The Millboard Envello Shadow Line+ Vertical Siding Installation Guide (PDF) provides complete instructions for installing Millboard’s premium wood-free composite cladding in a vertical orientation. This guide covers wall preparation, WRB and ventilation requirements, starter trims, internal and external corner details, furring strip options, fastening methods, window and door integration, stucco transitions, and long-term maintenance.
The guide begins with a breakdown of Millboard’s composition and performance (pages 4–5). Shadow Line+ boards feature a hand-molded grain surface, a non-porous elastomeric coating, a reinforced mineral-polymer core, and ASTM E84 fire performance. Storage and handling guidelines on page 7 recommend storing boards flat, carrying them on edge, and letting them acclimate for 72 hours.
Tools and PPE (pages 8–9) include standard woodworking tools, stainless fasteners, a laser level, carbon-tipped blades, and an N99 mask for cutting. Cutting is done face-up for the cleanest finish, and exposed cuts require Millboard Touch-Up Coating.
Wall preparation begins on pages 16–18. A compliant Weather-Resistive Barrier (WRB) is required behind the siding, and the manual emphasizes water management—especially in vertical orientations where more moisture may reach the drainage plane. In high-rainfall regions or where extra ventilation is desired, installers may add rainscreen drainage mats or furring strips, shown in the diagrams on pages 17–18.
Corner profiles (pages 19–20) must be installed before starter trims. Internal and external corner profiles can be fastened using perforated closures, or boards can be mitered and glued for a clean architectural edge. Starter trims (page 21) are installed level and aligned with corners so every course stays plumb.
Fasteners are installed through the board tongue (page 21) using approved stainless screws or siding nails. Face-fastening is only used when the tongue is removed around windows, doors, or edges. Multi-Spacers maintain consistent 1/4″ vertical shadow gaps.
Window and door details (pages 24–25) include 1/4″ uncaulked gaps at heads, Enhanced Grain trim options, and nail/screw placement rules. Stucco transitions (page 26) require casing beads and proper flashing.
Maintenance guidance (page 27) recommends annual cleaning and safe pressure-washing techniques.
Download the full Millboard Envello Shadow Line+ Vertical Siding Installation Guide (PDF) for complete diagrams and instructions. If you need help planning a Millboard siding project, your TimberTown team is always here to help.
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