Are you talking about the outside or the inside sill?

See this is when a picture comes in handy.

Please post a picture, so we know what you are talking about.

@BeverlyFLADeziner and @cat_ky okay I will post a photo first thing tomorrow morning!

I was talking about the outside. Here are a few photos (first one a window sill and the next one the patio door sill).

We had them redone professionaly last year. I assume it was not well done if it is already crumbling.

A sill is usually one piece. This appears to be something decorative in nature that was installed around a door opening. Have you contacted a mason to have this condition corrected? The water must flow away from windows and doors.

Probably not a good mix or application. Call another mason or look at something like Mor-Flexx if you want to do it yourself. I would request a mortar with some additional polymer additives next time.

Might need to dig it out well so you get a good amount in the gap. Too little will not have any staying power.

@BeverlyFLADeziner good question as to whether they are decorative (how can you tell?). That said they are still falling apart and it does not look good. It is actually a mason who did it last year… to correct the condition in which they were (they were starting to disintegrate but it had been about 10 years).

@cat_ky thanks, then we definitely have an issue. I think we will try a mortar/caulking type. No one on Houzz has suggested anything really so not sure where to go from here…

@millworkman yes I will do that as there are a lot of loose pieces/powder. I’m not sure how easy it is to work with the mortar caulking if there is a gap (from top to bottom for example).

You can try the concrete silicone caulk and backer rod after cleaning out enough of the crumbling mortar. Should work fine.

Okay I will try that thanks @millworkman.

I used hydraulic cement. I have no idea if that is a proper thing to use, but, it worked, and they still look just fine. I used the premixed type in a can.