I have a 2-car garage built on a block foundation that I wish to add an exterior door to in the back of, leading out to my backyard, opposite the wall with the garage door. However, the back wall's framing sits directly on top of the "open" block foundation. If I were to install a normal depth door (3.5" or so), it would leave about 4" of the "open" blocking exposed, leading to a big trip hazard.

What do I do to make a safe exit through this wall?

Few ideas I've had:

  1. Lay a thick piece of PT plywood at the bottom, covering the blocks, before installing the door. The downside is I'm concerned about strength.
  2. Fill the blocks with concrete where the door will be installed. The downside is I'm unsure how much concrete I would need, or if this would even work.
  3. Find a door with a wide enough threshold that will cover the entire width of the blocks.


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1 Answer 1


The PT plywood would be strong enough, but expensive for 1 sheet just for a bit for the bottom of a doorway.

Probably difficult to find a door with just the right threshold depth.

Simplest and cheapest solution. For the 36 inches or so you need for the door, fill the block cavity with stones until about 4 inches from the top. Fill the remainder with concrete and trowel smooth.
Probably 2 60lb bags of stones and 1 60 lb bag of concrete.

  • OP could carefully chip away concrete block the width of the threshold, deep enough to fit some 2x PT lumber, then fill with gravel and/or concrete, to get a more flush threshold. He'll obviously need to build up some jack studs on each side of the door, and a header. (Of course this says nothing about what he'll need to do on the outside of the wall.)
    – Huesmann
    Jun 21, 2023 at 13:39

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