This is a follow-up to my previous question: How can I fix a hairline crack in a thin wood panel of an exterior door?

While getting ready to apply wood glue (actually a mixture of wood glue and sawdust/sander dust) to the "hairline" crack in the door, I started scraping away spackling compound from my previous repair so the glue could find wood to stick to.

But after scraping for a while I realized that my spackling repair was not the only one. The house's previous owner had apparently spackled and painted over a huge crack in the door. After removing all the spackling, the crack turned out to be 1/8" wide all the way through the 3/8" thick panel. The crack runs for 12" top to bottom. The crack is oddly consistent in width throughout, except for a small part at the top where a thin chunk of wood is still in place on the inside.

Here's a picture. I put blue tape temporarily over the outside crack to prevent water damage and chilly winds while I figure out how to fix this.

enter image description here

Should I try to stuff a 1/8"x3/8" shim into the crack and glue it in place? If yes, what glue to use for a high-vibration, non-clampable, and exposed-to-direct-sun (under black paint) area like an exterior door panel?

If a shim is not advisable, what are other good options to fill such a large crack?

  • Again, a picture would really help us here. We can't really be sure what you've got by your description alone.
    – dbracey
    Commented Feb 26, 2012 at 20:52
  • I'll add a picture when I get home... Commented Feb 27, 2012 at 22:01
  • Justin, do you think it could be a joint between two separate pieces of wood? Such panels are usually "glued up" from multiple slats of wood. If the crack is straight and vertical and uniform in width, I'll bet it is an actual joint.
    – dbracey
    Commented Feb 27, 2012 at 22:49
  • In which case, I would put wood glue in it, and put some screws on either side of the crack (on the inside and the outside) and use rubber bands to "suck it together". Later, fill the screw holes and paint.
    – dbracey
    Commented Feb 27, 2012 at 22:50
  • The crack is not straight nor vertical-- it doesn't look like different slats. And regardless, the gap is painted into place on either side so thre's no way I could suck the pieces together without splintering the paint and/or the wood. Commented Feb 27, 2012 at 22:54

4 Answers 4


Though the crack is diagonal it looks relatively straight. In this case I'd take a piece of wood the approximate thickness of the crack at it's widest, cut it to length and then taper it so that it fits quite snugly - you should have to use a mallet to tap it home. Don't worry about the thickness too much - but obviously it should be fairly close.

Once this fits use wood glue to bed it in and fill the imperfections, though you might get a better finish using wood filler for this. Basically put more glue in than you need so it gets squeezed into every nook and cranny. Clean it off before it sets, then leave the repair to set.

Once set use a chisel to remove the excess from both sides of the panel and finally sand to make it flush with the panel. Fill any remaining (and hopefully small) holes, prime and paint.

By making the fit tight you minimise the chances for it to move, and therefore crack, further.

  • when tapping in the crack-filling shim, should I line the sides with wood glue to seal and adhere the sides better? Also, what does "use wood glue to bed it in" mean in your answer above? Commented Feb 28, 2012 at 19:04
  • @JustinGrant - yes line the sides with glue and that's what I mean by "bed it in". Basically put more glue in than you need so it gets squeezed into every nook and cranny. Clean it off before it sets.
    – ChrisF
    Commented Feb 28, 2012 at 19:09

If the repair is holding, leave it alone. You yourself did not know of its existence until you uncovered it. Isn't that evidence that it was doing its job?

If you really want to try to repair it in place, and it's a big gap, you could try a bondo repair kit (as in auto-body bondo). You will be making a fiberglass patch over the cracked area and sanding it to blend with the panel and painting over it.

I would try the Bondo Wood Filler or there's a Minwax High-Performance Filler that is similar. The key is that they are two-part systems based on polyester resin (like in fiberglass) so they don't shrink when they cure. The "wood" specialized versions of filler have stuff in them to make them more sandable than the auto-body bondo.

Epoxy-based products would also work similarly, and there are a bunch of those out there too.

  • The repair wasn't holding-- the paint on both outside and inside cracked and, after when I tried to patch over the existing patch, cracked again. My assumption is that the patching material used couldn't withstand vibration of a slamming door plus expansion/contration from direct sun exopsure plus rain. Commented Feb 27, 2012 at 22:13
  • I looked on Amazon for bondo and there's a wide variety of Bondo-branded repair kits. Do you have a recommended favorite? Commented Feb 27, 2012 at 22:59
  • I'm going to edit my actual answer because comments aren't long enough, so look above for more info.
    – dbracey
    Commented Feb 28, 2012 at 15:17

Rather than filling the crack, you could lay another panel over it on both sides. I would go with a thin AC plywood (AC is "good one side"). You can find 1/8" luan plywood and poplar - do the best you can.

Cut plywood panels to fit inside the trim on the panel, bevel the edges to make it look nicer, glue them down, and paint. If you could remove the trim pieces so that you could get the plywood to extend underneath (put the trim back over the top of the new plywood) that would probably look better.

And you will need to do this top and bottom, inside and out, to make it look right. A new door is sounding better and better :)


To build on @dbracey's answer, I think a good repair option at this point is to cover the crack with a new peice of wood on both the interior and exterior sides of the door. The width should be sufficient to center the piece and cover the crack. The thickness needs to take account for the trim surrounding the panel so that is is flush with the existing trim. Attach with Gorilla glue, let dry and then countersink wood screws to secure the interior and exterior pieces together. Fill in the screw depression, sand prime and paint. With all the thickness, a short screw (maybe a 1/2" at most) would be required taking account the 2 new pieces and the existing door panel to secure the three pieces together. Just glue might work also if the glue is water and temp resistent (outdoor side).

I've included a small diagram of a potential mock layout, the blue would be the new piece of wood. This would be the inside, just repeat the same for the outside.

Door Crack Diagram

Another option would be to replace the door entirely.

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