How to Repair a Rotted Door Bottom and Weatherstrip

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This project explains how to repair a rotted door bottom and weatherstrip. Also see How to Repair a Rotted Exterior Door Frame if the side jambs are also rotted.

The single light French Doors at the basement patio are both sagging, resulting in a torn weatherstrip on the active door and a significant gap between the doors near the center bottom. The doors are sagging because each door weighs 65 lbs and is a too heavy for the standard grade residential door hinges.

The patio doors are made of metal skins folded over an outer wood frame with a foam core. When I removed the door to replace the hinges and weatherstrip, I discovered the door bottom wood frame had dry rotted and was nearly gone!

Sagging Patio Doors

Sagging Patio Doors

Door Repair Jig

In anticipation of replacing the hinges on both doors, I made a jig out of scrap 2×4 lumber and 3 inch wood screws to hold the doors. French doors are expensive and I didn’t want to take a chance on breaking the glass panes.

Door Jigs and Wedges

Door Jigs and Wedges

My doors are 1-3/4 inches thick. Therefore the vertical 2×4 blocks are spaced 2-1/4 inches apart to form a slot about 6 inches deep to hold the door. Wedges are used to take up the slack. The other jig dimensions are not critical, but sized such that the can’t tip over. I found these to be rock solid.

If you’re worried about scarring the door faces, just lay an old towel inside the jig to protect door finish.

How to Repair a Rotted Door Bottom and Weatherstrip

This is bottom of the french door before I removed the old weatherstrip. I thought it would be simple repair to remove the old weatherstrip and install a new one. Little did I know the “fun” was just about to begin!

Patio Door - Torn Weatherstrip

Patio Door – Torn Weatherstrip

When I pulled off the old weatherstrip I discovered that most of the outer wood frame had rotted away. I scraped out chunks of what was left of the old wood. My first thought was termites but the side frames were solid and untouched. I saw no evidence of termite tunnels and the door jamb was also OK. Closer inspection revealed the tendrils and spider-veins of fungi due to dry rot.

Rotted Door Bottom Found after Removing the Weatherstrip

Rotted Door Bottom Found after Removing the Weatherstrip

The basement patio doors are shaded by the wood deck which created a cool moist environment that promoted fungi. Surprisingly the fungi only ate the bottom section and didn’t attack the side frames. My guess is the side frames are made of a different species of wood to take stresses of the door hinges and locks; or perhaps the door bottom was wet from splashing rain.

Here’s a closeup of the rotted wood. The bright area near the bottom left is the exposed foam core. I gave the inside a good spraying with bleach and water to kill any spores.

Dry Rotted Door Bottom

Dry Rotted Door Bottom

It was necessary to unbend the folded edge of the metal door skin to insert a new piece of wood. A pair of duck-billed sheet metal pliers (hand seamer) would have been ideal for the job. A large adjustable wrench did the job just as well, if more slowly. To minimize metal fatigue, I first bent the edge out  45 degrees along the entire length, then made a second pass to straighten it out flat as shown here. The lips on both sides was unfolded this way.

Unfolding the Metal Edge of the Door

Unfolding the Metal Edge of the Door

The dimensions of the replacement frame section is 1-11/16 inches wide by 3/4 inches thick by 31 inches long. The closest thing I could find was a 1 in x 4 in x 8 ft pressure treated board at Home Depot. Pressure treated wood resists rot and the outdoors. A nominal 1 inch board is actually 3/4 inches thick. To get a 1-11/16 inch wide board, I asked the Home Depot guy to rip it for me on the plywood saw because I don’t have a table saw. (Of course, you still buy the whole board, which is fine.) It was then a simple job to hand saw a 31 inch length when I got home. The new board fits in between the two end frames as shown in a notch that not too apparent in this photo.

Pressure Treated Replacement Door Frame Section

Pressure Treated Replacement Door Frame Section

The bottom of the door frame is filled with GREAT STUFF expanding foam insulation. GREAT STUFF expands to several times it’s initial volume and is very sticky. This will fill in all the voids in the door bottom and press the new wood frame tightly against the metal door edge.

GREAT STUFF in the Bottom Door Frame

GREAT STUFF in the Bottom Door Frame

The new pressure treated wood section is pressed into the door bottom. The GREAT STUFF is expanding and trying to push it back out:

New Wood Frame Pressed into the Door Bottom

I used a rubber mallet to bend the lip of the metal door skin over the new section wood. The outer corners of the wood strip acted as a sheet metal brake to accurately bend the metal just like the original construction. The GREAT STUFF is expanding and squeezing out nicely. This will hold the wood tightly against the door skin.


