Damp and moisture meters
A weep hole in the retaining wall drips after rain and the house wall above it is dry. What is the drip doing, if the house damp-proof course is clear?
The drip is the retaining wall weeping after rain, and it is not a failure of the house damp-proof course. A weep hole is there to let water out from behind the wall that holds the ground. The house wall above it was dry, and the course was clear, so the drip is doing that draining job rather than crossing into the house. The survey has seen the weep run and a dry house wall. It has not said the house is damp.
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?
Water builds behind a retaining wall when rain soaks the ground it supports. Weep holes are the planned outlet. Dripping after rain is what you expect if the hole is open. The house is a different wall, above that line, and it was dry with its damp-proof course clear. Those two observations stop the drip being rewritten as rising damp in the dwelling. The survey did not test drains, and it did not meter a prescription for the house from a garden weep.
Leave the weep as a working outlet unless it is blocked, buried or aimed at the house. Tell the solicitor the house wall was dry and the course was clear. Do not commission damp treatment of the dwelling because a retaining wall dripped after rain. If the weep is discharging against a door or a vent, that is a different detail and it should be described as such, not assumed from this note.
What should you ask your surveyor?
- Was the weep hole dripping after rain while the house wall stayed dry?
- Was the house damp-proof course clear of this drip?
- Have you kept the weep as drainage of the retaining wall?
What are the typical next steps?
- Read the drip as the retaining wall weeping, not as house damp.
- Do not specify damp treatment of the house from this weep.
- Tell the solicitor the house wall above the weep was dry.
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 weep runs hard, is the house course bridged?
A heavy drip means water is leaving the retaining wall. It does not bridge the house course. The survey found that course clear and the house wall dry. Flow at the weep is the outlet working, not a path into the house.
Does a dry house wall mean the retaining wall is sound?
No. Dry plaster above only separates the house from this drip. The retaining wall can still be doing its own job, well or badly. The survey has not passed the garden wall merely because the house course was clear. The house and the garden wall stay separate.