Advice need on

6 Apr 2021
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United Kingdom
Morning guys,

I hope you guys can give me some advice on the best to fill the edge of the window board (mdf). I was thinking perhaps use a two part wood filler all the way up the edge of the window wall. Once dry and sanded back, cut 1mm away and fill with a flexible non shrink caulk to stop any movement cracks down line before I paint over with primer and satinwood.

What would you recommend?

thanks in advance.


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I completely understand why you want to break the bridge between the filler/board and wall, makes sense. Unfortunately, the process of cutting back will probably break the filler away.

I would push some thin but rigid polythene (eg cut a rubble sack in to strips). It will stop the 2K filler from touching the plaster. Once sanded back, you can cut away the excess before caulking.

Alternatively, use a MS polymer rather than a caulk. They are far more flexible and able to bridge the gap but you will end up with a bigger radius. That said, I would use the 2k filler and caulk though.
May be fill the wall side with jointing compound and paper tape over that to give you a clean edge. Then fill the remaining gap on the sill board with hybrid polymer sealant that will not crack and paintable. Caulk will always crack.

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