Damp and moisture meters
A rainwater hopper overflows onto solid brick and the plaster inside is salt-stained. Which defect should you read first, the hopper or a damp treatment?
Read the hopper first. A rainwater hopper that overflows onto solid brick is putting water onto the wall, and the salt-stained plaster inside sits on that path. The survey has recorded the overflow and the staining. It has not specified a damp treatment, and it has not decided that the salts need a chemical system while the hopper still overflows. On solid brick the rain has no cavity to fall into. The defect to read first is the hopper that is discharging onto the wall. A damp treatment that ignores it treats the stain and leaves the water.
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?
Hoppers block, tip and lose their outlets, and the water then runs down the face that was never meant to take a concentrated flow. Solid brick soaks, salts move to the inner plaster, and the patch looks like a classic damp problem. The classic problem here has a visible tap: the hopper. Reading a damp treatment first inverts the order. You would be specifying a barrier or a tanking against a leak that is still running. The survey can see the overflow.
Photograph the hopper, the wet brick and the stained plaster as one set, and ask a roofer or a builder to put the rainwater right in writing. Tell the solicitor the first defect is the overflowing hopper, not an unspecified damp treatment. Do not pay for injection or waterproofing of the plaster while the hopper still discharges on the wall. A lender should be told about the rainwater defect the survey actually saw.
What should you ask your surveyor?
- Is the hopper overflowing onto the solid brick you have linked to the salts?
- Did you specify a damp treatment, or record the overflow and the stain?
- Which defect should be read first?
What are the typical next steps?
- Read the overflowing hopper before any damp treatment.
- Keep the salt-stained plaster as the inside of that same path.
- Get the rainwater put right before anyone specifies the plaster.
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 hopper only overflows in heavy rain, is it still first?
Yes. Heavy rain is when a hopper shows its fault. The survey links overflow onto solid brick with salt inside. Intermittent does not make a damp treatment the thing to read first. The hopper is still the defect ahead of it.
Does dry plaster in the next room clear the hopper?
No. The next room is a different wall. A dry room does not stop this hopper overflowing onto this brick. The salts here are still read with the hopper, not as a house-wide treatment. Anything further about the overflowing hopper would be a different visit, not this note.