Exterior insulation to '20s concrete block?

Friend is buying a 1920s concrete block house. Steep site, so the roads are flat and every house is either up or down steps. As a result of the valley and lack of sun, there are always problems with damp, path moss and cold.

Construction is a single leaf of concrete blocks. So it's one of the few forms of construction where "penetrating damp" is really a thing.

Overall, the best fix (inspired somewhat by reading The Yellow House eco-blog) would seem to be applied foamboard insulation on the outside, with render over. Any thoughts? Suggestions for materials? Technique?

This isn't going to be DIY (I ain't doing it, and they're moving to get themselves out of a live-in barn conversion that ground to a halt a decade ago). Still, good project management of builders is helped by knowing the score a bit.

Thanks

Reply to
Andy Dingley
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A whole lot of council houses round here were single skin concrete and have now had an external skin of brick and insulation fitted to bring them up to modern standards. Obviously not cheap but very standard and no need for repainting every few year either. No need for specialist trades and possibly a whole lot stronger than render on top of insulation. I often wonder what the latter are like to lean a ladder up against for decoration etc.

Reply to
Bob Minchin

Does not sound encouraging. It is their only option?

Philip

Reply to
philipuk

Are you sure they weren't Smiths houses? They jack the floor and roof up and knock the walls down and then rebuild a brick and block cavity walls.

Reply to
dennis

They did that with some 8 floor blocks of flats around here. It looks easy. You can get special fixings that screw/resin into the concrete that support the insulation and the cement board(?) you render over. They looked fine for a few years although they are growing moss on the render now.

Reply to
dennis

Are they real brick? The ones I have seen have a brick-effect either in or applied to the render.

Chris

Reply to
Chris J Dixon

In message , Andy Dingley writes

Umm.. polythene vapour barrier, 75mm PIR foam, 25mm x 38mm battens secured with adjustable screws, galvanised metal lath, cement render/ feather edge board/ vertical Larch board. Door and window openings need some thought.

Issues... minute cracks will form at the metal lath joins, feather edge board has knots which drop out and invite Pipistrelle Bats to colonise the space behind, Larch weathers to Grey.....

Reply to
Tim Lamb

In article , Tim Lamb writes

I've seen a proggy where this was done by a specialist contractor, PIR boards first then (I think) EML next, direct on to the boards then a coat with a special flexible render that could cope with the movement of the flexible substrate.

I imagine the difficulty arises with where the vapour barrier goes, obviously foil faced boards are impermeable (no additional barrier required there) but vapour barriers would conventionally go on the warm side and then there's the issue of existing penetrating damp, if that is sealed in then it could lead to problems.

Can't remember which proggy I saw it in but a search for external insulation with flexible render could pull up some results. Yep, just done that and plenty of likely hits.

Reply to
fred

I've certainly seen it done with a brick skin, I watched a job being done

Reply to
Chris French

It evaporates to the interior, which is about the same temp as the outer edge of the concrete once the insulation is in place.

NT

Reply to
meow2222

Tell him to walk away from it.

Reply to
Peter Crosland

Another vaguley remembered, but look up U.S. experiences of external insulation on concrete block construction, sure there are some issues....

Reply to
Adam Aglionby

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Reply to
Adam Aglionby

No, the interior was left the same and a full brick outer was built all round the outside. New windows were fitted into the outer skin and new reveals fitted inside. It was a real transformation to the appearance of the street. No more dirt mottled painted concrete, smart brickwork instead.

Reply to
Bob Minchin

Their simplest option is to move in and light the fire. They've gone on for a hundred years that way.

As it is, the chimneys are damp, there's some trivial cracking visible outs ide and the wall beneath the chimney stacks is going green. Inside is best described as "minging damp", but then that's probably more because the hous e has been empty for a year and it had a work-from-home laundress in it bef orehand! So, work is needed. If work is needed and scaff is to be hired, t he kitty is ample for making things somewhat improved - the question is how best to do it.

Other options were to buy the really nice house two streets down (I suggest ed this originally) or to buy the decrepit Georgian hovel alongside what's nearly the world's largest tidal range. They were keen on that (why?!), but having at least talked them out of that one, I think the '20s concrete is a reasonable choice.

Reply to
Andy Dingley

Windows (modern PVC of a few years ago) will get recessed a bit deeper. Not a big deal - there's no view from the front and the rear aspect is a bit d rier. Would it be sensible to insulate just half the house? It probably nee ds a stepped edge to the insulation with the next door semi- anyway.

Front door is possible getting wrapped in a porch anyway.

Galv lath or stainless? I have heard some comments saying that galv would fail too soon.

How's the lath (and thus render) attached structurally? Is there enough bo nd via the foam fixing bolts? If there's anything else used, is that a ris k of cold bridging?

I prefer render to larch. Render fits in with the character of the area (a Garden Suburb) and I think it's quite likely that council planners would ob ject to timber cladding in this area. I know I would, although I'm the next village along.

Reply to
Andy Dingley

They've got to live _somewhere_. This house is also unlikely to have foot+ deep snowdrifts on a half mile drive, like the last place.

Reply to
Andy Dingley

I had assumed it was a detached property. I can't believe anyone with any morals would blight a neighbouring semi detached property with a 3" step change wall front and back. The only consolation would be that the planners should throw it out on impact considerations.

Reply to
fred

I think ours is galvanised, 20 years so far. The original pargetting was done on unprotected expanded metal in 1938. Still sound in 1995.

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The lath was nailed to the battens.

This is Herts. next to Essex. Clapboard!

The barns are feather edge so we compromised with half and half.

Reply to
Tim Lamb

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