Building Concrete Houses

[Ivor Windybottom]

I was wondering if it was a disposable wooden box that they left in, perhaps 1x1 timber with plywood on either side. Just guessing, I really can't imagine removing formwork from a 2" cavity with a 3" aerated concrete wall without the whole thing falling apart.

Bricks are great, they're actually a pretty efficient way of building to last. We've buggered about with all sorts of methods over the centuries, the buildings we still have aren't all of them but are just the survivors and almost all are stone or bricks stacked on top of each other with mortar.

There's a current trend for wood in houses. It's all been done before, it's nothing new, it's just that the previous ones all got demolished or altered when they rotted away so don't exist any more. We keep re-inventing old fashions and not learning from mistakes of the past.

 

[stuart45]

I don't know the exact.method used for forming the cavity, but I'm pretty sure they didn't leave any formwork in. Would be interesting to know if they poured both skins together, or separately.

 

[jeds]

The walls weren't poured in one complete lift. From memory there are 4 panels per lift - which would make them, say, 2ft per panel. A re-bar was placed just above the last lift and the next panel poured. So it wouldn't be that difficult to extract a steel former and move it up.

 

[JP_]

Pouring concrete must get trickier when homes are set back from roads, or larger multiple stories?
Probably too intensive for most small building companies too - lots needs doing at once by many people, rather than just having a brickie and labourer cruise through a build over a month or so...

Sure I saw on Grand Designs something done with the hollowed out concrete blocks and steel pins, then pouring though - just pile em up and pour the concrete in.

 

[stuart45]

Couple of photos of Laing easyform.

 

[Ivor Windybottom]

It sounds like they decided they didn't need a cavity due to the trapped air in the "no fines" concrete. Then reality proved otherwise, so they ended up adding a thin cavity.

After adding the rebar, cavity and a load of other stuff to make up for the shortcomings of it, the process they ended up with was probably more complicated/skilled and just as expensive as building with brick anyway. But they'd already invested a ton of money in plant and equipment by this point so would have carried on until all the machines stopped working.

The fact is that nobody mass-builds using this sort of technique any more. If it made economic sense and you really ended up with houses that were sound in the long-term they'd still be doing it, and tackling the banks' fears of it.

There must be some pretty big voids in a 3" wide wall that's cast on-site. Its typical strength must be a fraction of that of a machine-compressed factory made brick, of either concrete or clay. Poured concrete gets used in all sorts of massive civil engineering projects, but casts are usually much wider than this, so it gets the space to move about as necessary for the air to bubble out.

Any semi-knowledgeable inspector could inspect a newly built brick/block house and know whether it's been built correctly - you can see the blocks, each of which you can assume is structurally sound and can easily look down/along the cavities. It would be much more difficult to check the quality of something made from slop with a 2" cavity.

 

[Harry Bloomfield]

Sure I saw on Grand Designs something done with the hollowed out concrete blocks and steel pins, then pouring though - just pile em up and pour the concrete in.

The formwork was polystyrene blocks.

 

[stuart45]

ICF is quite popular in the USA.