Using Prefinished Plywood
Cabinetmakers discuss why they use material that's finished on both sides, even where only one side will show. March 26, 2008
Question
If you build carcasses with pre-finished plywood, are you using it only where the finish is seen, appreciated, and required? Are you then using unfinished ply for all the other parts? What are you doing about the bottom sides of fixed and adjustable shelving?
Forum Responses
(Cabinetmaking Forum)
From contributor B:
I am able to get 3/4 vc maple ply finished 1 side or 2 sides. I use the 2 sided for shelves and dividers, and cap the shelves with 1/4" material that I have pre-finished. It's easy to get a bunch of 1/4" material when you process your own maple hardwood. There are always those narrower pieces. If it's a maple kitchen, I use the pre-finished 1 side and just stain the other side for the bottoms or outsides of the cabinets, unless the customer wants raised panel ends. On the occasion that I only have 1 sided on hand and I'm in a hurry, I'll just spray the other side before capping with the 1/4" stuff. Just make sure it's the underside, though.
From the original questioner:
For the carcass of a base cab with all drawers, why use pre-finished ply for the sides and bottom deck, if it never can be seen? For the tops or top stretchers of all base cabs, why use pre-finished ply if the finish can never be seen? Why would you not use 2-side pre-finished ply for all upper wall cab shelving?
From contributor A:
90% of our casework is beaded inset face frame going in multimillion dollar residential houses. We have never had one complaint by a customer or architect with these methods. Visible surfaces are pre-finished only. When we started using pre-finished ply, we tried to use pre-finish 1 side on unseen surfaces. The stuff comes so warped that it is a pain in the butt to work with. It can mess with your drawers. The other problem is mixing and matching 1 side and 2 side. We dado/rabbet all joints for ease of assembly, alignment, and to expose some wood for gluing. The 1 sided is never the same thickness as the 2 sided.
We switched exclusively to 3/4" 2 sided so we can use it for shelves, partition, etc. Also it can come scratched, only on one side. So it's nice to be able to pick a good side. On a drawer box we will use bare birch ply. Our rule is if you can't see it after install, it's okay. I believe the AWI book essentially says the same thing.
On exposed ends that don't receive framed plant-ons, there are 3 solutions:
1. Have a couple of 1 sided sheets kicking around.
2. Use regular birch ply and then skin the inside with 1/4"(contributor B style).
3. Sand the pre-finish with 100 grit and spray a coat of BIN shellac primer. It sticks to anything and can be topcoated with just about anything.
The product we really like is Columbia C2 white maple. It's a custom run that Atlantic Plywood carries. It's virtually perfect white faces.
From contributor J:
I use predominantly pre-finished ply and always have it finished 2 sides. As said before, anytime you finish only 1 side of plywood, it's going to cause it to warp (woodworking 101). Secondly, there's really no price incentive to use 1 sided as opposed to finished 2 sides. I got a lift of 1 side finished by accident one time and it was far more hassle than any cost savings would make up for. Thirdly it's a pain to have yet another material to order and store.
Most of my work these days is painted, all the interiors are pre-finished and for finished ends, I'll just sand the finish a bit and spray. If I need to do a stained piece, I just get unfinished maple and go from there.
When I'm cutting a kitchen's worth of cabinets, it would be a real pain to have to start using different sheets for different boxes, drawer box gets unfinished, wall cabinet gets finished 1 side, shelves get finished 2 sides - that's far too much complication for no benefit.
I suppose if you're fully automated and doing many dozens of kitchens or more a year, you could realize some savings using different materials for different cabinets. For me it's just easier using the pre-finished for as much as possible.
From contributor V:
Pardon my ignorance, but when you build with pre-finished plywood for your boxes, do you finish your face frames before you attach them? If so, how do you attach them?
From contributor H:
I pocket screw the sides and horizontal supports at drawers. Works great and no nail holes in face frame. I use pre-finished with painted or stained face-frame. Edgeband drawers and shelves.
From contributor J:
Yup, you pre-finish your face frames and how you attach them is up to you. Personally I pocket screw them on, but if you look in the archives, you'll find more different ways to attach the face frames than you'll ever need.
From contributor G:
Contributor B, how do you apply the 1/4" on your shelves? Do you trim the edges after it is applied? How do the rest of you apply edgeband to pre-finished shelves? How do you apply finished 1/4" end panel skins over pre-finished plywood?
From contributor B:
I mill what basically amounts to screen molding to 1/4" X 19mm out of my leftover rips from milling 1 1/2" and 2" maple stock for FF, break the edges on one side and pre-finish, then cut to length, glue, and nail. Regular pine or maple soft fill takes care of the holes. It sounds like a lot, but it's all leftover material and my customers like the thickness of the 1/4" over regular edgebanding. I only do the front edge and sand the exposed ply edges. Of course I break the sharp edges, I already have the sander in my hand anyway.
As far as skinning the end panels, normally I build raised end panels as a part of the cabinet itself, but if you have to skin with 1/4" material, I have used PL and a few 5/8" brads in inconspicuous places (under where trim would be). Any other holes can get filled with either soft fill to color, or hard fill, let dry, wipe with a damp rag, stain same color as cabs, and touch with lacquer on a tiny brush just to seal it. You'll only notice if you know where they are.
From contributor G:
At 19mm, is the edging the same as the thickness of the ply? I assume you do not need to trim after it is applied? How well does the edging line up with the shelf faces?
From contributor B:
It lines up very well. In fact, I've not had a complaint or anyone even mention it in the four years that I've been doing it this way. Great way to use up scrap, too.
From the original questioner:
Why in the world wouldn't you just edgeband it in real pre-finished maple? It is available in thin and thick (3mm) sizes. Let's tag your cost to do it the way you do at $65 per hour, and then extend how much you do out over a year. What is the cost per year to do it your way? I know you have said that it all comes from scrap, so let's say the wood part has no cost. But include in the cost the materials like finish, nails, and glue. Don't forget the sandpaper used for breaking the edges.
From contributor B:
I would be interested in looking into the 3mm stuff. Where can I get it and how do you attach it? Of course, whatever will I do with my scrap?
