Cavity wall insulation with existing damp problem

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Hi Guys hope you are all well

I own a 3 bed 1930 semi which I though was solid wall. i have just drilled a 4" core through the wall for a boiler flue and have discovered a cavity approx 2 -2 1/2" wide result I think :confused:

Anyway before we moved in we had an injected DPC and I installed a vertical damp as some numpty had breached the existing with a driveway and patio around the outside :rolleyes:

My question is should I get this done as I have had a damp problem would fibre wall insulation make the problem worse ?

The DPC was injected on the internal walls only and not all of the house

Many thanks in advance
 
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If you have a damp problem relating to a breach of the cavity or a continuously damp exterior wall, then you might want to avoid filling the cavity
 
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If you have a damp problem relating to a breach of the cavity or a continuously damp exterior wall, then you might want to avoid filling the cavity

Thanks for your reply

I am not sure whether the cavity had been breached or not ?

I have a DPC injected internally and assumed my damp was because someone had laid the driveway and patio 4" above the existing DPC.

I cut all of this back and dug down below the level of the existing DPC, then stuck a vertical DPC to the wall using b1tchumen sealed with flashband ( not pretty I know but will get painted) and then backfilled the trench with pea shingle. In the spring I will cut the slabs back and relay them to the level of the shingle trench. I also found a cemented over drain which I uncovered and then created a fall from the shingle trench to permiate into it.

Do you think this would be enough or have I wasted my time ?
 
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If you have breached the DPC on the external wall, then the cavity should prevent dampness spreading to the internal leaf - that is the whole idea of a cavity. However, many times damp at the base of a cavity wall is due to mortar droppings within the cavity

So if the inner leaf was getting damp, then it was either a breach of the cavity, or dampness rising in the inner leaf - or a combination of both. But injection is normally only good to stop damp rising in the wall and not moving sideways across it

Either way, if there is a damp issue at the base of the wall, then the insulation can make it worse or just get soaked and be no use at all

It may be worth investigating within the cavity to see if there is a breach, as you don't want to miss out on the benefits of the insulation unnecessarily.

Take some bricks out and see if it is breached or wet, if not insulate
 
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