Plywood vs MDF vs OSB: Which Should You Use?

What These Three Boards Actually Are

Plywood is made by gluing thin layers of wood veneer together, with the grain of each layer running at 90 degrees to the one below. That cross-lamination is the whole secret: it spreads load in every direction, which is why plywood is so stiff for its weight and why it resists splitting when you screw into it.

MDF, or medium-density fibreboard, is made from fine wood fibres mixed with resin and wax, then pressed under heat into dense, uniform sheets. It has no grain at all, which means it machines beautifully, holds paint perfectly, and never splinters, but it is heavy, it dulls tools faster, and it hates moisture.

OSB, or oriented strand board, is made from rectangular wood strands layered in specific directions and bonded with waterproof resin. It looks rough, like a giant flake of breakfast cereal, and that face is its main drawback, but the strands give it real structural strength and the glue makes it far more weather-tolerant than MDF.

All three come in the same standard UK sheet size, 2440 x 1220mm, and in a range of thicknesses from 6mm up to 25mm. The most useful thickness for furniture and shelving is 18mm. Buy a full sheet for big jobs, but for smaller projects you can often get the merchant to cut it down for free or buy half sheets, which saves hauling an awkward 8x4 through your front door.

Plywood: The Strong All-Rounder

Plywood is the board I reach for first when the project has to carry weight or live somewhere damp. A shelf made from 18mm plywood spans further between brackets before it even thinks about sagging, and the layered edges hold screws with real bite.

It also comes in grades that change the price dramatically. Interior plywood is fine for furniture, but exterior (or marine) plywood uses waterproof glue and can sit outside or in a damp shed for years. The difference matters: a cheap interior sheet left in a garage will delaminate, the layers peel apart like wet cardboard, while exterior ply shrugs it off.

The downsides are honest ones, and they start with the price. Plywood costs more than MDF and OSB, the surface is not perfectly smooth so painting needs more prep, and the edges show a striped veneer pattern that some people love and others hide with edging tape. Birch plywood, usually from the Baltic countries, is the premium option with a clean face and tight edges, and it is the go-to for anyone building furniture that will actually be seen.

Use plywood for: shelves, worktops, workbenches, shed and garage storage, anything that carries weight, and any project that might meet moisture. If you are only buying one board for a mixed list of jobs, make it 18mm exterior-grade plywood.

MDF: The Smooth Finisher

MDF exists for one reason above all others: it paints like a dream. The dense, grain-free surface takes primer and paint without showing a single wood grain underneath, which is why most flat-pack-style furniture, skirting boards, and painted shelving is made from it.

It also cuts cleanly with no splintering, holds fine detail when routed, and is cheaper than plywood, which makes it the default choice for painted furniture, alcove units, wall panelling and any job where a smooth painted face matters more than raw strength.

The weaknesses are real and you will hit them in order. MDF is heavy, a full 18mm sheet weighs around 25kg, so it is a two-person lift into a van. It swells permanently if it gets wet, which means it belongs nowhere near a bathroom, a kitchen sink or an unheated shed. And when you screw into the edge of MDF, it blows out unless you drill a pilot hole first, so always drill before you drive.

There is one more thing every UK maker should know: MDF dust is genuinely nasty. The fine fibres and the resin binders irritate your lungs, so wear a decent dust mask when cutting or sanding it, ideally one rated FFP2 or FFP3, and cut it outside or with extraction where you can.

Use MDF for: painted furniture, wall panelling, alcove shelving, craft projects, and anything where a flawless painted finish beats raw strength. Keep it dry and keep it indoors.

OSB: The Budget Workhorse

OSB is the sheet material builders actually buy by the lorry load, and it is easy to see why when you compare prices. It typically costs 30 to 50 percent less than plywood of the same thickness, and for structural jobs like sub-floors, roof sheathing and shed walls, it is genuinely strong enough to do the work.

The waterproof resin binder means it shrugs off building-site moisture far better than MDF, which is why it dominates floors and roofs in new-build homes. It also takes screws well, holds its shape, and comes in load-rated grades, so you can match the board to the job with confidence.

