Suitable Substrates for Laminate

A discussion of which countertop materials are compatible with laminate, and why. July 13, 2010

What's the recommended substrate for laminate? Iíve always used plywood, but due to horrible plywood lately Iíve been thinking of switching to particle board. Any advice or opinions?

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor Z:
You are aware that laminate companies will not honor their warranties if the laminate is installed on plywood correct? Some reasons are: plywood delamination, plywood not laying flat, plywood not sanded flat allowing telegraphing. Plywood moves at a different rate than laminate causing glue failure. Particle board is and has been the substrate of choice for most.

From contributor J:
What contributor Z says is true indeed. But we all know some homeowners beef at anything particle board. It is our job to explain why particle board is better. Some years ago a cabinet company I worked for made us use plywood but we had to cut curfs about a quarter inch deep at angles about 5" apart on the entire sub top. Iím not sure if that did anything but they made us do it.

From the original questioner:
Iíve never had a problem before but thatís a good enough reason for me to switch. I've always hated working with the particle board though. All the things you mentioned about the plywood are whatís making me hate working with it too.

From contributor V:
Other reasons are voids in plywood that your laminate trimmer bearing can fall into. For P-Lam counter top makers use particle board (core pine) and in the
fixtures trade MDF is used a lot.

From contributor K:
For standard tops, PB is the way to go. Although you can use MDF (we do from time to time for tops with bevel edging), just remember you need two coats of adhesive, as one is not adequate.

From contributor B:
Particleboard has been the standard for laminate substrate for a long, long time. MDF is also a more than adequate substitute. We ask for a waiver to the warranty when laminate cabinets with a plywood core door are specified and they won't change their mind. I show them the AWI Quality Standards that we follow - "veneer core doors will not be guaranteed against warping, telegraphing, or delamination."

From contributor C:
Do the research. It may be that vc plywood is the best core and in such situations the plastic laminate brand you select may or may not provide a warrantee for this application and especially if the laminate isn't adhered to an "A" face veneer. Furthermore, this particular requirement might be present in products where, PB, MDF, PB core plywood, Medex, and etc are all substrates used on that particular job.

From contributor H:
It doesn't have anything to do with the face veneer grade. Plastic laminate is made of paper and expands and contracts with changes in humidity levels. Plywood changes sizes at a different rate causing the glue line to sheer. PB and MDF are close to the same rate as laminate.

From the original questioner:
I've been thinking about this warranty issue. Would a countertop with a wood edge void the warranty as well? I do always use plywood with one "a" face. I'll still be switching over to the particle board for all future countertops though.

From contributor C:
Miters near sinks are what I believe to be the number one offender, followed by poor quality splash construction due to missing sealant. Particle board and MDF become vulnerable to water damage once the sealant is broken. Use glue that will properly meet each situation and not worry. Choose quality construction over blazing fast bench/ installation details and spend the rest of your life enjoying the woodworking business.

From contributor K:
The biggest offender to me is not sealing seams and backsplashes that are only hot glued, caulked or liquid nails to the wall, with no fasteners underneath and caulk between the splash and the top and at the seam. Over time, they open up with expansion and contraction and you get moisture between them and then swelling starts. Caulking after the fact just separates. It's happening in my house now (house is less than five years old, and no, I didn't build the tops, but will have to replace them soon thanks to the short cuts). PB, MDF, Ply - you are not going to see any of them after the install, so why pay more for A-faced ply? PB is one big block of glue after all.

From contributor L:
We only do commercial work but if the laminate tops may be exposed to water we use a water resistant board, mostly Medex. The same goes for under sink cabinets where we will laminate Medex to match the rest of the melamine interiors.