Window Leak: Can't Find the Cause

[Michael D]

I=92ve got a leak in some upstairs windows & just can=92t work out where it=92s coming in. Drops appear at the top of the window frame in 2 or 3 different places (see here:

but normally only 1 place at a time. It happens in strong wind & rain.

I guess the leak is either coming in from the outside through the window frame or is somehow coming through via the inside - above the room is the loft, but I can=92t see any obvious signs of water getting in on the inside up there.

There=92s a ledge on the outside of the window frame, about 3 inches wide which runs the length of the outside window frame (see the photos). It=92s just above where the water gets =96 is the most likely suspect?

The frames need painting, which I=92ll do in the spring, but I=92d love to track it down as it=92s rapidly getting worse.

Any experience of what=92s the most likely suspect or suggestions for tracking it down would be much appreciated.

Michael

[The Natural Philosopher]

Its getting in higher and coming down between the walls. I had this..final strawin demolishing the house, but you dont want to hear that.

I would have sugguested the bargeboards, but its more likely the weatherboding above the drip board is actually gone somewhere..paintwork looks bad. Also the drip board SHOULD be raked down a few degrees.

TBH faced with that, Id get up a ladder and rip those bioards off completely.

Depending on what is underneath a bit of plastic sheet, or Tyvek, and new boards sealed with mastic and more paint..is indicated.

[Jules]

I'd certainly start with that; as a very cheap test, seal along the join with some sealant and see if the problem goes away (nowt wrong with it as a more permanent solution either, but you'd be better off stripping all that flaking paint off, re-painting and then sealing afterwards if so)

If the above doesn't help, it might be worth noting what the wind speed / direction is whenever it does happen - maybe that'll give a clue as the source...

[Steven Campbell]

Picture 4 of 5 looks like the top overhanging board isn't sealed at the base of it. Water could be penetrating there when there is wind. I'd first seal there and then possible look above if water is still getting in.

[Phil L]

I'd have to say that it's getting in above the ledge that you mention.

In the first photo, of the peak and the window top, there is a joint where the ledge you mention meets something else - there is a black line along it and it looks like it could be a lead flashing - the five vertical beams look like they are stood on top of this, but I assume there is a horizontal one at the bottom, onto which this flashing will probably be fixed, to shed water which is driven towards the rendering, down onto the dripper above the frame - I think it's where the flashing meets the crossbeam where the water is getting in, but it's difficult to tell from that picture as I can't zoom in on it.

[Phil L]

Forgot to add here that the ledge is already past the outside of the window frame, even in the 'L' IYSWIM - so even if it was leaking through, the water would surely run down the outside of the frame, not the inside.

[Stuart Noble]

If it only happens in strong wind, chances are it's blowing into a joint somewhere. If it happens with rain and no wind, it could be soaking into the masonry above and working its way down on the inside. I'd try raking out and sealing all the timber joints as a start. Nice job for the new year

[Timothy Murphy]

I've a rather similar problem. What sealant would you recommend?

[Old Git]

I have a similar problem. Mine is down to some of the mortar being missing, under the tiles, on our side gable, just over the cavity of our back wall. A local builder replaced most of the mortar in the summer but couldn't get to all of it (awkward access) and that stopped the worst of it but when the wind is in the wrong direction, we still have a slight problem. Will get him to do it when the weather improves. It doesn't affect the bedroom window but leaks in above the ground floor 3m sliding doors to the conservatory. So, it may be worth checking that your tiles are set properly.