Drainage and septic tanks
The seller says soakaway crates lie under the new patio and nothing was dug up. What crate has the survey not seen?
The survey has not seen the soakaway crate the seller says lies under the new patio. Nothing was dug up, so the crate, its wrap, its inlet and the ground around it stayed buried. A seller's sentence is not a view of the crate. The survey can record the new patio and the claim. It has not confirmed that a crate is there, has not measured it, and has not decided that it drains. The home survey did not test the drains and did not open the patio.
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?
Soakaway crates are plastic voids meant to hold rainwater underground and let it disperse. Under a new patio they are, if present, invisible. The patio may cover them, cover something else, or cover nothing but hardcore. The survey takes the ground as it found it. It does not lift slabs because a seller points at them. A puddle on the patio, or the lack of one, is a surface note. It is not the crate. Recommending nothing was opened is the honest limit.
Ask the solicitor for any drainage drawing, building-control note or invoice that actually shows crates, and keep the seller's remark labelled as a remark. If the patio drainage matters, a drainage firm can investigate without you pretending the survey already saw the crate. Do not tell a lender a soakaway was inspected. The survey has not seen it. The newness of the slabs does not date a crate nobody uncovered.
What should you ask your surveyor?
- Did you see any crate, inlet or geotextile, or only the patio?
- Is the seller's claim recorded as a claim rather than as a finding?
- What surface signs, if any, did you note without opening the ground?
What are the typical next steps?
- Treat the soakaway crate under the patio as unseen.
- Keep the seller's claim separate from the inspection.
- Ask for drawings or a drainage investigation if the crate must be confirmed.
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 patio falls away from the house, has the crate been proved?
No. A fall on the slabs is about surface water on top. It does not show a crate underneath, and nothing was dug up. The survey has not seen the crate the seller described, whatever the paving does with rain.
Can an invoice for patio slabs stand in for the crate?
No. An invoice for slabs shows paving was bought or laid. It does not show a soakaway crate in the ground. The survey did not dig, so the crate remains unseen even if a bill for the patio turns up in the pack.