Gap filling expanding foam - rotten wood replacement?

[tellme_why]

Hi,
Can I use expanding foam to replace the rotten timber frame topside of the window frame?

I tried using wood filler but it takes forever and requires lots of material.

Expanding foam seems rather quick but 1) will last? 2) would ti too soft? 3) can I sand it proper to look like original timber 4) can I paint it over? 5) Can I put wood filler on top the foam?

I don't mind if it doesn't look great, better repair than replacing (apparently I would have to replace the entire window to replace the cill)..

Many Thanks

 

[Mr diy a lot.]

Expanding foam is very much the wrong product for this job. Cutting out the sections of rotten wood and glueing in a new section/patch is the best way short of replacing the cill.

Wood filler is the second best option here but remove all the old wood and sand down and treat with rot hardener before filling, sanding to shape and painting over.

 

[nitro23456]

Two part epoxy wood filler

 

[cdbe]

Maybe consider a uPVC "overcill" - eurocell plastics do one.

 

[Deleted member 174758]

Clean out with a stiff wire brush, treat with wood hardener, then fill with a flexible 2-pack wood filler (or similar car body filler). If the rot is particularly deep it needs to be cutboutcsnd a replacemne piece of joinery grade redwood splice in, planed to match, then the joints and minor damage areas 2-packed