Most houses in the UK are of ‘traditional’ construction – with brick and block cavity walls or modern timber framing. But not all. “Non-traditional” houses include steel-framed and various types of precast or in-situ cast concrete construction.

Instead of the usual visual inspections, these need engineers to carry out intrusive checks.

This case study outlines the inspection needed to assess a steel framed house, called a Trusteel MkII. Mortgage Lenders nearly always need the structural condition of the frames of these houses to be checked before they’ll offer a mortgage. It’s an important assessment that can sometimes find problems that otherwise would be unseen.

Houses such as these were promoted after WWII, as surplus manufacturing capacity was enrolled to counter increased demand combined with labour shortages.  Several hundreds of designs were developed, some being built by the thousand and others not progressing beyond a handful of prototypes.

Unfortunately, some of these were unsuccessful and suffered from premature deterioration, earning “prefabs” a bad reputation which in many cases is undeserved. First steps, then, were to identify the house type, before planning the correct means of investigating the structure. A sound knowledge of the various types of non-traditional buildings throughout the UK is essential.

Two the most common types are the BISF (British Iron & Steel Federation) and Trusteel Mk II and 3M, thousands of which remain in use today. A lender will typically request an intrusive inspection following guidelines published by the Building Research Establishment (BRE). In this case, we look at a Trusteel property.

Houses such as this Trusteel are generally brick clad, and the best way to inspect these is to have a builder remove bricks from the outside walls in selected locations, which can be replaced afterwards. An endoscope allows inspection of the interior behind the external cladding. If this is not acceptable or possible, it’s sometimes possible to drill holes from the interior, although the view with an inspection camera is less easy to interpret and sometimes frustrated by the presence of cavity wall insulation.

What the engineer was looking for was hidden corrosion which would weaken the structure.  Often changes to the building (new openings etc) can be just as damaging to the structural stability of the property and it is important to identify cases where changes have happened.

The engineer’s report in this case aimed to identify the characteristics of the building and any defects that would require urgent remedial action, beyond the usual routine of care and maintenance. Where appropriate, estimates for the costs of remedial work, are given.