RAAC?

As long as the roofing felt has never leaked then I wouldn't worry too much about any collapse. The photos suggest that there is no cracking or signs of lumps coming away. I would have thought that residential buildings were subject to higher standards than those applied to buildings where people were not present overnight.

If it is RAAC then your flat is now unsaleable or rentable anyway :-(.

When was the roof last re-felted ?. Building regs updates in 2008 require all replacement flat roofs to be insulated. Do you know it this was ever done to your block ?

Other parts of the roof have had repeated/persistent leaks go unrepaired for months, but I don't have easy access to those parts. Fortunately I don't live under that side of the building.

Should I start buying shares in Acrow as they may prove to be a better investment?

Owain

Overdue for replacement (and insulation) then. Have the leaks occurred since 1987 ?. If so, it might have been a cowboy job (mates of a councillor) and should have been replaced much before 30 years.

If it is possible to gain access to this roof via a stairway then it is possible that an aerial installer or similar tradespeople have been up there and caused the damage (sorry Bill).

Leaks are repeated in some places, but the council doesn't respond until 6+ months later so parts of the roof could be pretty soggy by now.

We suspect the council have been deliberately running down maintenance for years as they want to demolish the whole estate. I've seen the 'secret' plans for the redevelopment. We're also overdue new windows, external render, possible insulation, etc. Some of the blocks still don't have security entry.

If this is RAAC then demolition might occur even sooner than the council plan.

The estate is slightly more than 50% privately owned.

AFAIK the only people up there are the council staff and contractors, but that doesn't mean much.

If anyone wonders why I bought this, there are limited opportunities to get a 3-bed flat for under £50k and it was all I could afford at the time.

Owain

What I don't understand is why this material was ever used for structurally important work, Its quite clear that concrete is only strong in compression and this particular sort is mainly for decorative use. I don't care what sort of building it is, its not supposed to be designed for load bearing. If you want a strong concrete, you have normal concrete with rebar tensioned in it so the concrete is compressed by that even when weight is on the structure horizontally. Maybe the builders never saw the demonstrations back in the day on the Open University tv channels that I did. Brian

I believe much of this RAAC has rebar running through it. If rebar gets wet it will rust, expand and crack and split whatever it's contained in, whether frothy concrete like this stuff or solid concrete, witness the 'solid' concrete posts that held the chain-link fencing that bordered my garden and installed in the 1950's, that have disintegrated and now all had to be replaced.

It does seem to me that the building industry is inadequately regulated or monitored. First the Grenfell Tower disaster, now this.

There was also the high alumina concrete back in the 70’s that just turned into mud.

Indeed, Isn't the R of REBAR for "Reinforced"

And Mundic in Cornwall, Mica in Eire.

(a) it's cheap (b) it's lightweight, so the rest of the structure can be cheaper too

Builders never watched Open University which was on BBC2; they watched ITV and the most mathematically advanced programme on that was adding up the darts scores on Bullseye.

Article from 12 June 1959 – Wishaw Press – Costain Concrete Co Ltd will manufacture Siporex in Scotland from early 1960.

Siporex is a lightweight autoclaved aerated structural material with high thermal insulation value and low shrinkage and moisture movement. It is non-combustible, almost white and its density is about one-fifth that of normal concrete. Siporex will be manufactured as building blocks, storey high partition slabs, vertical and horizontal wall slabs, roof and floor slabs of a standard width of 24″ and up to 20′ lengths. Units other than blocks will be reinforced with mild steel. The accuracy and large sizes of the slabs allow simple finishes and virtually all dry construction. Siporex is synonymous with simple. rapid and cost-saving erection techniques.

Seven cost savings with Siporex.

1. Competes favourably in price with other building materials for the same purposes.
2. Provides its own insulation while functioning as a structural material.
3. Saves in field labour as it requires fewer man-hours to install.
4. Saves in structural framework because of its lightweight.
5. Speeds up construction schedule, being a dry, prefabricated unit.
6. Requires a minimum of surface treatment as it is smooth and white.
7. Needs no heavy machinery to be set in place.

... it bears a structural similarity to a certain well-known brand of aerated chocolate. Siporex is only one-fifth the weight of conventional concrete but couples high strength with its lightness. As an advertising pamphlet states: ” It is as light as wood but has the characteristics of stone and is incombustible. Siporex can be nailed, cut, sawn, drilled and chased with woodworking tools.

It's theoretically a good idea... the problem they didn't think about was the matrix acting like a sponge and holding water next to the rebar.

I was wondering whether any of these were RAAC:

I have tested mine and I can't dig a point into the panels, so I'm guessing this one isn't.

Theo

S Wernick & Sons Ltd (row 4 column 1) (garages from £72 and 12 shillings) have gone on to greater things, and look to profit from providing modular and temporary schools and other buildings.

Without the iron and roofing use, this sounds like something called breeze block?

Many walls are built with that, and common now is the use of expansion gaps and apparently a compatible mortar mix. I'm now looking at an inside wall crack in my eighties built extension.

The Ugly Truth About Reinforced Aerated Autoclaved Concrete (RAAC)

I've one in my 1970's extension. I didn't own the house then. The blocks are Thermalite - not Breeze.

Breeze was coal fly ash. not much of that around any more

I would have thought the aerated concrete itself is fine, it's the interaction between it and rebar that causes the problem?

IANA structural engineer but I think breeze blocks are ok in compression (as walls) but you don't use them in tension (for ceilings, joists, lintels). The idea with RAAC was it was reinforced so you could.

Theo

Breeze block ≠ aerated concrete.

Tim

Thermalite or celcon blocks are, widely used as better u value.

Probably just as well. Coal contains uranium at about one part per million, so coal ash is a bit radioactive.