Cracking wall
- Thread starter duffsparky
- Start date
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In one sense you are right joe. The very qualities that make blocks thermally efficient also make them susceptible to water content volume changes.
These blocks are full of air and can soak up water. As Shy has said, there are measures that the builder can take, that insure shrinkage and thermal movement do not occur or at least reduce the chances of s&m occurring.
I think that if people had a choice then they would want a warm efficient home. A cracked block beneath a dabbed board will go unseen. Ho hum. It ain't perfect but it is all we've got. The current alternative is to fit insulation boards to the inner face of the cavity wall which is a pain if you are say fitting a kitchen. Fixing becomes a nightmare.
I personally have only used and seen others use either thermalites, durox, or hemlites (or similar).
Standard spec':-
105mm external brickwork - 100mm full fill cavity (dirtherm) or partial fill with 75mm foam board 25mm air gap (foam board tight against the inner leaf) - 100mm 3.5n aerated block.
In ALL the extensions i have built, regardless of architect, the spec' is always the same. As above really. I have seen 7n dense used on the inner leaf of a garage or a subterranean parking bay for instance, or indeed used as exposed partition within a building, wherby the 7n dense blocks are pointed and 'decorative'.
It is unusual to see the use of dense blocks en masse, internally.
Standard spec':-
105mm external brickwork - 100mm full fill cavity (dirtherm) or partial fill with 75mm foam board 25mm air gap (foam board tight against the inner leaf) - 100mm 3.5n aerated block.
In ALL the extensions i have built, regardless of architect, the spec' is always the same. As above really. I have seen 7n dense used on the inner leaf of a garage or a subterranean parking bay for instance, or indeed used as exposed partition within a building, wherby the 7n dense blocks are pointed and 'decorative'.
It is unusual to see the use of dense blocks en masse, internally.
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Thermalite and other lightweight blocks have been in common use for the internal skins of cavity walls since 1975 when the U values were dropped from 1.7 to 1.0. Before that either bricks or clinker blocks were normally used. Recently some builders have been using medium density blocks on the internal skins because of the cracking problems with lightweight blocks. As long as the target U values are met it's OK.
They were around in the 50s and 60s also as Siporex blocks and panels, but not in common use. I think that they were invented in Sweden in the 20s. I never laid any myself until the mid 70s when most builders used them.`75I saw plasterers cursing them in 1970 for their bad suction habits
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