External insulation down to ground level

10 May 2015
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United Kingdom
The house we bought last year was having a problem with condensation along the bottom of the internal walls during autumn/ winter so I think ewi is needed because filling the cavity didn't cure it.
The problem I have is I need to continue the insulation down to ground level because internal floor level is around 450mm above external ground level, and the 450mm which is exposed outside is solid, the cavity ended at interval floor level.
I've been reading about using XPS along the bottom and EPS above, but I live in Northern Ireland and no one on the island of Ireland seems to have heard of XPS, and delivery cost from the mainland is mental.
So is there an alternative to XPS? And would I need to take the insulation down below external ground level? I've included a wee diagram to show how the external wall is constructed. Many thanks for any advice given, cheers


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At DPC level, the cavity should have continued 9 inch down. Also, full cavity fill is the worst thing invented for cavity walls.

The condensation is likely due to the full cavity fill being sodden so the cold just bridges across making the inner leaf cold and thus the moisture condensing on the inner leaf.

The joys of a complete botch.
Thanks for replying, Yes the cavity should have continued down, but it's an old house most likely built by the farmer who owned the land 60-70 years ago! The condensation was occurring before I got the cavity filled so it wouldn't be that, I'm guessing the solid wall below the dpc is a massive thermal bridge and causing the internal wall of the cavity to cool and so letting the air condense. Any idea about an alternative for the XPS? Cheers
i now nothin about XPS - after googlin it, it sounds like it needs professional insallation.
but until you find the cause its pretty hopeless attemptin to cure somethin?

remove a brick here an ther ansee if the cavity insulation is wet?
is the house rendered?
is ther a membrane below the solid floor?
are you on a hillside?

why not photo the damp signs an the exterior?
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You can use Eps down to and below ground level. Many insulate down to foundations.

You can also bridge the dpc with it as well.
Think about dirty splash back. You can put your track at dpc level and colour darker below or just pressure wash it from time to time.
Whilst the theory is correct, you need to be very careful with just slapping some insulation on and risking making another (or greater) damp problem and not curing the original issue.

That drawing layout shows that there should not be a condensation issue related to the solid wall, which implies that insulating it externally is not the answer. So you need to be dead certain that the cause is not something else and perhaps look at a defective DPC or more likely moisture moving down or across the cavity and remaining on top of the DPC.
Thanks for the replies,
I had thought it was condensation because it's not always on the wall, just in the colder months and we've had some pretty heavy rain this summer with no sign of wet walls. Although, the old pebble dash that was on was pretty ropey in places. It's since been taken off and had a coat of mortar applied in preparation for the ewi.
How does the eps bridge the dpc? does it draw moisture up and beyond the level of the dpc? I had thought thats why XPS was used below the dpc?
Thanks again

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