Advice for repairing window sill

Nanz · 23 Oct 2019

Hi there

First post here

I have an external concrete window sill that needs repair. As you can see in the photos, the render has fallen away from the vertical. What's the best way to repair this? Should I just use a standard mix of mortar and pva or is there a better way to do this?

Also what is the best way to repair the cracks, I can see moss growing through it now.

Also when it comes to painting it again, what should I use?

A few years back I stripped back the whole window sill and re-rendered it with mortar mixed with PVA. It seems to have held up pretty well apart from this part, but I want to make sure that when I repair this, I am doing it the right way.

Images attached.

bobasd · 23 Oct 2019

the amount of boxes and cables and comms is disgraceful - just thrown and stuck on anywhere. it is what it is.

the thin skim of whatever and oil paint(?) across the full sill has reached the end of its life - it all needs to come off back to stone.
the sill can then checked for a drip throat.
the sill can then also be examined for cracks.
and lightly gone over with an angle grinder stone.
and then a sander.
after prepping, take advice from the painters forum for painting stone.

like wise the pillars and frames could be sanded down, and then properly painted with all old silicone seals removed and replaced

Nanz · 23 Oct 2019

bobasd said:
the amount of boxes and cables and comms is disgraceful - just thrown and stuck on anywhere. it is what it is.

the thin skim of whatever and oil paint(?) across the full sill has reached the end of its life - it all needs to come off back to stone.
the sill can then checked for a drip throat.
the sill can then also be examined for cracks.
and lightly gone over with an angle grinder stone.
and then a sander.
after prepping, take advice from the painters forum for painting stone.

like wise the pillars and frames could be sanded down, and then properly painted with all old silicone seals removed and replaced

thanks for the advice. As for the cables, its horrendous, was like that when we brought the place. As far as I am aware, they are not in use anymore so I might just get rid of it all.

Any thoughts on what to use for the rendering / repair?

martin hill · 23 Oct 2019

If you don't fancy tackling yourself you can get a company in who refurb sandstone cills and windows. Its cleared of debris and cleaned down. Some build a little frame work and recast the edging of the cill.

https://www.plastic-surgeon.co.uk/stone-and-brick-repairs/header-and-cill/

If you do fancy tackling it You tube has a wealth of videos.

Nanz · 23 Oct 2019

martin hill said:
If you don't fancy tackling yourself you can get a company in who refurb sandstone cills and windows. Its cleared of debris and cleaned down. Some build a little frame work and recast the edging of the cill.

https://www.plastic-surgeon.co.uk/stone-and-brick-repairs/header-and-cill/

If you do fancy tackling it You tube has a wealth of videos.

I had never come across this company, ill give them a call to see what they think, thanks!

martin hill · 23 Oct 2019

If a company looks to be too costly try having a go. Dont rush it and this cement works a treat on repairs but only mix a little at a time

https://www.diy.com/departments/u-c...DeR1QzG9iKSEOY54QWxoCNR0QAvD_BwE&gclsrc=aw.ds

bobasd · 24 Oct 2019

does it need rendering or repairing?
wait and see until you've removed all back to stone, and posted pics on here of what you've done?

Nanz · 24 Oct 2019

bobasd said:
does it need rendering or repairing?
wait and see until you've removed all back to stone, and posted pics on here of what you've done?

On top of the stone currently is a mortar render which was done a few years back. I suspect its just the render that needs repair but ill see once i start to strip it back.

I just need a break in the weather now.

Nanz · 29 Oct 2019

Just an update, I managed to strip it back and had a chunk of the sill fall away. I cleaned it all up as best I could.

I have now rendered using TOUPRET TOUPRELITH F EXTERIOR MASONRY REPAIR FILLER. Got another layer to do.

I attached some images for viewing.

martin hill · 30 Oct 2019

It's looking good. Hope you get some dry weather to finish it. Good idea to do in layers as dries out better. If you do an more base layers put some criss crosses in so the final layer got something extra to grip too.

opps · 3 Nov 2019

Nanz said:
Just an update, I managed to strip it back and had a chunk of the sill fall away. I cleaned it all up as best I could.

I have now rendered using TOUPRET d MASONRY REPAIR FILLER. Got another layer to do.

I attached some images for viewing.

TOUPRELITH F EXTERIOR is great product, however it is a very soft filler, you will find that the the window cleaner's ladder will dent it. Tourpet Murex is much harder.

Nanz · 5 Nov 2019

martin hill said:
It's looking good. Hope you get some dry weather to finish it. Good idea to do in layers as dries out better. If you do an more base layers put some criss crosses in so the final layer got something extra to grip too.

Thanks for that advice Martin, yes I am doing it layers, just need another dry day and I should be able to finish it all off, good call about the criss crosses as well!

Nanz · 5 Nov 2019

opps said:
TOUPRELITH F EXTERIOR is great product, however it is a very soft filler, you will find that the the window cleaner's ladder will dent it. Tourpet Murex is much harder.

Ahh interesting, I will keep an eye on this and see how it handles. Luckily we never put anything of weight on the sills so hopefully it should be ok!

pilsbury · 8 Nov 2019

That looks a decent effort there. Well done.

opps · 11 Nov 2019

Sorry Nanz, as per above, yup it is looking good. Kudos.

Another alternative that you might not have considered is using 2 pack (polyester resin) filler. I use it on masonry window sills that I am going to gloss. The finish is far smoother than the likes of TOUPRELITH F.

When faced with smallish chunks out of the old sill, I apply SBR and then fill with 2 pack, then sand, apply more filler, sand again... and so on, and on and on.. I end up coating the whole window bay sill. A sill like yours (without the massive bit that you have had to replace) would be about 2 days labour. It might sound like a long time but you end up with really crisp and straight lines.

If you ever decide to go down that path purchase the 3.5L tins of Upol Easy 1 from ebay- you can get them for about £18. A lot of sanding is required but you can sand after an hour or two, thereby reducing waiting times.

There have been times when I used TOUPRELITH F and glossed over it but that was only because the client I changed their mind about about masonry paint after I had started. TOUPRELITH F doesn't like additional coats of TOUPRELITH F being applied directly over itself. You need to apply at least two coats of masonry paint over it first before you try to apply more filler and then feather it out. If you don't then the edge of the new filler will "rip" (slightly) as you try to feather it out.

That said, it is a great filler, it's just a shame that it is difficult to apply to large areas in one hit (mind you the same can be said of 2 pack filler- bar the feathering issue though).

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