Sheet materials guide: plywood, MDF, melamine & OSB

Most cabinet, furniture and sign projects are built from a handful of standard sheet materials. Picking the right one — and knowing the standard size, thickness and weight — is the first step to an efficient cutting list. This guide walks through the four families you will meet most often (plywood, MDF, melamine-faced chipboard and OSB), then shows how to combine that knowledge with the OptimalLayout cut optimizer so you buy the fewest sheets possible.

A quick note on sizes: European stockists typically sell in millimetres (2440 × 1220 mm or 2500 × 1250 mm), while North American yards stick to 8 × 4 ft (2438 × 1219 mm). The numbers look almost identical but the millimetre difference matters when you nest parts close to the edge — always enter the exact sheet size shown on the invoice, not the nominal one.

Plywood

Plywood is built from cross-laminated veneers, which gives it excellent strength in both directions and stable behaviour with humidity. Because the grain of each layer runs perpendicular to the next, it resists warping better than any other sheet material and holds screws well on both the face and the edge.

The main grades you will meet:

• Birch plywood (Baltic / Finnish) — dense multi-ply core, great for cabinet carcasses, drawer boxes and jigs. Common thicknesses 12, 15, 18, 21 mm.
• Hardwood-faced plywood — oak, walnut, ash or maple veneer on a softwood core, used for visible furniture parts. Order it with a book-matched face if you need a continuous grain pattern across doors.
• Softwood plywood (pine, spruce) — construction grade, rougher surface, used for sub-floors and site work.
• Marine plywood — WBP glue and defect-free veneers for boats, bathrooms and outdoor furniture.

Standard sheet sizes are 2440 × 1220 mm (8 × 4 ft) and 2500 × 1250 mm. Weight is roughly 550–700 kg/m³ depending on species — an 18 mm birch sheet weighs around 33 kg, comfortably a two-person lift.

MDF (Medium Density Fibreboard)

MDF is dense, perfectly flat and machines cleanly, which makes it the first choice for painted doors, templates, speaker cabinets and CNC parts. It has no grain, no knots and no voids, so a router leaves a crisp edge you can finish smooth with a light sand.

Trade-offs to plan for:

• It is heavy — around 720–780 kg/m³, so an 18 mm 2440 × 1220 sheet is close to 40 kg.
• Screw pull-out on the edge is weak; use confirmat screws, dominos or metal inserts for load-bearing joints.
• Standard MDF swells badly if it gets wet. For bathrooms or kitchens use moisture-resistant MR-MDF (usually tinted green).
• The dust is very fine — always cut with extraction and a P2 mask.

Standard sizes are 2440 × 1220 mm and the larger 2800 × 2070 mm panel that most European kitchen shops keep in stock.

Melamine-faced chipboard (MFC)

Melamine-faced chipboard is the workhorse of flat-pack cabinetry: pre-finished on both sides, cheap, and available in dozens of decors from plain white to convincing oak reproductions. Because the finish is already applied, one clean cut is the whole job — no sanding, no lacquer.

The catch is chip-out. Melamine is brittle, so a standard rip blade will tear the bottom edge on exit. Options that work:

• A dedicated fine-tooth melamine or laminate blade (60–80 teeth on a 250 mm blade, TCG grind).
• A scoring blade on a sliding panel saw, which cuts the underside first and eliminates blow-out entirely.
• Apply painter's tape along the cut line on a smaller job to keep the fibres held down.

Typical sheet: 2800 × 2070 mm, 18 mm thick, matched with 0.4 or 2 mm ABS edgebanding. Order edgebanding at the same time — decor codes should match to the letter.

OSB (Oriented Strand Board)

OSB is structural sheathing built from compressed, glue-bonded wood strands. It is cheap, strong in shear and dimensionally stable, which is why it dominates roof, wall and sub-floor construction. It is not a finish material — the surface is rough and the edges crumble — but for anything hidden behind cladding or plasterboard it is excellent value.

The grade you want for structural work is OSB/3 (load-bearing, humid conditions). Standard sheet: 2440 × 1220 mm, 12, 15, 18 or 22 mm thick. On a sub-floor use 22 mm tongue-and-groove sheets glued at the joints.

Choosing for your project

• Kitchen and wardrobe cabinets → 18 mm melamine carcass + plywood or MDF doors.
• Built-in shelving → 18 mm birch plywood for visible quality and stiff spans.
• Painted furniture → 18 mm MDF, edges sealed with primer or two coats of shellac before top-coating.
• Workshop jigs and fixtures → 12–18 mm MDF; flat, cheap and easy to route.
• Sub-floor, sheathing and hoardings → 18–22 mm OSB/3.
• Outdoor and wet areas → marine plywood or MR-MDF, never standard MDF or OSB.

Waste factor and offcuts

Whatever material you choose, order 10–15 % more than the parts list demands. Real sheets have edge damage, cosmetic defects and factory-cut edges that are not perfectly square — you will trim 10–20 mm off two sides before you start. On a five-sheet order that is a whole extra half-sheet of usable material, which is almost always cheaper than a second delivery run when a part goes wrong.

Feed it into OptimalLayout

Once you know the material, sheet size and part list, drop them into the cut optimizer. Set the kerf that matches your blade (see the kerf guide), lock the grain for veneered parts (see the grain guide), and hit optimize. The tool returns the minimum sheet count, a labelled cutting diagram and total cut length — everything you need to price the job and cut it in one pass.

Thickness — matching the job

Sheet materials come in a small range of standard thicknesses, and matching thickness to job is what separates a piece that lasts from one that sags. As a rough rule:

• 6 mm — cabinet backs, drawer bottoms, thin panels for door inserts.
• 9–12 mm — light shelving, template stock, small drawer sides.
• 15 mm — common European kitchen carcass thickness; slightly lighter than 18 mm.
• 18 mm — the default for cabinet carcasses, worktops (doubled), shelves up to 800 mm span.
• 22–25 mm — heavy-duty shelves, workbenches, unsupported spans over 900 mm.

Shelves are the most common failure. A 900 mm span of 18 mm MDF loaded with books will visibly sag within a year — either drop to 750 mm spans, step up to 22 mm, or add a stiffening strip glued to the front edge.

Cost comparison at a glance

Prices vary week to week, but the rank order is remarkably stable. For 18 mm sheet at typical European retail (2025):

• OSB/3: €15–22 per 2440 × 1220 sheet — cheapest by a wide margin.
• Standard MDF: €25–35 per sheet.
• Melamine-faced chipboard: €30–45 per sheet (white), €45–70 for wood decors.
• Softwood plywood: €40–55 per sheet.
• Birch plywood: €70–110 per sheet, more if you want B/BB face grade.
• Marine plywood: €120–200 per sheet.

When the material is a small fraction of the finished piece's value (a €2,000 kitchen cabinet), pick the material that suits the job. When you are building 40 identical shelves, the price gap between MDF and birch is real money.

Reference table