Waterproofing Existing Pointing

[drewks]

Hello All

I've got a stone chimney stack that is letting in water and it seems as tho it needs repointing - joints HAVE eroded back a bit and are a bit powdery.

Can you recommend a spray/paint on solution that will stabilise & waterproof as (maybe) a temporary measure till the summer - MAYBE even a permanent job with a bit of luck?! Is it possible to use PVA for this?

I live about a mile from the coast so I guess there ARE salts in the atmosphere.

Any suggestions would be great - many thanks in advance.

 

[^woody^]

The weathering/waterproofing of any mortar joint is the face of it, and once this goes the joint is in gradual decline.

As your joints are "powdery" then there is nothing which can be done apart from repointing. PVA is definitely no use

A temporary treatment could be something like Thompsons Water Seal- which is a silicone liquid. But if repointing is to be done in the near future, this kind of treatment may impact on the adhesion of any repointing

As this is a chimney, which by it nature would be quite thick and have a hollow flue, how can you be sure that the pointing is the cause of the dampness?

 

[drewks]

Thanks for reply woody.
I'm NOT 100% sure that this is the problem but there's nothing else that looks amiss - the flashing is all in tact and ok and the jointwork looks the prime suspect.
The stack is built of stone and where the mortar has eroded a little, I can see that some of the horizintal sections of the stone are actually pointing down as they go into the mortar - it looks to me as tho this is leading to the water collecting on these surfaces then penetrating the mortar.