IS 4021:1995 is the Indian Standard (BIS) for door and window frames (timber). 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.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
IS 4021 (1995) specifies Door and Window Frames (Timber) — covering timber-frame specifications for residential + institutional buildings. Wood remains a popular choice for door + window frames in Indian construction; this code defines the quality + dimensions.
Use when: specifying timber frames for buildings; carpentry contracts; renovation / restoration of older buildings; rural / traditional construction.
Timber selection: - Class A: Best quality (teak, sal, deodar) — for premium doors / windows - Class B: Good quality (sheesham, kail, oak) — for general use - Class C: Standard (sissoo, mango, eucalyptus) — for utility - Treated timber: mandatory for durability (per IS 401)
Frame dimensions (typical): - Door frame: 50 × 100 mm to 75 × 150 mm cross-section - Window frame: 50 × 75 mm to 50 × 100 mm - Length: per opening size - Per IS 4021 + project drawings
Quality requirements: - Straight grain (preferred) - No knots > 10 mm - No splits / cracks > 10 % of cross-section - Moisture content: 12-15 % for interior; 15-18 % for exterior - Surface: smooth + sanded - Treatment: anti-termite + anti-fungal (per IS 401)
Joinery: - Mortise + tenon joints (traditional) - Glued joints (modern) - Dovetail at corners - Iron / steel reinforcement at joints (for security)
Surface treatment: - Varnish (clear or stained) - Paint (any color) - Polish (premium finish) - Sealants for outdoor exposure
Door frame standard sizes: - Single door: 700 × 2000 mm typical (clear opening) - Double door: 1500 × 2100 mm - Industrial: variable per use
Window frame standard sizes: - Standard: 900 × 1200 mm to 1500 × 1500 mm (clear opening) - French / large: 1800 × 2100 mm - Bedroom / kitchen: typically 1200 × 1200 mm
Anchorage: - To masonry: hold-fasts (steel hooks embedded in masonry) - To RCC: anchor bolts + plugs - Wedges for plumb adjustment during installation
Installation tolerances: - Plumb: ± 5 mm - Level: ± 5 mm - Diagonal: ± 5 mm (rectangularity) - Cross-section dimensions: per IS
Acceptance: - Visual: no major defects - Joinery integrity - Treatment verified - Dimensional tolerance per IS - Treatment penetration
Service life: - Class A treated: 50-100+ years - Class B treated: 30-50 years - Class C: 15-30 years - Untreated: 5-15 years (premature decay)
Treatment importance: - Termites + fungal attack are major risks in India - Treatment essential for outdoor / damp locations - Per IS 401 (Methods of Test for Preservatives) - Re-treatment every 7-15 years for high-exposure
Modern alternatives: - Steel frames: durable, low maintenance - Aluminium frames: lightweight, no corrosion - uPVC: increasingly popular for windows - Composite (wood + metal): modern solution
1. Untreated timber → termite + fungal attack. 2. Moisture content too high → warpage + shrinkage. 3. Wrong wood class for application → premature failure. 4. Poor joinery → frame loose / falls apart. 5. Anchorage inadequate → frame movement. 6. No surface treatment → degradation + aesthetic issues. 7. Damaged sections not detected → secondary failures. 8. Wood quality variable → unpredictable life. 9. No maintenance → cumulative deterioration. 10. Steel / hardware corrosion at joints → frame failure.
1. Wood selection per quality + application. 2. Treatment per IS 401. 3. Frame fabrication per IS 4021. 4. Surface treatment (paint / varnish / polish). 5. Site installation + anchoring. 6. Hardware installation (hinges, locks). 7. Final adjustments + sealing. 8. Service: cleaning + maintenance. 9. Long-term: 15-50+ years depending on quality + treatment.
IS 4021 is the specification for timber door + window frames — applied on traditional + ongoing buildings in India.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Moisture Content (Humid/Coastal) | 16% ± 2% (Zone I, avg. RH > 70%) | 15% ± 3% (for exterior use, covered) | BS EN 942:2019 |
| Moisture Content (Dry/Arid) | 10% ± 2% (Zone IV, avg. RH < 40%) | 6% to 12% (for interior use) | WDMA I.S.4-15 |
| Tolerance on Cross-Sectional Dimension | ± 1.0 mm | +1.0 mm / -0.5 mm (for dimensions up to 100 mm, Class THM) | BS EN 942:2019 |
| Tolerance on Overall Height/Width | ± 3.0 mm | Tolerance classes are specified; a typical value would be ± 2.0 mm for Class 2 (per EN 1530) | BS EN 14351-1 (references) |
| Primary Jointing Method | Prescribed: Mortise and Tenon (plain or haunched) | Performance-based: Any joint meeting structural requirements is acceptable. | General practice in BS EN 942 / WDMA |
| Timber Selection Method | By species, from specified groups (e.g., Group I - Teak, Rosewood) | By properties, based on Durability Class (e.g., Class 3) and Use Class (e.g., Class 3.1) | BS EN 942:2019 |
| Knot Limitation (Example) | Max diameter 1/3 of face width, up to 25 mm | Defined by appearance class; e.g., 'J10' class permits sound knots up to 10 mm diameter. | BS EN 942:2019 |