Age and type of house
The parking bay under a coach house has a boxed bulkhead and the surveyor could not see why the headroom changes. What structure inside that bulkhead is unknown?
Whatever structure is inside the boxed bulkhead is unknown. The parking bay under the coach house changes headroom, and the surveyor could not see why, because the boxing was not opened. It may conceal a beam, a duct, a stepped slab or something else. The survey has not chosen among those. It has recorded a bulkhead and a change in headroom. It has not identified the structure inside. A painted lid is not a section through the floor.
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?
Coach houses put a room over a parking bay, so the soffit of that bay is often the floor structure of the room above. Boxing hides the members that make the headroom step. Looking at a plasterboard or timber lid tells you the lid is there. It does not tell you the size of a beam, whether a drain is boxed in, or whether the step is only a finish. The survey did not open it and did not claim a structural failure it could not see.
If you need to know why the headroom changes, ask for the boxing to be opened when access and agreement allow, and for someone who can read structure to say what is in it. Tell the solicitor the survey left the contents unknown. Do not guess a beam and then price a repair for a member nobody saw. Do not tell a lender the bay was proved adequate. The inspection stopped at the box.
What should you ask your surveyor?
- What structure inside the bulkhead did you leave unknown?
- Why could you not see the reason for the headroom change?
- Did you open the boxing, or only record that it was closed?
What are the typical next steps?
- Treat the bulkhead contents as unknown.
- Do not price a beam the survey did not see.
- Ask for the boxing to be opened if the structure must be identified.
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 box is neatly painted, is the structure adequate?
Paint shows a finish. It does not identify the structure inside, which remains unknown. The surveyor could not see why the headroom changes. A neat box can hide a beam, a duct or a poor bearing equally well. Adequacy was not the finding. The closed bulkhead was.
Does reduced headroom by itself prove the floor above has sagged?
No. Reduced headroom proves the soffit is lower there. Sagging would be a movement finding the survey has not made from a boxed change of height. The structure inside is unknown until it is seen. Do not convert a bulkhead into a failed floor.