[Default] On Tue, 11 Sep 2012 12:36:21 -0700 (PDT), a certain
chimpanzee, Garry , randomly hit the keyboard
and wrote:

We built our current garage a while back its a single skin breaze block rendered wall. We have Building Control for this.

We are wating to convert this to a habitable room and are going to brick the outside. Can I just lay the new foundations along side the old at the same depth

Firstly, why do you need to? You can generally dry-line the inside
with a stud wall & insulation, and unless you are altering the
structure, you don't need to increase the foundations.

If you don't want to dry-line the inside (maybe you need the space),
then building an external leaf onto an existing wall to create a
cavity wall is a difficult way to go, irrespective of the foundations.

The foundations would need to be widened, usually by digging slightly
below & under the the existing. This would need to be done in
sections, similar to underpinning.

The new outer leaf would need to be tied to the inner leaf, with ties
screwed in, and insulation installed. Any door or window openings will
need lintels over, which may need to be changed.

How will the roof be altered? Is there enough overhang to encompass an
increase of ~200mm in the wall thickness?
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have I strayed"?