The Millboard Envello Board & Batten+ Horizontal Siding Installation Guide (PDF) explains how to install Millboard’s wood-free composite siding in a horizontal orientation. This guide covers material composition, storage and handling, wall preparation, drainage requirements, fasteners, starter trims, corner details, window and door integration, and long-term maintenance.
Pages 4–5 introduce the material: a hand-molded oak-grain surface, a closed-cell mineral-polymer core, a UV-stable elastomeric top layer, and integrated fire retardants tested to ASTM E84. Boards are lightweight, moisture-resistant, and designed not to split, rot, or leach tannins. Before installation, boards should acclimate for 72 hours and be stored flat with bearers spaced no more than 16″ apart.
Tools and PPE on pages 8–9 outline the use of standard carpentry tools, carbon-tipped blades for siding boards, and aluminum blades for trims. Cutting must be done face-up for a crisp edge, and Touch-Up Coating is required anywhere a cut edge will be visible.
Wall preparation guidance begins on page 16. Horizontal installs require a compliant Weather-Resistive Barrier (WRB) and proper flashing at all transitions. Because horizontal siding sheds water differently than vertical installations, Millboard specifies drainable housewrap at minimum, with rainscreen mats or furring strips recommended in high-rainfall areas. Diagrams on pages 17–18 show drainage mats, furring layout, airflow gaps, and perforated closures to deter insects while maintaining ventilation.
Installation steps start on page 19. Corner assemblies can use Square Corner Trims, mitered Enhanced Grain boards, or butted boards depending on the design. Starter trims must be level to keep board courses aligned. Fasteners install through the tongue at a slight angle using stainless or galvanized screws. Face fastening is reserved for cut boards around windows, doors, and soffits using colored-head screws or stainless finishing nails.
Pages 24–26 detail flashing around windows, doors, penetrations, and stucco transitions, including preserving movement gaps, maintaining drainage paths, and touching up exposed cuts.
Maintenance guidance on page 27 includes annual cleaning, safe pressure-washing, and stain-removal recommendations.
Download the full Millboard Board & Batten+ Horizontal Siding Installation Guide (PDF) for diagrams and complete installation instructions. If you need Millboard help or project support, your TimberTown team is always here to help.
Download Resource
