Code of practice for construction of timber ceilings
1984 Edition

The code recommends using timber species listed in its Appendix A for ceiling planks, including durable hardwoods such as Sal, Teak, and Deodar suited for interior applications. For ceiling framework and beading, compliance with IS 3629-1966 ensures quality and proper species selection. Additionally, timber moisture content must align with IS 287-1973, seasoning must follow IS 1141-1973, and preservation treatments per IS 401-1982 are necessary. Protection against termites should be implemented as described in IS 6313 (Parts 1-3)-1981.

Timber must be seasoned according to IS 1141-1973 to achieve the moisture levels specified in IS 287-1973, promoting dimensional stability and longevity. Following seasoning, timber requires preservative treatment as per IS 401-1982. If water-soluble preservatives are applied, a subsequent seasoning process is needed to eliminate excess moisture. To protect against termite infestation, treatments conforming to IS 6313 (Parts 1-3)-1981 should be used. This sequence ensures timber remains durable and resistant to decay.

The code outlines several approved fixing methods: timber planks can be directly attached beneath floor or ceiling joists, trussed rafters, or roof trusses, forming closed ceilings. For open ceilings, timber fillets of approximately 400 mm² cross-section are nailed to bridging joists or tie beams, with planks subsequently fixed to these fillets from below. Planks should be joined longitudinally using tongue-and-groove joints and secured with screws or nails ensuring proper alignment and structural integrity.

The principal joint type specified is the tongue and groove joint, where a projecting tongue on one plank fits into a corresponding groove on the adjoining plank, creating a flush, tight connection. This joint helps achieve smooth, gap-free ceiling surfaces. Other joints include butt and beading joints and overlap joints, but tongue and groove is preferred for stability and finish quality.

Protection against moisture and termite damage is ensured through selecting durable timber species listed in the code, seasoning timber to specified moisture levels (IS 287-1973, IS 1141-1973), and applying preservative treatments as per IS 401-1982. Timber treated with water-soluble preservatives requires a second seasoning post-treatment. Termite resistance is achieved by following measures outlined in IS 6313 (Parts 1 to 3), including chemical treatments and physical barriers, thereby enhancing the longevity and durability of timber ceilings.