On Thu, 19 Aug 2010 13:55:43 +0100, The Natural Philosopher wrote:


All damp control is a balance between keeping the water out, and letting
it escape if it gets in.

Since the two solutions are normally diametrically opposed, this gives
rise to conflicting advice.

Breathable shower proof coatings are perhaps the best of both worlds

Yes, shift the equilibrium towards less wet.

In general you want to waterproof excessively wet areas (areas subject
to driving rain or standing in wet soil) , but let more sheltered areas
breath.

This leads directly to modern ways to deal with damp: High quality
engineering brick below ground with strong impermeable morytar, so that
water is unable to penetrate the wall and frost spalling below damp
proof is very unlikely.

Mine is just 2 courses of blue bricks, which I prefer to a DPC only. Every
Autumn I brush the walls to about 4 - 5 courses up to remove any dust; also
keep ant-heaps etc. cleared away.

Then a DPC, that limits the rise of the ground water, and more or less
making sure that walls are overhung by eaves and those are guttered, to
take water away from the walls. Also no paving near the house that can
cause splashing onto the wall above DPC. In addition, no flat projecting
surfaces like drip boards above windows, as these will act to collect
water. These should be sloped.

My eaves are small front and back and none at all on the gable end.
The concrete path runs adjacent to the house along the SW wall as the
'front' door is in the end (side) of the house - can't do anything about
that.

Its very rare to get driving rain IMMEDIATELY followed by a heavy frost.

So provided the rain soaked brickwork can lose its wetness in a day or
so, that's generally enough to avoid frost spallation.

Or ensure that the brickwork doesn't get saturated.

Areas where water collects..bases of parapets or internal corners (in my
case window drip boards) may need treating LOCALLY.. All that consists
of is filling the voids in the brickwork with something else, so water
wont soak in.

In my case spallation was confined to three areas, Working out WHY there
was instructive.

All were on the north west side in deep shade. the direction the rain
comes from and where the sun don't shine..

Two were directly above lead faced sloping drip boards. One might assume
that water ran down and collected in the base of the wall above the drip
board...

The third was directly above where I had carelessly left a scrap
horizontal slate covering the gravel surround of the house. Water had
bounced off it and saturated the wall. I removed the slate, problem when
away.


--
Peter.
The gods will stay away
whilst religions hold sway