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scudder scudder is offline
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Location: Bournemouth
Posts: 3
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Quote:
Originally Posted by The Natural Philosopher
scudder wrote:



Thanks for this. The position and guage of the dpms was put in the spec
at the request of the BCO so I'm puzzled now too. Its the second project
I've done like this. The pipes are insulated and layed in accordance
with the heating engineers advice/spec.


Oh well. As long as you know what you may be in for.

I understand that the slab is in contact with the 'wet' ground in other
projects - looking at BS8023/8024 seems to confirm this. I suppose
logically water shouldn't damage the concrete (provided its mixed
correctly) but still wonder about the A193 mesh reinforcement.


Concrete works as well under water as above it. Steel ereinforciong mesh
hepls prvent buckling and cracking. It won;t rust either - needs air as
well as water. As long as cement rartio is high enough the concrete is
relatively iompervioaus to aoir AND water both.

Screed however, mixed with less cement is full of holes. Screed can and
does absorb water and needs tio be above teh last DPM.


Also, if
the confined moisture might cause mould, humidity and/or smell if it
leaches out through the inevitable gaps where the upper dpm meets the
dpc in the wall.


No...inevitably there is always a gap in the DPM one way or another, but
as long as the rate of drying exceeds the capacity of the underlying to
generate moisture you are OK and mould won't form. You need a bit of air
for most moulds as well, you know.

DPM is not an absolute thing - its more about keeping the relative
humidity of evertything below the critical 100% at which actual water
forms, or if it does, making sure is where it doesn't matter. Like under
a DPM.


Maybe I'm being paranoid ....any other comments welcome!

Thank you, that info is very much appreciated.