Overall dimensions

Sheet goods are, generally speaking, a synthetically assembled sheet of material that can be machined with woodworking and DIY machines and tools. They’re usually made up of wood of some form or another. They’re most often found in 4′ × 8′ dimen­sions, though most Baltic birch plywood is also available in 5′ × 5′ dimensions. A big box store will likely have just 4′ × 8′ sizes, though they will often stock smaller panels cut from these larger panels that are 2′ × 4′, 4′ × 4′ or even 1′ × 8′. These smaller sizes make transportation easier, and are helpful for people with small shops and homes.

It’s always more cost effective to purchase a whole sheet, if you need it, rather than piece one together with parts. Some retailers will have a saw on hand so you can have them make a few cuts. Just remember, these cuts aren’t always super accurate, so leave yourself a bit of wiggle room.

Sheet goods are available in different thicknesses, as well. The most common thickness available at a big box store is 3/4″, though 1/2″ and 1/4″ are also quite common. If you go to a large lumber­yard that stocks sheet goods, you’ll likely also find some types of sheets 3/8″ and 5/8″ thick. Special ordering sheets will give you access to sheet goods over 3/4″ thick, though you may have to order a large quantity.

Some of these thicknesses will be very close to exact, while oth­ers will be about 1/16″ off, or more. For example, 3/4″ plywood, no matter what type you get, is often about 11/16″ thick. This is common across the different thicknesses.

There are a number of pros and cons for each type of sheet good, but before we get specific, let’s cover some general characteristics of all sheet goods.

Less seasonal movement than wood

The size of a piece of solid wood fluctuates as humidity levels change with the seasons. Sheet goods do this, too, but much less so. You generally don’t notice a difference in the dimensions of a sheet good if it’s in a piece of furniture and it’s cut to a relatively small size.

The main time I notice a sheet good moving with the seasons is when larger panels are used in a wall or storage unit and you’ve added some form of caulk to fill a small gap between the sheet good panel and the wall, ceiling or floor. This is especially true on the first year of its life, as it might have been slightly on the humid side when you bought it, and therefore might have been on the larger side when it was machined and installed. The dry condi­tions of an indoor room cause the sheet good to lose much of that moisture and shrink slightly. I find another bead of caulk often cures that problem for good, though you might find yourself need­ing to touch it up once in a while.

Great cores

The fact that sheet goods don’t move much at all means they can be more easily used in many situations. When building with solid wood you need to consider grain direction and in which direc­tion the workpiece will move with the seasons. This is only a small problem when using a sheet good to create a large workpiece.

The lack of seasonal change in dimension is one of the reasons sheet goods are often used as a core for veneering. Another benefit of sheet goods as it relates to veneering is that some sheet goods remain very flat and stable throughout their lifetime and make a good substrate for veneer. The edges of sheet goods pose problems when veneering, however, but we’ll get to that later.

Use them in the shop, too

Sheet goods are also great for shop fixtures. They’re relatively cheap and provide the user with a larger surface to use. Some types of sheet goods can hold a screw much better than others and are durable enough for shop use. Gluing fences and other things to most sheet goods results in a fairly strong joint.

Adding 1/4″ thick solid wood edging to sheet good jigs and fix­tures will keep them strong and sound for even longer, as the solid wood protects their edges.

Be careful of their edges

Generally speaking, sheet goods are made up of layers of some sort. There are inherent weaknesses to the different types of sheet goods that must be considered when building with them. The den­sity of particleboard and MDF is lower in the centre of the board’s thickness and plywood can delaminate along some of its lamina­tions. Both of these weaknesses mean that driving a screw or other fastener into the edges of a sheet good can quickly become prob­lematic, resulting in a split workpiece. There are a number of ways to protect against the workpiece splitting, but none of them will give you a joint as strong as if it had been made with solid wood.
Predrilling will ease the internal stress a screw or fastener builds up, and will reduce the chance of splitting, but it doesn’t leave you with a guaranteed strong joint; just a somewhat weak joint that hasn’t split.

