In article ,
"John" writes:
I have to replace the coping stones on top of a dwarf walk. The area (of
mortar) measures approx 2.4m long by 250mm wide by 20mm deep. A neighbour
tells me it is not wise to do any 'bricklaying' in this cold weather. Is he
correct or is it an old wives tale? When I have been driving around over
the last few days I have seen plenty of housebuilders working. Will it be
OK, or is there something I would need to add to the sand and cement mix? I
do not mind doing it in the cold but I don't want to redo it again if the
bond fails.

It's not the best time of the year to do this sort of thing.
You can get antifreeze to add to mortar mix if you really
have to.

The bond at the top of a wall is particularly important, as
there aren't tonnes of bricks on top to keep the bricks in
place. I would add a small amount of exterior grade (water
proof) PVA to the mix to improve the tensile bond strength
at the top of an outside wall.

--
Andrew Gabriel