Non-standard construction
At the party line of a BISF house the original profiled steel sheet is still visible in the loft. What of that sheet was not thickness-tested?
The thickness of that profiled steel sheet was not tested. At the party line of a BISF house the original sheet is still visible in the loft, so the survey can say the sheet is there and how it looked from that space. It has not measured the thickness, sampled any coating, or described the sheets hidden in the walls. A visible edge in the loft is not a thickness test of the party-line steel.
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?
BISF houses use a steel frame and profiled steel sheeting as part of the original construction. Seeing a sheet at the party line in the loft tells you that piece is still exposed there. It does not tell you how much steel remains in the thickness, whether the hidden face is rusting, or what the sheets are like where the walls cover them. Thickness testing needs access and a method this visual note did not use. The survey stopped at what the loft showed.
If a lender asks about the BISF construction, give them the survey limit rather than a thickness you do not have. A specialist who knows these houses can advise on the frame and the sheeting as a separate instruction. Ask the solicitor what papers exist for any previous repair. The home survey has not thickness-tested the sheet, and it should not be rewritten as if it had.
What should you ask your surveyor?
- Did you see the profiled sheet only from the loft at the party line?
- Was thickness left untested?
- What of the sheeting in the walls stayed hidden?
What are the typical next steps?
- Describe the loft view of the sheet, not a thickness.
- Do not invent a remaining thickness from that glimpse.
- Ask a specialist if the BISF steel needs a closer inspection.
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 visible edge looks bright, is the sheet sound throughout?
No. A bright edge is the face you could see in the loft. It was not thickness-tested, and the sheets inside the walls were not exposed. Brightness at one edge does not describe the rest. The party-line sheet is still undescribed as a thickness. Looking bright is not a measurement.
Does the party line being steel mean the neighbour's house was surveyed?
No. The sheet was seen from this loft at the party line. The neighbour's side was not inspected, and no thickness was measured on either face of that steel. A shared wall line is not a survey of the house next door. The visible edge stays a loft view only.