Door Warping Mystery

      Tall veneered-MDF cabinet doors are warping badly. Why? February 20, 2008

I have made some flat panel slab style doors that are approximately 18" x 80". The doors were made of maple veneered MDF core. We put some molding on the exterior side of the doors. After installation the doors began to warp toward the side with the molding. They warped almost 1/2" at the top and bottom. Has anyone experienced this? If so what would be the solution? I have put molding on smaller doors in the past without a problem. I didn't want to do the doors this way but the decorator insisted and so I did it against my better judgment, but now I feel responsible to fix the problem.

Forum Responses
(Cabinetmaking Forum)
From contributor D:
Never build according to a designer's specs. They know nothing about how wood works. Is it one large panel? I would break a door that size into 2 or 3 panels. How many hinges are you using? I would use 5 at least on a door that size. Were space balls or other panel spacers used in the construction? Did the wood come from a reliable source and was it allowed to acclimate before you started machining? What are the humidity conditions of the home it is in? There are many factors that could cause this problem, moisture being the biggest.

From the original questioner:
These doors were just solid panel doors. A slab door from maple veneered MDF core. This should not have warped, as MDF does not have any grain. That is why I suspected the molding may have had "pull" and caused it to warp in the direction of the molding. The doors seemed to be flat in the shop, but when we installed them in the house they were already warping. There are 6 hinges on each door. I have brought two of them back to the shop and removed the molding and put them in the vacuum press to hold them flat over the weekend and we will see by Monday if they stay flat. The doors are just like a piece of plywood, only MDF core instead.

From contributor C:
Hafele sells a truss rod system that might be of some use in this sort of situation. Maybe someone else can think of the name or part number. I think it is called Plan-o-fit?

From contributor D:
Sorry, I assumed it was a framed door with a 1/4" panel. MDF does warp and sometimes severely. I cut everything on a CNC and I have had sheets so badly warped the vacuum won't even suck them down. I have also seen the warp amplified after being cut. I have also seen nice flat and stable MDF. You may have just gotten a bad batch from your supplier; maybe you should get them involved. Also, if one side has thicker veneer than the other, this could cause an imbalance in the sheet, causing the warp. I doubt the trim is causing the warp.

From the original questioner:
These doors were not veneered after the fact. They were just factory veneered panels. I did not notice the panels being warped when they were in the shop. Nor did I notice them warping after the trim was installed on them. I only noticed it after we put the doors on in the house. Next time I will override the designer or make a disclaimer if they want to do something I don't think is a good idea, but this time I am stuck. I have seen the item in the Hafele catalog that was suggested, but I don't think the customer would want to see it on their doors. Two of the doors cover an entertainment area and they stand open when the TV is being watched.

From contributor R:
My bet would be one of two things, but most likely one side of that door has some steady heat applied to it, causing it to warp, or maybe the finisher put one or two more coats of finish on the fronts vs. the back. I do coat my doors one more time on the front sometimes, but not on large and especially not large slab doors.

From contributor X:
18 by 80 - flat slab. My opinion is, 3 hinges and a 1" x 2" x 72" stiffener added to the back side of the slab door. One side is secured by the hinges and the other side is secured by the stiffener to keep it from bowing. Shelving must be set back or notched for the stiffener, though.

From contributor Y:
I don't offer doors that large no matter what material and no matter what type of door. I deal with Decorative Specialties for the doors I outsource and they have a disclaimer that states they do not guaranty doors over a certain size. I think it is around 48". That, to me, is saying "Don't offer large doors or they will warp."

I have also had trouble with MDF warping, so that is not a solution, nor is particleboard. Every wood product is affected by the elements, some more than others.

The fact that a door hangs with one side facing the inside of the cabinet and the other facing out can contribute to warping. Those are two different environments. Inside the cabinet there is no light, either natural or artificial. Outside there is light, which can affect the amount of heat as well as humidity. Inside these conditions are slower to occur. When the furnace in the house comes on, it changes the temperature quicker on the outside of the cabinet than the inside.

A very drastic change can occur to wood when the sun comes in contact with it. The sun will only hit one side of a door and you can guess the rest. If you have a large shop door and have ever staged your finished cabinets at the opening ready for delivery, you may have experienced this. I did. Not pretty.

From contributor P:
I take it the molding is applied as a "frame" around the entire door face? I would think that as the molding dries out, it would shrink and cause exactly what you're seeing. I doubt that it's the MDF. I assume both faces are veneered the same? If so, what's the likelihood that they'd all warp in the same direction?

Like contributor X says, if there's room inside the cabinet, you could try attaching two 1x boards to the back of the doors, kind of like battens. Or you could do the same thing as the front of the doors. Then you'd be back to having balanced panels.

From contributor T:
Panels must have the same surface tension on both sides, such as a free hanging door. The moulding... the bigger, the more effect. Has more mass and causes that surface to have more stress than the inside. Even a finish will affect this surface tension. If those panels had been standing up in your shop over the weekend, you would have seen movement already.

