What is the difference between Interior Grade (Type I) and Exterior Grade (Type E) MDF?

Exterior grade uses a synthetic resin binder that provides high resistance to moisture, making it suitable for high humidity applications. Interior grade is for dry conditions only. (Part 1, Clause 3.1.2)

What are the formaldehyde emission classes for MDF?

The standard defines two classes based on emission levels: E1 (<0.1 ppm) and E2 (0.1 to 0.25 ppm). (Part 1, Annex C)

What is the minimum bending strength (MOR) for a 19mm Interior grade MDF board?

For boards thicker than 12mm, the minimum Modulus of Rupture is 30 N/mm². (Part 1, Table 2)

How are hardboards classified?

Hardboards are classified based on density and treatment as Standard (S), Tempered (T), and Medium (M). (Part 2, Clause 3)

IS 7638

: 1999

Fibre Boards (Medium Density Fibreboard and Hardboard) - Specification

CurrentFrequently UsedSpecificationBIMMaterials Science · Timber and Wood

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This standard provides the specifications for fibreboards, published in two separate parts. Part 1 covers Medium Density Fibreboards (MDF) for general purposes, and Part 2 covers Fibre Hardboards. It details the classification, dimensions, tolerances, physical and mechanical property requirements, and testing methods for these engineered wood panels.

Lays down the requirements for medium-density fibreboard (MDF) and hardboard, covering their types, properties, and test methods.

Quick Reference Values

MDF Interior Grade (Type I) DensityAbove 600 kg/m³

MDF Exterior Grade (Type E) DensityAbove 650 kg/m³

MDF (Type I, >12mm) Modulus of Rupture, Min30 N/mm²

MDF (Type I, >12mm) Swelling in Thickness (24h), Max12 %

Standard Hardboard (Type S) DensityAbove 800 kg/m³

Formaldehyde Emission Class E1 Limit< 0.1 ppm

Practical Notes

Always specify the grade (Interior/Exterior) and formaldehyde emission class (E1/E2) for MDF based on the application. E1 is highly recommended for all interior living spaces.

MDF's performance heavily depends on the resin used. Exterior (EXT) grade uses moisture-resistant binders (like Phenol Formaldehyde) making it suitable for humid areas, unlike Interior (INT) grade.

The edges of MDF are particularly porous and susceptible to moisture absorption, leading to swelling. Effective edge banding or sealing is critical for durability in furniture and cabinetry.