Repair or replace window sill?

[Lacan07]

Morning all

I came downstairs and discovered this rather odd patch on my living room wall. Pretty sure it wasn't there before. This wall was limed in the summer. Like everyone else theres been a fair bit of rain here recently. My window sill the other side is not in good shape and scheduled for a revamp. I checked it and its not coping well, the drip guard is failing, the bricks directly beneath the ledge are wet, and those exposed bricks are wet too. I'm thinking I might as well just replace the sill for new rather than repair whats there but never tackled one before. Any tips, any particular type of sill? They seem to range from cheap and basic to quite advanced.

 

[stuart45]

I'd go for a decent stooled cill if you're replacing it.

 

[Cubist]

It may be coincidence but that crack to the left in the cills render coat in the last photo looks to align closely with the damp patch indoors. That suggests to me rainwater is tracking through it and beneath cill to reach the plaster coat. Assuming the bricks/pamments(?) used in its original construction are in good order my first thought would be to remove and replace the render coating.

Are you firmly wedded to the idea of replacing the cill entirely?

 

[Tuffa]

Hi,

I replaced some similar sills when having some new windows installed; the new windows did not sit in same places as the originals. The sills were recreated in same style to be consistent with other windows in the same wall. The old sills were removed and then a carpenter made formwork into which the new sills could be poured. The formwork included a groove in the underside to force rain to drip. I’ll try to add some photo’s to show the steps. I don’t know whether bricks were included in the final pour.

 

[Lacan07]

I'd go for a decent stooled cill if you're replacing it.

Thanks, I wasn't aware of the terminology so that's a big help. I googled stooled cill and I like your thinking, is the raised back end cited behind the window outside edge? I'm assuming it sits in front with a little under lap which is obviously then sealed.

The patch was far worse this morning so definitely the Sill I think. Trouble is I think I want to bed / point it in lime so I'm going to have to wait a few months, so a temp fix is in order

 

[Lacan07]

It may be coincidence but that crack to the left in the cills render coat in the last photo looks to align closely with the damp patch indoors. That suggests to me rainwater is tracking through it and beneath cill to reach the plaster coat. Assuming the bricks/pamments(?) used in its original construction are in good order my first thought would be to remove and replace the render coating.

Are you firmly wedded to the idea of replacing the cill entirely?

You may well be right cubist regarding the crack. Those exposed bricks on the front ledge feel pretty wet to.

My thinking is a new sill would be easier, I'm not sure I want the hassle of creating formwork to re render and if the bricks beneath are really wet the concrete may well trap the moisture. And to be honest all the sills on the side of the house (about 5) are in similar condition so they will all need replacing eventually. I don't know how easy it will be with regard to getting a good sized fit.

Edit: it seems a nice stone cill isn't cheap

 

[Lacan07]

Hi,

I replaced some similar sills when having some new windows installed; the new windows did not sit in same places as the originals. The sills were recreated in same style to be consistent with other windows in the same wall. The old sills were removed and then a carpenter made formwork into which the new sills could be poured. The formwork included a groove in the underside to force rain to drip. I’ll try to add some photo’s to show the steps. I don’t know whether bricks were included in the final pour.

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Thanks Tuffa, very interesting to see, this will be a big help if I decide to re render what's already there.

 

[Lacan07]

I had to leave the ledge covered in plastic sheeting before going to work, I think I might patch those bricks and cracks as beat I can at the weekend and fix a plastic drip guard to the front fascia

 

[stuart45]

Thanks, I wasn't aware of the terminology so that's a big help. I googled stooled cill and I like your thinking, is the raised back end cited behind the window outside edge? I'm assuming it sits in front with a little under lap which is obviously then sealed.

The patch was far worse this morning so definitely the Sill I think. Trouble is I think I want to bed / point it in lime so I'm going to have to wait a few months, so a temp fix is in order

Setting the frame slightly forward of the stooling is more cosmetic, as it hides the joint. Some people set them flush. On new builds years ago some cills and frames had grooves cut into them for a galvanised steel weather bar bedded in red lead for a seal. Nowadays it's a job for the mastic gun.

 

[Lacan07]

Setting the frame slightly forward of the stooling is more cosmetic, as it hides the joint. Some people set them flush. On new builds years ago some cills and frames had grooves cut into them for a galvanised steel weather bar bedded in red lead for a seal. Nowadays it's a job for the mastic gun.

Stuart, would you use a concrete mortar to 'bed in' the sill rather than a lime?

 

[stuart45]

Lime mortar would have been used originally, so there's no problem with using it again. Cement mortar probably wouldn't be an issue for the job though. With heavy cills they tend to tip forward anyway, so you'll need a couple of wedges to push into the joint at the front.