concrete floor

[plasticpigeon]

It seems to me that there are two things that people into conservation believe that don't sit easily with one another. One is that impermeable solid floors make the ground below them wetter than if a permeable floor was laid (which seems logical), increasing the risk of the bottom of the walls becoming wet. The other is that rising damp is either a myth or very unusual. If the second point is true, then surely it doesn't matter if masonry walls are built on or adjacent to damp earth if that earth is below the finished floor level.

 

[Keith Bowman]

If one wishes to believe that damp cannot rise through material such as a soft brick, then one also has to believe that candles and oil lamps will not work! The real question is how far can it rise in any given set of circumstances.

 

[88v8]

...that rising damp is either a myth or very unusual.

Hobnob... cuppa... QED...

Ivor

 

[Flyfisher]

I don't think a concrete floor is totally impermeable though, just a lot less permeable than a limecrete one.

If concrete was truly impermeable then there wouldn't be any need for DPC layers in new builds would there?

 

[Gareth Hughes]

 

[El Greyo]

tsk, they really could do with a french drain.

 

[JHD]

Gareth, at risk of sounding terribly ignorant, but where's that house? Looks awesome.

 

[Flyfisher]

Oxburgh Hall, Norfolk. I'm not usually so knowledgeable but as we're only about 8 miles away it would be slightly embarassing not to know it. :wink:

http://www.nationaltrust.org.uk/oxburgh-hall/history/

 

[Gareth Hughes]

The point is, it's soft, old brick, and has been sitting in a pond for 500 years. If the hobnob analogy was correct, even allowing for the ventilation it gets, it should be soaked all the way up to the wall plate. I can see damp patches where the rainwater splashes into the moat from a height, but nothing much else.
Capillary action does exist, and there are heights above which it cannot sustain the weight of water it can pull up. But "rising damp" as a catch all term is lazily and wrongly used in 99% of cases to describe a problem that is no such thing.
As for concrete floors (especially over a sheet of plastic), all the penetrating ground moisture that in traditional construction would evaporate across the whole, breathable, floor surface in quantities that are large when considered overall but tiny when one considers any given patch of floor, is unable to do so creating permanently wet conditions underneath and an increase in the amount of moisture being pushed to the edges, which may then show up in the lower part of the wall.

 

[88v8]

...it should be soaked all the way up to the wall plate.

Exactly. See, they couldn't even get that right

As for concrete floors....an increase in the amount of moisture being pushed to the edges, which may then show up in the lower part of the wall.

The perimeter of the concrete floor is our sitting room was so damp that the Gripperods had rotted. At least is created a habitat for the woodworm, which I cruelly evicted.

Ivor

 

[andrew gayton]

The very building I suggest that people look at in such arguments.

 

[paddytt]

Where on earth would Propotec drill their holes along the outside of that...?!

 

[JohnB]

I posted these two views of my concrete floor in another topic recently, showing a cross section through it, and a wet bit at the base of the wall under it. The bottom of the walls are wet, not helped by a concrete path at floor level outside along this wall. The floor level is also a bit higher than I think it was originally. So I tend to agree that water under the floor finds its way to the walls. I didn't get an answer to my question, so if anyone could help, it's here http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14132.