injected damp-proof course for a crack in the render.
If you need a repair scope, ask someone to look at that coat, not only at the plaster inside.

Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.

Also asked about this

Is all render a damp defect?

No. A sound coat is a finish. It becomes a path for rain when it is cracked, hollow, or taken across the damp-proof course.

Can the course also be bridged on the same wall?

Yes. High ground is a separate check. Do not let that check replace a look at the cracks above.