The material you pick for a dimensional letter sign decides how it looks on day one and how it looks after several Colorado winters. When it comes to dimensional letter materials in Boulder, CO, the short answer is this: aluminum is the safest all-around exterior choice, stainless steel and brass are premium metals for high-end looks, HDU suits carved and traditional styles, and acrylic and PVC work best indoors or in sheltered spots. The details below explain why, and when each one makes sense.
Why Boulder’s Climate Changes the Material Decision
Boulder sits at over 5,000 feet against the foothills. That brings conditions that are hard on signs:
- Strong UV: thinner air means more ultraviolet exposure, which fades paint, yellows some plastics, and chalks low-grade finishes.
- Big temperature swings: a sunny winter afternoon and a sub-freezing night in the same day cause materials to expand and contract.
- Freeze-thaw cycles: water that gets into a seam, crack, or mounting hole freezes, expands, and slowly pries things apart.
- Hail and wind: spring and summer hail can dent or crack softer letters, and downslope winds test any loose fastening.
A south- or west-facing wall on Pearl Street or in the Flatiron Park business area will see much more sun than a shaded entry under an overhang. Orientation is as important as the material itself.
Comparing Dimensional Letter Materials for Boulder, CO
Aluminum
Cut or fabricated aluminum is the workhorse of exterior dimensional letters.
- Strengths: lightweight, does not rust, stable in heat and cold, and takes high-quality paint or powder coat well.
- Weak points: the finish is what faces the sun, so paint quality matters. Thin letters can dent in a hard hail storm.
- Best for: most storefronts, office buildings, and industrial walls.
Stainless steel
- Strengths: very durable, corrosion resistant, and available in brushed or polished finishes that do not need paint.
- Weak points: heavier and more costly to fabricate. Polished finishes show fingerprints at reachable heights.
- Best for: corporate lobbies, entry monuments, and upscale exterior applications.
Brass and bronze
- Strengths: a warm, classic look that suits historic and traditional architecture.
- Weak points: brass naturally darkens and develops a patina outdoors unless it is clear-coated, and coatings need periodic care. It is also one of the more expensive options.
- Best for: law offices, banks, and buildings in historic settings such as downtown Boulder.
Acrylic
- Strengths: crisp edges, many colors, and a polished, modern look. Cast acrylic holds color well.
- Weak points: can crack on impact and is more vulnerable to hail. Thin acrylic letters on a sunny wall can move with heat.
- Best for: interior lobby and reception walls, and sheltered exterior spots.
PVC
- Strengths: economical, light, and easy to cut into thick letters.
- Weak points: softer than metal and can warp in direct sun, especially in dark colors.
- Best for: interior signs, temporary or budget-sensitive projects, and shaded exterior locations.
High-density urethane (HDU)
- Strengths: does not rot or absorb water like wood, can be carved, routed, or textured, and is dimensionally stable.
- Weak points: must be primed and painted, and the paint system is what protects it. Can dent if struck.
- Best for: carved or traditional-style letters and signs that need a wood-like look without wood maintenance.
Quick Guide: Matching Material to Location
- Full-sun exterior wall: aluminum or stainless steel.
- Historic brick facade: painted aluminum, brass, or HDU with a traditional profile.
- Covered entry or canopy: aluminum, acrylic, or HDU.
- Lobby or reception wall: acrylic, stainless, brushed aluminum, or PVC.
- Hail-exposed low wall or monument: thicker aluminum or stainless.
For a look at how these materials are used across sign types, visit our dimensional letters page and our outdoor signs page.
Interior vs. Exterior: Different Priorities
Indoor and outdoor letters solve different problems, so the best choice changes once you step inside. Outside, weather resistance and fade resistance come first. Inside, the priorities shift to appearance up close, weight on the wall, and how the letters work with lighting in the room.
- Viewing distance: lobby letters are seen from a few feet away, so edge quality and finish show every flaw. Acrylic and brushed metals shine here.
- Wall type: drywall can carry lighter letters with the right anchors, while heavier stainless or brass may need blocking behind the wall.
- Lighting: spotlights or wall washers can make polished finishes glare. Satin and brushed finishes are more forgiving.
Many businesses use two sets of dimensional letter materials in Boulder, CO: durable painted aluminum outside, and a more decorative acrylic or metal finish in the reception area. Matching colors and fonts between the two keeps the brand consistent.
Finishes Matter as Much as the Base Material
In Boulder, a good material with a poor finish will still fail early. A few points to ask any sign company about:
- Paint system: exterior-grade, UV-resistant coatings designed for signs rather than general-purpose spray paint.
- Clear coat: extra UV protection, especially on bright reds and yellows, which tend to fade first.
- Edge sealing: sealed edges on HDU and PVC keep moisture out.
- Metal laminates: a thin metal face over acrylic or PVC can give a metal look at a lower cost, best in sheltered spots.
Cost Factors by Material
Without quoting prices, here is how materials generally compare, from typically lower to higher cost:
- PVC
- Acrylic
- HDU and cut aluminum
- Fabricated aluminum
- Stainless steel, brass, and bronze
Other cost drivers include thickness, letter height, number of letters, custom colors or metallic finishes, mounting method, wall type, and permit requirements for exterior signs.
How 303 Sign Company Builds Your Letters
- Site review: we look at sun exposure, wall material, and viewing distance.
- Material and finish recommendation: matched to your location and budget, with samples where helpful.
- Design approval: a scaled rendering showing size, color, and finish.
- Permitting: for exterior signs, our in-house team handles the City of Boulder application.
- Fabrication: cut, finished, and prepared for mounting in our Longmont shop.
- Installation: mounted with hardware suited to the wall and the material’s weight.
See finished examples on our work page.
Material Mistakes to Avoid
- Using thin PVC or acrylic on a south-facing exterior wall.
- Choosing unprotected brass outdoors and expecting it to stay bright.
- Picking dark colors on plastic letters in full sun.
- Skipping a clear coat on high-fade colors.
- Selecting a material by sample alone without checking where the sign will face.
Dimensional Letter Materials FAQ
What is the most durable material for exterior letters in Boulder?
Aluminum and stainless steel are the most durable general choices. Aluminum offers the widest range of colors; stainless gives a premium metal look without paint.
Can acrylic letters go outside?
Yes, but they do best in sheltered spots. On exposed walls, metal is usually the better long-term choice.
Is HDU better than wood?
For signs, usually yes. HDU gives a carved look without the rot, checking, and swelling that wood can suffer from moisture and freeze-thaw.
Will brass letters tarnish?
Uncoated brass will darken and develop a patina outdoors. A clear coat slows this, and some owners prefer the aged look.
Get a Material Recommendation for Your Building
From Gunbarrel to University Hill, we will look at your wall and suggest the dimensional letter materials that make sense for your Boulder, CO, location and budget. Call (888) 303-3936 or contact us to schedule a visit. We are open Monday through Friday, 8:30 AM to 5:00 PM.