Damp in window stone cottage

[Dinksio]

Hi
We have an 18th century stone cottage with solid sandstone walls.

We recently had a window replaced in the gable end wall ground floor room.
There had been water ingress from above due to what we presumed was a poorly fitted window whose top edge actually protruded outwards slightly beyond the lintel.

When the new window was fitted by our window installer we took some photos of the area. Damage to the plasterwork is evident on the vertical faces of the window opening.

In addition a rather mysterious area of damp was evident on the cemented area underneath the temporarily-removed interior oak window sill.

This damp has not disappeared since the new window was installed about a month ago from all around the frame internally. I think this damp has got worse during driven rain from a storm, and I noticed a small gap in the new exterior silicone sealant at the right-hand bottom corner in the photo. I have resealed this gap yesterday.

I can’t work out where the water is getting in.

Could it be possible that the damp on the cement of the sill is rising up approx 1.2 metres from the ground? From my observations when the new window was fitted the damp on the cement did not go all the way to where the original frame was fitted. Or Is it more likely to be ingress at window height travelling under the cement near the window and then up to the surface closer to the internal wall face?

This end gable wall has problems- the outside earth level is about 200mm above the ground floor level inside so we have rising damp. There is no simple option to lower this level outside as there is a main drain running below ground on the outside.

Photos attached

Thanks.

 

[a twig]

From first glance that is not a particularly nicely installed window, that amount of sealant / mastic smeared around the outside and not even properly smoothed off isn't usually a good sign of a competent and careful install, for gaps that big I would have expected to see new pointing around the window rather than gunking it up with sealant.

Do you know how the window was installed? I assume wedges / packers, large screws into the stone surround and then foam? Damage to the plaster always happens when changing windows, it is to be expected and should be made good afterwards. A more conscientious trade would probably have pointed out the wet plaster and mentioned that it probably needs to be removed and repaired.

Peering at the photographs I have a few other questions:
1) Might just be perspective but does the external cill slope the wrong way back towards the window? If it is then you are just creating a water trap, it should be sloped slightly away from the window so any water that gets into the frame drains out the bottom and is directed out and away from the wall rather than back into it.
2) Is there a rain drip cut into the stone head/lintel or is water able to run back towards the window on the underside?
3) Non-breathable finishes - if there was already damp, then it will take time to dry out which isn't helped by modern finishes, I can see cement pointing externally, and what looks like gypsum internally, so moisture trapped in the walls will struggle to escape. In a previous property, rather than re-plaster the entire room, I hacked off the plaster just in the reveals up to the corner bead, and re-did that area in an NHL based lime plaster which helped.
4) Definitely worth investigating the waste pipe above just to make sure there are no leaks, and no water ingress where it penetrates the wall.

 

[Dinksio]

No

From first glance that is not a particularly nicely installed window, that amount of sealant / mastic smeared around the outside and not even properly smoothed off isn't usually a good sign of a competent and careful install, for gaps that big I would have expected to see new pointing around the window rather than gunking it up with sealant.

Do you know how the window was installed? I assume wedges / packers, large screws into the stone surround and then foam? Damage to the plaster always happens when changing windows, it is to be expected and should be made good afterwards. A more conscientious trade would probably have pointed out the wet plaster and mentioned that it probably needs to be removed and repaired.

Peering at the photographs I have a few other questions:
1) Might just be perspective but does the external cill slope the wrong way back towards the window? If it is then you are just creating a water trap, it should be sloped slightly away from the window so any water that gets into the frame drains out the bottom and is directed out and away from the wall rather than back into it.
2) Is there a rain drip cut into the stone head/lintel or is water able to run back towards the window on the underside?
3) Non-breathable finishes - if there was already damp, then it will take time to dry out which isn't helped by modern finishes, I can see cement pointing externally, and what looks like gypsum internally, so moisture trapped in the walls will struggle to escape. In a previous property, rather than re-plaster the entire room, I hacked off the plaster just in the reveals up to the corner bead, and re-did that area in an NHL based lime plaster which helped.
4) Definitely worth investigating the waste pipe above just to make sure there are no leaks, and no water ingress where it penetrates the wall.

thank you very much for your careful analysis. Much appreciated.

Yes, I think the sealant is badly done too. Other windows installed by this fitter are much better.

I do believe you might be right regarding the cill dlipung inwards. That was in situ with previous window.

No drip strip on lintel.

Could water still ingress between cill and sealant if slope is incorrect?

Gypsum plaster is not ideal- agreed. And we have lime pointed another face of the house, but not this one.

I don’t think the waste pipe above is leaking as the ingress occurs with driven rain, but I agree that it’s worth keeping an eye on.

