Balanced Construction of Plastic Laminate Doors

Experience shows that balancing P-lam doors can prevent the occasional case of warping. Here are thoughts on how to lay up balanced P-lam panels. February 12, 2010

I have been making plastic laminate covered doors not using what would be described as balanced construction for many years. (We use plastic laminate on melamine with no backer sheet). I have read and keep reading that unbalanced construction will without a doubt lead to warping. Is there any science or scientific testing that shows "unbalanced" door construction leads to warping? I have seen plenty of warping in melamine doors or panels without any plastic laminate on it, so it seems to me that some warping is inherent in those basic core materials. Thanks for any information.

Forum Responses
(Cabinetmaking Forum)
From contributor L:
I have had warping problems using "good one side" 3/4" white melamine. I switched to laminating both sides of particle board or MDF with much better results. There is a slight warp, but less noticeable. It is always passable. I use white cabinet liner on one side of hardwood plywood with a little warping, but not enough to be a concern.

From contributor J:
In the commercial world of door/drawer fronts using panel stock with cab liner on one side and laminate on the other is quite common. Doesn't the liner on one side and laminate on the other side seal each side equally from the environment?

From the original questioner:
I would think that a melamine surface would provide as good a barrier to moisture (which I think would be the only real environmental issue in most situations) as high pressure laminate. One possibility I thought of is that the glue used to attach the laminate shrinks when drying, thereby "pulling" the sheet. But it seems a stretch to think a .025" thick sheet of laminate would cause a .75" thick board to bend or warp. It does cost more to make a door with it laminated on both sides - it just appears to me to be adding cost without any real benefit to the customer. That is why I was curious if there has been any scientific testing that drove this being the standard for AWI, and for most of the industry.

From contributor V:
I cannot point you to any serious controlled experiments or studies but the idea that lamination's need to be balanced has been shop proven and known for quite a while. Plywood for instance is always balanced and has an odd number of plyís. Starting at the center ply they glue a ply to each face and so on until final thickness is reached. In professional veneering the practice is to veneer both faces with the same thickness and even the same species of veneer. The fact that a panel will be held flat by framework or fasteners etc will be taken into consideration.

From contributor J:
I didn't know it was an AWI thing but then I don't deal with AWI much. I do light commercial - schools and medical type stuff. Initially I used P-Lam two side for no reason other than that's how I thought it should be done - not anymore. I learned that a cab liner backer is almost always used for these kinds of projects. I've never heard of problems, it is less expensive and does blend well with white mel interiors.

From contributor L:
The best of balancing a panel would be to laminate both sides with an equal thickness laminate. The cabinet liner is thinner and will still warp slightly. It is the laminate that is acting on the substrate that is usually the significant factor.

From contributor R:
No science that I know of, but in my experience an unbalanced panel is more prone to warping than a balanced panel. My theory - in a laminate panel all three plies - (laminate, core, laminate) are moving seasonally. If the laminates are of different thickness they will shrink at different rates, pulling the panel out of flat. In my shop, we used melamine with laminate on the face for 15 years, and rarely had a problem with warping. I also know that many people, including many on this forum have used this panel method with few problems. But the problems we did have were significant, usually occurring in larger doors.

We also never got caught, because the local architects were not familiar enough with the AWI quality standards. About eight years ago, I decided not to take the risk anymore and I put together a laminating line. I can do up to 100 panels in a shift with one person and if anything, with the greatly reduced cost of labor and lower cost of glue, the finished product is less expensive than a laminated melamine panel. We buy bulk white vertical grade very inexpensively (not liner, which is thinner) for most jobs, unless color both sides is required by specification. When you add the fact the glue line is far better than contact cement, and the glue is non toxic with no VOCís, the choice becomes obvious. We also use the glue line for all of our laminate tops, which we then miterfold, and we sell laminated panels locally at a profit. And we market the fact that our product is superior to the local competition.

From contributor M:
I have been using the method you describe to build laminated doors for many years without a problem. I cut the melamine board, turn it upside down to put the saw chipping up, and contact cement on the plastic laminate. I then trim the edges and put PVC tape on the edges to match the face. It isn't even necessary to "rough up" the melamine face with sanding for the contact cement. This is a quick, cheaper way to produce these doors without the time and expense of gluing laminate on both sides or having a lamination company do it for you. A further advantage is that the melamine back is much easier on your hinge boring bits since they stay sharp much, much longer.

From contributor R:
If you are doing commercial and the specs read that you must meet AWI Quality Standards, you can't use p-lam over melamine. AWI QS is firm on using balanced construction, which means laminate to laminate or cabinet liner. If you use melamine and you're caught by a sharp architect or GC, you could get to do it over again. I used to use melamine/laminate a long time ago, we just prefer laying up laminate to liner, it's faster for us. I believe there is less warpage and it just eliminates any potential liability with regard to the specs.

From contributor T:
This ties back to a number of posts over the last few years - when you are doing commercial construction beyond the small tenant improvement/handshake/relationship level you are tied to the specifications. You can often negotiate the specifications after you have a contract, especially if you offer price reductions, but you can't count on it. If you don't know the AWI Quality Standards, which the specifications of most jobs are based on, and you don't read every page of the spec book, you are putting yourself at risk. The balanced panel issue is among the top ten problems cited by the AWI Quality Certification program.

From contributor J:
I've been doing p-lam cabinets for over 20 years and I was taught that you need to balance out the board. We always used Vgrade laminate on 11/16 substrate. Depending on the size of the door and how many hinges you, you should be ok. If you can use a resin glue with a press compared to spraying contact cement would be even better.

From the original questioner:
To all who responded I appreciate the information. What I was hoping to learn was that there has been some type of scientific testing that helped establish the need for balanced construction and the reason it is in the specs since there is a flatness spec in AWI for doors that I think would cover any warping issues. I agree that if you are going to play the game, you should play by the rules (specs) since you risk getting caught.