How to investigate Vertical DPC in solid 18" wall

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Hello again chaps, You've all been very helpful in the past.

I'm a director for managing company for a block of late 60's flats where the walls are solid.
There are 2 adjoining flats on the ground floor on sloping ground where the higher flat has built a wooden deck unofficially. The lower flat is set forward at the back from the other by about 2metres. The deck and its brick structure underneath has caused damp in the lower flat along that wall where the decking runs off. No damp protection was built at the end of the deck.
A Expert witness surveyor has said that the vertical damp proof membrane is probably missing but we think otherwise.
My question is,
If we get the decking removed, can we drill through the 18" wall to find the membrane? How can we investigate whether it is there or not without making a very big hole in the wall?
Please help if you can?
Penny
 
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I can't quite get my head around the layout. if we extend the party wall backwards. The lower flat is set backwards (?) from the back of the upper flat, giving the upper flat a corner and they have used this as the corner of their decking?
You say its a 1960s building with 18" thick walls, so is it reinforced concrete? I would have though that the options are either an external DPC of applied bitumen or internal tanking of bitumen. The latter needs to be allround the internal faces including power points etc. So I would have though some externally applied solution would have been used. So any fixing for brickwork/woodwork below ground level could have pierced this layer leading to water ingress. Likewise if the ground level has been built up above the waterproof layer this could cause the damp problem.
I think the first thing to do is to find out how the original waterproofing was done. Digging a hole up against the side of the building should expose any external plastic sheeting/bitumen/waterproof rendering..? then make sure everything is cleared down to this level - soil, woodwork, brick piers. . . Then finally water seal any holes found in the layer due to "illegal" fixings.
Frank
 
Sorry not easy to explain and no idea how to draw it on here. It is a 9" solid wall, not 18" sorry. Looking at the back of the flats where the decking is, the left hand lower flat is set forward by about 2 metres. The decking is to the right of that 2m return at a higher level. It is on that corner a that sticks out and along the 2metre return where the damp problem is. Would we be able to find a vertical dpc in that 2m return? Hope that helps.
Thanks
 
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I cant see the relevance of a vDPC in the context of this decking situation. This type a DPC is specific with a specific function, and one wchich would not relate to any decking.

So what is your expert actually refering to and what probelm is it supposed to be preventing?
 
Hello Woody,
We intend to remove the decking outside completely so there is no penetrating damp from that.
The survey was for the damp inside the lower flat in the wall where the decking abuts. There is some damp but not a lot in the higher flat. The surveyor's report said that there was probably not a vertical DPC in the party wall between the 2 flats. We need to check if it missing or not. How do we do it?
We don't intend to tank the lower flat as that is the leaseholders job. Hope this helps.
Penny
 
Sorry all I don't think I've made myself very clear here so will close this post and try again.
Thanks for your time.
 
I suspect that your expert is not really one.

There will not be a vertical DPC in that wall because it would not be possible to have installed one, and one would make no difference at all to damp from decking.

The only DPC that would make the slightest difference would be a horizontal tray. This would be difficult but not impossible in a 9" wall. And it would certainly be evident from the removal and replacement of bricks.

No need for a new thread, I know what you meant, but it's your expert that is confusing things. And I wonder if his other conclusions are correct.
 
Here we go.

The main pic shows what your expert probably means but it's not practical.

The pic in the circle is a more practical solution with a quality water repellent brushed onto the wall.
 

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