What corrugated plastic is
Corrugated plastic sheet, often sold under trade names such as Correx or Coroplast, is the material behind most of the temporary signs you see outdoors: estate agent boards, election signs, open house arrows, construction site notices and event direction signs. It is made from polypropylene and built like corrugated cardboard, with two flat skins joined by thin internal ribs called flutes. That structure makes it light, stiff and waterproof, and cheap enough to use for signs that only need to last weeks or months.
This guide explains how corrugated plastic signs are printed, which thickness to choose, why flute direction matters, how to mount them and how long you can expect them to last outdoors.
Common uses for Correx signs
- Yard and lawn signs. Pushed into the ground on wire stakes for estate agents, events, garage sales and political campaigns.
- Construction and site boards. Safety notices, contractor boards, hoarding signs and directions on building sites.
- Event wayfinding. Car park directions, entrance and exit signs, queue information and venue maps.
- Short-term retail signs. Sale boards, opening announcements and price signs for markets and pop-up shops.
- Protective sheeting. Unprinted sheet is also used to protect floors and surfaces during building work, which shows how tough the material is.
Thickness: matching the sheet to the job
| Thickness | Good for | Notes |
|---|---|---|
| 3 mm | Small indoor signs, short-term notices, A4 and A3 posters on boards | Very light and inexpensive. Bends easily in wind if large. |
| 4 mm | Yard signs, site notices, event directional signs | The most common thickness for outdoor temporary signs. |
| 5 mm | Larger site boards, signs fixed to fences or railings | Stiffer, holds its shape better in wind. |
| 8 to 10 mm | Large freestanding boards, heavy-use signs | Much more rigid. Used where a thin board would flap. |
As a rule, the larger the sign and the more exposed the site, the thicker the board should be. A 4 mm board is fine for an A2 yard sign but will flex and rattle at 1200 x 900 mm on an open fence.
Flute direction matters more than you think
The flutes run in one direction through the sheet. For most signs that does not affect the look, but it changes how the sign can be mounted.
- Yard signs on H-stakes or wire stakes: the stake legs slide into the flutes from the bottom edge, so the flutes must run vertically. If the board is cut with horizontal flutes, the stakes have nowhere to go.
- Signs cable-tied to fences: flute direction is less important, but holes punched through the ribs hold better than holes in a single skin.
- Bending and folding: the sheet bends easily along the flutes and resists bending across them. Folded A-frame signs are scored along the flute line.
Tell your printer how the sign will be mounted so the boards are cut the right way. It is a simple detail that is easy to miss when ordering online.
How Correx is printed
Direct UV printing
Most corrugated plastic signs are now printed directly on flatbed UV printers. The ink is cured instantly by UV light and sits on the surface of the board. Polypropylene is a difficult surface for ink to grip, so printable sheet is usually surface-treated during manufacture to improve adhesion. Using the right treated board and an ink system made for polypropylene is what stops the print flaking off later.
Printed vinyl applied to board
The alternative is to print onto self-adhesive vinyl and apply it to the board. This can give a slightly smoother finish and allows lamination on top for extra scratch resistance. It costs more in labour and is usually chosen for longer-lasting signs.
Screen printing
For very large runs of simple one or two-colour designs, such as election signs, screen printing is still used because the cost per sign is low once the screens are made.
Double-sided signs
Yard signs and directional signs are often printed on both sides, so they can be read by traffic from either direction. Make sure the two sides are supplied as separate pages and that the design is the right way up on both when the stakes go in. For more on how specialist inks and films behave on plastics and other materials, see our guide to printing on specialty substrates.
Artwork tips for outdoor signs
- Read in seconds. Drivers and passers-by get two or three seconds. Use a short headline, large type and high contrast. One message per sign.
- Letter height. The further away the reader, the taller the letters need to be. Print a full-size test of the headline, stand where your readers will be and check it from there. Directional arrows should be large and bold.
- Keep content away from edges. Leave a margin of at least 10 to 15 mm for holes, cable ties and stakes.
- Night and low light. For site safety or roadside signs, reflective vinyl can be applied over the board. Our article on glow-in-the-dark, fluorescent and reflective printing explains the options.
- Supply vector artwork where possible, at full size, with any logos as vector files.
Mounting and fixing
- Wire H-stakes for lawns and verges. Quick to place and remove.
- Eyelets and cable ties for fences, railings and Heras panels. Eyelets reinforce the holes so the board does not tear in wind.
- Double-sided tape or screws for fixing to walls and hoardings.
- A-frames and pavement stands with replaceable Correx inserts, so the frame stays and only the printed board changes.
Before placing signs on public land, roadsides or lamp posts, check local rules. Many councils restrict where temporary signs can go and for how long, and signs placed without permission can be removed.
How long Correx signs last
Corrugated plastic is designed for temporary use. Outdoors it typically gives good service for several months, and often a year or more in a sheltered spot. Over time sunlight makes the plastic brittle and fades the print, especially on south-facing sites in strong sun. UV-cured inks and a protective laminate extend the life, but if you need a sign to last several years, a rigid material such as aluminium composite is the better choice. Our guide to printing on acrylic, metal and wood covers the longer-lasting options.
Polypropylene is recyclable where facilities accept it, but signs need to be clean and free of vinyl, tape and metal fixings. Reusing boards with replaceable vinyl overlays is another way to cut waste on repeat events.
Ordering corrugated plastic signs with us
We print Correx yard signs, site boards, event wayfinding and sale signs in 3, 4, 5 and 10 mm board, single or double-sided. Through our large format printing service you can add eyelets, H-stakes, cable ties and reflective overlays, and we will cut the boards with the flutes running the right way for your mounting method.
Send us the sign size, quantity, how and where the signs will be placed and how long they need to last, and we will recommend a thickness and finish. For campaigns and events with tight dates, tell us the day the signs need to be in the ground, and we will plan printing and delivery around it.
