Age and type of house
A cob wall has a hole at the base where the earth has fallen out and the render above is intact. What splash and what animal path is that hole, before anyone injects the wall?
The hole is a splash hole and an animal path at the base of the cob, not a case for injection. Earth has fallen out where rain splash, or a mouse or similar, has taken the base of the wall, and the render above is still intact. Cob fails when the foot is kept wet or is burrowed, not because it lacks a chemical damp course. The survey has recorded the hole and the intact render higher up. It has not specified injection, and it has not rebuilt the missing earth.
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?
Cob walls are built of earth and straw, and they need to stay dry at the foot and be able to breathe. A hole at the base is where splash from a hard path, or an animal, has removed material. The intact render above says the face higher up has not fallen with it. Chemical injection is a treatment aimed at masonry damp courses. It does not replace lost cob, and pumping fluid into earth can make the wall worse. It did not prescribe a chemical.
Ask someone who repairs cob, not a general damp contractor selling injection, to say how the hole should be made good and how splash at the base should be reduced. Tell the solicitor the defect is lost earth at the foot, with render above intact. Do not agree a chemical damp contract on the back of this note. The survey has not specified one. Keeping water off the base and closing the animal path matters more than a cream in a wall that is not brick.
What should you ask your surveyor?
- Is the hole at the base splash, an animal path, or both?
- Was the render above recorded as intact?
- Have you left chemical injection unspecified?
What are the typical next steps?
- Treat the hole as lost cob at the foot, not as a call to inject.
- Ask a cob repairer how to make the base good and limit splash.
- Do not sign an injection specification off this report.
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 render above is intact, can the hole be ignored?
No. Intact render above the hole only means the upper face has not fallen. The base has already lost earth. That is the splash and animal path. The survey has not specified injection, and it has not said the hole can stay. A sound render higher up does not refill the foot of a cob wall.
Will a new chemical damp course stop an animal using the hole?
No. Injection does not close a hole and does not stop an animal. The survey has not specified a chemical treatment. The path is the missing earth at the base, where splash and burrowing have taken the cob. Closing that hole, and keeping splash off the foot, is the repair to discuss. A damp cream does not do it.