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There is a small patch of what looks like damp on the plaster of the downstairs bathroom wall. I suspect that it is slight damp penetration caused by the recent unusually heavy rain.

The reason I suspect this is that the rain has been off now for a day and the bricks outside on that wall are really damp. They look as if they've been given a real soaking (which they have since this is the windward wall).

I think this will be an infrequent occurrence but I might consider sealing the bricks on that wall anyway?

What is the best way to do it, or the best clear(ish) sealant to use?

You could try Thompsons (which is really a watered down pva) but charges for the privilege. I have for some obscure reason had much success over the years with Isoflex clear primer. The downside is the gloss/shiny finish. A property I did a couple of years ago is still not affected by the rain and have subsequently coated the 3 or 4 course below the DPM on my own property. It has worked a treat.

I suppose for a more permanent cure you could consider injection treatment in this area. Is this the only place? Have you run a meter round teh walls?

Mike

injection treatment is to cure damp risning from the ground, and if this is being caused by constant rain may not be effective.

I would use weathershield, a clear product that will certainly help if the problem is how you describe.

It's clear and applied in two coats with a brush, very easy to use.

Thanks guys,

I'll check these out...

STOP PRESS! After reading the info below (and some from an American site) I am re-thinking the whole idea:

From http://www.brick.org.uk/about-us/faqs.html

We believe the use of sealants and water repellent treatments on brickwork is totally unnecessary and take the view that properly specified and built work performs perfectly satisfactorily in resisting water penetration by wind driven rain, without their need. Brickwork inevitably gets wet in rainy weather and dries out later. This is the way it works and has done so for thousands of years.

Brickwork is a very cost effective facing material that retains its good looks. Many people feel its appearance actually improves with age and requires little if any routine maintenance for many decades. Some repointing of mortar joints may eventually become necessary in very exposed parts of the structure, e.g. chimneystacks.

The application of a surface treatment sacrifices this major advantage. Regardless of whether they are matt or 'invisible' finishes they change the natural weathering of facing brickwork, sometimes causing a patchy appearance. They are not permanent treatments, deteriorate over time and therefore would have to be reapplied at some date in the future. This results in an unnecessary maintenance liability and expense.

Furthermore the use of sealants on brickwork can cause problems. They can reduce the rate of evaporation of any water from the wall and depending on exposure conditions, particularly if it has full fill cavity insulation. The quantity of water in the wall may increase because the surface drying is inhibited by the sealant on the face. In certain situations it could be enough to saturate the brick sufficiently for frost attack to occur resulting in spalling i.e. when the brick surface breaks away exposing the soft and porous core of the brick.

If there were problems of water penetration through the walls, a surveyor or builder would be able to identify and correct the cause of the problem which is likely to be a fault in the detailing or construction of the brickwork. Applying a sealant or water repellent treatment to the brickwork is unlikely to correct such defects.

Properly built brickwork will give many years of trouble free service. Waterproof sealant or water resisting treatments has no place as the routine treatment of brickwork.

ok