Wet walls

[Socksitis]

HI, have a serious problem with wet interior walls. So the house faces into the weather (south-westerly). Recently had the concrete render removed from outside and had the stonework pointed with lime. These are granite face stones. on the inside the walls were plastered with pink plaster some 25 years ago. One part of wall I have replastered with lime. I can see there is moisture in this part of the wall, but it does not feel wet, but is subject to black spots and mould - made the mistake of putting plastic paint on it. plastic paint on other walls is peeling off because of the wet.
Picture a typical house, four windows and a porch in the middle, that is what we a re looking at here.

There is a porch in the middle of the front wall and I think there may well be issues with the leadwork where the porch roof joins the wall and also where the upright framework abuts the front wall, both potential sites for water ingress.

So inside, there is an issue with damp rising up the front wall of room one as this has a stone floor. It has rotted out the carpet and the skirting board. We have dug a ditch outside of this area to see if we can put in a drain?

The water/moisture is apparent on most of this front wall, all the way up to the ceiling.

Room 2 downstairs on the other side of the porch, this is even worse. Floating floor in this room, still the inside of the front wall is seriously wet. This front wall on the inside is wet from top to bottom. The ceiling has an area of damp adjacent to the front wall.

Upstairs, things are very different, there is no moisture at all on the walls.

So this leads me to some conclusions:
There is an issue with rising damp, but by digging a drain this may help?
There is an additional issue with water ingress from a certain height, say from the bottom of the upstair windows down. Perhaps it could be no drip line on the underside of the cills? Perhaps it is the small groove underneath the wooden window frame (new) that should be filled with lime render and isn't?

Maybe it is the front wall that is just not keeping the water out by stone and pointing? Do I need to take off the pink plaster inside and put lime plaster back?

But, this is not damp, this can be just about running water on the walls.

Any thoughts would be very much appreciated.

 

[TheForge]

Black mould normal requires fresh water to develop and won’t normally tolerate salts which suggests these areas are subject to condensation not penetrating or rising damp, likely forming on surface of the modern impervious paint.

Many will argue rising damp doesn’t exist but either way I doubt capillary action would draw moisture all the way to ceiling level except in exceptional circumstances and certainly not in granite which has limited permeability.

Pictures would help but I suspect this moisture is either penetrating through the joints or entering from above and tracking down the wall, trapped behind the impervious paint.

My first course of action would be to try and remove all the modern paint coatings and then reassess.

 

[Abi Cott]

I agree that black mould forms on fresh water, but this can be caused by penetrating damp rather than condensation, IF the water is penetrating fairly rapidly and therefore not picking up much by way of salts on its way in.

I'd be looking for leaks first. The windows, the porch and any radiators conveniently placed under those front windows or other plumbing in the vicinity.

 

[TheForge]

A colleague of mine has recently completed a study into the drying response of lime-mortar joints in granite masonry after intense rainfall, based on church towers but possibly relevant here.

https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-019-0277-7

As Abi says finding any points of ingress is key but equally important may be the mortar mix and aggregates used in previous repointing. Not all lime mortars are equal and poor quality workmanship in repointing, or the use of less permeable aggregates (such as the grantite sand used at Castle Drogo in Devon) can also create issues with slow evaporation out of the wall.

 

[CliffordPope]

You imply but do not say that this problem arose after the exterior render was removed?
If so, it strongly suggests water getting in from outside. Perhaps the old render was not so bad after all?
In my observation, dampness from any source causes cooling as it evaporates, and this then causes further condensation, so you end up with condensation whatever the primary source.

 

[MatthewC]

You imply but do not say that this problem arose after the exterior render was removed?
If so, it strongly suggests water getting in from outside. Perhaps the old render was not so bad after all?

I agree - even concrete render ( :evil: ) had a reason to have been applied. I'm not sure if NHL render would be sufficient to stop driving rain etc.

There is one other point - I haven't seen any mention of the ground level in the front, nor of the quality of the rainwater goods. You need to have the ground level well below the floor level inside and also outside to avoid anything solid like concrete or stone flags which go right up to the wall (this causes splashback so that bottom of the wall is often very wet).

 

[CliffordPope]

We had exactly this situation. The concrete (?) stucco was bowing away from the wall, several inches in places, and some water was getting in. We had the whole lot removed, revealing a nice stone wall with red brick edging and shallow arches over the windows and doors. We had all the stonework and bricks carefully cleaned of old mortar, and the wall repointed by a firm of specialists using the proper lime mortar. The newly-revealed stone and brickwork looked beautiful.
But come the first autumn storm and drenching rain poured straight through the mortar - you could see the outlines of the stonework on the inside, damaging a lot of period wallpaper.

We got the firm back and they advised treating with chemical sealant. A few gallons of Wickes No-nonsense sealant and the wall is now bone dry. I don't understand how a "breathable" wall is supposed to expel or resist water that is wicking straight through porous mortar - it seems obvious now with hindsight that an old wall needs a damp barrier of some kind - render, or a chemical equivalent, or as suggested previously on this forum, slates or corrugated iron. Lovely!
It's not damp in the air, it's rainwater blown in sheets running down the outside of the wall.

Condensation is another matter. The walls are solid, thick and cold. The more you heat the house the more water vapour the air holds so the more it condenses. We could totally eliminate it by having no heat whatsoever and leaving all the windows and doors wide open in all weathers.
But we have found the sensible solution is extractor fans in bathrooms and kitchen, and a dehumidifier on each floor.

