Going to be ordering a new exterior door and want to be sure I have the correct jamb measurement. I read where you should measure from the back of the interior trim to the back of the exterior trim.

I did this and my measurement is 5". Is the the same as the 4" 9/16 measurement I see on doors in the store?

 

If your wall thickness is 5", it probably means that you either have 1" ISO foam as sheathing, or some other combination of sheathing and insulation, like 1/2" plywood with 1/2" Thermax.

A 4 9/16" door is made for a 2x4 wall with 1/2" drywall inside and 1/2" sheathing outside.

If your wall is really 5" thick, and you get a 4 9/16" door, you can do a couple things. Add a 7/16" jamb extension onto the inside of the door (this would leave a gap between the existing flooring and the new door, which would also need to be addressed with a filler or additional trim). You may also want to use an extended or adjustable strike plate for the door latch.

Another scenario would be, remove the brickmould from the jamb and add a 7/16" jamb extension to the outside (provided the new door has brickmould and not a nailing flange) then reinstall the brickmould.

A third option, remove the brickmould, cut a 7/16" rabbet in the outside edge of the profile, reinstall the brickmould. This last method would probably move the exterior trim in deeper than where it is currently is positioned, which may not be a good idea, depending on what you currently have surrounding the trim.

You can also order a door that is made to the exact wall thickness you specify. Usually all this means is that they add the filler onto the exterior side of the door for you, along with any threshold extension that is needed.

 

Thanks. This home was built in the late 40's if this makes a difference in how the wall would have been constructed.

 

In my area, houses of that era usually have 1/2" wallboard covered with a thin 1/8" veneer plaster. And the exterior sheathing is probably 7/8" shiplap. Good luck with your project!

 

Your 2x4's could be 3 3/4" as well. That's what I have in my house, built in 1928.