Code of practice for construction of timber floors
1992 Edition

Timber flooring materials should comply with relevant Indian standards specifying quality and dimensions suitable for floor construction. The allowable floor height and span depend on timber thickness and the presence of lateral supports. Generally, lateral supports such as beams or joists should not be spaced more than 36 times the timber thickness to maintain structural integrity. Floors without top support have more restrictive height limits. Typical timber thicknesses used range from 50 mm to 100 mm, selected according to design requirements and load conditions.

To minimize cracking and deformation, vertical and horizontal reinforcements are essential. Reinforcement includes placing steel bars or mesh within timber members, especially at joints and critical stress points. Bars commonly used are around 12 mm in diameter and approximately 400 mm in length, embedded appropriately within timber cores or between layers. Additionally, resilient packing materials like wooden fillets or fibreboard are placed at edges to allow movement and reduce stress concentration. Surface mesh reinforcement can also be applied before finishing to enhance durability.

Timber floors must be securely fixed to the primary building structure to ensure stability. The base of the floor should be positioned above the skirting level, and edges must be firmly attached to permanent supports such as walls or beams. Grooves or channels are recommended to receive timber edges, avoiding rigid bonding that can cause cracking. If lateral supports are present at the top, floors should be wedged and pinned securely to the ceiling or beam to prevent movement. Maximum height and span limitations apply based on timber thickness and support spacing.

Sound insulation in timber floors is achieved by incorporating edge isolation techniques and using resilient materials to prevent direct rigid contact between the floor and surrounding structures. This reduces sound transmission by blocking vibration paths. Materials such as fibreboard, felt, slag wool, or glass silk are recommended for packing at edges, particularly around walls, floors, and ceiling junctions. Proper design to avoid cracks and open joints also enhances acoustic performance.

The recommended mortar for timber floor laying combines binders and aggregates that provide strong bonding and durability. Typically, a mixture of one part calcined gypsum to up to three parts fine aggregate or sand by weight is used, with about 0.25% sodium citrate added as a retarder to control setting time. For finer joints, a mix including gypsum and unslaked lime in a ratio of 1:3 by weight, with the same retarder percentage, is prescribed. Timber surfaces should not be excessively wetted before laying to maintain adhesion and prevent material degradation.