Sign material

Coroplast

The yard sign material. Cheap, light, weatherproof for a season or two, and the one substrate where getting the flute direction wrong ruins the job.

Also called	Corrugated plastic, corflute, fluted polypropylene
Thicknesses	4mm (3/16 in) is the standard for yard signs. 6mm and 10mm (3/8 in) exist for larger panels that need to stay flat.
Weight	Very light. A 4 x 8 sheet of 4mm is comfortably carried by one person.
Outdoor life	About two years outdoors before the surface chalks and the colour goes. Printed election and real estate signs are usually retired long before that, which is the point of the material.
Ballpark cost	Roughly 14 to 20 dollars a sheet for 4mm, about 45 dollars for 10mm.

Ballpark trade prices for a 4 x 8 sheet as of August 2026, before markup. Yours will differ by supplier, region and how much you buy at once — treat these as a sanity check on a quote, not a price list.

What it actually is

Extruded polypropylene with a fluted core between two thin skins, exactly like cardboard made of plastic. The flutes are what make it stiff in one direction and floppy in the other.

What it is good for

→ Real estate and election yard signs on H stakes
→ Short run event and directional signage
→ Anything disposable where cost per sign matters more than lifespan
→ Site signs that only need to survive one season

What to watch for

Flutes must run VERTICALLY for an H stake. Horizontal flutes let the wire legs split the sheet on the first windy day, and it is the single most common way a yard sign order gets remade at your cost.

Polypropylene has low surface energy, so vinyl and ink do not want to stick. Use material rated for it and give UV ink a moment to cure properly rather than stacking hot sheets.

It creases if you look at it wrong. Stack flat, never lean a full sheet against a wall overnight.

It is not rigid enough for anything above roughly 4 ft unsupported without going to 6mm or 10mm.

Printing and finishing

Direct print on a flatbed is the norm for volume. Vinyl applies fine but the flute lines telegraph through on large solid areas, which shows most in dark colours.

Pricing a Coroplast job?

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Coroplast — FAQ

Which way should the flutes run on a yard sign?

Vertically, so the H stake legs slide inside the flutes. Horizontal flutes leave the stake nothing to grip and the sign tears off the wire in the first strong wind.

How long do Coroplast signs last outside?

Plan on about two years before noticeable fade and chalking. In full southern sun it is closer to one.

Is 4mm or 10mm Coroplast better?

4mm for anything on a stake up to about 24 x 36. Go to 10mm when the panel gets large enough to oil can in the wind, or when it is being fastened to a frame rather than staked.

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