Repointing patio slabs: failed after frosty winter

[mike004]

Last summer I repointed some York stone patio slabs. I used Wickes ready-mixed pointing mortar, as I didn't need a lot of mortar for this job.

After a frosty winter, the repointing has failed. It has turned grey and crumbly. In some areas it is practically jumping out of the joint!

What's the secret to repointing that will last?

Mike

 

[tawelfryn]

I always use a "wet mix" ie the same consistency for laying of bricks/blocks, maybe a little drier. Its a bit more fiddly, because of the risk of staining. Pushed down and compacted into the joints, then jointed with a half round jointer, I find it is a more secure joint, than the other methods people use with a semi dry/dry mix. With these methods there are "voids" in the mortar, penetrable by water, which freezes, and then the joint blows.
So like I say use a slightly drier than normal mix something like 4.1 make sure compacted right in with your jointer, smoothed off to make a "seal" on the front of the joint, shouldn't be a problem.