How to install Millboard Cladding

by Ben Powney March 12, 2025

Pre installation

· Stored on flat surface with bearers max 400mm apart

· Stack face to face

· Corner profiles should be fully supported along their length

· When moving boards make sure each end is lifted and not dragged to protect the end of the boards

· We advise boards are on site 72 hours before installation to allow boards to climatize

· Tolerances – manufacturing width +-2mm, length +-5mm and thickness +-2mm

· Tools required mitre saw, jigsaw or hand saw, tape measure, PPE, spirit level and standard combi drill

· Where do you start? Each project is different.

· Most people put all their battens in place. Every 600mm centres. 400mm for high load areas

Corners

· Our top tip is to start with the corner profiles.

· Difference between shadow line corners and board and batten corners and internals

· You can butt boards into an external corner or mitre them on external corners but we do recommend corners.

· They also hide movement, shrinkage and generally give a much neater finish

· Perf is fitted to back of corner using 20mm screws at 200mm centres

· *show box screws

· These are then fitted to the corner battens

· *Example of board slotting in behind the shadowline

Reveals

· What are reveals – dimensions.

· Outer surface more brittle

· Typically used for details around windows and doors

· All reveals must be fitted with colour head screws

· The back edge of the board will need to be painted with touch-up

· You can use a clear polymer / sealant behind the reveal boards that are used around the opening

Starter trims

· Starter trims will be fitted at the bottom of the battens

· Difference between different types

· Use 20mm screws with heads countersunk

· Important they are installed level

Boards

· Cladding boards should be fitted through the tongue using 30mm screws

· One screw per batten or two where boards join

· Screws should be slightly angled down and on the fixing guide groove

· Head should sit flush with the surface

· It does not need to be pre-drilled

· The first board is installed then the next board can be fitted over it

· Check boards are level and spaced correctly

· End on end boards should be fitted with 20 degree scarf joint

· We recommend all joints are not in a line but spread out

· We recommend all ends are cut before installed.

· When the tongue is taken off to fit around windows, doors or soffits, you need to use the 40mm colour headed screws.