sealing window frames from the rain

[Simon Wilson]

Hi,

I wonder if anyone can suggest a good way to seal an old window frame in a stone house from the rain please.

We've discovered that the rain comes through under the bottom part of the window frame that sits on top of a flat granite block. The are no drainage channels or ridges to stop the rain driving in, especially in the right hand corner. There's a picture here:

've raked out all the old mortar, various bits of silicone sealant, old socks etc. from underneath, and re-mortared with a hydraulic lime.

In heavy rain it still seeps underneath as of course the lime is porous. Also over time the wood's going to move etc. and cracks will open up.

For now, I've just blathered on water repellant, but I don't think that's a good long term solution. Can anyone think of a solution that won't look too gash. So far I've thought of either slapping silicone sealant all over it (which I think will look awful), or white flashing tape (ditto).

TIA,

/Simon

[Dean Heighington]

It looks and sounds to me like you need to get the water away from the cill and stop it pooling against the frame. It obviously isn't draining away from the cill- is there a slope to it? If not, then I would suggest cloaking it with lead and forming a run off. Lap the lead up onto the bottom of the frame and cover it with a strip of wood or PVC with perhaps a rebate along it's length to house the thickness of the lead. You could alternatively apply a sloped band of screed on top of the stone cill but the lead might look better and more 'natural'. It all depends if the water is pooling and won't naturally drain off!

[The Natural Philosopher]

Actually that's a decent enough idea. But I am dubious that the lead to wood seal will be maintained.

Since the OP mentions granite, which is impervious, I still think the 'rake out the mortar and use the expanding foam' is the way to go. its possible to use a decorative lime mortar fillet at the front for virtual reasons, or a paintable frame sealer. I'd go for the latter frankly.

So out with the mortar, in with the foam, trim that back and go for frame sealer last of all.

[Simon Wilson]

Ideally, yes.

Indeed not.

No.

Hmm. Interesting. That might not look too bad.

Yes, some of the windows had been bodged with a wedge of mortar, but badly - wasn't doing any good at all and also looked rubbish.

Thanks,

[robgraham]

I've got old wooden windows in a stone house and I've got wooden windows in the modern extension.

It is noticeable that, for a start, the stone cills are all cut so that there is a several degree run of angle. The other feature is that the wooden window cill, also angled for run off, is bedded onto a small raised lip so that the water can run off it and drip onto the stone.

When the extension was built - concrete cills with dpm and drips - all the windows leaked at the cills under storm conditions. The builder failed to resolve this. I then noticed that for some inexplicable reason he had taken a saw along the wooden window cills and removed the overhanging drip so the water was running off and straight down into the mastic seal. I found that all the leaking stopped immediately when I screwed and glued a nominally 25mm wide batten back on, containing a drip such that the water was thrown clear of the window to concrete seal.

It may not be that easy to do, but I would make sure that the stone cill has a slope on it, and I would add a batten of wood with a drip to the window frame such that the water is away from the wood/ stone joint water and has somewhere to go.

[Simon Wilson]

Yes in an ideal world this is probably the best, but, to do this I think involves more work/cash that I can afford to put into it. The sill does slope slightly, but not enough to stop the wind driving the water uphill.

[Simon Wilson]

I'm going to take a look but it may be possible take the lead all the way up, and a short distance under the opening windows, which would solve that problem.

One one window, we did try crazy foam followed by sealer, with the intention of putting a mortar bead over the top for looks. But, it still seemed to leak with the 'bucket of water' test. It did turn out subsequently that the water was coming between the window and the frame in this case - we have solved that now.

Many attempts with sealant have obviously been tried in the past, hence my feeling it really needs something different. Over the years the leaking has caused a huge amount of damage to the wooden lintels in the floor below.

[Phil L]

Cut a piece of wood the width of the window and about 50mm to nothing in height, so that the 50mm part is sat on the cill - a triangular section IYSWIM

Set this in silicone on the cill and affix to the bottom of the frame with screws, sealing the gap between both with more silicone, then remove excess silicone and paint so that it matches the frame.

[Dean Heighington]

Welcome. As for joining lead to wood, brick glass et al... Use leadmate or flashpoint. In essence you will be making a lead 'tray' to cover the cill. The PVC (or wood) cloaking will hide the edge between the timber frame and the lapped up lead.

[robgraham]

A strong enough wind will always drive the water uphill and under an overhanging window frame cill, but the gap is no more than 5mm high and is a good 15mm deep so that seal between the window frame and the stone cill is protected. The extension windows that leaked are bedded on silicone, but leaked until I added a drip batten to them. The traditional (Scotland) sash frames in the older part of the house are probably bedded on lime cement and have an overhang of some 30mm over the stone cill.

Maybe Phil L's solution with a 50mm silicone bed under a triangular batten but as my extension windows leaked with presumably a similar length of bed, and didn't after re-instating the proper drip, I favour drips !!

One thing to watch out for when adding any wood with silicone sealing is to make sure it doesn't get on any of the surfaces to be painted.

As an aside, but intriguing all the same, I was at a friend's flat in Edinburgh recently when new DG sash windows were being fitted. The boxes (window frames elsewhere!) were made absolutely identical to those 150 or more years old - fair enough the design has been shown to be effective. What did surprise me was that they weren't sealed in with silicone but the old fashioned putty made I think from linseed oil and some sort of reddish sand - I have used this but can't remember now what it is called. It may well be that that is still the most effective seal for wood against stone.

[Simon Wilson]

Interestingly, I've just been to parts foreign, and started looking at the stone houses. I hadn't noticed before, but these all have some kind of metal (not lead) protection over the whole sill. See here:

It also extends the sill over the stone to produce a nice drip. Just what I need. I couldn't do this in lead because the lead would get knocked about (on the ground floor at least). What's the metal likely to be - zinc?

[robgraham]

zinc, aluminium, copper ?. But what is also noticeable is that there is a wooden batten attached to the window frame as a drip to carry the water away from the seal area.