Bonding cavity wall to solid wall

7 Jul 2010
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United Kingdom
I am constructing a 10m x 5m building with 3 sides at ground floor level (open as 2 bays on one long face for parking access) and a room above with 2 UB's to support a wall over the open side. The 3 sides at ground floor are 4" dense blocks for inner and outer leaves with a 4" cavity. At first floor level the inner leaf will be 4" lightweight concrete blocks whilst the outer cavity leaf will remain as 4" dense concrete blocks. The wall over the UB's will be 6" or 8" thick (the UB is only 171 wide but assume I can put 8" blocks onto it ?) lightweight concrete blocks.
My question is should I just normally bond the 2 cavity skins to the solid wall or use cavity ties to bond to avoid cracking due to differential thermal expansion ?
The 3 faces will be rendered whilst the solid wall with be timber clad.
Any advice or thoughts much appreciated.
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Block bond the outer leaf to the solid wall and hang some ex-met out of the solid wall every course to tie the inner leaf at the corner
So bonding the outer leaf 4" dense concrete blocks to the 8" lightweight block solid wall should not give to many problems with differential thermal expansion ?
Can I use cavity ties to bond the inner leaf to the solid walls - wall are all going up at the same time.
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You need to consider that the potential for cracking at the cavity to solid wall is exactly the same whether you tie in with ties or bond it normally. In this instance, there wont be an issue with block bonding the outer leaf to the solid wall. Tying with ties has more of a potential to crack at this connection

It will probably the same for the internal leaf, it all depends what the building is used for and if internal temperatures will be relativity stable.

I cant see any problem in bonding the inner leaf in too, but its just an awkward joint to build, so metal ties would be easier. Expanded metal will give a stronger joint than ties. Ties may do, and I would also put ties across to the outer leaf to at this location every 225mm

That 10m wall should have a movement joint in it on the external face in any case.

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