Windows with Gaps at base - normal/ok?

redman

See attached pics
Working on preparing window ledges for repainting and noticed two of my double glazed windows at the rear have 2 cm gaps at their base.
Handn't noticed from the inside, only in the house a couple of years.
The glazing is ?x years old.

Any comments on whether I should seal this up, as the rest are fine.

Redman

rooferPete

Hi redman,

The space is normal for PVC, the window should be sitting on a bedding compound that is applied to the top of the cill before the window is fitted.

If there was no bedding under the window you would have felt the draughts in a very short time.

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redman

Thanks Pete, the gap goes all the way back to the back of the window, where the back of the window meets the back of the concrete sill.
Thus the wind can reach effectively the whole base of the PVC.

Why not just have it filled?

Mellor

The whole base isn't exposed, the gap goes back to the upstand on the cill, but the window sit on this upstand. I know it might seam sensable to get a snug fit, but windows and cills come in al shapes and sizes and would be a night mare getting them to fit. As for sealing with a compound, they is no need so who would bother, and it could easily look worse.

rooferPete

Hi redman,

The cill is a boot shape rising higher at the back, the line on your window about 15mm up is the bottom of the window, the last piece is added when the window is in place.

I wouldn't try to seperate the two pieces to see if I am correct because the bottom strip locks into grooves in the window

There is a chance of causing capillary attraction between the cill and any sealer you might use to fill the space, the bottom strip serves as a drip detail as well as finishing the window.

The only time it might be necessary to seal behind the strip is if you have draughts at or under the window board inside.

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redman

Thanks to you both for the informative replys.

Cheers

Redman