Sandstone Wall Repairs

[Skirlie Dumpling]

Hi, newbie hoping you can help.

I own a Sandstone Georgian property in a seaside town. The back of the property above the downstairs windows leaks during storms (needs heavy rain and wind). We think we've narrowed this down to the badly weathered stone around the windows above (there are visible gaps). I've consulted a few local stonemasons and am very confused as they all recommend a different approach to repairs. The options are:

1. Rebuild the windows using a sympathetic lime (lithomex?) product. Pick out and repoint the surrounding brickwork using lime. Sand(?) the current stones back so there is no crumbling. This stonemason says they are thick bricks, and as they don't need to look perfect, he wouldn't use any form of render.
2. As above but using lithomex to rebuild out the crumbling stones.
3. Completely rebuild the windows using new (sympathetic) stones. Pick out and repoint the surrounding brickwork using lime. Use a combination of new stones and lithomex where needed.

Apologies if 'sanding' the stones isn't the correct term. They explained the process but I'm new to this.

What option is correct? They quotes are very different, but cost isn't the deciding factor here, we want to do it right.

Thanks in advance!

 

[Glenn586]

Best off whacking some photo's up. Too difficult to give an opinion on something that one can't see.

 

[Skirlie Dumpling]

I’ll try and take some tomorrow, but here’s an old one. The timber sashes have since been replaced (with new timber sashes). Some of the more obvious gaps have been filled already, so we don’t need to pinpoint the leak, we’re pretty sure we’ve found it through a process of trial and error, but everything now needs to be correctly repaired.

 

[aockenden]

Lithomex? I just looked it up. Looks like some lime-based stone repair product… and they want to use that for bedding or pointing mortar during a total rebuild of the reveal? Either you misunderstood that part of their description to you or they’re doing the usual tradie crap of latching onto yet another branded product to save them having to actually deeply learn the materials they are working with and mix their own mortars from base ingredients.

Pics definitely needed. I had to partially rebuild 2 of our stone window reveals, one of which was causing leaking down into the window below it, which sounds similar to your situation.

Check your sill level. Ours was (and still is) sloping back into the building. It needs to slope down away from the building to avoid redirecting rain water back down into the stone wall. Then the other big improvement which I’ve made was to lime render the interior face up of the stones within the reveal as shown in this pic. It bridges the gap between the window frame and the surrounding stone. That render has stopped 90% of the dripping problem. I expect correcting the sill level will stop the last occasional errant drip we get coming into the window below during heavy driving rain events.

 

[Skirlie Dumpling]

Lithomex? I just looked it up. Looks like some lime-based stone repair product… and they want to use that for bedding or pointing mortar during a total rebuild of the reveal? Either you misunderstood that part of their description to you or they’re doing the usual tradie crap of latching onto yet another branded product to save them having to actually deeply learn the materials they are working with and mix their own mortars from base ingredients.

Pics definitely needed. I had to partially rebuild 2 of our stone window reveals, one of which was causing leaking down into the window below it, which sounds similar to your situation.

Check your sill level. Ours was (and still is) sloping back into the building. It needs to slope down away from the building to avoid redirecting rain water back down into the stone wall. Then the other big improvement which I’ve made was to lime render the interior face up of the stones within the reveal as shown in this pic. It bridges the gap between the window frame and the surrounding stone. That render has stopped 90% of the dripping problem. I expect correcting the sill level will stop the last occasional errant drip we get coming into the window below during heavy driving rain events.

View attachment 15936

Thanks. All three suggest building out the sill. Two want to use a render like you have done above, and one wants to rebuild using sympathetic bricks rather than using render.

 

[Skirlie Dumpling]

I've clarified a bit:

1. Rebuild/render the windows using a sympathetic lime-based product. Pick out and repoint the surrounding brickwork using lime. Sandblast the current stones back so there is no crumbling. This stonemason says they are thick bricks, and as they don't need to look perfect, he wouldn't use any form of render.
2. As above around the window, but using lithomex to rebuild out the crumbling stones so they look like they did 200 years ago. No sandblasting.
3. Completely rebuild the windows using new (sympathetic) stones and lime mortar. Pick out and repoint the surrounding brickwork using lime mortar. Use a combination of new stones and lithomex where needed.

 

[fernicarry]

I had some of the sandstone quoins on this house repaired with a product that sounds like what they are suggesting. They were quite badly eroded and, well, sandy. It worked fine, but its obviously a repair because its smooth not dimpled and the colour match leaves something to be desired. New stone would of course look better but I imagine that's in a totally different cost bracket and like they say from a structural pov what's there will still be doing a perfectly good job of holding the house up.

Sand-blasting sounds way too aggressive but they might mean that in a generic sense using a more appropriate media. A house near us had a paint covering removed with glass media blasting and the sandstone details (its almost identical construction to us) looked very good afterwards, far better than ours actually (did the paint protect their sandstone? Shirley not..). I understand its not cheap however...

True there's not much of an overhang on that sill, but it was obviously built that way. The problem I usually encounter is water being blown between the stone sill and the wooden sill which then tracks down internally. When I fit new sills now I go to quite extreme lengths to try to prevent this.

I'd get the pointing sorted and repair the stones around the window reveals to give a good sound surface to seal the window frames against. The traditional way to seal around the window is with burned sand mastic. I don't find that to be sufficient so I use modern mastic and then put the traditional stuff on as a decorative detail afterwards. Some gun foam has been known to find its way in as well... With timber frames you're really up against it due to seasonal movement.