Repair Sandstone Bay Windows - bottom of window cill?

NoisyGiraffe

Hi,

We're in the process of repainting our bay windows. They hadn't been done in about 20 years, previous repairs done badly (sand and cement just thrown in and not smoothed out etc), paint cracking off in big sections when we bought the house. 

So far we've scraped all the paint off (fairly easy, all the layers came off together as though nothing was even stuck to the stone anymore). A fair amount of the previous repairs came off with the paint (thankfully in some cases as they were badly done!). 

The stone for the mullions and headers is still very stable and has life left in it, even if its not looking the best cosmetically. We've used Touprelith-F as the filler on the bits that need it. Next steps will be to prime and paint.

The bit I'm stuck on, and can't find any info online, is what to do with the bottoms of the cills that have eroded quite badly. Plan is to use the same filler and build it up a bit/try to level it off. You can see what looks like the original level at the middle of the first photo. I can fill underneath using the front face to fill 'up to', but also need to extend the front face down in places to be able level it all off, which I'm not sure how to do.

Does anybody have any pointers on the best way to do this?

I'm not expecting anything near perfection here, just an improvement and some protection from the coastal weather we get to prevent further erosion.

Also just to note, we know that professional repairs/replacements by a stone mason will be needed in the future. It's not in our budget right now so we're just trying to make the most of what we have in the mean time. 

stuart45

You need to get someone to hold a bit of hardboard along a bit of the curve and use a pointing trowel to fill in a bit at a time. Slide the hardboard along a bit to break the seal before taking it off. Build it up a bit at a time. When finished cut a drip in.

NoisyGiraffe

Just a quick update and to say thanks again @stuart45 for the advice, it worked really well! I ended up using a plastering trowel that I could hold in one hand while filling with the other. Very happy with how it's turned out! 

stuart45

Glad it turned out well for you. Looks really good. Doing the bottom of a cill is a tricky job.