On 26 Feb 2021 at 17:21:14 GMT, "newshound"
wrote:

On 26/02/2021 10:26, RJH wrote:
Any recommendations for coating/sealing cellar walls? I'd like to tidy up
the
appearance, and avoid the mess that builds up.

The cellar has high humidity (always 70%+), and water will form if anything
is
left up against the floor/walls, but is basically dry. What looks to be
masonry paint has stuck where the other side of the wall is open to air, but
where there's soil the other side it's crumbled away. The main cellar walls
are made of what look like stone rubble held in place with coarse mortar.

As Clive and Davey say, heat and ventilation are your friends. The
danger with sealing is that it will trap water behind and only a
substantial treatment will hold it back (e.g. tanking, I know of one
basement that was sorted with about a quarter of an inch of pitch,
applied molten, then covered with a sand-cement render).

I don't have a cellar, but I have a rubble-stone cottage built straight
on the limestone bedrock, with a hill reaching 120 metres within a few
hundred metres on one side. Although the road and pavements are drained
effectively, in wet weather the water table is at ground level.

So, at one end of the house I had a *very* wet wall. The previous
owners' solution had been to batten it, cover with polythene sheeting
and then plasterboard and plaster, so that it all looked OK.

The building society discovered damp and required all this to come out,
put in an electric DPC and render with impermeable render. I had to
replace the bottom half of the staircase, a window frame, and a few
joists for the ceiling which dry rot had reached thanks to the previous
"solution". Within a few years the impermeable render was blown from
water behind, and I figured it was not worth fighting over the
"guarantee". My solution was to have all the rendering off, expose the
stonework as a feature and repair and repoint with lime mortar, while
adding a ventilated wainscotting (mounted on treated timber) to the
lower part on the end and one side wall. The exposed stonework above
keeps the wall dried out (there are a few salts to brush off every
couple of years). (Oh, as an aside, this is not penetrating damp, the
outside has been very carefully fixed). Anyone who claims there is no
such thing as rising damp, I could show you photos of it reaching 6 feet
from the floor.

Thanks, and to the other posters. The ventilation isn't that bad - 2 12"
square vents in a 4m x 4m room. But I'm loathed to heat a space with that
level of ventilation, and cutting off the ventilation and heating doesn't bear
thinking about. And however unlikely it might seem, nothing rusts down there,
and even cardboard's OKish for very long periods.

The problems to be solved are appearance, and the constant crumble mess - just
cleared half a bucket of the stuff yesterday - which prompted the post.
Repair/repoint with lime mortar would seem to be the way forward from posts
here. Still wondering if a permeable coating, like a lime wash might do what
I'm after.

--
Cheers, Rob