Cracked concrete window sill

[greenchimneys]

I'm just getting round to doing some much needed maintenance work on my windows (repainting sills, filling cracks, replacing sealant) but after removing the paint on this sill I can see that the cracks are worse than I thought. Some of the pieces are loose.

I was going to use some Toupret exterior filler for the cracks but I'm wondering now if I need something more serious?

 

[blup]

Toupret is cement based, Bosch cementone from SF is good.

Blup

 

[Wayners]

I've seen a box made as new concrete sill poured.
I prefer the Idea of using bricks like this.

Bricks for window sills

www.randerstegl.com

You can also repair then tile over sill but that may not last

 

[DiyNutJob]

Remove the loose bits, and fill with cement sand mix. 1 cement to 2 sand or 1:1. Use flat wood plank as as a former for the sides. Leave it exposed to the elements to harden for a couple of months, then masonry primer and paint.

 

[greenchimneys]

Okay, I was thinking of using filler to kind of stick the pieces back together and fill the cracks but maybe it does make sense to just take out the loose bits and replace those bits completely.

I have another bay window at the front that I haven’t stripped the paint from yet and I have a feeling at least some of those sills will be similar to this one.

I’m wondering whether it might be easier to replace the window sill completely instead of trying to piece them back together if there’s more than one that’s this badly cracked.

 

[DiyNutJob]

The sill goes below the window.