Adding solid wood edging to a sheet good workpiece will offer some grip for a fastener, and also go a long way to keeping the sheet good from splitting, but it’s far from a cure-all. The thickness of the edging will affect the results; a thin edge will offer a small amount of screw-holding benefit, while a thicker edge will offer much more, but there are limits. A wood-to-wood edge joint is very strong, while a wood-to-sheet good joint ranges from being some­what weak to a lot weaker.

It’s also possible to cut mortises into the edges of sheet goods and glue in strips of solid wood so screws can get a bit better grip on the workpiece, but that’s not always an easy process to machine accu­rately, nor is it going to provide a bomb-proof joint.
When all is said and done, edge joints that include a sheet good aren’t nearly as strong as edge joints with solid wood, so there are limits to how much stress you subject them to and how the different stresses are applied to them.

Screwing into their faces

Driving a screw into the face of a sheet good is going to give you better results than driving a screw into its edge, but there are still things to consider when doing so. Plywood, with its cross-grain construction, naturally holds itself together better than parti­cleboard, MDF and thinner sheet goods like wiggle wood and hardboard. Plywood is not only less likely to split, but it’s obviously going to be more successful when it comes to keeping a screw in place.

Tensional strength on a screw that’s driven into particleboard or MDF will be lower than shear strength, meaning if there’s a force pulling the screw directly away from the sheet good it’s more likely to fail than if the force is sideways.

Also, don’t overtighten a screw that you’ve driven into any type of sheet good, especially particleboard and MDF. Strength is drasti­cally reduced the moment the fibres around the screw start to give away which happen more easily with the softer fibres in particle­board and MDF.

Cores and faces

Generally speaking, most sheet good cores are available with or without a face and back veneer. For example, it’s possible to buy a sheet of particleboard with or without face and back veneers adhered to it. The main exception is plywood. Some types of ply­wood are available in many different domestic and exotic species, while others aren’t. Sheathing and Baltic birch plywood are two of the most common examples. Both will have a layer of wood on the face and back, though you won’t be able to specify what species that is. When it comes to sheathing, it’s a softwood like spruce. With Baltic birch, the species you’ll get is birch.

Adding a face and back veneer to a sheet good increases the price substantially, though it means you can use that sheet good for a nicer finished piece of furniture or cabinetry, as opposed to either having to veneer it yourself or only using it for a struc­tural part or in a location like an unfinished basement or garage. There’s nothing saying sheathing plywood isn’t strong enough for a living room wall unit, but because it’s much rougher and less attractive than other types of sheet goods, it’s very rarely used for this purpose.

Plywood options

When it comes to plywood, there are many different varieties on the market. The quality, price and end use of these different plywoods range quite a bit. You also might be able to easily find one type in certain areas of the country, while not in other areas. If you’re at all confused about what type of plywood your local retailer carries, speak to a salesperson about your needs so they can steer you in the right direction.

Keep them dry

Sheet goods are generally meant to be used indoors. Water will very quickly ruin most sheet goods, causing them to swell up, weaken dramatically and fall apart. While plywood will stand up to water better than other sheet goods, it’s not meant for continuous water contact. The best option for outdoor usage is marine grade plywood, which is water and decay resistant, though it still needs to be finished and maintained properly to stand up to the elements for any length of time.

It’s a good idea to keep MDF and particleboard out of bathroom vanity construction. I’ve also seen some kitchen cabinet manufac­turers use plywood for cabinets around the sink and dishwasher areas just in case something goes wrong with the plumbing.

Protection

Handling sheet goods can be very hard on the hands. Whether it’s slivers from plywood, cuts from melamine or just the sheer weight of lifting and moving these sheets around, a decent pair of gloves will save the day. For less than $20 you’ll find something at your local hardware store that will fit nicely, grip sheet goods and protect your hands while you work.

Dealing with the edges

Most sheet goods have edges that will need to be covered in order to blend in with the rest of the piece of furniture or cabinetry, unless the edge is either hidden inside a joint like a dado or groove, or will never be seen, like the back or side edges of an adjustable shelf.

