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Posted: Mon Nov 20, 2017 12:33 pm
by CoyoteRob
Hi - over the last year or so, a couple of parquet flooring blocks in our bay window have started to come up (1939 house). On investigation, we found the screed has started to blow. A surveyor came, drilled holes in the wall and floor and did some tests. The result was a slightly raised level of damp. He blames the block paving being too high (only the edge of the bay window is affected). The original block paving installation (Bretts Approved) has the run off running to the house. The water then runs along the front of the house (to the left in the photo) and into a drain. The block paving and engineering brick levels can be seen in the linked photo (note the line at the top of the engineering bricks is a phone cable, not a DPC sticking out).
https://drive.google.com/file....sharing
The internal floor level is approx 50mm above the level of the block paving. Do I need to lower the level of the block paving and maybe also add a drainage channel - what are the option for a channel around a bay window?.
Thanks in advance - first time poster to this forum.
Posted: Mon Nov 20, 2017 5:21 pm
by lutonlagerlout
Hi Rob
IMHO the block paving is fine
chances are in 1939 no DPM was used in the floor
all old houses have slight damp issues like this
(mine does similar bay 1922)
a lot of it is to do with lack of insulation and ventillation
so when warm air meets cold air it condenses ,runs down the window and causes damp
if you have the heating on try to keep a window slightly open and dont try clothes on radiators
sounds stupid but this is the commonest cause of damp
also check for leaking gutters
cheers LLL
Posted: Wed Nov 22, 2017 8:13 am
by ResiblockBoss
I agree with LLL.
I also think you may find a dehumidifier to be invaluable.
Posted: Wed Nov 22, 2017 9:35 am
by CoyoteRob
Thanks both for the replies.
The surveyor is a proper expert - specifically in damp - even lectures on the topic and is called as an expert witness in court cases. He is highly critical of most 'damp proof course' sellers and says ( as you also identify above) that most damp is caused by condensation and not rising / penetrating damp. However in our case he says it is rising damp we have (he has done a salts analysis test etc) , and is most likely caused by the block paving being too high / water from the drive being allowed to run to and then along the external wall. This seems to concur with info elsewhere on this website which shows various options for drive levels against DPC. I'm just trying to find out what the best option is for modifying my current drive.
Posted: Sun Nov 26, 2017 9:43 am
by Tony McC
I can only see one photie in your link.
The only way to recommend a remedial plan of action is to have the pavement assessed, so that the levels, the drainage outlets, and the sub-structure can be understood.
It could be that a simple linear channel outfalling to an on-site soakaway would do the trick, but without knowing the site, this can only ever be guesswork.