Paul Sellers' Blog

Why Ply Wood?

Whereas plywood has a long history, and we can trace its roots to past millennia, it’s a material that’s still quite young when you see how long it’s been available as a fully commercial product. It’s also true that beyond the run of the mill manufacturers there are the specialist makers who have established themselves by developing every kind of plywood you can imagine from curved plywood walls six metres high to tubes and containers of every size as desk tidies, desks, chairs, modular cases and very much more. Whereas those in the wood trades may know that well enough, plywood is still very much one of those continually evolving materials few if any will see the end of. That being so, we have yet to understand its full worth to different industry possibilities and even individual designers can enjoy allowing their thoughts to drift to design totally new concepts.

Combine plywood with solid joinery construction and you have a product built to last

Plywood is a product I have always both liked and from time to time disliked, but I do especially like the high end material that is not so much veneered for an artificial misrepresentation, as a substitute for real wood, but for its structural strengths, stability and of course its supremely wide span. Seal its surfaces and edges well, use resins and bonds impervious to water and chemicals, and it will likely last for a century or two, although, as yet, because of its infancy, there is no substantive proof as to its longevity in every application.

In many cases, in its unrefined state as in the case of this dividing wall, it is quite ugly.

It’s an interesting material

At the V&A I was surprised by the interest level in visitors to the exhibition. Yes, people were perusing the projects from the past, but they were indeed at least mentally considering the visual concepts and then reading the information panels studiously too. Far from a casual pass through, people were trying to wrap their heads around concepts they most likely had never heard of or considered before. I think that the exhibition was well put together and interesting, what was missing just a little was the more down to earth every day uses of the material.

I admit a tea chest is pretty down to earth, but what I mean is the places we might know it for say on the backs of cabinets and drawer bottoms, kitchen cabinets, cabinet doors and then the inner core uses where plywood is used for its unbelievable strength and resilience under pressure. There was limited space at the exhibit and smaller exhibits are always more punchy as I said, so not really a criticism so much as a perspective really.

Whereas the primary purpose for plywood is indeed in the mass-making of goods we rely on today, concepts fabricated from plywood as well as laminated wood go far beyond the mass-made goods. I have used it and watched it emerge to create bent components such as curved aprons for tables, curved drawer fronts, waste paper baskets, legs for tables and chairs too.

It is an unfortunate element to plywood that parts and pieces made from it are often abandoned long before it is worn out or worn through. This is more a factor of fashion and disposability culture rather than built in or manufactured obsolescence.

Cross layering the veneers with opposing grain direction and using the right adhesive takes care of the expansion and contraction problems associated with using solid wood. A solid wood drawer bottom will usually expand or shrink and this must be allowed for in the joinery and construction. The same is true with panels in doors and drawers where here too it can present some serious conflicts. It’s the same with other component parts to doors, boxes, box lids and so on. Plywood has its place in most all cabinet makers shops and it is indeed an answer to many construction problems.

Competition for sheet goods

Engineered plywood has faced much serious competition in many ways except that the plywood manufacturers such as Georgia Pacific are often MDF and pressed fibreboard, chip board manufacturers too. Many sheet goods are made as more appropriate related products these days and they take many forms to meet industry standards. In the USA, with it’s multiple millions of papier-mache houses framed from 1 1/2″ by 3 1/2″ softwood studs, the walls are clad with fibreboard, wafer or OSB (oriented strand board) and then so too the roofs hide the same wafery material beneath a thin veneer of mineral felt called shingle; the kind of stuff we cover our shed roofs with.

Far from hurricane proof, it’s generally accepted as fairly good weather protection so long as there is not too much wind or turbulent force. Plywood on the other hand, with good quality hardware, though a costly product by comparison, would indeed  beef up the superstructure many times more.

Sheet plywood will only be as good as the infrastructure it’s fastened to although it will add much extra strength when affixed with screws and structural adhesives. The gussets for roof trusses to form ‘A’ frames dates back to the 50s and has remained a jointless way of assembling and uniting components.

Commercial chairs made by the millions like these in my local Waitrose cafe, and then corresponding tables, are stamped, steamed and bent out of flatness.

The tables, when skinned top and underside with plastic laminate (above) take quite a bashing in the day to day of life. There can be no doubt that plywood has its place and that can indeed be in fine furniture too. I say that because many of our fine furniture makers now rely heavily on MDF. That being so, how much more a really good grade of plywood.

For my sub wood beneath the squares I used plywood. The edges of the ply fit tightly into grooves of the frame.

In essence, plywood pretty much uses the whole tree stem without very much waste. Peeling it into thin sheets for layering and manufacturing 4 foot by 8 foot sheets in many thicknesses means almost all components using squared off rectangles and squares are custom cut to make economy really work. Seats for chairs and then sleds to can be s=custom sized to minimise waste.

How does it work

Walk into any woodworking machine shop and the odorous smell of machined ply and MDF quickly fills your nostrils with an obnoxious scent that in no way resembles the smell of wood. In the USA the better quality cabinets are made from boxes made of plywood. A face frame of maple or oak is popular still and has been for decades. Customising sizes is quick and simple and when you think that whole houses are scaled to the size of a plywood sheet you can see then how plywood sheets often economise the production of cabinets for kitchens, bathrooms, office cabinetry and much more. Biscuit joinery and pocket-hole fastenings have indeed replaced all joinery and in an era when such furnishings follow the fashion conscious, people are less reluctant to replace the cabinets with something newer even when there is nothing wrong with the so called ‘old‘.

