What it is
A steel-framed house has a skeleton of steel columns and beams that carries the floors and roof. The walls are made of cladding and linings fixed to the frame, sometimes with a brick or block outer skin. Steel-framed houses were built in the UK in several periods, including after both world wars, when bricks and building labour were short, and in later system-building programmes.
Besides BISF houses, systems include Howard, Trusteel and Dennis-Wild, among others. The designs differ in their frames, claddings and details, so it helps to identify the exact system. A surveyor or engineer who knows it can then say where to look.
How to recognise it
- Metal, render or other lightweight cladding, often different from neighbouring brick houses.
- Walls that sound hollow when tapped inside.
- Steel columns, beams or roof members that may be visible in the roof space.
- Houses of the same design nearby, some re-clad and some original.
- An EPC that describes the walls as "system built".
Many steel-framed houses have been re-clad, sometimes in brick, which can make them look conventional.
Common problems
- Frame corrosion. Steel rusts where water reaches it, especially at the base of columns near ground level, at connections, and behind leaking cladding, windows or roofs.
- Cladding. Panels, sheeting or render can deteriorate, and fixings can corrode.
- Condensation. Cold steel inside poorly insulated walls can attract condensation, which adds to the risk of corrosion.
- Fire separation. In semi-detached and terraced designs, the fire separation between homes needs checking where it can be seen.
- Alterations. Cutting, drilling or welding the frame without an engineer's design can weaken it.
- Materials of the period. Asbestos can be found in any building built before 2000, so get an asbestos survey before any work that disturbs old materials.
Mortgages and insurance
Lenders' views differ by system and by the condition of the frame. Some lend on certain steel-framed systems, often with a structural engineer's report, and others will not lend at all. Check with your lender or broker before you pay for a survey, and give your insurer accurate details of the construction.
When a structural engineer is needed
A Level 3 Building Survey is a visual inspection: we do not open up walls or remove linings. With a steel frame, the parts that matter most are usually hidden. We will recommend a structural engineer where:
- there are signs of corrosion, such as rust staining, cracked or bulging finishes near the frame, or damp at low level
- critical parts of the frame cannot be seen
- your lender asks for an engineer's report
- you plan alterations that affect the frame
The engineer may open small areas, often at the base of columns, to see the steel and judge its condition. The RICS Home Survey Standard expects a surveyor to refer matters for further investigation where they cannot reach a conclusion with reasonable confidence.
What we have found locally
Apart from BISF, none of the named steel-framed house systems appeared in the reports we analysed. That does not mean they are absent from our area.
Reports that recorded BISF construction:
1 DBISS survey report since 2022
Sources
- RICS: Home Survey Standard
- BRE: SAP 10 and RdSAP 10 specifications, which define the wall types used on EPCs
- Health and Safety Executive: Asbestos