T&G (Tongue and Groove) Siding

The Full Picture

Tongue and groove boards are milled so the tongue of one board fits the groove of the next. The joint hides fasteners in some installations, resists gaps from shrinkage and gives a continuous surface. Common profiles include plain, V-groove and beaded faces, and the boards can run vertically, horizontally or diagonally. Wood is the traditional material, and similar profiles exist in other materials, but this page focuses on wood. T&G is used as exterior siding, porch and eave soffits, interior wall paneling and ceilings, and the same joint is used for flooring.

The detail estimators need is coverage width. A nominal board is wider than the face it covers, because the tongue overlaps the neighboring board. Mills state a coverage or face width for each profile, and takeoff should use that number and not the nominal width. The supplier may sell by the linear foot or by the board foot (1 MBF is 1,000 board feet), so the estimator converts from SF of wall to the unit the quote uses. Waste depends on the pattern, run length, the number of openings and the cut-offs. It commonly runs higher for diagonal layouts, short runs and heavily cut-up areas, and it varies by project, so many estimators set it by layout and not a blanket percent.

Wood moves with moisture. The Forest Products Laboratory explains that the moisture remaining in the wood tends to come to equilibrium with the humidity of the surrounding air, so boards that arrive on a site wetter or drier than their service conditions shrink or swell after installation. That is why the spec may call for acclimation and for specific moisture content at installation. For exterior use, finishing is a real cost: the Forest Products Laboratory says that protection from water, sunlight, and weathering is most important for wood used outdoors, so priming or sealing all faces and end cuts is usually specified, and the finish is a separate scope.

In the documents, T&G siding appears on exterior elevations and wall sections as a material tag, in the finish schedule for interior paneling or ceilings, and in the reflected ceiling plan when it is used overhead. Specifications are in Division 06 (Wood, Plastics and Composites) for finish carpentry and paneling and sometimes Division 07 for exterior siding systems. Pitfalls are using nominal width for the coverage, forgetting backing, furring or blocking, omitting trim, corners and nails, and not including finish or sealer on all sides.