Finish Cracks at Joints in a Five-Piece Door

Wood movement causes inevitable finish cracking at joints in cabinet doors. Here's advice on how to allow for it. April 10, 2008

We are painting maple five piece solid doors. Where the stiles and rails meet, we are getting cracks. Is there any prep to stop this from happening? Will more coats of primer/topcoat help? We are using Chemcraft products - 522-1410 primer and Plasticolor top coat. We are applying one primer and sanding it down, followed by another coat of primer, then scuffing just the primer. Followed by 5 mil wet of Plasticolor.

Forum Responses
(Finishing Forum)
From contributor J:
Welcome to the wonderful world of wood. Wood moves. The only thing you can to it is find a stronger, more durable finish that will allow the wood to move, and that would be 2k urethane. I think it allows for up to 4 mils of movement, whereas lacquer allows 1. Then only other option I have found in 15 years of finishing is have the doors made of a solid piece of MDF on a CNC machine.

From contributor C:
The reason manufacturers use what is called a quirk, aka a fine routed line, where joints meet is just because of this problem. I'm in full agreement with this practice. If the client will not accept the fact that wood moves, then I would create a quirk/reveal/route line at the joint to show him, and if that was not acceptable, then use a one-piece solid substrate such as phenolic MDF. If by chance you're making these doors yourself, you could possibly use a corebox construction to make the frame and then inset a plywood panel or other.

From contributor N:
You might try solid maple rails with MDF centers or premium grade maple. Premium grade maple costs more, but so does repairing it.

From contributor S:
I don't know what the maximum build on the Plasticolor is, but that seems high. That said, the way I have gotten around the problem has been to use auto body filler, Bondo, over the joints. Just apply a thin skim of it over the joint and sand most of it off. The filler tends to work into the wood at the joint and helps hide the joint when you paint it. The other thing I have done is to use a quick dry enamel, but the only problem with that is that you have to wait 72 hours between coats or all hell breaks loose. I use white lacquer undercoat as a primer. By the way, only use the quick dry if you want high gloss finish.