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When building a new brick outside, block inside extension, where it joins an existing brick wall. How should the new wall be tied into the old. ie should the outside brick AND the inside block be tied to existing or is brick only with block tied to new brick via cavity fixings.?

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There's two aspects of the answer: aesthetic tie-in and structural-integrity tie-in. Are you asking primarily about one, or both? –  DA01 Jun 26 '13 at 16:21
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1 Answer 1

If the new wall joins in the middle of the existing wall (eg making a T shape), you can use either wall starters (eg such as these ) fixed to the existing wall to accept both the inner and outer leaf of the wall or you can use frame cramps (eg such as these ) fixed individually for both leaves of the wall.

If the new wall continues along the same line as the old wall (ie it joins it at what is presently a corner), you would typically cut out the "half" bricks (ie every other course) to allow the extension wall to tie into the existing wall such that the bonding pattern matches and continues in the new wall. You would then use wall ties or starters for the inner leaf.

In both cases you should cut right though the outer leaf of the brickwork in the line of the cavity and insert a damp course (DPC) to prevent mositure tracking across and appearing as damp in the corner of the new extension. Ideally, you would cut out sufficient to allow an insualted DPC to be used to also prevent a "cold bridge" along the existing wall.

As you have correctly identified, you will also need cavity ties in the new wall.

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