How to fill in exterior doorway (add bottom plate) with sloping threshold?

samh25

Am wanting to fill in an existing exterior doorway. Curious how I would go about attaching a bottom plate when the existing concrete threshold slopes downwards? How would I build this up so new bottom plate sits level? Is building a little form and using non-shrink grout appropriate here?

FWIW all interior tiles will be removed.

MitchellMc

Welcome to the Bunnings Workshop community @samh25. It's wonderful to have you join us, and many thanks for your question about filling a doorway.
 

That sounds like a solid plan. Forming up the area and pouring your structural grout will provide the flat base you'll need to begin framing the doorway.

I can't quite tell from you're image how significant the slope is, but the other alternative is to bolt a bottom plate down with plastic shims under the outside edge to account for the deviation.

Please let me know if you have any questions.

Mitchell