Concrete Floor Missing DPC (1800's)

[dirtyh87]

Hello everyone.

I currently have a project ahead of me and have a question about a missing damp proof course. The property was built in the 1800's so will likely not have one (concrete floor), and may not even have one in the walls (sandstone construction). The walls are showing signs of damp (surprising for sandstone, I know!), and have been cement rendered in the past. This cement render will be removed (to stone), allowed to dry and then lime rendered (+ Keim painted), to allow the moisture to pass through the finish (+ some wall vents to help it all along).

My problem was raised by a planning officer - the property is in a conservation area so there's one round every 20 minutes. When talking to him during one of his visits, he suggested that he's known builders to cut a relief channel along the length of the concrete flooring (internally, along the length of the affected wall), down to soil to prevent bridging from the floor to the wall. This made sense and I nodded my head, but having thought about it, I'm not sure how this would be finished without problems down the line.

Would this just be left as a small (I'm picturing 25mm), open channel in the floor (with the flooring covering it)? If so, wouldn't the damp from the earth floor move up into the chosen flooring? Even with a DPM (visqueen), laid onto the concrete flooring before a carpet or hardwood/laminate was laid, wouldn't that just trap the moisture? Surely this would make its way through in a short period of high foot traffic?

Or would this channel be capped with frame sealant or silicone. Surely that's not the way and would defeat the object of cutting the channel in the first place?

The external street level is pretty much at the internal flooring level and can't be played with (conservation), so this is pretty much a loosing battle (which the home owner is aware of), and all of this is merely out of curiosity, but i'd be interested to know if anyone has heard of this being done before (or cares to throw their 2 pence in)!?

Answers on a postcard - cheers!

[Someone-Else]

Could you not wait till next time the planning officer is visiting and ask him? or ask him what it is called / known as?

[dirtyh87]

Yup. I was just interested if anyone from the trade knew of it being done