Another bloody damp Problem Bay Window...

[JoeS]

Hello Chaps,

Another damp problem in my house... AND i would be very grateful for the forums advice. I have a bay window where water is leaking internally into the bay window (leak marked in red).

The outside shows that under the exterior sill a considerable amount of material has been eroded away by i suppose water tumbling over the lip of the horizontal masonry sill and then getting in behind the wall? I wonder what the best method to fill this would be, and rebuild up the material which has been washed away. I then wonder how best to seal the area. Should i use some sealant between the bottom of the sill and the brick wall?

There is also a crack which might be letting water in through the stones...should this be filled with a caulk of just with a regular masonry filler?

Over to you UK Workshop!

 

[Ollie78]

This is a pretty common issue, it has obviously moved a bit over time. Looks like the cracks could well be the cause of this but it could be a red herring, water has a habit of creeping in all over the place so check the mastic around windows as well.

The solution I have seen done is firstly to remove the paint from the stone bits. This can be difficult to do without trashing the surface underneath, there are various products for this purpose.
Ideally you should not paint these stone elements because then water gets trappped and freeze thaw cycles cause damage or so I am told, trouble is once they are painted its a nightmare to go back.
Once cleaned up you can scrape back the joints to sound material and use stone dust and resin or some kind of stone repair lime and stone dust mix ( I forget the proper name of it. maybe Bath stone mix ?)to fix the cracks and repair the missing bits.

Ollie

 

[Bristol_Rob]

Couple of comments from the photos you have provided?

That air brick/vent. What is its purpose? As the wall is solid with no cavity the only real purpose maybe to vent the ground floor void. (confirm?)
But it looks high and possibly behind the radiator that is there? Investigate that vent and understand its purpose? (Otherwise it might just abe a lovely route for driving rain etc.

Also damp under these bay windows internally is not uncommon. If previous damp walls weren't repaired properly then there is a chance you need to fully hack off all the plaster and re-render/plaster to ensure you don't have salt affected walls that will never dry out.

The next item I saw was the drip detail under the cill. Is there one? Does it need cleaning out and possibly cutting a new one. If you use a grinder, take care and clamp a section of timber to act as a straight edge guide.

Stripping everything back, so you can let the dog see the rabbit is a good idea and then carefully put it back together after some research.

All very DIY'able

 

[Jacob]

Maybe needs a deeper drip groove under the front edge of the stone cill, so that water runs off nicely.
That air brick looks like an afterthought? Does it go anywhere?
Maybe take off the sash pockets nearest the damp corners and see if it's coming from higher up?

 

[niall Y]

Mmm..., this might be a difficult one to pinpoint. I notice that the original windows have been replaced with plastic D/G ones. With these any water that enters , them exits through weep holes at the base. In the normal course of events, this would spill onto a deep plastic cill.

I notice that the flush wooden cills that belonged to the original sash windows have been retained,( or replaced like-for-like ) and the units have been fitted on top of these. If I am reading the photos correctly there also looks to be a splice in the side window cill.

It might be worth checking these to see if water is entering at this point, If these are replacements, then one would expect there to be some sort of damp course beneath them.

Also, when did this start? In our part of the country, we haven't had any rain for three weeks, so unless someone is being heavy handed with the watering can , then the problem should have lessened for a bit/

 

[HOJ]

Look like plastic windows to me, that would be my first port of call, look at how well they fit, presume the air brick is just that, for a fire/woodburner?

 

[John Brown]

Look like plastic windows to me, that would be my first port of call, look at how well they fit, presume the air brick is just that, for a fire/woodburner?

Look like plastic to me, also. Never seen a timber window with a mitre joint.

 

[Bingy man]

Couple of comments from the photos you have provided?

That air brick/vent. What is its purpose? As the wall is solid with no cavity the only real purpose maybe to vent the ground floor void. (confirm?)
But it looks high and possibly behind the radiator that is there? Investigate that vent and understand its purpose? (Otherwise it might just abe a lovely route for driving rain etc.

Also damp under these bay windows internally is not uncommon. If previous damp walls weren't repaired properly then there is a chance you need to fully hack off all the plaster and re-render/plaster to ensure you don't have salt affected walls that will never dry out.

The next item I saw was the drip detail under the cill. Is there one? Does it need cleaning out and possibly cutting a new one. If you use a grinder, take care and clamp a section of timber to act as a straight edge guide.

Stripping everything back, so you can let the dog see the rabbit is a good idea and then carefully put it back together after some research.

All very DIY'able

Air vents supplying combustion air to boilers and/or gas fires were often fitted behind radiators so the customer didn’t have to sit in a draught. Solid fuel fires and wood burners req ventilation direct to outside.

 

[MikeJhn]

Not surprised your getting water into the building, looks like 9" solid brick not cavity, the cill and mullions have been neglected and the joints have opened allowing water into the structure, Get rid of the water retaining pocket, sheared underside of the cill, and clean out the drip, Rake out the joints in the cill and to the mullions, clean the joints well and mastic seal, also the cracked brick on the corner, then re-assess.

And be careful when watering that plant on the cill preferably put some kind of water retaining tray under it and don't overflow the plant pot.

 

[JoeS]

No idea what the point of the vent is - but they are in the same position in the whole street. So not something that has been added later on.

They are plastic windows... the problem started a couple of years ago. I suspect you're right that watering the flower box has made things worse.

 

[niall Y]

Hi there @JoeS
I believe that these vents connect to under the floor in some way to allow ventilation. My old Victorian house had a rather ornate cast iron one, in this self same position, though most of my neighbours had ,had theirs replaced with ceramic ones like yours

 

[JoeS]

yes i suspect it vents under the floor as well - thanks

 

[MikeJhn]

If the purpose of the grill is to ventilate under the floor there should be corresponding grills at other locations, side and back of house, to allow through flow of air otherwise it does nothing, looking at its position below the plant pot externally and what can be seen internally its position says there has to be some very clever ducting to ventilate under the floor which is at a lower level, as someone pointed out it was an addition to the house, was the house Council owned at one point? Contractor appointed to put in the grills and did not care if they worked or not, poke a rod into the grill and see if the rod can go any further than 100mm, if it does then it may be connected to something else, but I suspect it is just a show piece and just one brick depth. Contractor did not want to cut into the external rendered skirt as it would make the job more difficult to make good.