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Hi,

I’m about to buy a BISF house in Loughton.
The seller said the walls were made of ‘clinker’ blocks. Then there was a layer of insulation, which he described as concrete with straw like material. Then plasterboard.

This sounds quite odd to me. But if left me wondering how warm it would be? Any idea?

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Thanks Guys,
That makes a lot more sense

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Hi and welcome, perhaps they are confused by the party wall or the outhouse and have assumed that the exterior walls are the same? The party wall in our house (and all BISF houses?) is made of a double layer or very dense concrete blocks that could have been made from some sort of clinker or other waste material. Basically very dense breeze blocks. The outhouse is made of a single layer of the same blocks with a flat concrete roof, but I believe in other areas they are usually timber framed lean to structures.

There is a large amount of confusion about exactly what BISF houses are. Especially the concrete render on steel mesh laths on the downstairs walls confuses a lot of people because it’s an unusual building material. The easiest way to imagine it is as an industrial version of the old lath and plaster that was used in the days before plasterboard for ceilings and internal walls, but with steel mesh laths instead of wood and a cement based render instead of lime plaster.

A lot of people assume that a BISF house will be very bad at retaining heat. Yes it will be poor compared with a modern home but I don’t think it will be much different from a traditional house of a similar age and in my experience even unimproved it is better than a traditional house with solid (pre cavity) walls. Ours was certainly more comfortable even before I started insulating it than the solid walled flat we used to live in or my parents solid walled stone house.

Ed

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Hello Theotetus and welcome

The description that you have been given sounds completely wrong and inaccurate.

The lower walls of a BISF house are constructed with a cement based render that affixed to a steel lathe mesh framework. Behind that is a layer of thin insulation which sits inside the cavity, surrounded by timber studding onto which plasterboard or even hardboard is applied. The hardboard was fitted to many houses but some were fitted with plasterboard which may be the case in Loughton.

If the building is in original condition it should also have pressed steel panels affixed to the upper elevation which many people have overclad with a variety of materials, especially white UPVC cladding.
behind the steel sits the same insulation etc as downstairs but obviously there is no cement render on the upper elevation.

In general the houses aren’t well insulated and in the winter they can get pretty cold. on the plus side, you can insulate the wall cavities yourself using insulation boards such as Kingspan panels, alternatively external insulation is also an option but expect to pay anything between £6,500 and £12,000 for external wall insulation.
I recently arranged a street wide project using funding from the soon to be defunct Green Deal scheme. The cost to externally insulate the properties was around £8,500 each with the Green Deal fund paying £6000 of this. At present though, we need to wait and see what new scheme the Department of Energy & Climate Change come up with but I doubt that any forthcoming funding will be as generous.

I wouldn’t let this out you off though as the prices in Loughton are very good compared to a like for like brick house in the area, and prices for the BISF houses continue to rise which is a good sign.

I have attached some images below from a property that was being fitted with patio doors in the existing dining room window space. You will be able to see the render, with the odd glimpse of the supporting mesh, along with the insulation etc.

I hope this gives you a better insight.

Marc

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