There are three main approaches to covering edges. None of them are necessarily better or worse than the others. They all have their pros and cons, so select the best approach for you in each situ­ation you’re using them.

Solid wood headers – If you’re building a desk, for exam­ple, adding 3/4″ thick × 1-1/4″ wide solid wood headers around all four edges of a plywood top would work nicely. The solid edges will cover the unsightly edges of the top, will protect those four edges from wear and tear, and the solid wood edge can also be routed to add a nice visual detail.

On the downside, this takes more solid wood material, can be tricky to glue up nicely and you have to be careful how the upper edge of the headers mate with the upper face of the sheet good. As long as the header finishes above the face of the sheet good it can be flushed up with the sheet later. Just be careful at that point, because using tools to flush the header with the sheet good may cause you to sand or plane through the veneer on the sheet good, causing major problems.

Solid wood edging – Instead of using a large header, a strip of solid wood about 1/4″ thick can be added to the edge of a sheet good to offer protection and a visually clean edge. This approach is usually quicker and easier, though it doesn’t offer many routed edge options. Adding these edges to the workpieces before assembly means you can more easily rout or plane them flush, though that may cause challenges near the corners of mating parts that need to be considered. Stopping edging a certain dimension before the end of a workpiece might be needed.

Iron-on tape – Iron-on edge tape will do a good job at cover­ing the edges of exposed sheet goods. Iron-on tape is available in many species of real wood and many colours of melamine so you can likely match your project exactly.

It’s not hard to apply, though if this is your first time doing so, it’s good to practice on some scrap. Too much heat, or applying the correct amount of heat for too long, will cause burns. Too little heat, or applying the correct amount of heat too quickly, will leave you with an edge that’s likely to fall off. As a general rule, apply enough heat to cause the tape to stick, then leave the iron in contact with the tape for another second or two. I generally use a fairly high setting on my iron, though irons may differ in how hot their hottest setting is.

As you move the iron across the edge, use an object (I use a shop-made push stick that’s rounded at the end) to press the iron-on edging down. Running the push stick over the edge a few times is good assurance to keep it down until the heat-activated adhesive cools and sets.

Ways to trim the edges differ, depending on whether you used a melamine edge or wood edge. Melamine can be trimmed with a plane iron set flush on the face of the sheet good. A file with a rect­angular cross section and teeth on its edge can trim wood tape flush with the workpiece. In both cases, practice makes perfect. Some light sanding after the edges are trimmed will leave you with an attractive edge that’s ready for the next step.

Don’t be afraid

If sheet goods are new to you, this is probably a lot to take in. Like any other material, there’s a time and place for each of these sheet goods and knowing when to use them is an important skill to have. Sheet goods can make many larger cabinet and storage projects much easier and faster to complete.

Watch the Edges

Melamine, like any material, has its pros and its cons. One of its cons is that it’s prone to chipping when machined and these chips are very noticeable in the finished project. Stack the deck in your favour and use a sharp blade, though that alone is unlikely to solve the chipping problem.

Some of these parts only need a clean edge on one face of the mate­rial. An outer gable that will be against a wall will only have its face seen, so any chipping can be positioned facing the wall. For parts like vertical dividers, that’s a trickier situation, as they’re visible from both sides. In this situation I use what I call a “double cut” technique. A scoring blade takes care of this in a production shop setting, but few of us have that luxury at our disposal.

First, a bit of chip formation science. Generally speaking, the underside of a workpiece will chip out as the blade exits the workpiece and dam­ages the lower face. This is in large part because the exit angle of the blade is too close to perpendicular to the lower face of the workpiece. A strange thing happens when the exit angle gets closer to parallel with the under­side of the material – it stops chipping. If you make the first pass with the blade set to about 3/16″ high, chipping will virtually disappear on the underside of the workpiece. The workpiece can then be re-cut, with the top of the blade above the workpiece. This should drastically reduce chipping, maybe even eliminate it. I’ve also seen people do two half passes with the blade set ever so slightly higher than half the thickness of the mate­rial. They flip the workpiece over after the first cut and run the same edge against the fence. Try both approaches and see what works best.

