Rigid signs are deceptively simple — pick a substrate, print on it, install. But pick the wrong substrate and you either overpay for indoor-only material rated to 2 years when you needed 5, or you cheap out on a lawn sign that turns into a flapping mess after one storm. This is the decision tree we wish every first-time sign buyer had.
The five substrate tiers
- Coroplast (corrugated plastic) — the workhorse for lawn signs and short-term outdoor. Thicknesses from 4mm (light) to 10mm (heavy-duty). Lifespan 6–24 months. Cheap.
- Aluminum composite (ACM) — 3mm aluminum-bonded panel for permanent outdoor. Holds bolt mounts. Lifespan 5+ years. Premium.
- Sintra (rigid PVC) — indoor premium. Smoother print surface than aluminum, lighter to install. Lifespan indefinite indoors, ~1-2 years outdoors.
- Foam board — indoor trade-show and short-term retail. Lightweight, cheap, fragile.
- Styrene — semi-flexible plastic for in-store hangers and menu inserts. Stays flat but accepts curves.
Outdoor / indoor matrix
The single biggest spec decision: will the sign live outdoors? If yes, your only durable choices are aluminum (permanent), 10mm coroplast(year-plus), or 4mm coroplast (single-season). Anything else degrades.
Indoor signs have many more options. Sintra is the premium choice. Foam board is the budget choice. Styrene wins when the sign needs to flex.
Mounting drives substrate choice as much as durability
- Wire H-stand in soft ground: 4mm or 6mm coroplast. The H-stand frame slips into the corrugation rails.
- Bolt-through to wall or post: aluminum holds threaded bolts indefinitely; Sintra works for indoor lighter mounts.
- Magnetic backing: only Sintra and styrene accept magnetic mount cleanly.
- Hanging from a ceiling track: foam board and styrene are light enough; aluminum needs heavy-duty hangers.
Cost ranges (per square foot, finished + printed)
- 4mm coroplast: ~$2–4
- 10mm coroplast: ~$5–8
- Foam board (4mm): ~$3–5
- Styrene (20pt): ~$4–7
- Sintra (3mm): ~$8–12
- Aluminum (3mm ACM): ~$10–16
The decision tree in one paragraph
Outdoor > 1 year: aluminum (or 10mm coroplast if budget is tight). Outdoor < 6 months: 4mm coroplast. Indoor permanent: Sintra. Indoor temporary / trade show: foam board. In-store hanger / menu insert: styrene.