Injected dpc needed for timber frame lean-to on masonry?

JonEC

New Member
Hi guys

I'm planning to put a side porch onto an 1890s semi, architect has specified on the drawing that there is a need to inject a dpc along the existing external (soon-to-become-internal) masonry wall along the new roof line to stop moisture coming down within the masonry wall into the house. Does this sound reasonable? I'm no expert but own research online suggests that injected dpcs are of limited effectiveness in general and I've not seen any mention of them being used in this way in the context of timber-on-masonry extensions, and would be happy to avoid any needless cost...

Grateful for any thoughts..
JonEC
 
One of the big problems with injected DPC is that it prevents the masonry from breathing, so any moisture that gets into the brick etc, cannot get out and freezes in the winter causing surface damage. I would not use it.
 
Never heard of that been spec’ed, by the same principle every conservatory should be done too, does your architect have a relation with a damp proofing company ;)
 
I didn't know John Wayne was an architect. But apparently he must be, because ANYONE recommending an injected DPC is nothing but a cowboy.
 
Many thanks for all your replies, confirmed my suspicions! I will decline this recommendation and instead ensure that there is good ventilation around the masonry wall section that's becoming internal. It's a bit frustrating to be the one pushing back on the spec as I'm paying the architect good money for it, but they've been pretty good otherwise.

Cheers
Jon
 
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