Age and type of house
Expanding foam fills the skirt vents of a park home. What underfloor ventilation of the chassis has that foam blocked, and what of the steel was not seen?
The foam has blocked the underfloor ventilation that those skirt vents were there to give the chassis, and the steel behind the foam was not seen. Expanding foam fills the openings in the skirt, so air that should move under the park home is stopped at the vents. The survey has seen the filled vents. It has not seen the chassis steel in those openings, has not described the frame behind the foam, and has not decided that the steel is sound or corroded. This note does not set the pitch fee and does not replace the written agreement.
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?
Skirt vents are the breathing holes for the void under a park home. Fill them with expanding foam and the void loses that path. Moisture under a chassis is then more likely to stay there, which is why the steel matters, and why not seeing it matters. Foam is also a cover. It hides the members, welds and any existing rust at the very points that used to be open. The survey cannot grade steel it could not see, and it did not pull the foam out.
Ask the solicitor to read the written agreement and the site rules, and keep the foam note as a condition limit on the unit. GOV.UK treats the purchase as a special case. The survey of the unit does not set the pitch fee and does not replace that agreement. If the chassis must be seen, that is a separate look past the foam, not a pitch-fee discussion. Do not tell a lender the steel was inspected through vents that are full.
What should you ask your surveyor?
- Which skirt vents are filled, and did any remain open?
- What of the chassis steel could you see past the foam?
- Are you recording blocked underfloor ventilation rather than a steel grade?
What are the typical next steps?
- Treat the skirt vents as blocked underfloor ventilation.
- Treat the steel behind the foam as unseen.
- Ask the solicitor to read the written agreement separately from this note.
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 foam looks neat, is the chassis ventilation intact?
No. Neat foam is still foam in the vents. It blocks the underfloor path the skirt vents were meant to provide. The steel behind it was not seen. A tidy fill is not an open vent and not a view of the frame.
Does the survey set the pitch fee because the skirt has been altered?
No. GOV.UK treats buying a park home as a special case. The survey of the unit does not set the pitch fee and does not replace the written agreement. Foam in the vents changes neither the fee nor the agreement.