Larger view of the new wood frame in the door bottom. The GREAT STUFF at the red arrows completely filled the end gaps and is trimmed flush with the bottom.

Replacement Door Bottom Frame Section

Replacement Door Bottom Frame Section

Install the New Door Bottom Weatherstrip

The old weatherstrip attached by two ribs that fit into matching kerfs, or slots, in the door bottom. The new door bottom lacked these slots so I used a U-Shaped B79/35H Vinyl weatherstrip by Frost King. It attaches to the outside of a metal door with screws.

The weatherstrip is tested fitted on the door and marked to cut the length to fit the door. The installation was simple – test fit, mark the length, cut, test fit again, mark the screw locations, drill pilot holes and attach with screws.

Frost King B79/36H U-Shaped Door Weatherstrip

End view of the U-shaped weatherstrip showing how it slides over the door bottom.

End View of the Frost King U-Shaped Door Weatherstrip

This is the new U-shaped weatherstrip installed on the door.

U-Shaped Weatherstrip on the Repaired Door

The new weatherstrip sealed well against the door sill, but a couple of things bothered me:

  • The screws might rust.
  • Water could seep in along the top of the weatherstrip and pool along the door bottom.
  • The appearance didn’t match the other door.

I recommend caulking the screw heads and the top edge of the weatherstrip to seal out moisture.

I decided that I didn’t like the appearance of the U-shaped weatherstrip, so I removed door and cut slots in the wood door bottom to install the original kerf-mount weatherstrip as described in How to Repair a Rotted Door Bottom and Weatherstrip – Part 2.

Thanks for reading,

Bob Jackson

Copyright © 2019   Reproduction strictly prohibited.


  1. R. Patton March 6, 2011 at 10:32 pm - Reply

    I just found this website when I was searching for information on how to repair our exterior doors which have rotted on the bottom. Your explanation and pictures are amazing and are exactly what we needed to help us through this project. Our doors were ruined by the hurricane and insurance would not pay to replace them. With five doors we were looking at a very expensive problem. Now we have your how-to in hand, we are ready to tackle this project and will be doing so in the next week. Thank you, thank you, thank you for your wonderful article.

  2. FJ_2 May 3, 2011 at 8:22 pm - Reply

    Excellent article, and I’ve been around!

    I have wondered about that expanding sealant — didn’t realize it keeps expanding after it’s out of the can. Not sure how to use it in any other situation.

    But mainly great practical details on how you pulled it all together.

  3. Beth Wood May 3, 2012 at 5:52 am - Reply

    Thank you for this excellent tutorial. Pictures were great. I completed this project with your assistance giving me the confidence it could be done. I did run into a little bit of a complication w/ internal dado joints, so simply cut those flush with my beloved Dremel tool and nailed the replacement wood to this internal bracing. Worked fine. Would have not thought of the clorox spray. Good idea. Taught my son how to do it as well with your site. On to my next project, an automatic gate opener…

  4. Martin May 22, 2012 at 8:10 am - Reply

    I am having same problem. One question about sagging, after you replaced the hinges and strip, did it fixed the gap in between the doors?
    In my case I have heavy duty hinges and gap between door and frame and suspect possible rotten wood in framing. (I can see that previous owner did some work on the door, makes me believe that this might more work…:(

    • Bob Jackson May 22, 2012 at 4:33 pm - Reply

      Installing heavy duty door hinges was what trued up the doors to fix the gap.

      The hinge screws need a solid door frame to carry the weight of the door. A rotted door should be replaced – remove the doors, hinges and trim boards, then replace the failed 2×4 framing members. See this project for how to replace an exterior door.

      • Brian May 18, 2016 at 7:39 am - Reply

        The top hinge holds the loin’s share of the weight. It’s a good idea to use a screw long enough to reach past the door frame, and into the stud. I even use at least one 3′ or 4′ in screw in the center hole of a top hinge on interior doors because sometimes it’s not the hinge that will sag over time. The misalignment could be a sag in the frame, and often times is due to a sagging foundation under the building causing walls to lean.

  5. Kristy October 16, 2012 at 3:37 pm - Reply

    I have a double opening french door. I opened the door and the rubber plug in the bottom stuck to the threshold pulled out and tore in half. What are these called and where can I find a replacement part? I’ve tried every where. Please help because water and bugs can get in. It is a Stanley french door no parts list can be found. Thank you so much I hope you can HELP.

  6. Andrea November 16, 2012 at 2:47 pm - Reply

    thank you thank you thank you, my door is doing this too I search around everywhere on how to fix this, it didn’t occur to me that my door used to have a piece of wood at the bottom it was just chips of wood falling down, and the door sweep would never stay on.

    this was excellent thank you!!

