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Tiling up to a bathroom window - can the pvc windowsill be removed/tiled over?

Hi All, another window question please :)

Can a C-shaped windowboard be cut off flush to the wall and tiled over? Would this cause any problems?

(In more detail...)
I'm having a wall taken down between my bathroom & loo and am having the room fully tiled. My problem is that the bathroom window is not central, it starts at the left wall, which is the wall that is coming down.

The (front) fascia trim around the frame has been cut down to about an inch thick on this left side to meet the wall, whereas the top and right side trims are about 3 inches wide. The left hand side of the windowsill finishes at the wall too, so when the wall comes down I'm going to have a chunk of windowsill missing and a half bit of trim on the left side.

I've been told that the 3in trim can be replaced easily but have no idea about what to do with the sill, as it will be a couple of inches shorter than the trim (at full width). As I understand, the sill/windowboard sits underneath the window unit when it is fitted so it can't just be pulled out.

The C shaped window boards (in both rooms, actually) have not, in my opinion, been fitted correctly - they are flimsy, sag in the middle when pushed, and move up and down, which suggests that the fitters did not level/make good the existing surface before the window board was sat on top. One side of the board is also cracked where it meets the wall. Basically, they look very tatty and may spoil the look of a lovely new bathroom if they stay the way they are. In this respect, ideally I'd like for the sills and possibly all of the pvc fascia trim to be removed and have tiles right up to the window (including the recesses). Alternatively, I could keep the 3in pvc trim and somehow fit new windowsills which are symmetrical (and not broken). For me to do this, I'd have to cut the old ones off.

Can the C shaped sills be cut off flush with the wall - either so that I can have a more solid sill/nosing board stuck down straight on top with tiles running up to the lip vertically, or so that I can have a tiled windowsill instead?

Epic question again, sorry! Appreciate any suggestions, though :)

**thanks for your replies .. re Kevin & Harry's answers - unfortunately I think my boards do go under the window unit. It was many years ago but I vaguely recall the fitters putting quite a deep piece of this board down, which extended right to the outside of the house. They then sat the unit with the glass in on top of that and filled over all the outside with mastic & trim to seal it.
If I assume it can't be removed, I need to at least be able to cut the C shaped bit off level with the wall, try to solidify the underside a bit (will expanding foam do??) and then put a new thicker board (with a lip) on top, which can be tiled up to underneath. It'd be a bit of a bodge job but might work, what do you reckon? **

7 Answers from MyBuilder Window & Door Fitters

Best Answer

By the sound of it the the windowboards need to come out. If the boards move when pressed on the tiles on top may crack, and also the tiles might not bond well to the pvc.

The windowboard shouldn't run underneath the window and will usually come out quite easily. I find the best way is to cut through the middle of the board then prize up from where you make the cut, this will make things easier and minimize the damage to the plaster.

There may a board underneath but you probably will be left with blockwork and a cavity. You will need to put ether tile backerboard, plasterboard or ply (which ever you have) on top of the blocks and up to the window to tile on. The easiest way to fix and level it is to use an adhesive such as no nails.

This is assuming the window board does not run under the window.

I hope this is helpful.


re; yes I'm sure that would work, you should be able to cut the edge off with a panel saw. Just don't go crazy with the expanding foam.

Good luck.


Answered 1st Oct 2011

window board does not fit under the window so you can remove it and do whatever you want with it.
Hope this helps-Kevin


Answered 27th Sep 2011

He is right a window fitter won't fit a window on top of a window board, so the whole lot should come of. Use a a multi tool if having problems you can get one for around 40 pounds and it will come in handy for many jobs. Cheaper than getting someone out. The beads around window are about 2 pounds each and are simply stuck on with mastic.


Answered 7th Jul 2019

I’d cut off whatever you can using a multi tool and then simply tile over the rest with normal adhesive. It may not bond properly and fail however. I’d make sure you’ve got a few extra tiles in case this does happen and then, if it happens, do that bit again using something like a good grab adhesive to fix the tiles in that area which definitely will bond.


Answered 29th Dec 2019

Simple solution is remove window boards and if needs be pack up with water proof board and timber and tile over to window frame ,


Answered 21st Feb 2020

Yes, other comments are most appropriate, however, it is certainly true that the upvc should really be removed, they are rarely if at all fitted under the window itself, but ensure there is no gap under the window once the upvc cill has been removed, such a gap is usually filled with expanding foam which can be left and covered with a upvc cover mould (45mm max is usually adquate for this), tiling can be laid up to it. Alternatively, if there is any gap at all that has been filled as described above it may be possible to fit ply thick enough to at least cover the gap and tile up to the window as previously mentioned.


Answered 12th Nov 2020

I would trust your instinct. You know what you want.
Personally I would remove it with a Stanley knife, if I’m imagining your cill correctly, I’d tile up to the window frame. Make sure the base is level and secure for the tiles. You can’t have tiles moving!! You can always get a perfect fitting sill cut at Travis Perkins and other outlets afterwards if you want to.

If it’s bowing and moving, I’d investigate. May need a bit of cement to level it ( which you can get ready mixed if you are doing it yourself. Or some waterproof board. Expanding foam is a handy thing to possess as well, great stuff, but go easy, it really does expand. When you remove cills you can find a bit of a draught afterwards so make sure it’s airtight.
Best of luck.


Answered 10th Jan 2021

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