Shiplap is one of the most widely used timber cladding profiles for both decorative exterior cladding on houses and for garden buildings. Its distinctive overlapping profile creates a visually attractive horizontal banding while providing effective weather resistance at the board joints.

The Shiplap Profile

Shiplap boards are machined with a rebate cut along each long edge, so that when boards are overlapped vertically the rebated edges interlock. The rebate on the top edge of the lower board and the corresponding rebate on the bottom edge of the upper board fit together, creating a lap joint that prevents wind-driven rain from penetrating between the boards. The interlocking joint also allows timber movement with seasonal moisture changes without creating gaps in the cladding.

The finished appearance of shiplap cladding is a series of parallel horizontal boards with a consistent shadow line between each course, created by the overlapping profile. The face of each board is flat, giving a cleaner, more contemporary appearance than featheredge or waney-edged cladding.

Materials

Traditional shiplap cladding is made from treated softwood, typically redwood or whitewood, pressure-treated to extend its service life in exterior use. Untreated softwood shiplap requires regular application of wood preservative, paint, or stain to prevent deterioration. Hardwood shiplap in species such as Western red cedar, Siberian larch, or American oak provides naturally better durability and an attractive weathered appearance without requiring painting. Composite shiplap boards, made from wood fibre and plastic, are increasingly available and offer the appearance of timber with virtually no maintenance requirement.

Installation

Shiplap cladding is fixed horizontally to vertical battens, which in turn are fixed to the structural wall and provide a ventilated cavity behind the cladding. This ventilated cavity is important for allowing any moisture that penetrates the outer face to drain and evaporate rather than accumulating behind the boards. Boards are fixed with stainless steel or hot-dipped galvanised nails or screws at each batten to allow the timber to move without splitting. Fixings must be through the upper portion of each board, above the overlap zone, so that the lower overlap can move freely.

Summary

Shiplap cladding uses rebated or chamfered boards overlapped horizontally to create an interlocking weather-tight joint with a clean, contemporary appearance. It is available in treated softwood, hardwood, and composite materials. Installation over vertical battens creates a ventilated cavity essential for moisture management behind the cladding. Planning permission is required in conservation areas where cladding would otherwise be permitted development.