Should I use 15mm or 18mm plywood for a camping box?

Use 15mm birch plywood for the entire structural build of a standard camping box (sleeping platform up to 200 cm long, two adults, max 250 kg). 18mm only adds value for spans wider than 120 cm without supports, or for pickup-bed builds carrying heavy gear on top of the platform. For 90% of cars, 15mm is the correct choice — lighter, cheaper and strong enough.

How much heavier is 18mm plywood?

18mm birch plywood weighs roughly 11 kg/m² vs 9 kg/m² for 15mm — about 22% heavier. On a typical camping box build (~3.5 m² of plywood) that’s 7 extra kilograms you carry every day. It also raises material cost per sheet by 15–25%.

Does 18mm hold more weight?

Yes, but only meaningfully on long unsupported spans. With internal supports every 50–60 cm (as in the Campboxy plan), a 15mm panel already supports 250 kg evenly distributed — more than two adults plus storage. Adding 3mm only matters if you skip the supports, which you shouldn’t.

Can I mix thicknesses?

Absolutely — and you should. Use 15mm for the sleeping platform top, sides and main supports. Use 9–12mm for drawer bottoms, dividers and small lids that don’t carry load. Mixing thicknesses cuts total weight by 15–20% without losing strength.

What thickness for the drawer fronts?

12mm is ideal for drawer fronts and small lids: stiff enough to look solid, light enough not to sag the drawer slides. 15mm works too but is overkill for a non-load-bearing panel.

Does thicker plywood hold screws better?

Yes, marginally. 18mm gives you 3mm more screw engagement at the edges, which helps if you’re using cheap screws or skipping pilot holes. With proper M5–M6 screws and pilot holes, 15mm birch already holds permanently — there’s no real-world failure mode being solved by going thicker.

Is 12mm plywood enough for the platform?

No. 12mm flexes noticeably under bodyweight on spans over 40 cm and the screw edge holding is weaker. 12mm is fine for non-structural panels (drawer bottoms, dividers) but not for any panel you sleep or stand on.

What does the Campboxy plan use?

The Campboxy plan is engineered around 15mm birch plywood for all structural panels and 9–12mm for drawer bottoms. The full cut list fits on a single 2.5 m × 1.25 m sheet of 15mm + half a sheet of 9mm — keeping material cost in the $60–$100 range.

15mm vs 18mm Plywood for a Camping Box — Which Thickness to Use?

15mm vs 18mm birch plywood for a DIY camping box: weight, load capacity, screw holding, price and which thickness to use for the platform, sides and drawers.

Frequently Asked Questions

Should I use 15mm or 18mm plywood for a camping box?: Use 15mm birch plywood for the entire structural build of a standard camping box (sleeping platform up to 200 cm long, two adults, max 250 kg). 18mm only adds value for spans wider than 120 cm without supports, or for pickup-bed builds carrying heavy gear on top of the platform. For 90% of cars, 15mm is the correct choice — lighter, cheaper and strong enough.
How much heavier is 18mm plywood?: 18mm birch plywood weighs roughly 11 kg/m² vs 9 kg/m² for 15mm — about 22% heavier. On a typical camping box build (~3.5 m² of plywood) that’s 7 extra kilograms you carry every day. It also raises material cost per sheet by 15–25%.
Does 18mm hold more weight?: Yes, but only meaningfully on long unsupported spans. With internal supports every 50–60 cm (as in the Campboxy plan), a 15mm panel already supports 250 kg evenly distributed — more than two adults plus storage. Adding 3mm only matters if you skip the supports, which you shouldn’t.
Can I mix thicknesses?: Absolutely — and you should. Use 15mm for the sleeping platform top, sides and main supports. Use 9–12mm for drawer bottoms, dividers and small lids that don’t carry load. Mixing thicknesses cuts total weight by 15–20% without losing strength.
What thickness for the drawer fronts?: 12mm is ideal for drawer fronts and small lids: stiff enough to look solid, light enough not to sag the drawer slides. 15mm works too but is overkill for a non-load-bearing panel.
Does thicker plywood hold screws better?: Yes, marginally. 18mm gives you 3mm more screw engagement at the edges, which helps if you’re using cheap screws or skipping pilot holes. With proper M5–M6 screws and pilot holes, 15mm birch already holds permanently — there’s no real-world failure mode being solved by going thicker.
Is 12mm plywood enough for the platform?: No. 12mm flexes noticeably under bodyweight on spans over 40 cm and the screw edge holding is weaker. 12mm is fine for non-structural panels (drawer bottoms, dividers) but not for any panel you sleep or stand on.
What does the Campboxy plan use?: The Campboxy plan is engineered around 15mm birch plywood for all structural panels and 9–12mm for drawer bottoms. The full cut list fits on a single 2.5 m × 1.25 m sheet of 15mm + half a sheet of 9mm — keeping material cost in the $60–$100 range.