howto repair around wooden window sill & frame

[troybison]

Evening all. This is my 1st house (built 1934) & I'm just getting started in DIY. I found that the brown silicone sealant around outside of kitchen window has deteriorated & wooden sill beginning to rot in corner by bricks & mortar. After poking around I found the mortar to be crumbling away & has broken up badly in the gap visible below - which goes back several inches, as far as some white insulation stuff. The photo maybe doesn't show how deep it goes due to the angle.

I have started by applying Ronseal wood hardener to the end of the wooden sill after cutting away the small amount of softened damp wood.

My question is how can I repair this? Should I fill the gap up with mortar (any particular product suggestions welcome, as I've never bought mortar or mixed cement eg Sika Mix&Go). I've seen people suggest using 'expanding foam' - is that an option too?
I assume that it would make sense to apply a thin waterproof silicone sealant layer on the outer surface also.

Any help welcome. Cheers.

Kitchen window seal

• troybison
• 15 Oct 2014
• 1

crumbling mortar

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[foxhole]

Cement mix packed tightly into the hole and silicon, does not look like there is much timber missing so should look the same when finished.

 

[troybison]

Thanks for suggestion. I've ordered some Lafarge eady mix mortar for some re-pointing, so will try to fill with that. Should I try to leave a small gap (few mm?) between mortar & sill end to allow for the wood to expand?

 

[mattice]

I can't quite see the cavity but just refurbed 18 of our windows with similar symptoms, my friend was wood hardener, two part filler held off the brick work by a thin square plastic food container, left to harden, removed plastic leaving 2-3mm gap, coat of primer and then silicon frame sealant. Very pleased with result. Any big gaps between frame and wall I used mortar, but not to replace where wood had rotted.

 

[troybison]

Started by replacing 'lost wood' from the end of sill

repair 1

• troybison
• 19 Oct 2014
• 1

wedged in 2 strips of hardboard covered in gaffer tape to form mold for wood filler.

filled with Ronseal wood filler (I think the 'brown version' would've been easier to colour match, but was out of stock) & sanded down:

repair 2

• troybison
• 19 Oct 2014
• 1

Used Ronseal high performance wood filler & sanded down

I'm going to try to use a removable bit of hardboard again when doing the mortar to leave a small gap to fill with something softer like silicone filler...

 

[troybison]

Filled with mortar

repair 3

• troybison
• 21 Oct 2014
• 1

Filled cavity with mortar

 

[troybison]

Used a Unibond brown silicone sealant & painted over sill with Ronseal wood stain. Finished!

completed

• troybison
• 26 Oct 2014
• 1

Used brown silicone & painted over sill with Ronseal woodstain.