The Millboard Envello Board & Batten+ Vertical Siding Installation Guide (PDF) provides complete instructions for installing Millboard’s premium wood-free composite siding in a vertical orientation. This guide covers material characteristics, wall preparation, drainage and ventilation, fasteners, starter trims, corner assemblies, window and door detailing, and long-term care.
Pages 4–6 introduce Millboard’s composition: a hand-molded grain surface, a durable elastomeric coating, a mineral-polymer core, integrated fire retardants tested to ASTM E84, and tonal color variation designed to mimic real oak. Storage and handling (page 7) note that boards must be stored flat on bearers spaced no more than 16″ apart, carried on edge by two people, and allowed to acclimate for 72 hours.
Tools and cutting guidelines on pages 8–9 recommend standard wood-cutting tools, carbon-tipped blades, appropriate PPE, and cutting boards face-up for the cleanest finish. Touch-up coating is required anytime a cut edge will be exposed.
Wall preparation on pages 16–18 explains how to set up a compliant Weather-Resistive Barrier (WRB), install flashing, straighten wall irregularities, and create drainage pathways. For vertical installations or high-rainfall regions, Millboard recommends drainable housewrap or furring strips to create 1/4–3/8″ of ventilation space. Diagrams on pages 17–18 show drainage mats, horizontal furring on vertical furring, and angled furring layouts for airflow.
Corner details begin on page 19. Installers may use Square Corner Trims, mitered Enhanced Grain boards, or butted boards. Perforated closure strips help anchor external trims and maintain airflow. Joining trims uses a downward-sloping 22.5° scarf joint for shedding water.
Starter trims (page 21) must be level to keep all boards upright. Fasteners are driven through the tongue at a slight angle using approved stainless or galvanized hardware. Where the tongue is removed, colored-head screws or 2″ stainless finishing nails may be used through the face.
Pages 24–26 show window/door flashing, 1/4″ uncaulked gaps at heads, trim options, wall penetrations, and stucco transitions with casing beads and proper drip-edge flashing.
Maintenance (page 27) includes annual cleaning, safe pressure-washing, and stain-removal recommendations.
Download the full Board & Batten+ Vertical Siding Installation Guide (PDF) for complete diagrams and installation practices. If you need help planning a Millboard project, your TimberTown team is always here to help.
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