Crumbling internal concrete sill??

[x60rsa]

Hi

I am going back to brick in my bathroom as the plaster was shot. Anyway, after removing the tiles around the window it appears that there is a concrete sill thats cracked and needs replacing. Its about 25-30mm thick and.completely loose.

Can you suggest what I should do to bould this back up before plastering? Some people have suggested cutting thermolite blocks and cement them in?

Thanks

 

[Deluks]

Probably just sand and cement at that thickness. Just use the same again to level it off. Insulated tile backerboard (jackoboard/marmox etc) is available in 6mm, 10mm, 20mm and can be used to build up the height.
Are you insulating the wall? The above products can also be used on the wall itself.

 

[^woody^]

Expanding foam, applied carefully and then cut back to suit. Or foam and strips of plaster board.

If you take the existing off and expose the back of the wall below the frame, fit a DPC first.