Render on random stone building in South Wales


Postby jTeez » Wed Sep 28, 2011 8:41 pm

Hi all,

I know damp can be a seriously hot topic but just trying to firm up some ideas.

I am modernising an end of terrace (at the bottom of a hill) stone walls (450mm thick, probably rubble filled) 3 bed in Wales. I'm living there at the moment. No Heating, earth floor in one room, crittle windows, it's fun :D

Damp is not too noticeable because there's no heating/hot water but I know it will be... There's all kinds of problems that will be dealt with from down pipes going nowhere to concrete gulley/drains that are messy and leaking.... Lot's of woodlice crawling around...

Anyway... Almost all the houses here have pebble dash render with a belling at the bottom then smooth render set in (thinner than the pebble dash) below to the ground.

Surely this is bad! I've just down some exploratory digging/hacking and found a single even course (assuming it's a slate type dpc), and an entire eco-system living behind the cement render, that is approx 180mm below the approximate final interior floor level. Quite convenient because having to take out that much to put a slab in the room with the earth floor so will tie up with DPC quite nicely.

So scene set. Surely, on the outside, the stone should be exposed and not rendered from the about 4" above the DPC and not all the way to the ground (bridging the DPC) on the outside like all the hundreds of other houses around here.

Hopefully that made sense :D

If we get a simple response we can move on to dpm detailing around existing slabs ;)
jTeez
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Joined: Fri Jul 08, 2011 5:31 pm

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Postby welsh brickie » Thu Sep 29, 2011 11:27 am

you cannot effectivly cure damp in a random build stone wall all the way through the wall.The pebbledash render and bell bead is to try and reduce penitrating damp as much as possible.
the only way to stop damp effectivly is to tank the walls with a buitumin paint,to do this you need to hack of all the lime plaster internally to a height of at least 1 metre above dpc height,And seal it with pva and then a 1st rough coat 0f 4:1:1 sand,lime,cement then paint the walls with at least 3 coats of buitumin and then throw sand on the last coat to aid grip for the final render and plaster finish.
With the floor in your house the floor consists of a sand&lime mix and terracotta tiles,Damp also is a problem.There are 2 methods
1.dig up the entire ground floor lay dpm and insulation then concrete then screed to finish.
2.Lay hot ashphalt over the floor,this will stop any damp whatsoever.This is done by a specialist company and is completed in one day.
I personally prefer method 2 its less costly,less mess and stops damp efficently.
welsh brickie
Posts: 1958
Joined: Sat Apr 12, 2008 7:54 am


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