I have a 1970 home with a sliding patio door I'd like to replace. The sill is set into the concrete though. I want to replace with French doors, so I'm curious of a few things…

I assume the sill can begrudgingly be ripped out of the trough. If that is successful, I guess I just fill the trough with concrete and set the new door on top of that?

Can you post a pic ?



Usually on a retrofit from slider to french you will have to add a treated 2x6 at the bottom to bring it up to make the existing rough opening height work.

That makes sense. Thanks. Not sure how far inset into the concrete it is.

You could probably fill with concrete. It's not going to be set very deep.

I would be worried about a thin layer of concrete that it will not bond and would be subject to cracking. This in turn would become a weak foundation for the threshold. It needs to be thoroughly cleaned, then I think I'd look into something more along the lines of thinset or a self leveling compound that's designed to adhere to existing concrete. Of course then my treated 2x on top of that.

Depending on how level the flooring is on whichever side you want the doors to swing is, you might be able to take advantage of that recess and have a flush sill on your french doors. I wouldn't rush to fill it. If you need to shim just a bit, I would rather use a PVC board vs treated that will still inevitably rot.

Thanks for the replies

I went from sliding to french doors in a remodel where it was set in the concrete. Not sure how they installed the new door, but they did.

Yeah. It was my wife's grandparent's house. Built in 1960. Guess that was the style. We lived in it for 3 months to get an idea of what we wanted to do to it. Then we moved out and gutted it.