I have suspicions about porosity or leakage through the filled-in window and water ingress down rubble-filled void between inner and outer skin. But only way to really identify cause is to strip away wet plasterboard internally above the window.

 

[a twig]

Could water still ingress between cill and sealant if slope is incorrect?

It’s definitely possible, particularly against rough stone it will find any gaps, or permeate in through the stone at the edges of the sealant - it can be relatively easily rectified (albeit very dustily) as a diy job with an angle grinder equipped with a vanity disc - proper PPE / mask highly recommended

No drip strip on lintel.

A rain drip can easily be cut into the stone head/lintel - if you are confident you can use an angle grinder with a wooden batten as a guide or if the thought of that makes you nervous a narrow masonry chisel and dummy means more work but less chance of big mistakes - you’re after this sort of effect

Obviously I’m not aware of your situation, how much you use the room etc but if you can stomach stripping the board and wet plaster away I would get on and do it, it will at least allow the moisture that is getting in out again so the wall can dry while you are investigating.

Window above is certainly a possibility but I’d personally resolve the obvious issues with that first and wait a month or two to see if it dries / improves - softly softly and all that

 

[Stevers]

There seem to have been a number of recent posts on this forum reporting damp patches round UPVC windows and doors in old houses. This shouldn't be too surprising when modern building materials and components, requiring a cavity, cavity tray, DPM, DPCs and good workmanship to function are bodged into installed in an old house with none of these 'refinements'.

There's just the one UPVC window, here and it too is mounted pretty much flush to the outside wall. In this case it's facing the weather, and yes there's an occasional leak from above that disrupts the gypsum plaster that is over the cementitious tanking. This opening didn't have a functioning window when we bought the house, and I have every reason to think it was where coal was originally delivered. The opening had been widened by a couple of inches in the past to receive a BS sized frame, and I remade the right hand reveal so that the opening was symmetrical again. I added a cill made from quarry tiles, and I sealed round the installed window with NHL mortar. My current thinking is that the water is tracking in from a band of defective cement/lime pointing that is some distance above. Being chunky UPVC there is much less glass compared with the custom made wooden window that was my first attempt to fill the hole, but had rotted out!



In reality my window is almost doomed to fail, and really ought to be inset to give it a bit of shelter, something that I didn't do this time as one side and the bottom of the internal opening are heavily splayed, presumably to aid the past delivery of coal. Repointing further up than currently will happen when I've found a truly satisfactory way of colouring the NHL mortar. Internally, replastering the affected area in NHL plaster to add damp tolerance is on the agenda for the next decorating cycle.

 

[Dinksio]

There seem to have been a number of recent posts on this forum reporting damp patches round UPVC windows and doors in old houses. This shouldn't be too surprising when modern building materials and components, requiring a cavity, cavity tray, DPM, DPCs and good workmanship to function are bodged into installed in an old house with none of these 'refinements'.

There's just the one UPVC window, here and it too is mounted pretty much flush to the outside wall. In this case it's facing the weather, and yes there's an occasional leak from above that disrupts the gypsum plaster that is over the cementitious tanking. This opening didn't have a functioning window when we bought the house, and I have every reason to think it was where coal was originally delivered. The opening had been widened by a couple of inches in the past to receive a BS sized frame, and I remade the right hand reveal so that the opening was symmetrical again. I added a cill made from quarry tiles, and I sealed round the installed window with NHL mortar. My current thinking is that the water is tracking in from a band of defective cement/lime pointing that is some distance above. Being chunky UPVC there is much less glass compared with the custom made wooden window that was my first attempt to fill the hole, but had rotted out!

View attachment 12112

In reality my window is almost doomed to fail, and really ought to be inset to give it a bit of shelter, something that I didn't do this time as one side and the bottom of the internal opening are heavily splayed, presumably to aid the past delivery of coal. Repointing further up than currently will happen when I've found a truly satisfactory way of colouring the NHL mortar. Internally, replastering the affected area in NHL plaster to add damp tolerance is on the agenda for the next decorating cycle.

Really interesting reading your reply. Your technical skills are better than mine. Also I have two young kids and a disability so I can’t do everything I’d want to do myself.

Very interesting to see your thoughts re the UPVC frame not designed for this kind of window opening and your idea for your window that it was a coal hole! I wonder if this opening in our house was meant to fulfill same function i.e. it wasn’t constructed properly when punched through the wall.

Either way, some serious thoughts required - I’d even consider blocking in the window, but it would be a nice feature if it didn’t let water in.

We’re having our house reroofed next year so hopefully some of our myriad leaks will be solved then and maybe this one if water ingress is coming from right up top of gable end.

I’ve done lime pointing but not lime plastering. Appeals to me though.

