Stuart Noble wrote:
" They were clearly either cowboys or just incompetent as there would be

no way for trapped moisture to escape thus accelerating the decay ... I
would imagine that pebbledash would be effected in a similar way.


Providing a coating adheres to the surface, and is in itself waterproof, no
moisture should get in in the first place. This is near impossible to
achieve with render because invariably there is a gap between it and the
wall

I am not an expert but I would imagine your comments are assuming you have:

a) a physical DPC to stop moisture rising behind the render
b) no chance of moisture condensing or getting in to say a cavity and
c) no water contained within the wall already before treatment.

In my case a) & c) were certainly not true as the solid 2 foot random
stone wall had been damp for over a hundred years (and still is on the
outside ).

The coating suggested was not a render but a clear proofing agent which
would totally seal the wall thus frost etc would just blow the surface
right off (which had already happened in some areas without any "help").



If you can find the source of the penetrating damp (gutters, down pipes,
gullies, roof tiles etc etc) it might be simple to eliminate it rather
than the symptom.


Penetrating damp is usually just rain hitting a porous wall. You're lucky if
there's an obvious source. If the wall is already painted, or you can bear
to make it so, solvent based masonry paints are very effective IME

Or pouring down a wall keeping it permanently wet maybe which was the
root of my comments?


Alex