What preservative is recommended for plywood used in exterior locations like cladding?

For Hazard Class H3 (Exterior, above ground), Copper-Chrome-Arsenic (CCA) or Borated Copper-Chrome-Arsenic (BCCA) preservatives are recommended as per Table 1.

Can I use this code for treating solid wood doors?

No, this code is specifically for panel products like plywood and particle board. For solid timber, refer to IS 401.

What is the minimum required retention of CCA for interior plywood?

For interior use (Hazard Class H1), the minimum retention of CCA preservative is 4.0 kg/m³ according to Table 1.

Is pressure treatment mandatory for all plywood?

No, for lower hazard levels like H1 (interior), processes like dipping may be sufficient. However, for higher hazard levels (H3 and above), pressure treatment is generally required to achieve adequate protection (Clause 5.2).

IS 12120

: 1987

Code of practice for preservation of plywood and other panel products

CurrentSpecializedCode of PracticeBIMMaterials Science · Wood and Other Lignocellulosic Products

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This standard provides a code of practice for the preservative treatment of plywood and other lignocellulosic panel products like particle boards and fibreboards. It details the types of chemical preservatives, methods of application (such as pressure treatment and dipping), and the required retention levels of preservatives needed to protect the products against bio-deterioration under different environmental hazard conditions.

Code of practice for preservation of plywood and other panel products

Quick Reference Values

Min CCA preservative retention for exterior use (H3)6.5 kg/m³

Min BCCA preservative retention for exterior use (H3)8.0 kg/m³

Min CCA preservative retention for interior use (H1)4.0 kg/m³

Min Boric Acid (Boron) preservative retention for interior use (H1)2.5 kg/m³

Min CCB preservative retention for exterior use (H3)6.5 kg/m³

Practical Notes

The effectiveness of treatment heavily depends on achieving the specified preservative penetration and retention, which varies significantly with the product type and density.

Always select the preservative and treatment level based on the end-use hazard classification (e.g., H1 for interior, H3 for exterior above-ground).

Glue lines in plywood can act as a barrier to preservative penetration, making full impregnation challenging compared to solid timber.