A newly installed door has become very sticky at the bottom. Inspection shows the bottom portion of frame is bulging up. My guess is that the wood used to prop up the door threshold has swollen due to rain. Wood was a pressure treated type. Or it could be foundation issue.

Should I remove the wood and use some other material?

How do I flatten the threshold of the door?

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  • 1
    "Should I remove the wood and use some other material?" It is that or raise the rest of the house ;). Do you know how the upper piece of wood is attached? You may have to un-install the door to get at the fasteners. I would start with removing the lower piece of wood and see if that has an effect.
    – Alaska Man
    Jan 12, 2021 at 19:49

2 Answers 2


Step 1: Properly size the support lumber

What we see there looks like more than just swelling to me. It seems like someone jammed a full-thickness two-by in there out of haste. Swelling was just the final straw that caused rubbing.

You'll need to remove it. Use a reciprocating saw (Sawzall) to cut any fasteners running through it, then pry it out.

Then flex the threshold back into shape. Support the ends when you do--you don't want to tear it from the jamb sides.

Use a dry piece of lumber to fill the void. Cut it to the correct size (thickness and length), and use construction glue or silicone caulk to set it in place. If there's room you could toenail a few screws from the front.

Step 2: Flash the area properly

None of that wood should be visible. Fit a piece of aluminum stock or other water-repellent material under the threshold and down the face of the wall. Tuck it back under the bottom board if possible, and caulk that seam, or leave a short flange protruding outward from the wall and caulk under it. Caulk between the threshold and the flashing and along the side casing as well.

_________________________|<-- threshold
            top board    ||<-- flashing
          bottom board   ||
                            *<-- caulk beads (here and above)
  • Wouldn't wood eventually have the same problem? Wood is easiest to work with, but are there alternatives? I removed the bottom board and threshold is in much better shape now. Problem seems to have come from an error in original foundation pour. The threshold sticks out by about an inch causing all this problem.
    – Maesumi
    Jan 25, 2021 at 15:45

I'd verify the threshold is level and if it's not note which side is higher. Remove the treated 2x underneath the threshold and check for level again.

If the side that's binding is too high tapping it down with a hammer and a wood block on top of the high spot should at least enable the door to shut smoothly.

Once the door functions properly you'll need to shave the treated 2x so it fits snugly enough to support the threshold, but not so tight as to warp the metal.

You may want to install a 2x that is long enough to span the entire threshold. It's also wise to apply some type of caulking to the 2x before setting it in place. Flashing (Pan-type) should have been installed in the rough opening before the door was set in place, but.... caulking will have to suffice.

  • You won't do much with level at this point--the jamb is secured. You'd have to tear the threshold loose to level it. Did you mean straight?
    – isherwood
    Jan 12, 2021 at 22:09
  • What I meant is it's good to know if the threshold is level or not. When the support is removed and it's still pitched the problem may be some where else.
    – ojait
    Jan 13, 2021 at 1:01

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