The door is way too long. Should be at the least half that long. I too would batten the inside with same size as outside if they insist on this design and then have them sign off a waiver. Again, as stated, if you, as an experienced cabinetmaker, see a problem, you should resist it and if to no avail, get a signed waiver. That alone will stop almost all those quirky ideas we get from a customer every once in awhile.

From the original questioner:
Lesson learned! I should have gone with my gut instinct and said no. I do not like to make long doors for this reason, however the decorator insisted that she saw furniture with doors this long all the time. I overrode my instincts to satisfy the customer and now I am paying for it. Of course the decorator will assume no responsibility in this matter so I am stuck with it. Now the question is what to do to satisfy the customer as the cabinets are already in place.

I don't think there is any way with this design to divide the doors in half and keep the same look, so I need another solution. I don't think I can run molding on the inside of the doors as the horizontal partitions are too close to the back side of the doors. I am probably, at the very least, going to have to start with new material as I took off most of the molding and put the doors under vacuum pressure over the weekend to see if they would flatten out. They did flatten out some but not enough to be called "straight." Hopefully someone out there has encountered a similar situation.

Here is a picture of the doors.

Click here for higher quality, full size image

From contributor T:
Consider using the same door, but building doors thicker and re-hanging? Keeping in mind you have to flatten them back out and hold them there? You will have to edge band them is all. They do look different, though. What are they supposed to be complimenting in the room? The 4 panel looks good. Maybe the closet doors should be similar? Would solve a big problem.

From contributor X:
After seeing your picture, I have a wild idea. Install angle iron (L), dado it in flush 14 inches outwards, or dado it in on the outward edge. Then paint to blend in. Just a thought.

From the original questioner:
Thanks for all the input. I think what we are going to do is cut the doors in half horizontally and then splice them together from behind so they will in essence be 2 doors each but acting as one when opening. If that doesn't work with the existing doors to minimize the warp, then we will start over and paint the design on them rather than have it built up with molding. That is not what I want to do, but what we might have to do in order to get the look without the problem of it warping. Ironically, the warp is from corner to corner diagonally - they are pulling toward the front on the opposite side of the hinges. I thought about the suggestion of dadoing in a piece of metal angle, but I don't think this customer would go along with that. I also looked at the Hafele door straightening (sort of a turnbuckle idea) and that didn't fly either. This was just a bad design idea from the decorator and I won't be doing it again unless the decorator wants to assume the responsibility.

From contributor Y:
Those are interesting looking doors! Your thought about cutting them in half was a thought I had also, but I didn't know if your design will permit it. I have done standard cabinet doors that way and it worked fairly well. You will be relieving the tension by cutting them. I would bet that will be the solution.

My suggestion for the future is to simply tell this story to any designer that requests large doors and politely bow out. Even with disclaimers and signed agreements, it will still be up to you to solve the same problem if you go ahead and build large doors again.

From contributor D:
It sounds like the warp is more of a cupping than a warp. If this is the case, then cutting the panels would just give you more cupped panels. I would suggest looking for a lumber core product or have some lumber core panels made up.

From contributor Z:
I can see why the designer wanted the doors this way. They are really good looking. Before you go cut them up, you should take a look at some door straighteners that Hafele sells. They are basically a 1/4 inch all-thread rod that you drop into a groove in the back of the door. These rods have some special nuts on the end that resemble the ones you use for drawing butcherblock countertops together. As you dial the nut one direction or the other, the door is tensioned to move in or out. This might solve your problem. Like the others said, I generally follow my intuition when accepting or rejecting a design. If you even think the idea is weak, don't paint yourself into the corner.

From the original questioner:
Well, here is some more info on these troublesome doors. I cut one in half and the warp is still there, even after pressing them flat in a vacuum press for two days. Also noticed that it is more of a twist than a warp. It seems that the warp or twist is diagonal from corner to corner. However, having taken all molding off and pressing it flat, as soon as the pressure is off, it pops right back to the same position. I am going to have to remake the doors and hopefully the homeowner is going to let me paint on the design rather than use molding. I am also going to see if she will let me split the doors in two and then put a strip on the back side to make them swing as one door. I won't be doing this again... guaranteed! Any other suggestions?

From contributor G:
You can make the doors like a torsion box construction, with a gridwork inside and 1/4 skin on either side. It is kind of like a hollow core door, but much better construction.

From the original questioner:
For all of you who responded to this post originally, here is what we did. We remade the doors and had a sign company mask off the areas that we were going to paint on the stripes. We painted the stripes with black lacquer and then took off the mask. We then clearcoated both faces equally and the doors came out perfectly flat. We just hung them today and thought I would take a picture of the new doors for all of you to see. Thanks again to all who responded. I will not be doing this again!

Click here for higher quality, full size image

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Cabinetmaking

  • KnowledgeBase: Cabinetmaking: Cabinet Door Construction

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2016 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article