"No-Fines Concrete" House - what does it mean?
Most concrete will contain a mix of course aggregate (gravel), fine aggregate (sand) and cement. This is mixed together with water, and before setting it is reasonably fluid and can be poured. After pouring it will generally be vibrated or tamped-down to remove excess air gaps or voids, which if it has been properly blended means the sand and smaller particles will fill all the gaps between the larger pieces of gravel. It will set to form a dense mass of solid looking material that we are all used to seeing. So... if you leave out the fine aggregate, hence the name "no-fines", then the mix remains with a gravelly appearance, with the course aggregate coated in cement that bonds it together, but the gaps are not in-filled by the missing sand. The finished texture has a rough appearance with relatively large air gaps and voids.
As a simple statement: a "No-fines Concrete" house is one that has been built using concrete without the finer particles.
The method of construction was used during the period of 1920s to the 1970s. Quicker and more cost effective to build, instead of laying bricks, the walls were poured as vertical 'slabs' between a board framework ("formwork"), once set the boards could be removed and the concrete coated on the outside with render and inside with plaster to give the finished appearance. Without knowing what to look for, you could be buying a house without knowing how it was constructed.
There were a number of companies that used "no-fines concrete", and these vary from region to region. Often they are generically referred to as "Wimpey No-Fines", being one of the major house builders at the time, but there are others listed by the British Research Establishment (BRE) including "Banton", "Blackburn", "Boyd Gibbons", "Brydon" (they are the "Bs" but there are about 14 or so others). They can also be referred to as "Formwall" or simple "No-Fines". Because this construction method broke-away from the traditional brick & blockwork walls then they are now classified as "Non-traditonal houses". If we then take a moment to mention "non-traditional houses" then often that sets off alarm bells, as they can commonly (but mistakenly in many instances) get grouped together as "designated defective houses".
Even if not classed as "designated defective houses" it is important to understand some limitations and 'faults' that can arise with "No-fines Concrete" houses, and the problems do vary from one type to another, even though there are often common themes. The one pictured above, for example, we were looking for vertical & horizontal cracking in the render, tell-tale evidence of corrosion to wall ties in any brickwork, tell-tale signs of carbonisation of aggregate in the concrete beams (and plenty more besides).
As with any house what suits one owner might not suit another, so there is not a single argument that can be put that someone should buy or should not to buy a non-traditional house, but it is really important to understand what you are buying if you do. You should also bear in mind that some mortgage lenders and building insurers might not be willing to take on non-traditional houses, which could make selling more difficult when that time comes.