Mixing Blocks and Bricks

22 Feb 2004
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United Kingdom
Potentially dim question coming up.

I'm replacing the back wall of an extension (cos the lintels supported 6 blocks of internal skin and none of the bricks in the external skin which then cracked and crumbled). The wall has sliding patio doors which I'm replacing with French windows and glass side panels, and of course the boss wants the doors sited 3 foot to the left of the original hole. Not a problem, original wall suitably demolished following deployment of acrows etc.
Now, I'm no builder, so I'm getting as much advice as I can on this (please!). Back wall will be rendered and dashed once built, so I'm using blocks for ease & quickness (7 newtons exterior, 4 newton thermalites interior, 2.7m cavity wall steel lintel).
Part of the advice I have been given is that I cannot put the external blocks on top of bricks (about 10 courses of wall remain in one corner). In other words, I've been told that I must build the remainder of that skin in bricks.
Is this right?
Thanks in advance - apologies for the dim question.
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I cannot see any major probelms with undertaking this method of construction.

I would use a lightweight 3 Newton block rather than a 7.5 & also use 100mm thick rather than say a 120 or 115mm so that slightly smaller than the bricks width. There is no weight, other than self load on an external leaf anyway. If you are going to render then why use bricks?

It is a standard form of construction used by housebuilders as blockwork is cheaper than bricks in both material & labour i.e. less cost of a block, less mortar, less time to lay etc.
Thanks K2. I managed to get a hold of a brickie mate and he told me that the only problem might be that I get a cold spot on the wall. Since it's the external skin I don't care!
Quite a voyage of discovery this project, so i'm going to start a My Projects thread in case of other interest.

I'm told by BCO that I have to use a 7newton for the external skin - would be much easier with the 3.5s !

Thanks again.

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