Reference

MDF vs plywood vs pine: which material for your shelves?

The short version: Kamba builds in MDF, plywood, or pine. MDF is the cheapest and smoothest but sags the most and dislikes moisture. Plywood is the stiffest and strongest for its weight, best for long spans and heavy loads. Pine is solid wood with a natural look, stiffer than MDF and moderately priced. For everyday 18 mm shelving, any of the three works; for wide shelves or heavy loads, plywood or pine beats MDF.

The key difference: stiffness

Stiffness is what stops a shelf sagging. Both plywood and pine are roughly twice as stiff as MDF for the same thickness, so they hold a longer span or a heavier load before they bow.

Property	MDF	Plywood	Pine
Stiffness (resists sag)	Lowest	Highest	High
Weight	Heaviest	Light	Light
Cost	Lowest	Highest	Moderate
Look	Paint only	Paint, or clear-finished edges	Natural wood, stain or paint
Edges	Smooth, paint-ready	Need edge-banding	Solid, sand and finish
Moisture	Poor (swells)	Better	Moderate (seal it)
Screw holding	Fair	Good	Good

When to use each

MDF: everyday shelving, light to medium loads, painted finishes, a tight budget. Keep spans shorter.
Plywood: long spans, heavy loads (books, records, tools), damp rooms, whenever sag must be avoided.
Pine: you want a natural wood look, a solid feel, and a good stiffness-to-cost balance. Watch for knots and let the boards acclimatise before building.

As a rule: if 18 mm MDF is not enough for your width and load, switch to plywood, pine, or a thicker 25 mm board.

See standard shelf dimensions

How Kamba uses this

Kamba lets you choose MDF, plywood, or pine, and validates your design for the material you pick. Each material has a different stiffness, so Kamba checks the span and load for your exact choice; if it is not safe, it recommends a stronger material or a thicker board, so you never build a shelf that will sag.