Red sandstone/Whinstone leaking wall

[DIYbod]

I live in a 110 year-old house constructed of whinstone with sandstone quoins lintels etc. The locality is subject to high rainfall and gales during winter. My first winter in the house was a shock when persistent wind blown rain drove water through a bay window wall. I ended up with water dripping into my living room over the window lintel. I noticed that cement had been used to repoint the wall previously, and also that the bay wall is only 11 inches thick not 22 inches like the walls of the rest of the house. To address this I attended a natural lime pointing course, and then repointed the wall in natural lime mortar over the summer, taking all the necessary curing protective precautions against rain/wind etc., and then awaited the winter storms for their verdict on my work. Sadly the wall still succumbed to the rain with almost no difference. The following summer I installed guttering over the bay to deal with any rain water dripping from the small bay roof, and resealed the double glazing frames. The following winter saw the same ingress with little difference. I am now intending to treat the area with the Stormdry product as I don't really want to have the wall roughcast. This product claims to be a breathable silane based product. Will anyone who has used this product give me their views on its efficiency and long term consequences for the stone? Thanks.

 

[pinenot]

Stones don't absorb water, mountains are testimony to that, cracks or fisure in and around the stone will, so something else is causing the problem.
May sound a little aloof, but actually quite easy to verify. Next time the internal wall surface is wet drill one of the stones (somewhere not seen easily) somewhere about the centre, after 1/4" or so you will come against dry stone.
Now what's the actual problem, that's the difficult part. In heightened external humidity, internal moisture is possibly a problem. Try running a domestic dehumidifier once or twice in good conditions as a benchmark, mark down the results. Next time the condition arises, run the tests again see what if any difference there is. It may be you need to deal with a bad case of condensation, which can be a very difficult problem...pinenot

 

[mikeey84]

Whilst Pinenots point about mountains is true, and they dont absorb water, some stone is permeable, so the problem could be with penetrating damp.

 

[stuart45]

Stone will allow some moisture through, the amount depends on the type of stone. However, as with brickwork the majority comes through the joints. Heavy driving rain will eventually get through a solid wall. Lime mortar only allows the wall to breathe better, but won't stop the water.

 

[DIYbod]

Thanks for your comments. I agree that the Whinstone is fairly impermeable but have seen a demonstration of how various stones including Sandstone can act a little like blotting paper when stood in water. The bay wall is 75% sandstone and 25% whinstone. I'm uncertain about the extent that this absorbed water would be responsible for allowing the amount of leakage I get once the wall becomes saturated. This usually happens after about 12 hours of wind/rain. During a 6 hour period, I collect about 3 pints from just one window! I suspect it is due to water saturation/ingress caused by rain and wind pressure into both the lime pointing and the sandstone, which is why I want to treat them with StormDry to beef up their resistance to the rain. Back to my original question - do any of you have knowledge or experience of this type of treatment that you could pass on?