Clause 9.1 sets the minimum requirements for RC shear walls in ductile structures. The minimum thickness is 150 mm for uncoupled walls and 200 mm for coupled shear walls. Reinforcement must be provided in two curtains (one on each face) with at least 0.25% of the gross area in each direction on each face. The maximum spacing of reinforcement is governed by the smallest of 1/5 of the wall length, 3 times the wall thickness, or 450 mm.
Key Requirements
•Minimum thickness of shear wall shall be 150 mm
•For coupled shear walls, minimum thickness shall be 200 mm
•Minimum reinforcement shall be 0.25% of gross area in each direction (horizontal and vertical) on each face
•Reinforcement shall be provided in two curtains (two layers) if the wall thickness exceeds 200 mm or factored shear stress exceeds 0.25√fck
•Maximum spacing of reinforcement in either direction shall not exceed: (a) Lw/5 (1/5 of wall length), (b) 3tw (3 times wall thickness), (c) 450 mm — whichever is smallest
•Shear walls shall have boundary elements at each end when the extreme fibre compressive stress exceeds 0.2 fck
•Boundary elements shall have the special confining reinforcement as specified for columns (Ash formula applies)
Reference Tables
Maximum Reinforcement Spacing in Shear Walls
Wall Length Lw (mm)
Wall Thickness tw (mm)
Lw/5 (mm)
3tw (mm)
450 (mm)
Governing Spacing (mm)
3000
150
600
450
450
450
3000
200
600
600
450
450
4000
200
800
600
450
450
5000
200
1000
600
450
450
2000
150
400
450
450
400
1500
150
300
450
450
300
For shorter walls, Lw/5 governs. For most full-storey-length walls, the 450 mm cap governs.
Practical Notes
✓Two curtains of reinforcement (one each face) are mandatory when the wall thickness exceeds 200 mm. In practice, even 200 mm walls typically get 2 curtains for constructability.
✓Boundary elements are essentially column-like regions at the ends of the wall. They follow the same Ash formula and confining zone rules as columns — do not treat them as simple wall end zones.
✓The 0.25% minimum in each direction on each face means for a 200 mm wall: 0.25% × 200 × 1000 = 500 mm²/m per face per direction — typically 10 mm bars at 150 mm c/c (524 mm²/m).
Common Mistakes
⚠Providing only one curtain of reinforcement in walls 200 mm thick or less when the factored shear stress exceeds 0.25√fck — two curtains are required in this case.
⚠Not providing boundary elements at wall ends when the compressive stress exceeds 0.2 fck — unconfined wall ends can crush and fail suddenly.
⚠Using the 0.25% reinforcement as the total for both faces combined instead of on each face separately — the requirement is 0.25% on each face in each direction.