Many thanks for the replies.
In response to some questions raised.
I think the old mortar was cement but not entirely sure. (would that make a difference?)
The mortar was raked out to 25mm.
The plasticiser/waterproofer was mixed in water beforehand at proportions calculated from figures on the back of the container.
Since I did this over several days each batch (hand-mixed) yet the entire wall is affected.
Out of interest ( Or becoming neurotic went and checked a little I'd done some years before. Still as hard as rock!
ORIGINAL POST
Three years ago I did some pointing to a north facing above a conservatory. I recently had to get back up there to sort out a leak and then noticed that the pointing had failed. A thin layer had been pushed out at the front and then behind that it felt moist and quite soft. Ironically that’s why I replaced the old stuff. I seem to remember the mix was 4:1 sand to cement and I added some Wickes plasticiser/waterproofer. The only other thing that happened is it was late October and I did get caught by an early frost a couple of times. Was wondering if the cement was off. Any ideas as I don't want to repeat the error.
In response to some questions raised.
I think the old mortar was cement but not entirely sure. (would that make a difference?)
The mortar was raked out to 25mm.
The plasticiser/waterproofer was mixed in water beforehand at proportions calculated from figures on the back of the container.
Since I did this over several days each batch (hand-mixed) yet the entire wall is affected.
Out of interest ( Or becoming neurotic went and checked a little I'd done some years before. Still as hard as rock!
ORIGINAL POST
Three years ago I did some pointing to a north facing above a conservatory. I recently had to get back up there to sort out a leak and then noticed that the pointing had failed. A thin layer had been pushed out at the front and then behind that it felt moist and quite soft. Ironically that’s why I replaced the old stuff. I seem to remember the mix was 4:1 sand to cement and I added some Wickes plasticiser/waterproofer. The only other thing that happened is it was late October and I did get caught by an early frost a couple of times. Was wondering if the cement was off. Any ideas as I don't want to repeat the error.
