PVC Trim Installation in Longmont, CO

Corner boards, window casings, door surrounds, fascia boards, and rake trim are where most exterior renovations fail first. These transition points collect water, go through the most dramatic temperature swings, and take direct UV exposure — and wood trim, even properly painted, is fighting a losing battle in Colorado’s climate. Cellular PVC trim is the right material for these applications. Josh Brooks Construction and Renovation Inc. has been installing PVC trim alongside LP SmartSide and James Hardie siding across Northern Colorado since 2014.

What Is Cellular PVC Trim?

Cellular PVC trim is a closed-cell polyvinyl chloride board manufactured specifically to replace wood trim in exterior applications. It’s called “cellular” because the manufacturing process creates a closed-cell foam core inside a solid PVC shell — giving it the workability of wood (cuts, routes, nails, and sands like wood) with the weather performance of PVC (won’t rot, won’t swell, won’t absorb moisture).

Leading brands include Azek (now TrexTrim), Versatex, and Kleer. All three come in standard lumber dimensions (1×4, 1×6, 1×8, 5/4×6) and can be ordered in custom widths and thicknesses. Profiles can be routed on site to match traditional wood molding details — ogee, cove, beaded, and others — making PVC trim an appropriate choice even on homes with traditional architectural profiles.

Where PVC Trim Makes the Most Difference on a Colorado Home

Corner boards — the most critical PVC application. Corner boards are where two siding surfaces meet and where water collects, drains, and infiltrates. Wood corner boards on a Colorado home typically fail within 10-15 years due to moisture cycling and freeze-thaw expansion. PVC corner boards last indefinitely with no maintenance.

Window casings — window perimeters are the highest-moisture-concentration zone on any exterior wall. Water runs down the siding, gets behind poorly maintained wood casings, and rots the sheathing and framing behind them. PVC window casings eliminate this failure mode entirely.

Door surrounds — same principle as window casings, with the added mechanical stress of door operation and the transition from siding to door frame. PVC handles this junction without cracking or separating at caulk joints the way wood does after 5-10 seasons.

Fascia boards — the fascia is one of the most exposed boards on any home — directly exposed to weather, attached to the gutter, and often the first thing to show rot on an older home. PVC fascia eliminates gutter-related rot entirely.

Rake boards and frieze boards — the trim along the roofline and at the wall-ceiling junction. These surfaces take the most direct UV exposure and benefit enormously from PVC’s UV stability.

PVC Trim Installation: What We Do Right

PVC trim requires specific installation practices that differ from wood:

• Expansion gaps required — PVC expands and contracts more than wood with temperature changes. We leave the correct expansion gap at every joint so the trim doesn’t buckle in summer heat. Most failures in PVC trim are due to contractors installing it like wood with tight butt joints.
• Stainless steel or hot-dipped galvanized fasteners only — standard bright nails will rust and cause staining. We use corrosion-resistant fasteners on every PVC installation.
• PVC-compatible adhesive at miters — miter joints on PVC are bonded with PVC cement and mechanically fastened, not just nailed. This prevents joints from opening seasonally.
• 100% acrylic latex paint only — solvent-based paints can cause PVC to warp. We specify the correct paint for PVC applications and note it in your project documentation.
• Back-priming optional but recommended — painting the back face of PVC before installation is not required (PVC doesn’t absorb moisture) but improves paint adhesion on the face and reduces color variation.

PVC Trim + LP SmartSide or James Hardie: The Winning Combination

The photo at the top of this page shows exactly what we recommend on most exterior renovations: LP SmartSide lap siding on the field of the wall, PVC corner boards and window casings at the transition points. This combination gives you:

• The wood grain aesthetic of LP SmartSide where it has the most visual impact
• Zero-rot performance at every vulnerable junction where water collects
• A paint schedule of 10-15 years rather than 5-7 years for all-wood exteriors
• No rot callbacks at corners or windows in year 8 when wood trim typically starts showing moisture damage

We pair James Hardie fiber cement with PVC trim on hail-exposed homes where Class 4 impact resistance is the priority. The PVC trim performs identically in both combinations.

Frequently Asked Questions

Completed Project — Fort Collins, CO

LP SmartSide Panel Siding with PVC Trim Boards — Tudor Gambrel Home, Fort Collins

This Fort Collins Tudor-style gambrel home had failing original wood panel siding on the upper gable sections. The curved gambrel roofline and Tudor board-and-batten detail required precise LP SmartSide panel cuts and carefully fitted PVC trim boards to maintain the home’s architectural character.

• LP SmartSide vertical panel — dark gray factory-primed
• White cellular PVC trim boards at horizontal bands and window surround
• Curved gambrel profile maintained with precision panel cuts
• Tudor board-and-batten trim detail preserved
• Installed December 2023 — Larimer County permitted