Often the whole carcass of a cabinet will be made from plywood using biscuit ellipses for the joined edges.

In the sphere of the imaginative woodworker there is an inevitable bent on making something non-angular and square. Bending wood has an appeal all of its own and there is nothing new or even odd in that. Thonet’s chairs (pic to follow) are still being manufactured today and indeed the design has plenty of merit not the least of which is speedy assembly, fast manufacture, lightness of weight, intrinsic strength and then too the ever important stability in a chair that doesn’t tip. What more can any restauranteur want? When I go into  cafe I love seeing his chairs and I have seen them throughout Europe, my own country, the USA and in Israel too.

When we were in the V&A we spent half our time in the Furniture section of an exhibition. Much, much gaudy stuff, cleverly and carefully master crafted, gave examples of the works through the century. much of the work came from past eras when the crafting artisans were ‘owned’ rather than free.

They made designs into realities for the wealthy kings and queens, sultans and emperors of all the different continents. I often wonder what they would have made, what they could have made if they had been unshackled from their chains to make just whatever they wanted to. Of course these existing examples would not exist had it not been dress up the nobility of the times and epochs too. I at one time enjoyed seeing the manorial homes of Britain’s past wealthy but today I wonder the cost to the freedoms of the working men and women. Slavery produced many crafting artisans but slavery can never be truly a just thing. Even today slavery comes in many forms including paid workers in sweat shops whether in Britain or elsewhere.

So diving into design

I love the considerations the plywood visit brought to me even though, as I said, there were no real surprises for me. I will be looking all the more into plywood in the future and reconsidering how such material will be of value to us as we grow. It is ever more important to look at wastage in what we buy and make as crafting workers whether that comes from making disposable furniture as big box stores of flat-pack manufacturing does or in our individual designs in small one man shops. I see plywood in a good light provided we indeed know our material and our processes. We should not mistake laminated wood for plywood.

Though the process of gluing layers against one another is the same, it’s the orientation of the layers that makes the difference. Here in this picture above the bent leg formed is laminated with the grain all oriented the same direction. It may look like plywood to the uninitiated, but it is not.

Rigidity versus Compliance Bend, Yield and Stiffness Considerations

Thinness allows flex in two key areas; for and throughout the construction, and then allowing flex and contortion in actual use. Flex in hollow vessels like sailing vessels helps them to resist snapping through being overly rigid. A canoe like this one, skinned with fibreglass, coated with resin, makes the ply waterproof and resistantly strong even though it is made from thin plywood only  5mm (1/4″) thick. Two elements to the canoe increase resistance to the kind of splitting that you might associate with a single layer of wood alone, the cross-plied layering of the plywood and the inner and outer skin of fibreglass.

Plywood grades

As with many things, plywood comes in different grades usually resulting in more or less layers, different densities and weights and different surfaces to suit particular needs. Some of the lowest grades made for the construction industry in the western world are also amongst the cheapest both in cost and quality. The layers are often thicker, resulting in less cross layers resulting in a less stable material. This ply type is nailed and or stapled to studs, frames or trusses, which inevitably straightens out the distortion just fine. Covered with shingles or some other type of facing material it works fine. In cultures like the USA and others, more and more modular homes are being built. This has resulted yet again in a variety of grades of home. Modular homes come in the form of mobile units assembled on a multi wheeled chassis and pulled trailer like by a tractor unit. Other factory-built assemblies are produced for final assembly on the lot as modular assemblies. At one time these would have been plywood but today OSB has pretty much replaced plywood in the construction of pre-stressed walls and such. With styrofoam sandwiched between inner and outer skins of OSB, walls several metres wide and tall arrive on site ready for standing either as walls or roof panels.

Oriented strand board is ubiquitous on most building sites these days and is used for a wide range of uses but no matter what you do with it it is very ugly stuff.

In recent decades China began manufacturing and exporting plywoods to the rest of the world using Asian hardwoods. The quality has generally been regarded as a lesser quality and here in the image you can see why. The bottom plywood has nine layers of unequal thickness and there are  voids and overlays at the meeting levels of the layers. The two outer faces are so thin they are barely discernible.

The top plywood on the other hand  has no voids and no overlays at the meeting points in the strata. It has full thickness on all 9 ply levels with no variation in the thickness the material. The bottom one is sold as hardwood plywood, which, though it is made from hardwood, the wood itself is soft and much less dense than the top plywood which is a Scandinavian plywood that is even in density, hardness and thickness throughout each layers.

One of my drawers using plywood for the bottom. I often go between solid wood and plywood depending on the quality of work. At the high end it is always solid wood though.

The grading of plywoods goes far beyond the purpose of this article, which is to help us rediscover plywood as a product that lends itself to the development of new ideas and recognise that earlier developments were indeed just the beginning if indeed you want to explore new possibilities for developing ideas in designs. If that is you then start researching for yourself. Your investigation into past present and then future will be sure to turn up products you never thought could possibly exist.