Join between house and extension

[Craig]

Hello - we are rebuilding the top two floors of a 5 storey extension. Where the new brick work butts up against the house, we were just intending to have a mortar layer and then point it up. Our builders wanted to use silicone sealant.

Any views either way would be welcome?

The extension has been there a while and its overall weight isnt changing so I am not too concerned about settlement, etc, but I was wondering about differential thermal expansion.

 

[Lime]

My immediate feeling about the silicone sealant is what an odd way to join two brick buildings.
I presume you mean the vertical joint!

What sort of attachment to the main part of the house is used?
Metal ties?

 

[Craig]

Yes, sorry - the vertical join! We are using a variety of metal ties for both the brick work and to tie in the new joists.

 

[Lime]

I presume your builder expects some movement and ordinary pointing between the bricks would crack.
Cracking is highly likely particularly in the first few years.
I wouldn't like to look at it though.
Perhaps a compromise could be come to where the sealant is used primarily and about 3cm of pointing used on the outside?