  7. Richard December 31, 2012 at 9:21 pm - Reply

    I too followed your instructions and it was a success!!! I didn’t have a lip to contend with, so I merely cut the treated wood to fit and sprayed the filler around it. I am about to put the weatherstrip on tomorrow. Great idea to save a metal door! THANKS!

  8. Greg May 13, 2013 at 9:16 am - Reply

    Thanks for publishing this great article! I am not the handiest of guys, but the excellent pictures and step-by-step instructions made it very easy for me to follow. I completed this project yesterday and am very impressed with the results!

  9. robert December 28, 2013 at 7:21 am - Reply

    Would drain holes drilled into wood help keep moisture from collecting?
    Also a video of there construction would be nice know of any and thanks for this fix.

    • BobJackson December 28, 2013 at 7:52 am - Reply

      I’ve not seen a door bottom weatherstrip manufactured with weep holes and think that would defeat the purpose of a waterproof barrier. I believe what caused the wood rot on my basement patio door are it’s in a shady location that promoted condensation and the original wood frame was not pressure treated.

      I didn’t make a repair video because I think the high resolution and extensive photos better explain the repair steps. YouTube may have something.


  10. Doug November 30, 2014 at 1:27 pm - Reply

    My door is doing the same. Also the metal is rusting on the outside and is really thin. I was thinking of attaching a piece of aluminum or something over it to reinforce. Thanks!

  11. michael w. November 28, 2015 at 12:40 pm - Reply

    Dear Bob,
    I think I have a fairly typical damaged french door bottom. Without removing the door just yet, I was able to remove the u-shaped metal door piece on the bottom of the door that opens. (The other door does NOT have any damage, which I attribute to it’s staying closed and the wood rot damage to the u-shape unsealed metal strip.) Before I saw your excellent How-to repair, I assumed the bottom of the door would be solid wood all the way from the bottom of the window glass to the bottom of the door. After reading your explanation, I am now having second thoughts. (By the way, the door bottom has no metal other than the U-shaped metal piece.) Question 1: Would it be wrong to just get a good solid piece of wood across the bottom of the door? 2. Are Most Exterior Doors filled with foam? 3. If my door is filled with foam, how much time do you have to put the bottom strip of replacement of wood on before the spray in foam sets up? 4. How do you get the replacement wood to set up squarely when the spray in foam is so random? I have a metal square that is 16 inches by 24 inches long. 5. Should I build something similar to your jig to make the replacement easier to do? Thank you. Michael W.

    • Bob Jackson November 29, 2015 at 10:14 pm - Reply

      Hi Michael,
      Is your French door solid wood or metal skinned like mine?

      Replies to your questions…

      1: A solid piece of pressure treated wood across the bottom of the door should be such that it replaces the entire rotted bottom rail. This is how I repaired my metal skinned door.

      2: I suspect most metal skinned residential doors are filled with foam or equivalent material for lighter weight and better insulation properties.

      3: GREAT STUFF Window & Door foam sealant is tack free in 10 to 15 mins, so you have about 5 minutes to set the wood repair strip in place to be on the safe side.

      4: The replacement wood rail must fit “squarely” (a better term is “snugly”) in the door bottom as shown in this this dry fit photo. Thus, there’s no guesswork and no need for a carpenter’s square. The wood strip is held in place when the metal door skin is folded over the repair strip and the foam expands to fill the voids.

      5. Definitely build a door jig. It’s simple and I made mine in a few minutes from scrap 2x4s. The jig will free up your hands and reduce the risk of the door falling over and break the glass.


  12. Brian May 18, 2016 at 7:53 am - Reply

    Great write up! A word of caution if I may be so bold: Expanding foam insulation (Great Stuff) forms lots of tiny bubbles, and pockets that will collect and trap a surprising amount moisture which as we all know will lead to more rust and rot. I try not to use it on wood, or in places where moisture my be a problem such as the bottom of a door. ;)

    • Bob Jackson May 18, 2016 at 6:36 pm - Reply

      The GREAT STUFF product literature states it’s “water resistant”. The expanding polyurethane foam forms Closed Cell bubbles as it cures and is basically impermeable to water.

      If GREAT STUFF really did absorb moisture and promote wood rot (which it does not) I doubt it would be so successful for weather seal applications.

