How to prepare crumbly mortar, before re-pointing.

[Crimea]

What do I need to apply to crumbly exterior brick mortar, before re-pointing?

I have repointed here and there in the past, as I'd like to think I'm a keen and competent DIYer, but I haven't done it where the existing mortar is so crumbly and sand-like.

It is only one course of mortar that I need to fix and it is only in patches along the damp-proof course line of bricks. I think the mortar mix the builders of the extension began with was poor, as they must have changed it for the rest of the pointing, which is fine, right up to the roof line.

Cheers for any help.

 

[Blagard]

You don't need to apply anything. But you do need to rake out the joint deep enough for the repointing. I would suggest rake out the joint to 25/30mm deep before repointing. Can be less if your bed and perp joints are small.