I am building a small garage extension. I want the walls in plane with the existing walls, but the existing slab in this area extends 3" beyond where the sill plate will sit.

What is the proper way to deal with this? I was going to use pressure-treated lumber for the sill plate with a sill gasket underneath and caulk the edge. I was thinking of creating a small sloped curb out of stucco and lathe to help move water away from the sill. Or maybe I could use flashing but that would be ugly and possibly sharp.

I haven't been able to find what the "correct" solution for this scenario is.

1 Answer 1


Not sure if this is "correct", but one solution would be to lay one course of block underneath the sill plate. This would keep the plate plenty high above the concrete. You would probably still want to slightly taper the outer edge of the slab away from the building, to avoid water sitting there and seeping in through the block.

  • Good idea. Only not going this route because it would look odd against the existing structure.
    – kenchilada
    Feb 7, 2019 at 19:02
  • Would you be able to bring the siding down over the block, so it would not be visible?You might just have to fur out the wall in the inside or outside to match the thickness of the block. Feb 7, 2019 at 19:31

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