Popular on both sides of the Pacific, vertical board and batten obviously appeals as a practical cladding for homeowners. The 12”-wide boards in native timbers are no longer available in New Zealand, but H3.2-treated radiata pine boards are a good substitute for those durable natives and they can be left to weather naturally to a silver-grey, or painted. When painted, a light colour should be chosen to prevent over-heating and splitting or crazing as shown in Figure 1. There seems to be a preference for roughsawn boards, whether painted or not, to provide some texture to the face of the board. Rough-sawn boards, often with a band-sawn face, provide a more stable board because they are thicker. But they tend to provide less weathertightness because they do not seal as well against the battens and are more difficult to paint.
Weathergrooves needed
Battens and boards should both have weathergrooves machined in them. The size and position of these grooves is critical if they are to help keep water out of the joint. The most common size of board is 150 × 25 mm with a 75 × 25 mm batten. This allows the weathergrooves to be positioned as shown in Figure 2.
Joints
It is preferable to use board and batten only on single-storey construction and in single lengths. Joining boards with a bevel cut is not satisfactory as the differential shrinkage or cupping of boards opens the joint and exposes the cut end. Where joints are required, for example on a gable end, use a flashing as shown in Figure 3. The tops, or cut ends, should always be covered.
Fixing
If boards and battens are fixed directly to framing then wind barriers should be considered and these requirements are given in NZS 3604: 1999. In very-high wind areas or on exposed sites an alternative cladding should be considered.
Take care to ensure the weathergrooves line up before fixing in place (see Figure 2). Boards should be fixed at each dwang, at the centre with a single 60 mm galvanised nail, or with a spiral- or grooved-shank stainless steel or silicon bronze nail for ACQ or CuAz treatments. A longer nail is required for fixing through rigid sheathing. Dwangs are required at not more than 480 mm centres.
Windows
Windows are easier to install if a facing is used. The window can then be fixed to the face of the boards with a head facing protecting the head flashing. This also provides a surface for the battens to finish to. If the board and batten module is worked to, a batten can form the side facing and protect the edge of aluminium joinery facing. A sill facing, preferably bevelled to shed water can then be installed to protect the sill flashing and the cut ends of the battens below the window.