What is the permissible tolerance on the cross-section of timber frames?

± 2 mm on the width and thickness of the frame cross-section.

How many holdfasts are required to fix a standard door frame?

A minimum of 3 holdfasts are required on each vertical member (side) of the door frame.

Does the code allow timber defects?

Minor defects like live knots up to a specified diameter are allowed, but dead knots, decay, and active borer attacks are strictly prohibited.

IS 4021

: 1995

Door and Window Frames (Timber)

CurrentFrequently UsedSpecificationBIMArchitectural · Doors, Windows and Shutters

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This standard specifies the requirements for materials, dimensions, construction, workmanship, and finish of timber frames used for doors, windows, and ventilators in buildings.

Specifies requirements for timber frames for doors, windows and ventilators.

Quick Reference Values

Tolerance on overall width and height± 3 mm

Tolerance on cross-sectional dimensions± 2 mm

Holdfasts for door framesMinimum 3 on each side

Holdfasts for window frames (height > 900mm)Minimum 2 on each side

Depth of rebate15 mm minimum, corresponding to shutter thickness

Practical Notes

Ensure timber is properly seasoned (IS 1141) to the moisture content suitable for the climatic zone (IS 287) to prevent warping and shrinkage post-installation.

Preservative treatment (IS 401) is strongly recommended for sapwood and moderately durable timber species to protect against termites and decay.

Mortise and tenon joints should fit snugly, be glued securely with synthetic resin, and be pinned with hardwood or bamboo dowels.