  13. Carole M Pluckrose November 11, 2016 at 7:01 pm - Reply

    I need urgent help please. To protect our hens from 4 legged and 2 legged predators, we have turned our bricks, mortar and double glazed potting shed into a new, safe home for them. (The previous owner had everything, including the garage, double glazed), however the door is a wooden shed one. The bottom of the door has rotted in places and is desperately in need of repair or replacement. This I have to do myself, not easy for a disabled woman, with a wonderful husband who cannot help due to a stroke. Should I repair the door by sawing off the bottom third and replace it with clean wood or treat the lower part of the door and then use metal to cover that part of the door on both sides? As it is, the rotten part is secured by bricks and an extremely heavy flower pot, which I am becoming quite good at struggling with, but it is not a suitable long term solution and our beautiful girls are still at risk from attack. Incidentally, we have had dog and badger attacks, hence the 4 legged predators and our girls, at that time, were stolen by the 2 legged ones. Would a new door be a better solution, if so what would be the very best replacement? Please help our girls and save us from heartbreak.

    • Bob Jackson November 13, 2016 at 12:24 am - Reply

      I’d replace the door but a picture would help me understand the door construction (store bought or homemade), size, type of hinges, etc. You can e-mail photos to bob[at], replace the [at] with the @ symbol.

  14. Robert June 29, 2017 at 1:04 pm - Reply

    This is exactly the problem I’m having with my exterior double doors. The one problem I do have is that the metal corner at the bottom is already bent backward because I’ve put off the project too long and closing the door from the outside has bent the inside metal corner into the living area. What is the best way I can make sure the metal connects to the new wood I’m putting in since simply using the mallet to cover the new wood with the metal isn’t very secure as in your pictures. Do I need to put a screw into the living area side of the metal to the new wood strip?

    • Bob Jackson July 1, 2017 at 3:34 pm - Reply

      Hi Robert,
      Thanks for sending the photo. Smear construction adhesive between the metal skin and wood frame. Get as far back as you can for maximum contact area. Construction adhesive comes in caulk gun tubes and available at the home improvement store. Use bar clamps with wood blocks to evenly press against the metal skin until the adhesive cures.

      The two V shaped creases on the door skin can be tapped flat with a hammer. The vertical edge of the door skin can be bent inward by pressing with a wide flat metal tool. A flat head screw drive will do the job if you work along the seam at little at a time to avoid divots. The outside jaw of a hand seamer would be better than a screw driver (creative way to use a hand seamer).

  15. Wanda October 10, 2017 at 2:19 pm - Reply

    Thank you so much for all the good information! Makes life easier for all of us who can’t afford professional help.

  16. K Brown May 3, 2018 at 8:15 pm - Reply

    Bob – I have a french door that has rot at the bottom. Your solution is giving me hope that I don’t have to replace the door.
    I know that I don’t have the skill to do this repair. If I hired someone to do this what is a reasonable fee. I’d like to understand because it might be smarter to buy a new door. thanks

    • Bob Jackson May 4, 2018 at 9:37 am - Reply

      The repair will take an hour or two. Handyman labor hourly rates vary but somewhere in the range of $120 to $200 would be reasonable plus the cost of materials.

  17. Bobbo August 24, 2018 at 3:22 pm - Reply

    Just found this website. I have a theory that whatever problem I have, someone else had the same problem and found a solution. My rotted door bottom is the latest proof of this. I appreciate the engineering that you posted; saves me all that time! One question, though. The height of my replacement wood strip is 1-1/8 inch. I was hoping to screw the new weather strip into the new wood, but it appears that the predrilled holes in all of the weather stripping I found are higher up than 1-1/8 inch. That means, unless I can find one that is not predrilled, I will be fastening into the foam. That doesn’t sound very secure. Any thoughts? BTW, I want to use an aluminum U-shaped mounting to give the door bottom more strength to counter the rust down there. As far as your early comment about screws on the exterior rusting, I will use SS screws.

    • Bob Jackson August 25, 2018 at 11:32 am - Reply

      Fasten the new weatherstrip with 3/8 inch stainless sheet metal screws set in the factory made pilot holes. Sheet metal screws have coarse threads for the metal door skin.

      Next, drill three pilot holes (left, middle and right) a bit lower where the screws will sink into the wood door frame bottom. Put a dab of mildew resistant exterior silicone caulk in each of the pilot holes for a watertight seal, then set the screws. If you want to paint the screws to match the weatherstrip, take care to use *paintable* silicone caulk.

  18. Phil Levinson September 17, 2018 at 9:03 pm - Reply

    The bottom of my exterior side door was rotten and looked identical to the bottom of your door. I followed this method and with only slight variation was able to completely repair the bottom of the door and install new weather stripping. Thank you for your detailed instruction and photographs. You made it easy and I did this project in less than 2 hours including the run to the Home store for just $20. Thank you!

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