Crumbling mortar of party wall in loft

[marcus02]

I live in a terraced house built around 1900 I think. The walls are solid no cavity.

In the loft the party wall mortar is crumbling away. You just have to touch the mortar and it crumbles to the floor. I think the bricks are quite soft as they are very easy to drill into.

should I repoint with lime or cement based mortar. At some point I may render as it gets very dusty up there.

any help would be appreciated

thanks

[welsh brickie]

I would rake out the brick joints,Paint on a pva solution and repoint the wall.