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Outside my flat there was a flower bed against the external wall . At some point someone had 'tanked ' the property with a concrete render and bitumen paint.
This had , at some point pulled away from the wall leaving a gap of few mm , for a few meters.
Over the weekend I dug out the flowerbed to trench out to the footings, and smashed off the render. Some brick faces came off attatched to the render at this point.
There was also a crack in some mortar where a drain grid was situated and this was leaking through a small brick casement and down into the old flower bed, and this has now been fixed.
I intend to use that fabric to keep the mud approx 40cm from the house and back fill with 20 -30mm shingle to allow any rain run off to soak through , can put a fall on the base with a 90' to help any deluge water move away quicker.
So I have sorted the issues with the causes of the bricks failing, what I now have is 10 odd blown bricks , 4 or 5 courses below the DPC ,which need addressing
The interent says cut them out individually and puddding in new ones, which seems expensive and very time consuming, plus risk of movement .- load bearing outer cavity wall C 1935 )
2 builders I spoke to reckon use something to bond the blown faces and re skim with render , and paint to match, but I have no idea what to use. PVA , SBR , Silicone .????
I appreciate this is not the perfect way of doing this but i dont live in a million pound listed building and its not every brick, just randome ones which I guess were not as strong when installed.
Best solution is to cut out the individual bricks and replace.
Risk of movement is miniscule for removing individual bricks.
Because it's below DPC level anything that you try and bond on will, most likely , fall back off in pretty short order as the substrate fails further once the winter rain / freeze / thaw cycle kicks in.
If you do want to just patch it up you might be able to source matching brick slips.
I'd use a slurry of SBR, cement, and a splash of water. Add a bit of sand, and mix not as wet, if its a big gap to fill.
The only value of trying to reattach the brick faces would be to maintain appearance, but as you say they're going to be rendered and then painted there seems little point in attempting to do this, or trying to cut out whole failed bricks. If it were me I'd dig out the individual failed bricks with a hammer/chisel until you get to something solid, then patch the resulting holes with a small aggregate trowelable concrete mix (with a bit of SBR mixed in to improve the bond), then render/paint as you were intending.
By the way - what probably caused the brick faces to fail was water getting into the bricks and then freezing - cyclic freeze/thaw will gradually generate small cracks > failure. As you probably can't avoid the freezing all you can do to stop it happening again is keep the masonry/repair as dry and well ventilated as possible.
These building threads remind me of the '70s car body work repairs, cataloy filler a pea of hardener to a golf ball of paste file it down and paint it job sorted looks great from a distance. If your diff was whiney sawdust did the trick job sorted next owners problem.
noodles?