What is the difference between IS 4990 plywood and commercial plywood?

IS 4990 plywood is BWP (Boiling Water Proof) grade made with Phenol Formaldehyde resin, designed to withstand wet concrete. Commercial plywood (IS 303) is MR (Moisture Resistant) grade made with Urea Formaldehyde resin and will delaminate on contact with water.

What does BWP grade mean?

BWP stands for 'Boiling Water Proof'. It signifies that the plywood uses a specific adhesive and can pass a 72-hour boiling water test without delamination, as per Clause 8.2, making it suitable for exterior and wet conditions like concrete shuttering.

What is the expected number of reuses for shuttering plywood?

The code requires a minimum of 10 repetitions in a lab test (Annex C). In practice, non-film faced plywood can be reused 5-10 times, while good quality film-faced plywood can be reused 15-25 times with proper care.

What are the standard thicknesses for shuttering ply?

The most common thicknesses are 12 mm (for slab bottoms, beam sides) and 18/19 mm (for column boxes, walls). The code covers a range from 6 mm to 25 mm (Clause 6.1).

IS 4990

: 1993

Plywood for Concrete Shuttering Work - Code of Practice

CurrentFrequently UsedSpecificationBIMMaterials Science · Timber and Wood

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This standard specifies the requirements for plywood intended for use in concrete formwork, commonly known as shuttering plywood. It details the timber species, adhesives (BWP grade), manufacturing process, dimensions, tolerances, and mechanical properties like bending strength and water resistance to ensure durability and reusability.

Provides guidelines for the selection, use, maintenance, and reuse of plywood used as formwork for concrete construction.

Quick Reference Values

Standard Sheet Size2440 mm x 1220 mm

Common Thicknesses12 mm, 19 mm

Water Resistance Test (BWP Grade)No delamination after 72 hours in boiling water

Minimum Modulus of Rupture (parallel to face grain)50 N/mm²

Minimum Modulus of Elasticity (parallel to face grain)8000 N/mm²

Minimum Reusability Test Cycles10 repetitions

Practical Notes

Always check for the ISI mark, 'IS 4990' and 'BWP' (Boiling Water Proof) grade marking on the plywood. Absence of these markings often indicates non-compliant material.

The number of reuses heavily depends on site handling. Applying a suitable mould release agent before each use and proper cleaning and storage significantly increases its life.

Ensure the edges of the plywood sheets are sealed with water-resistant paint. Unsealed edges are the primary point of moisture ingress, causing swelling and delamination.