Spalling external bricks

[ntl142]

I've got some spalling external bricks and need to do something about it. I've been in the property 2.5 years now. On day 1 there was evidence of a very slight amount of previous spallation. It's been dormant until the last couple of weeks, and recently there has been a lot more coming down. 75% of what you can see in the photos has been in the last few weeks. The house is in Scotland. I know what the cause of it is (expansion of freezing moisture), but can't help thinking that the root cause is moisture getting in from somewhere, rather than just the rain on the wall - why is it localised to such a small area?





The spalled bricks are all in the top few courses, none lower down or anywhere else. It's the kitchen external wall, facing east. There are concrete slabs/capping stones on top of the wall. Behind this is a flat roof, the top of which is about 4 or 5 courses down from the concrete slabs. Is this a coincidence? Is water getting in from behind? Soaking down from under the slabs? Or is it just normal?

Either way, what do I do about it? There are coatings like this around, but I've no experience of them - any good?

https://www.watco.co.uk/masonry-waterproofer-1.html

Thanks in advance.

 

[Hpd]

What type of flat roof is it? And what's it's condition?

 

[ntl142]

Felt on ply (or whatever wood it is), with gravel/chippings on top, in reasonable condition. The felt tucks into the bricks a few courses above the level of the roof. I'll get a photo and post it up.

 

[^woody^]

Parapets are very exposed, but I suspect that those copings don't have a wide enough drip causing rain to soak those top few courses, which then freezes.

The face of a brick is always susceptible to blowing, but that does not mean that the rest of the brick is necessarily bad and will follow suit quickly.

To avoid lots of work replacing them and the unsightly result, consider coating the whole parapet and copings with a quality silane water repellant (not silicone). Changing the copings for something better (wider) would then be optional but beneficial.

 

[ntl142]

Here are some photos from the reverse side of the parapet. I'm wondering if the problem is worse in the top few courses of brick because they will be significantly colder than the rest of the wall (not heated from inside the house) and therefore more likely to experience freezing conditions.

I can't change the temperature of the bricks, but can reduce moisture. Woody, thanks for your suggestion of a silane water repellant. Do you have any recommendations of a specific one to use? Perhaps a simple gutter is needed, joining the downpipe on the corner?