I also like to lightly ease the fresh cut edges of melamine once it’s been machined unless I’m going to apply iron-on tape to the edge. Think of the two sides and one back edge of an adjustable shelf. The edges of melamine can chip easily, unless you ease them. This may leave a very slight gap between mating parts, but it’s much better than medium-sized chips. Easing some of the edges will also greatly reduce cuts on your hands while you work.

Types of Sheet Goods

Particleboard Core

PROS

• cost effective
• remains flat, unless weighted
• medium weight
• smooth enough faces to apply veneer to
• commonly available

CONS

• medium screw-holding strength in its face
• weak screw-holding strength in its edge
• not overly strong or durable
• very poor when wet
• faces must be veneered to look good
• edges need to be covered to look good
• prone to splitting if used improperly
 

Melamine-Covered Particleboard

PROS

• the melamine surface is surprisingly durable and water resistant
• no finish is needed, speeding up the project considerably
• available in different colours and patterns
• very cost effective

CONS

• the particleboard core is very susceptible to water damage
• doesn’t have the “wood” look some makers are after
 

Medium-Density Fibreboard (MDF)

PROS

• smooth faces are good for veneering
• fairly stable in terms of flatness
• fairly cost effective
• edge composition is even and can be routed and primed / painted

CONS

• heavy
• very weak when wet
• faces usually need to be veneered to look good, though an opaque finish can be applied to them with success
• depending on the look you want, edges usually need to be covered to look good
• edges chip somewhat easily and are sharp while machining
• faces can swell near where a screw is driven
• prone to splitting if used improperly
 

Baltic Birch

PROS

• both faces and edges can be finished as-is
• lightweight to handle
• strong overall strength
• smooth surface that can be veneered
• strong screw-holding strength in face
• can handle a small amount of water without dramatically weakening, though it’s far from waterproof
• good dimensional stability
• often available in 4’x8′ and 5’x5′ sheet sizes

CONS

• easily warps
• expensive
• slivers while machining are common
• sometimes large splinters form at the edges, causing an uneven look
 

Furniture-Grade Plywood

PROS

• can easily be used to make quality furniture and storage cabinets
• screw-holding strength in face is relatively strong
• fairly lightweight to handle
• fairly high overall strength
• available with many different species of face / back veneers
• available in many different qualities and end uses
• good dimensional stability

CONS

• easily warps
• expensive
• face and back veneers can be thin
• slivers while machining are somewhat common
 

Sheathing Plywood

PROS

• cost effective
• commonly available
• fairly strong
• can handle a small amount of water without dramatically weakening, though it’s far from waterproof

CONS

• faces are unsuitable for furniture construction
• doesn’t stay flat
 

Marine Plywood

PROS

• water and decay resistant
• good dimensional stability
• appropriate for outdoor projects like signs, decks, furniture and marine applications

CONS

• expensive
• not completely waterproof, so must be treated properly and cared for
• harder to find
 

Flexible Plywood /Wiggle Wood / Flexi Ply

PROS

• constructed so it will easily flex / curve in one direction
• can be laminated with multiple layers to produce fairly tight, strong curved workpieces
• 4’x8′ sheets are constructed so they will either roll into a 4′ long roll or an 8′ long roll

CONS

• easy to buy the wrong orientation
• hard to handle full sheets, as they bend very easily
• multiple layers usually need to be built up to create parts strong enough for lasting furni­ture, though single layers are sometimes used in curved parts of a house’s interior (think some non-structural curved stair parts or curved bulkheads)
 

Hardboard

PROS

• high strength-to-weight ratio
• resistant to splitting
• good dimensional stability
• good material for cabinet backs
• available with or without a melamine face

CONS

• only available in thin sheets
• too thin to properly hold screws or other fasteners
• can be hard to handle full sheets, as it’s flexible