5mm Foamex boards

Example one: a set of A1 exhibition panels.

Imagine a heritage group putting up a display in a library. Each A1 panel leans on a shelf or stands on a table with a strut, and volunteers will lift the set in and out twice a year.

At A1, 3mm Foamex is £12 and 5mm is £14. The panels will be handled by their edges and stored on their sides. At this size a 3mm board would probably do, but it can bow when leaning, and its corners take knocks. The thicker board feels more solid and keeps its shape in storage. For a set with a long working life, 5mm is an easy call.

Now change the facts. If the panels were going straight onto a wall for a single fortnight, with Velcro along the edges, the wall would be doing the work. In that case 3mm would be fine.

Example two: a car park sign at 60in x 40in.

Now picture a tenant who wants a large sign fixed to a brick wall outside. At that size, 5mm Foamex is £37.50 and 3mm Dibond is £55.

Foamex is light, cuts easily and will take the weather for a period. But it softens and moves in heat, and a big panel on a sunny wall can ripple between its fixings. If this sign is staying up for a season, 5mm could be a fair answer. If it is meant to stay for good, the aluminium board is the better spend. Our guide to rigid boards for outdoor signs compares the choices.

Drilling tips for outdoor fixing

Plastics expand and contract with temperature more than masonry does. Fixing holes drilled a little larger than the screw, with washers, give a sign room to move, so the board is less likely to buckle. Keep holes back from the edge.

Guide prices from our price list. They exclude VAT and delivery and assume print-ready artwork.

What the table shows

The jump from 3mm to 5mm is small at every size, while the jump to 10mm is much bigger. So 5mm is often the sensible middle. Move up to 10mm Foamex only when you want a thick edge or a board that must hold itself upright. See choosing board thickness for a wider view.