Porous brickwork and treatment

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

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.

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.

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.

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.

Reply to
The Natural Philosopher
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Just read any SPAB damp related pamphlets for basic info. If you want it explained more, check out the periodpropertyuk forum. Its not a trivial subject though.

There are plenty of people making common wrong assumptions, a classic one being that damp moves from the outside of a house inward, and thus coating the outside helps. In fact overall vapour movement is from inside to out, and coating the outside increases water content in walls by blocking evaporation. There are several common misperceptions on this topic.

NT

Reply to
Tabby

It soaks in and coats the particles, reducing water absorption and evaporation. But when applied repeatedly it builds up, blocking pores, forming a coating. It just isnt a useful part of damp control.

NT

Reply to
Tabby

Yes, shift the equilibrium towards less wet.

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.

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.

Or ensure that the brickwork doesn't get saturated.

Reply to
PeterC

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