In my house (England) there are multiple holes from old pipes in the walls. The walls are made of red bricks and the house is approximately 70 years old. I want to fill in those gaps - also in some of them there are still pipes, but they are loose, so the space around the pipes also needs filling in.
Now, I understand that because my bricks are old, a modern, strong mortar might not be suitable as it might crack the bricks - is that so?
I was thinking of filling in the holes with expanding foam and only finish off with mortar on the outer surface, like 1/2" deep only. Is that a good idea? Is the expanding foam safe for old bricks?