What it will never be is pretty. The strand-textured face looks like a mistake to most people, and while you can paint it, the texture shows through every coat. OSB belongs where it will be covered: under a floor, behind plasterboard, inside a shed, or as a cheap workshop wall that will get covered in tool storage anyway.

Use OSB for: sub-floors, shed floors and walls, roof boarding, garage shelving that will never be seen, and any budget structural job where appearance does not matter.

Which Board for Your Project? The Quick Answer

If you only remember one rule, make it this: plywood for strength and moisture, MDF for painted finishes, OSB for hidden budget structure. The specific call for common UK jobs looks like this:

• Shelves to hold books or tools: 18mm plywood. It spans further without sagging and holds edge screws properly.
• Painted alcove units or panelling: MDF. The painted finish will look factory-made and the weight is not a problem against a wall.
• Shed floor or roof: OSB, load-rated, on treated battens. Nobody sees it and it handles the damp.
• Kitchen worktop or utility room: exterior plywood. Anything near water needs the waterproof glue.
• Workshop bench top: 18mm plywood, possibly doubled up, or plywood over OSB for a cheap thick top.
• Small craft and sign projects: 6mm or 9mm MDF for painted pieces, birch plywood for anything that needs a clean edge.

The classic beginner mistake is choosing MDF for a garage or shed project because it is cheap and smooth, then watching it swell the first winter. Another is paying for exterior plywood indoors where interior grade would do the same job for less. Match the board to the environment first, then to the finish.

Cutting and Working with Sheet Material

A full 2440 x 1220mm sheet is unwieldy and dangerous to cut freehand, so set yourself up properly before you start. A WORX Pegasus folding work table is the best cheap answer for cutting sheet material in a UK garage: it clamps the board, holds it off the ground, and folds flat against a wall when you are done. For full sheets, prop them on sawhorses with the offcut supported so the piece you cut off does not drop and snap the blade.

For the cut itself, a circular saw beats a handsaw or jigsaw for long straight lines on 18mm board. The Makita HS7600 is the saw I recommend for this: a 190mm blade with 1200W of power, and it cuts plywood, MDF and OSB cleanly all day.

Clamp a straight edge or a length of timber to the board as a guide, set the blade depth to just over the board thickness, and cut in one steady pass. For the smoothest cut on MDF, use a blade with more teeth, a 40-tooth or finer blade leaves a cleaner edge than the stock 24-tooth.

Cut with the good face down when using a circular saw, because the blade tears out on the underside, and support the offcut side so it cannot drop and bind the blade. Work outside or with the garage door open, and wear a dust mask, especially with MDF.

After cutting, sand the edges and faces before assembly. A DeWalt DWE6423K random orbit sander with 120-grit paper knocks the fuzz off plywood edges and the cut marks off MDF in minutes, and the hook-and-loop disc change makes it painless. Sand MDF edges to a slight bevel so paint does not crack along the corner.

For assembly, drill pilot holes before you drive screws into the edge of any board, and definitely before screwing near the end of MDF or plywood, or the board will split. A DeWalt DCD778S2T combi drill drills the pilot and drives the screw in one go, and it has enough torque for 18mm board without breaking a sweat. Use a countersink bit so screw heads sit flush, and for load-bearing joints add wood glue to the joint before screwing.

For finishing: prime MDF edges and faces before painting or the porous edge will drink your topcoat and look patchy. Plywood takes wood stain or varnish beautifully, and exterior ply should be edge-sealed if it will live outside, because the layered edges are the one part moisture gets into first.

Products Mentioned in This Guide

Frequently Asked Questions

Final Verdict

There is no single best board, only the right board for the job. Plywood is the default when strength, moisture or longevity matter, MDF wins whenever you need a flawless painted finish indoors, and OSB is the budget answer for hidden structural work.

For most UK makers starting out, the practical setup is a sheet of 18mm exterior plywood for load-bearing jobs, a sheet of 18mm MDF for painted furniture and panelling, and a budget OSB sheet if you are flooring or lining a shed. Cut them with a Makita HS7600 on a WORX Pegasus table, drill pilot holes with the Bosch MS4041 set, and sand the edges with a DeWalt DWE6423K.

Choose by environment first, then by finish, and the board will last as long as the project deserves.