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Front Door Sill Overhang Size

I’m replacing a front door (36 “ x 80”) on my house. The walls are 2” x 4” construction, so a 4 9/16’ jamb. The existing door sill is 6 ½” wide with a ¾” overhang on the front stoop. Under this ¾’ overhang is a 1” x 3’ board nailed to the front bottom sill of the house.

The existing sill is also totally flat, that is no sill cap under the door. When entering or leaving the house (for 35 years) we have always stepped directly on to the sill, not over it.

The replacement door will be a pre-hung Therma Tru door. The door sill size is the problem. Therma Tru doors come with either a:

1. 4 9/16” sill - too short. I would need to add a 2” extender. However, the way the sill is built (see picture), if I add an extender, then I would have to put some type of support under the front of the sill where the extender is attached. I’m also concerned that with constant stepping on the sill, it might snap off.

2. 7 ½” sill - too wide.

3. 5 ¾” sill - too short. But what if I replaced the 1” x 3’ board under the sill overhang with a true ¼” or ½” thick board. A ¼” thick board would give me a ½” overhang, while a ½” board would give me a ¼” overhang.

I like option 3. It eliminates the extender and its problems.


• Is there a standard for what the overhang length should be?

• What is the minimal overhang length that is acceptable?

No luck uploading picture - oh well!

Re: Front Door Sill Overhang Size

There doesn't seem to be a real standard here- I've seen several variations. When I do one of these I just cut and fit whatever sill support is needed based on the new unit, that way it always fits!


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