Choosing board thickness
Thickness buys you stiffness, and you only need enough for the size of panel and the way it is held. Beyond that you are paying for weight.
Start from the size of the panel.
A sheet that stays flat at A2 can sag at A0, because the same stiffness is being asked to span far more distance. This table gives a sensible starting point for Foamex fixed to a wall.
| Finished size | Start with | Move up if |
|---|---|---|
| A2 and smaller | 3mm | It will be handled a lot |
| A1, 30in x 20in | 3mm or 5mm | It stands on a strut or hangs from two points |
| A0, 40in x 30in | 5mm | It stands alone, or gets moved around |
| 60in x 40in | 5mm or 10mm | Fixed only at the top, or on show for a long time |
Then adjust for how it is held
A board stuck flat to a wall is supported across its whole back, so it can be thinner. One held at two top corners has to support itself. One standing on a strut has to resist bending and knocks. The less support it has, the thicker it needs to be.
What each thickness is for
1mm is a backing, not a sign. It works for inserts that slide into a frame or holder, and for gentle curves, but it will not stand up.
3mm is the everyday choice for smaller signs and framed work.
5mm is the all-rounder for exhibition panels and larger display boards.
10mm is chunky, and you can see that from the side. People choose it for stand-alone panels and for the shadow it casts on a wall, as much as for its strength.
Watch where the price jumps
Read across the rows below. At A2, going from 3mm to 5mm takes the price from £7 to £8, while moving up to 10mm takes it to £20. Going thin saves little too: at A2 and 30in x 20in, 1mm and 3mm are the same price. So 5mm is often the good-value choice, and 10mm should be saved for when you really need it.
| Thickness | A2 | A1 | A0 | 30in x 20in | 40in x 30in | 60in x 40in |
|---|---|---|---|---|---|---|
| 1mm | £7 | £10 | £15 | £10 | £18 | £30 |
| 3mm | £7 | £12 | £20 | £10 | £20 | £35 |
| 5mm | £8 | £14 | £25 | £11 | £22 | £37.50 |
| 10mm | £20 | £30 | £40 | £25 | £35 | £60 |
Guide prices from our price list. They exclude VAT and delivery and assume print-ready artwork.
When thicker is the wrong answer
If a 5mm panel still bows, a different material may work better than more foam. 3mm Dibond is thinner than 5mm Foamex and much stiffer, because its aluminium skins do the work. Likewise, Polyboard in 10mm gives you the chunky look with less weight, provided the panel stays indoors.
Check what it has to fit
Frames have a fixed rebate depth, and rails and holders have fixed slots. Measure those gaps before you pick a board. Thick panels also take up more room in a van and in storage, which matters on a large set.
Boards at different scales.
Your questions.
Does a thicker board look better?
It looks heavier, and that can suit a stand-alone panel. On a wall, a thin board sits neatly, and most visitors will not notice its depth unless they look from the side.
Is 3mm enough for a sign on a door?
Usually, for sizes up to around A2, if it is fixed flat. Tell us how it attaches and how often the door gets knocked.
Why does my large board bow slightly?
A print on one side can pull a sheet very gently out of flat, especially with changes in heat and humidity. Fixing it across more points usually solves it.