Board fixings

Figure 2: Secret nailing and face nailing options

Board fixings are required at each framing support (e.g. ceiling joists or wall studs). Table 1 specifies maximum spacings and nail sizes to suit different board thicknesses.

It is only necessary to use one nail at each support where boards are less than 90mm wide and can be restrained along an edge by a tongue and groove (or rebate). Boards that are 90 to 135mm wide require the addition of adhesive or an additional fastener. Boards that are wider than 135mm require extra nails. In such instances 'secret nailing' is unrealistic and care should taken when matching timber fillers with timber colours as the timber typically darkens with exposure to ultra violet light.

Where the installation is over masonry construction, or where a wall or ceiling needs levelling, the best option is to first fix timber battens to the wall or ceiling. Battens should be spaced to suit the requirements in Table 1. Batten size is generally 50 x 25mm or 70 x 25mm, and these should be mechanically fixed to the substrate with masonry anchors. Care should be taken with ceiling battens as they require higher pull-out loads and should therefore be checked for firm anchorage. Battens also need to be located to provide fixing points around openings, penetrations, and at butt joints in boards.