|
|
Author |
|
Message | |
|
cuff
Joined: 02 Apr 2006 Posts: 133
|
|
|
|
|
Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
|
|
|
|
|
cuff
Joined: 02 Apr 2006 Posts: 133
|
|
|
|
|
digit
Joined: 23 Aug 2009 Posts: 88 Location: Neath,South Wales
|
|
|
|
|
Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
|
|
|
|
|
Treacodactyl Downsizer Moderator
Joined: 28 Oct 2004 Posts: 25795 Location: Jumping on the bandwagon of opportunism
|
|
|
|
|
beean
Joined: 04 Jun 2009 Posts: 254
|
|
|
|
|
Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
|
|
|
|
|
dpack
Joined: 02 Jul 2005 Posts: 45372 Location: yes
|
|
|
|
|
Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
|
|
|
|
|
dpack
Joined: 02 Jul 2005 Posts: 45372 Location: yes
|
|
|
|
|
digit
Joined: 23 Aug 2009 Posts: 88 Location: Neath,South Wales
|
|
|
|
|
Gervase
Joined: 17 Nov 2004 Posts: 8655
|
Posted: Thu Oct 15, 09 6:59 am Post subject: |
|
True, the join is critical, as are the way the footings are excavated.
Much depends on what your place is built on - if it's subsoil rather than rock, don't dig straight down - make sure that any excavation adjoining an existing wall has a 45 degree batter to avoid undermining the compacted soil on which the building sits.
The existing building has had 300 years to settle and work out its loading on the subsoil, whereas the new build will settle slightly over time if the subsoil beneath has not been loaded before, so you'll need to to ensure that there is some sort of slip joint between old and new to allow for movement.
This can be done with two layers of vertical DPM with flexible stainless ties every other course if using blockwork. I'd also use a 1:3 hydraulic lime: coarse sand mortar (absolutely no cement) for the join. No problem with doing the rest of the extension with ordinary compo, but you need the flexibility of a lime mortar to managed the bridge.
You'll have to accept that, for a couple of years at least, the bridging joint will be sacrificial. Once the extension has bedded you can repoint down the join with a new lime mix and that should last you out.
Your builder may prefer to use a standard brickies' expansion mastic; it's OK, but if you get movement in the first year or so it's a swine to take out and replace. |
|
|
|
|
Nick
Joined: 02 Nov 2004 Posts: 34535 Location: Hereford
|
|
|
|
|
dpack
Joined: 02 Jul 2005 Posts: 45372 Location: yes
|
|
|
|
|
|