If you must use particleboard for counters, any deep thread screw that is the right length (to not poke through the top) will work. We only use plywood exterior grade G1S for countertops. We have never had a callback do to swelling from poorly installed sinks or steam from dishwashers.
If you check the specs for P-lam installations you will find particleboard or MDF are the recommended substrates, not plywood. The expansion rate for these materials approximates that of P-lam. Wood materials expand and contract with changes in moisture content and if they are not at the same rate, you will shear the glue line. P-lam, being made of paper, expands and contracts at a different rate than plywood, causing this shearing of the glue line. Particle substrates are not the problem, leaking sinks are.
What do you guys who use veneer core do with all your scrap? If you are making 25" kitchen decks, 30", 36", 42" wide bars, what do you do with all the offal? Also, how do you handle the additional labor of butt joints for anything over 8'? The additional labor of ripping your material? We have a fair amount of scrap and we stock countertop sizes, (25x97, 25x121, 25x145, 30x97, 30x121, 30x145, 36x97...). I couldn't imagine cutting tops out of 4x8's.
Brian Personett, forum technical advisor
Our kitchen counters are 25 1/4-25 1/2 and even if you use particleboard at 49x97, you still have scraps and often have joints. We use 5/8 plywood. The leftovers are used to double up the counter to 1 1/4 and for our bases, which we make separate from the cabinets. We level the base first and then install the cabinets easily on the level base. We also use this plywood for the bottom base shelf of all our vanity or sink units, covered with white laminate so that it looks like white melamine, but has better resistance to the liquids that often spill under sinks.
Expansion of the plywood has never happened to us in the 15 years we have been building kitchens. However, we have had problems with particleboard and MDF, with swelling at joints or from steam from a dishwasher.
I use 5x12 sheets to avoid seams whenever possible. I do not encourage post formed counters and although the look is nice, my customers prefer the plywood base and not having 45 degree seams in the corners.
We are going to have to agree to disagree on the merits of VC vs PB for a substrate.
We have two separate shops here, one which builds cabinets and one which builds tops. Although there are sometimes tops that go with cabinets, we rarely sell to the same customers. We sell tops to dealers, kitchen and bath retailers, Lowes, etc. Shuffling scrap back and forth is not a particularly good option.
Here in the Midwest US, I had never heard of 5x12 plywood. It can be had, custom order 1 unit min. I also checked on pricing for 5/8" 4x8's. My price is 789/M. I currently pay 428/M for 3/4" PB. Depending on which brand laminate, I pay anywhere from 1.02 sq ft to 1.27 sq ft, for this illustration I'll use an average of 1.145. PB price of 1.145+.428=1.57 per sq ft for materials less glue. VC price of .789+1.145=1.934 per sq ft for materials less glue. My material cost has gone up a smidge over 23%. There is no way I can compete in the market using VC. It is simply too competitive. We feel like we have built a good relationship with our dealers, providing a quality product, good service, and a fair price. But I don't think the first two are going to overcome a substantial price increase to cover the additional expense of using VC.
Every laminate company that I know of recommends the use of PB for a substrate. We also feel like it is the best solution. VC is not without it's problems as well, telegraphing, voids, delamination of the plys.
No matter what you do, if you have a top that is over 5x12, there will be seams, because that's the largest size the laminate companies make. We too make seamless tops up to 5x12, if the customer requests it. I'm not certain how practical it is in most cases.
The downside of all of this is it seems that PB gets a bum rap for a leaking sink, or a bad gasket on the DW. The plain simple truth is, it's only the symptom of the problem. Sinks should be properly caulked, plumbing should not leak, DW's should not leak steam as they are working, and that puddle of water should not be left to stand on a seam in the plastic. I have two small children and I assure you no ones DW gets opened and closed during the cycle more than mine, yet I have not had a problem with the PB swelling. We also have more than our fair share of water/pop/Kool-Aid standing around, yet no problems. Even if you don't follow all of the rules, the rate at which PB fails is fairly small and in extreme cases, where I'm quite certain that eventually VC would fail as well.
Brian Personett, forum technical advisor
As a small custom shop of four employees doing one-at-a-time large custom kitchens, the extra cost for the counters is too small to worry about as opposed to the volume you are doing. For the same reason, I only use 170 degree clip-ons and Accuride full extension slides. The plywood is only 4x8, the laminate 5x12 when required.
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