---
title: "Sheet goods"
description: "Plywood, MDF and veneered MDF — thicknesses, sheet sizes and the properties that make a panel behave differently from a board."
url: https://kaicad.barpom.xyz/docs/catalogue/sheet-goods
schema: "0.1"
source: packages/catalogue/data/materials/sheet-goods.yaml
---

# Sheet goods

```yaml
materials:
  - id: panel_stock
    from: sheet.plywood.birch
    thickness: 18
```

Sheet materials take a thickness and no width — the width comes from the sheet. They also
carry **their own properties** rather than inheriting from a species, because a panel behaves
the way it does because of how it is built, not what tree it came from.

Set [`grain`](/docs/schema/parts#grain) on the part anyway. Plywood is stiff along the face
grain and noticeably less so across it, and a veneered sheet has a visible direction.

## `sheet.plywood.birch`

Birch plywood. The default choice for a structural panel.

| | |
| --- | --- |
| **Thicknesses** | 4 · 6 · 9 · 12 · 15 · 18 · 21 · 24 · 30 mm |
| **Sheet sizes** | 2440 × 1220 · 2500 × 1250 · 3050 × 1525 mm |
| **Rough allowance** | length 10 · width 10 · thickness 0 mm |
| **Cost** | ≈ 95 per sheet |

| Density | E | MOR | Movement | Screw face / end |
| --- | --- | --- | --- | --- |
| 680 | 9500 | 60 | 0.15 / 0.15 | medium / low |

## `sheet.plywood.poplar`

Poplar-core plywood. Lighter, cheaper and softer; fine for a back or a bottom, marginal for a
shelf.

| | |
| --- | --- |
| **Thicknesses** | 6 · 9 · 12 · 15 · 18 · 22 · 25 mm |
| **Sheet sizes** | 2440 × 1220 · 2500 × 1250 mm |
| **Cost** | ≈ 55 per sheet |

| Density | E | MOR | Movement | Screw face / end |
| --- | --- | --- | --- | --- |
| 470 | 6500 | 40 | 0.15 / 0.15 | low / **poor** |

## `sheet.mdf`

Medium-density fibreboard.

| | |
| --- | --- |
| **Thicknesses** | 6 · 9 · 12 · 15 · 18 · 22 · 25 · 30 mm |
| **Sheet sizes** | 2440 × 1220 · 3050 × 1220 mm |
| **Cost** | ≈ 38 per sheet |

| Density | E | MOR | Movement | Screw face / end |
| --- | --- | --- | --- | --- |
| 750 | 3600 | 32 | 0.25 / 0.25 | low / **poor** |

**Very poor edge screw holding.** Anything structural wants a
[threaded insert](/docs/catalogue/knock-down-hardware) or a through bolt rather than a screw
into the edge. It is also the least stiff material here — at E 3600 it is a third of birch
ply, so an MDF shelf of the same span sags roughly three times as far.

## `sheet.veneered.mdf`

Veneered MDF. The one sheet material that takes a species.

| | |
| --- | --- |
| **Species** | `walnut` `white_oak` `ash` `maple` `birch` |
| **Thicknesses** | 18 · 22 · 25 mm |
| **Sheet sizes** | 2440 × 1220 · 2800 × 2070 mm |
| **Cost** | ≈ 130 per sheet |

| Density | E | MOR | Movement | Screw face / end |
| --- | --- | --- | --- | --- |
| 760 | 3800 | 34 | 0.25 / 0.25 | low / **poor** |

The veneer is directional and the sheet has a show face, so parts cut from it are
grain-constrained in a way plain MDF is not. Set `grain:` and mean it.

Units: density kg/m³ · **E** MPa · **MOR** MPa · movement % per 10% change in moisture
content, tangential / radial.

## What to notice

**Movement is tiny, and equal both ways.** Plywood at 0.15% barely moves in plane, against
2.5–3.5% for solid timber. That is the whole reason a panel goes in a groove and a solid top
does not: a plywood panel can be captured on all four sides and glued, and a solid one cannot.

**Stiffness is the deciding number.** Birch ply at E 9500 is close to softwood; MDF at 3600 is
not close to anything. For a shelf, the deflection check will make the choice for you and give
you the thickness that passes.

**Panel stiffness figures are along the face grain.** Across it, plywood is considerably less
stiff. The shelf-sag rule accounts for that separately, using the part's `grain`.

**Edge screw holding is the failure mode.** Every sheet material here rates `low` or `poor` in
the edge, which is where people put screws when assembling a carcass. The fastener checks will
raise it; the fix is an insert, a dowel, or a through bolt.

## Sheet sizes and nesting

The cut list nests parts into sheets and tells you how many you need. Two things follow:

- **A part longer than the sheet is an error, not a warning.** Sheets have sheet sizes rather
  than a list of lengths, so the check is against both dimensions of the sheet — and it is the
  compiler's job, not yours.
- **Sheet choice matters.** `sheet.plywood.birch` at 3050 × 1525 will yield a 1600 mm panel in
  one piece where the 2440 × 1220 sheet will not.