Ideally I’d cut away internal plaster and plasterboard above window to identify the ingress points but my wife might not allow that at present as when would I finish the job whilst being main carer for my little boys!! Needs the luxury of time methinks.

Very appreciative of your kind response.

 

[Dinksio]

I have a further question and would be very grateful if anyone could answer.
If water is coming in from above the window - and I cannot locate the source of the ingress easily - is it possible for a good builder to install a new window with some kind of “drip tray” above the window that allows water to escape to the outside of the wall above the window?

 

[a twig]

There are trays, but they are usually only used in timber construction, and usually only below a window to ensure any leaks are directed back outside rather than above. Systems like this are required by building regs in NZ for e.g

https://www.renovate.org.nz/assets/Uploads/_resampled/ScaleWidthWyI2OTYiXQ/Fig-3.52.jpg

In cavity wall construction you would have a cavity tray above the head/lintel which would do that job but I don’t know how you would (or even if you should) try and do the same on your solid stone wall.

I suppose you could try and yeehaa some sort of zinc sheet/tray in above the window but it would need to extend out past the width of the window into the wall to avoid the water just travelling round the edges.

Either way you’re starting to look at a fair bit of work which is still ultimately treating the symptom rather than the cause.

Highly recommend going outside with a brolly next time you have a heavy downpour and taking a good look at the wall, often this brings to light overflowing or failed gutters causing water to sheet down the wall or other issues that are contributing and can be cheaply addressed for significant improvement

 

[Dinksio]

There are trays, but they are usually only used in timber construction, and usually only below a window to ensure any leaks are directed back outside rather than above. Systems like this are required by building regs in NZ for e.g

https://www.renovate.org.nz/assets/Uploads/_resampled/ScaleWidthWyI2OTYiXQ/Fig-3.52.jpg

In cavity wall construction you would have a cavity tray above the head/lintel which would do that job but I don’t know how you would (or even if you should) try and do the same on your solid stone wall.

I suppose you could try and yeehaa some sort of zinc sheet/tray in above the window but it would need to extend out past the width of the window into the wall to avoid the water just travelling round the edges.

Either way you’re starting to look at a fair bit of work which is still ultimately treating the symptom rather than the cause.

Highly recommend going outside with a brolly next time you have a heavy downpour and taking a good look at the wall, often this brings to light overflowing or failed gutters causing water to sheet down the wall or other issues that are contributing and can be cheaply addressed for significant improvement

Thank you.

Yes, you’ve confirmed what , deep down, I know is the only proper solution, which is identifying the ultimate point of ingress.

Trouble is the upper part of the gable-end wall on which this window is situated is not accessible by ladder due to proximity of neighbouring builfing.

I might just have to wait until the re-roof takes place and see if that reveals - and solves - any obvious point of ingress on the roof, though it seems a long way down from the ridge to this window!

In summer/ springtime- once the plasterboard on the ceiling of the window opening has dried out - I might try spraying wall with hose at points that look possible culprits for ingress and observe if water appears on the plasterboard, but there’s only so far up the wall I can safely look.

The worst case scenario would be that the water was ingressing from an indeterminate point on the wall higher up above the window. Then - on top of reroof - it’s a lime repoint job on the whole wall.

I appreciate your thoughts. And happy Christmas!

 

[Dinksio]

Just a follow up after further investigations:

There is some damp plaster that has recently appeared - following driven rain from powerful storms - on internal wall well above the window opening. I now believe the water is being driven in through the wall higher up. But how high up?

Based on measurements of where the internal damp appears, the current prime suspects in my unprofessional opinion - in order of likelihood - are:
1. The filled-in arched window on the external wall that is in one of my photos. I can’t verify internal damage in the room on first floor above as it is bathroom and so dry-lined and tiled.
2. Waste water pipe exiting wall with elbow- I have already applied an exterior silicone sealant on the small gaps around the hole in the wall around the pipe, as a desperate if slightly bodged attempt to cure the ingress. It didn’t stop the ingress! If it wasn’t for the symptom being related to driven rain this would be a stronger contender as the main cause.
3. The roof: this is being redone in 2024, but I will go up to roof space to see if I can spot any water ingress streaming(!?) down internal face of bare wall up there
4. Pointing

If it’s 1 , could anyone suggest the best approach for remedying? Do I spray water on the filled-in arch to see if it’s definitely the culprit? If so, I’m thinking to remove existing render/cement and re-fill with some kind of lime-based render.
The stone behind the render will be very damp as verified by seeing damp patches on internal (gypsum!) plaster, as these walls are 40cm-50cm thick. Will this influence strategy for remedying e.g. timescales etc?

Thank you.