Laminate-clad Casework

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Author Message Ralph Liebing, RA, CSI Senior Member Username: rliebing Post Number: 788 Registered: 02-2003 Posted on Friday, February 08, 2008 - 02:15 pm:    Please share experiences/advice, successes/failures with use of plywood as base/underlayment for plastic laminate clad casework, particularly doors [as well as all other surfaces]. Is warpage a problem? Are you aware of any flat out prohibitions of this use? Can you refer to any AWI information that addresses this issue. Plaminate makers seem to prohibit this but with no explanation that we can find-- you have anything from them? Thanks much Nathan Woods, CCCA, LEED AP Senior Member Username: nwoods Post Number: 230 Registered: 08-2005 Posted on Friday, February 08, 2008 - 02:26 pm:    I don't "know" the answer, but I might hazard a guess that you need to treat both sides of the plywood for it not to warp, which typically poses a problem in millwork where only the external side is laminated. You also probably need to use kiln dried, low moisture material, which raises the price. Just a theory. Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 230 Registered: 01-2005 Posted on Friday, February 08, 2008 - 02:44 pm:    I recall being told that AWI prefers particleboard or MDF substrates because their flatness, uniformity, lack of voids and stability are superior to those of plywood. On the other hand, where sinks are inserted, some specifiers call for marine grade plywood, for its lack of voids and water resistance. I don't know that there's a comparable marine-grade MDF or particleboard. Lynn Javoroski CSI CCS LEED™ AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 723 Registered: 07-2002 Posted on Friday, February 08, 2008 - 02:45 pm:    Check Panel Products, Section 200-02: "What many think of as traditional 'plywood,' a panel made up of alternating layers of thin veneers, is called veneer core." Architectural Cabinets, Section 400; specifically, balanced construction and cores defined as "particleboard if not specified for all 3 grades. Section 400A-T-3: Flush Cabinet Door Limits..."Veneer core doors will not be guaranteed against warping, telegraphing, or delamination." Veneer cores are rated fair for flatness and surface uniformity (Section 200-G-3). You really should have a copy of Architectural Woodwork Quality Standards in your office. There is moisture-resistant MDF. Richard A. Rosen, CSI, CCS, AIA Senior Member Username: rarosen Post Number: 27 Registered: 08-2006 Posted on Friday, February 08, 2008 - 04:22 pm:    From the APA website in reference to Marine Grade Plywood: "Marine-grade plywood is a specially designed panel made entirely of Douglas-fir or Western Larch. The grade of all plies of veneer is B or better, which means it may have knots, but no knotholes. The panels are sanded on both faces, and are also available with Medium Density Overlay (MDO) or High Density Overlay (HDO) faces. The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a “premium” panel grade for use in situations where these characteristics are required, i.e., for boat hulls and other marine applications where bending is involved." I was told years ago by a local plywood distributer that marine grade is not an acceptable substrate for construction of furniture, cabinetwork, or anything else that architects think should be fabricated with marine grade. It is just too flexible. Particle board as a substrate is superior to plywood because it can be waterproofed, does not delaminate, and retains cleaner edges when cut. The quality of the edge issue is very important to keeping the edge laminate or decorative wood edging attached. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 720 Registered: 07-2002 Posted on Friday, February 08, 2008 - 04:37 pm:    well... it is typical to see particle board substrates for plastic laminate faced casework, but fastener holding is a problem especially in high-use or abusive use casework. the University of Washington (for example) ONLY allows plywood as the substrate for its boxes, because they have had too many maintenance problems with composite board substrates. the stress point is always where the door hinges meet the boxes. at the very least, if you use a composite board, you will need to test for screw holding capacity of the boards first. This value will change depending on the type of particleboard -- I've seen some spectacular failures with straw-type boards. Also: look at AWI for the bearing capacity of the shelves. Even when faced with plastic laminate on both sides, a particle board shelf doesn't have very much capacity before it bends. you will need to use short shelves, support them at regular intervals and probably have to make the shelf thicker (3/4" rather than 1/2" or 1" rather than 3/4") if you plan to support any length. The standard is only 5 pounds per lineal foot, by the way. You can require greater capacity if you specify it. I would also recommend specifying that the bearing capacity be per shelf, not "per lineal foot of cabinet". Require the installer to engineer the connections with the wall and make sure there is enough backing in the walls. a few years ago, we all passed around photographs of a hospital where the wall mounted cabinets just pulled out of the backing and fell onto an adjacent desk. for the best use, the particle board should be faced on both sides and edge treated as well. Verify what edge they are planning to use; that tape stuff doesn't last very well. Also: if you use vertical grade plastic laminate, confine it to the upper cabinets only. at the thinness they are laminating these days, the vertical grade is simply too brittle and it won't take much impact for it to fracture (like: a vacuum cleaner). In general, I don't allow ANY vertical grade on my projects. the cost savings isn't worth the maintenance headaches. I've definitely done miles and miles of plam casework for all sorts of applications, and it can be a good substantive product. However, I will reiterate that my experience with institutional use (universities, labs, and the like) generally requires the use of a plywood substrate for rigidity and holding power. Don Harris CSI, CCS, CCCA, AIA Senior Member Username: don_harris Post Number: 173 Registered: 03-2003 Posted on Friday, February 08, 2008 - 05:25 pm:    A cabinetmaker told me many years ago that the only time I should specify a plywood substrate is when I need to support a substantial load, i.e. bookshelves or storage shelves. He said, as Bob states above, that MDF and particleboard are more stable and create a better product. I personally prefer the MDF. This advice has worked for me for a while now. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 845 Registered: 03-2002 Posted on Friday, February 08, 2008 - 05:33 pm:    I have specified only particleboard or MDF for plastic laminated cabinets for quite some time. Having had a cabinet shop at one time, I can tell you that it is far superior in flatness to veneer core plywood. I do not specify core, but let it default to the AWI standard (which is PB or MDF). Lynn's comment about plywood is germaine. MDF with hardwood veneer on both sides is considered plywood by AWI, even though this is not how we use it generically in the profession. We usually mean veneer core plywood. As to screw holding, much depends on the type of hardware, how it is fastened, fastener type, and proper fastener hole size. Plywood edges are not very good for screw holding, or for as a substrate for plastic laminate or wood veneer. I'd probably explore alternative hardware or construction technique rather than resorting to plywood cores. I believe straw board is supposed to meet the same ANSI standard as particleboard (at least it does for door cores). Whether in practice that occurs I can't say. Jerry Tims Senior Member Username: jtims Post Number: 10 Registered: 04-2005 Posted on Tuesday, February 12, 2008 - 11:20 am:    AWI Section 400 requires the use of Euroscrews to secure concealed (European style) hinges. This supposedly alleviates some of the screw holding issues that occur with the use of MDF/particle board/straw board. Since I suspect very few fabricators really look at the AWI manual all that often, I've added the Euroscrew requirement to our casework section.