If the sign gets shaped — routed letters, screwed edges, formed returns — or lives indoors, use PVC foam board. If it is a large flat panel that goes outside, use ACM. The gap outdoors is not close, and the numbers below are why.
Expanded PVC is a rigid closed-cell foam. It cuts on a table saw, routs without chipping, takes a screw straight into the edge, comes in thicknesses up to 3/4″, and costs less. It is the right board whenever the part has to be made into a shape.
ACM is aluminium skin over a polymer core. It is dead flat, stays flat, and its factory-coated metal face survives sun for years rather than seasons. It is the right panel whenever the sign is large, flat and outdoors.
Picking expanded PVC for a big exterior panel is how a sign goes wavy by its second summer. Picking ACM for routed dimensional letters is how you find out a 3mm panel has no edge to work with.
This one chart decides most exterior sign jobs. The gap is roughly five to one, and it comes down to what the surface is: ACM presents factory-coated aluminium to the weather, expanded PVC presents plastic holding pigment. In sustained Nevada sun that difference compounds fast.
Expanded PVC moves about ten times as much as wood and roughly three times as much as ACM. Calsak put a number on it: a 12-foot PVC board can travel about a quarter of an inch across one hot day. On a small interior panel nobody notices. On a large exterior face fastened at the edges, that is exactly the movement that produces oil-canning, waviness and fasteners tearing out.
PVC foam is the lighter of the two, which matters on a hanging sign or anything a single installer has to hold up on a ladder. Both are a fraction of solid aluminium. Weight is the one category where expanded PVC wins outright.
| Property | Expanded PVC | ACM |
|---|---|---|
| Service life outdoors | 6 months – 2 years | 7 – 10+ years |
| Weight, 3 mm | ~0.40 lb/ft² | ~0.55 lb/ft² |
| Thermal movement | 3.2–5.0 ×10⁻⁵/°F | ~1.3 ×10⁻⁵/°F |
| Stays flat on a big panel | Oil-cans on large faces | Dead flat, stays flat |
| Thicknesses stocked | 1/8″ to 3/4″ | 2 mm and 3 mm |
| Routs and shapes | Yes — clean edge, no chipping | Yes, but the cut edge shows the core |
| Screw into the edge | Yes | No — nothing to bite at 3 mm |
| Folds into returns | Heat-formed | V-grooved and folded cold |
| Cut edge appearance | Solid colour all the way through | Dark core line visible |
| Takes print and vinyl | Yes, matte, no primer | Yes, matte, no primer |
| Takes paint | 100% acrylic latex, no primer | Coated face, not designed to be painted |
| Laser cutting | No — releases chlorine gas | No — aluminium face |
| Relative sheet cost | Lower | Higher |
| Cost per year outdoors | Higher | Roughly a fifth of PVC |
| Building facade over 40 ft | No | Not the sign-grade panel — see below |
Service life, weight and PVC thermal-movement figures are from Calsak’s published substrate and construction guides. Remaining values are typical published ranges offered as a design starting point. If your job turns on a specific number, ask and we will supply the manufacturer’s data sheet for the exact panel we ship.
At comparable thickness in white, ACM runs meaningfully more per sheet than expanded PVC. That is real, and on an interior job or a short-term sign it settles the question — buy the PVC.
Outdoors it inverts, and not by a little. Run the two service lives against the two sheet prices and ACM works out to roughly a fifth the cost per year of expanded PVC in exterior service. The PVC panel is cheaper once. The ACM panel is cheaper every year after the first replacement.
And the sheet is rarely the biggest number. Reprinting the graphics, pulling a crew back out, renting the lift again and explaining it to the customer all cost more than the panel did. If the sign has to be there in five years, that is the calculation, not the invoice.
Worth saying plainly, because ACM gets specified onto facades by people who bought it as a sign panel. Sign-grade ACM uses a polyethylene core. Under IBC Section 1403.5, exterior wall assemblies over 40 feet on Type I–IV construction must pass NFPA 285, and PE-core ACM does not. NFPA 285 tests a complete two-storey wall assembly, not a sheet — so an ASTM E84 class printed on a panel does not answer the question your inspector is asking. If you are cladding a building rather than making a sign, tell us the height and construction type and we will source a fire-rated core with the documentation to match. More on ACM cores →
Not down to two yet? The plastic selection guide narrows it by heat, wear, chemicals and clarity first.
Tell us three things — how big it is, whether it goes outside, and how long it has to last — and we will tell you which one to use, including when the answer is neither and you want acrylic or polycarbonate instead. We stock both in Sparks and cut, rout and V-groove them here, so this is a conversation with material on the floor behind it rather than a catalogue lookup. Call (775) 358-8211 or send us the details.
Both, for different halves of the job. Expanded PVC is the everyday board — interior work, backers, shaped letters, anything that gets fabricated. ACM is the exterior panel. A shop doing a monument sign will often use ACM for the face and expanded PVC for the internal structure and the dimensional elements. They are complements more than competitors.
Yes, for short-term work — site signage, real estate, a season of event graphics. It will not rot or absorb water, which is its real advantage over wood substrates. What it will do is fade, chalk and bow over a couple of summers. If the sign only has to survive one, it is the cheaper answer. If it has to be there in five years, it is not.
Usually it is not ACM — it is expanded PVC that was used where ACM belonged, and it is oil-canning from thermal movement. If it genuinely is ACM, the usual causes are a thin skin on a large unsupported span, or fastening that did not allow for movement. Our 3mm comes in .005 and .008 skin; the heavier skin holds a large panel noticeably better and is the one to specify for anything big or handled.
Expanded PVC, almost always. It comes in 1/4″, 1/2″ and 3/4″, so the letter has real depth, and the routed edge is solid colour instead of showing a core line. ACM at 3mm makes a flat letter unless you fold it, and folding small letters is not practical. Use ACM for the backer panel and PVC for the letters on it.
Yes. We V-groove it on the CNC — a groove through the face and core, back skin left intact — and the panel folds along the line into a clean return. Send a DXF or a sketch with the finished dimensions and we will lay out the grooves. That is the capability that makes ACM worth buying from a shop rather than off a rack.
Both, in Sparks, cut to size same day. Expanded PVC in black and white from 1/8″ to 3/4″ in 4×8, plus 4×10 in black at 1/2″ and 3/4″, and rigid grey. ACM in matte white and black, 2mm and 3mm, 4×8 — and black in 5×10, which most shops do not carry and which saves a seam on a large panel.
Full PVC foam board specs and stock → · Full ACM specs and stock →
Whatever you need — one piece or one hundred, a quick cut or a full fabrication run — we're here. Serving Northern Nevada since 1979.