 

[andrew gayton]

as with any stone walling, the external pointing / internal plastering is one thing, but the core of the wall may well be full of voids and fissures which will allow easier passage for moisture. With my own flint house, i had to gravity grout the core in a number of places to achieve overall solidity (using a lime grout). I am firmly of the view that vapour permeability is key and that the mass of the wall should be sufficient to prevent ingress of water from the outside. i am also of the view that 'rising damp' does not exist - what may appear to be rising damp is usually associated with capillary action through impermeable layers, ground level disparity or horizontal passage of moisture due to core voids.

 

[Socksitis]

Thank you so much to all who have responded, what an amazing network!
It is so comforting to know that our house is not alone with this problem of running water inside when it rains!

As to ground level, on one side of the porch the front room has a stone floor and we have just dug a trench (moat comes to mind) outside of the wall so we have nothing up against this wall, we will see what happens when it rains.

I have ordered some stormdry masonry protection as has been suggested, I will try this and see it if works. It can only be water coming through the walls. We will add some additional lead work to the porch roof, just to make sure it is not that, but as my builder friend said, that cannot cause such an extreme problem. We will also add some lime to just under the window boxes and add drip lines to underneath the cills. Guttering and facia is all relatively new and new down pipe and I know the drain is clear.

Rising damp - interesting that some do not agree with it, but if we clear any earth touching the outside, treat the wall with stormdry product, then all should be well.

Interesting how a house was well built to withstand the weather, I wonder if this would have been slate hung? Would the render and the lime work and lime mortar internally become too weak over the centuries to be able to cope with the weather? I don't believe people who say 'it must have been rendered for a reason' when this house was built it would have been waterproof, so what changed? Can only be the porosity of the internal part of the wall that has weakened with age?

Just thinking about how much cleaning of the substrate is needed before application of the wonder product?
Any thoughts?

 

[TheForge]

My thoughts would be don’t!

Stormdry is a proprietary barrier solution to reduce the permeability of your wall. It’s the antithesis of why you pointed your wall with lime and a very muddled approach.

If moisture is entering the wall through defects or capillary action it will now only be able to effectively escape inwards, exacerbating the evidence of moisture on your internal decorative finishes.

Further, you say the outer skin is granite, from what I can read of stormdry it’s a cream that effectively blocks the ‘pores’ of masonry units to reduce permeability. I wonder how effective this will be on granite anyway.

You will be mixing two approaches here and I suspect the net result will be further issues.

 

[andrew gayton]

I wouldn't use or advocate the use of any waterproofing agent - even if they state that it is 'breathable'.

 

[Kearn]

.
Rising damp - interesting that some do not agree with it, but if we clear any earth touching the outside, treat the wall with stormdry product, then all should be well.

Thoughts?? - do not do this. I’m not sure of the specific product, but the majority of this stuff is non-reversible. So the error is permanent. If you have moisture in your walls, which an old house will have by design, then it needs to be able to get out. Blocking an area will only push moisture to find another exit.

Rising damp is not necessarily sourced from the base of the external wall where you can apply this stuff. More the foundations that sit on the soil. Regardless, from the info provided and some assumptions, it doesn’t sound like this is the cause, so a different debate for another time!

.
when this house was built it would have been waterproof, so what changed? Can only be the porosity of the internal part of the wall that has weakened with age?

Old buildings weren’t built to last indefinitely, they were built to be regularly maintained and kept in order, including refreshing sacrificial materials. Problem is, not all buildings are maintained correctly and/or frequently enough. And then there’s those which have original features to protect against weather, removed or altered, changing the way the building works.

The internal part of the wall wouldn’t be my default focus, find the source of moisture.

There’s is a heap of info on this forum, to give more background on why modern materials should largely be kept away....

 

[andrew gayton]

remember that not all rubble walls were intended to be exposed.

 

[MatthewC]

Don't do this without further thought. I'm not totally clear of your issue but if the damp is only below the upstairs windows (and then the whole way down) then it could certainly be caused by water dripping down the wall rather than dripping off the cill. So do fix the drip line on the cill.

I would also check the operation of the RWG during heavy rainfall - get out there with an umbrella and have a good look! Just because something is new doesn't mean it's working properly. Perhaps the new gutter is incorrectly installed and water drips over the edges (and thus down the window and wall) rather than running away?

Isn't granite impervious? I have a memory of breaking open a bit of granite at the seaside and it was dry inside. In that case the water is not getting in through the stone unless it's cracked. So if the above doesn't fix it then you should address the pointing (which is intended to be sacrificial), not the stone.

I also recall, in my less informed days, of applying a bit of some chemical damp proofer to a bit of limestone with words on it. It was clear a couple of years later that the lettering on this bit had been eroded much MORE than on the untreated bits. Even having granite (not the limestone I had), you don't know the long-term effect of anything synthetic on the stone. The trouble is that if you apply anything as I did, then at best you waste your money, at worst you cause irreversible damage.

 

[TheForge]

Isn't granite impervious

It has limited permeability but isn’t impervious. It however has quite high secondary permeability via fissures etc.

 

[MatthewC]

Isn't granite impervious

It has limited permeability but isn’t impervious. It however has quite high secondary permeability via fissures etc.

I just found this thread http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14427&p=197931 where the late KeithJ gave some good figures including a comparison of figures for cement, granite and sandstone. This works out that granite is (rounded figures) about 100 times more permeable than fully cured cement, while sandstone is about 50 times more permeable than granite (and 5,000 times more than cement).