Damp and moisture meters
External render continues below the damp-proof course and the plaster inside is marked at the skirting. What bridge is the render?
The render is a bridge over the damp-proof course. It continues below the course on the outside, so moisture from the ground or from splash can travel up the render and into the wall, past the barrier the course was meant to provide. The plaster inside is marked at the skirting, which lines up with that path. The survey has recorded the render crossing the course and the mark inside. It has not specified a chemical treatment, and it has not said the mark is only condensation. The bridge is the render itself, taken down too far.
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?
A damp-proof course works only if the outside face does not climb over it. Render taken down across the line joins wet ground, or a wet path, to the masonry above the course. That is a physical bridge. The skirting mark is consistent with moisture arriving low on the inside face. It is not, by itself, a specification to inject the wall. The survey saw the render line and the plaster. It did not design a cut for the render, and it did not sample the plaster in a laboratory.
Ask a builder familiar with this wall to cut the render back to above the course and to make good in a way that does not bridge it again. Tell the solicitor the inside mark sits with that bridge. Do not lead with injection while the render still crosses the course. The survey has not specified a chemical. Plaster repair inside achieves little if the outside bridge is left where the survey found it.
What should you ask your surveyor?
- Does the external render continue below the damp-proof course?
- Is that render the bridge, with the skirting plaster marked?
- Was a chemical treatment left unspecified?
What are the typical next steps?
- Read the render as a bridge across the damp-proof course.
- Ask for the render to be cut back above the course.
- Do not treat injection as the survey's specification.
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
If the mark is only at the skirting, is the whole wall wet?
The survey has not said the whole wall is wet. The mark is at the skirting, in line with render that bridges the course. That is a low-level path. It does not map damp to the ceiling. The report has not specified a chemical treatment. Deal with the bridge that was seen. Do not stretch one skirting mark up the full storey.
Can a coating inside clear the mark while the render stays low?
A coating hides the mark on the plaster. It does not cut the render that bridges the damp-proof course. The survey recorded both the low render and the skirting stain, and it has not specified a coating as the remedy. The bridge stays until the render is taken back above the course. Covering the stain is not that work.