Post-war system-built and concrete houses

Britain built a very large number of houses quickly after the war, using methods that were not traditional masonry: precast reinforced concrete panels and frames, steel frames, timber frames and various proprietary systems, many known by the name of the firm that developed them.

There is a lot of this stock across Yorkshire, particularly in the former coalfield areas and the post-war estates. The structural question on these houses is unusual, because it is rarely about cracking. It is about what the building is made of, what condition that material is in, and whether anyone will lend against it.

Why some of it was designated defective

Certain precast reinforced concrete house types were found to have a systematic problem: the steel reinforcement within the concrete components corroding, because the concrete cover over it was thin or the mix was permeable. Corroding steel expands, which cracks and spalls the concrete around it, progressively weakening the component.

Because the problem was inherent to the type rather than to individual houses, a number of these types were formally designated defective under legislation now consolidated in the Housing Act 1985. That designation is a legal status attached to a construction type, and it is the origin of the mortgage difficulty that follows these properties around.

The names come up repeatedly in this region and elsewhere - Airey, Cornish, Woolaway, Wates, Reema, Unity and others. If a property particulars sheet uses one of those words, or says 'non-traditional construction', that is what is being referred to.

What that means in practice

• Many lenders will not lend on a designated defective type in its original condition, which limits the buyer pool and therefore the value
• Where a house has been repaired under an approved scheme - typically rebuilding the external walls in traditional masonry around a retained or replaced structure - it can normally be mortgaged again, and the certification for that repair is the critical document
• That certificate is specific to the property and the scheme. Ask for it, read it, and check it covers the whole building rather than part of a semi-detached pair.
• A repaired half of a semi-detached pair with an unrepaired neighbour is a common and awkward situation, and it is worth identifying before you offer
• Cash purchases happen at a discount precisely because of the lending position - which can be a genuine opportunity or a trap, depending on the condition and your exit

Not all non-traditional housing is defective

This is the point most often lost. 'Non-traditional' is a description of a construction method; 'designated defective' is a legal status attached to specific types. Plenty of post-war system-built housing - steel-framed, timber-framed, large-panel and various proprietary systems - was never designated, performs perfectly well, and is mortgageable.

What all of it shares is that a valuer or a surveyor will want to know what it is, and will frequently ask for a structural engineer's opinion before a lender commits. That referral is the most common reason we inspect these properties.

What an inspection actually establishes

• What the construction type actually is - which is not always what the estate agent or even the vendor believes
• The condition of the primary structure: the frame, the panels or the columns, and any visible signs of reinforcement corrosion such as cracking along the line of a bar, rust staining, or spalled concrete
• Whether the property has been repaired under an approved scheme, whether the work looks consistent with that, and what the certification covers
• Whether later alterations - a new opening, an extension, a removed internal wall - have compromised a structural system that behaves as a whole rather than as separate walls
• The condition of any steelwork at damp-prone locations, particularly at the base of columns near the damp-proof course
• Whether cracking present is structural or, as is often the case, in a non-structural cladding or infill panel

The last two points matter more than people expect. In a framed building the walls may not be carrying the load, so cracking in them can be far less significant than the same crack in a masonry house. Conversely, corrosion at a column base can be significant while looking like almost nothing.

What is normal

Hairline cracking in render and in non-structural panels, some weathering and staining of exposed concrete, and the general appearance of a building constructed to a 1950s standard, are all ordinary. The presence of a system-built construction is not, on its own, a defect.

When to call an engineer

Get an inspection before you buy any non-traditional property, and particularly before you buy one as a cash purchase at a discount - because the discount is priced on a lending problem, and you want to know whether there is also a structural one. Get one if a valuation has been referred, if you own one and are planning to alter it, or if you have been offered a repair scheme and want the specification checked.

Also get one before altering a framed or panel building at all. Cutting a new opening in a system-built wall is not the same operation as cutting one in a masonry wall, and the system may be relying on that panel.

How we would approach it

By identifying the type first, then inspecting the primary structure for the failure mode that type is prone to, then reporting plainly on condition, on what any repair certification actually covers, and on what a lender is likely to want. Where the answer is that the building is in sound condition for its type, that is what the report says.

We do not carry out repairs and take no commission from anyone who does. A structural survey and report is a fixed £580 + VAT, report inside 10 working days of the inspection, guaranteed - which is often the deciding document on a purchase of this kind.