The Fastener Landscape in Indian Construction
A typical commercial construction project in India uses dozens of different fastener types — from M8 wedge anchors for interior partitions to M36 HSFG bolts in the primary structural frame. Each has a specific function, standard, and quality requirement.
This guide provides site engineers, QS teams, and procurement managers with a systematic understanding of the construction fasteners they purchase every month.
Category 1 — Structural Steel Connections
IS 1367 Grade 8.8 Hex Bolts
The standard bolt for steel-to-steel connections in PEB (pre-engineered buildings), trusses, and secondary structural members. DIN 933 (fully threaded) or DIN 931 (partially threaded) equivalent.
- Size range: M12 to M36 (most common M16, M20, M24)
- Coating: HDG for outdoor structures, zinc plated for indoor/protected
- Documentation: EN 10204 2.2 for general, 3.1 for primary structural
IS 3757 Grade 10.9S HSFG Bolts
High Strength Friction Grip bolts for primary structural connections in bridges, heavy frames, and multi-storey steel buildings. These work by friction — the bolt is tightened to high preload, clamping the connected plates so tightly that the shear force is transferred by friction at the plate interface.
Critical requirement: HSFG connections must be tightened using calibrated torque wrenches, DTI (Direct Tension Indicator) washers, or the turn-of-nut method per IS 3757 Part 3. DO NOT use impact wrenches without torque verification.
Category 2 — Anchor Fasteners
Wedge Anchors (also called anchor bolts)
The most commonly used concrete anchor in Indian construction. Available in carbon steel zinc-plated (interior), HDG (exterior), and SS316 (corrosive or coastal).
Common sizes: M8, M10, M12, M16 in lengths 65mm to 200mm
Applications: Column base plates, equipment bases, MEP equipment (AHU, pumps), racking and shelving, façade bracket anchoring
Chemical Anchors (Epoxy Anchors)
Used for high-load applications and where wedge anchor edge distances can't be maintained. Also the only option for cracked concrete and rebar connection.
Common system: ETA-approved two-component cartridge with mixing nozzle. Insert depth = typically 8–10× anchor diameter. Minimum cure time before loading (temperature dependent).
Foundation Bolts (J-type and L-type)
Cast-in-place anchor bolts for equipment foundations — typically J-bolt (bent end) or L-bolt. Embedded in concrete during pour.
Material: IS 5624 Grade 4.6 or 6.8 for light equipment; Grade 8.8 for heavy equipment; ASTM F1554 Grade 55 for heavy plant and tower foundations.
Category 3 — Roofing and Cladding Fasteners
Self-Drilling Roofing Screws (TEK Screws)
These are the most common fastener in pre-engineered building cladding and roofing — they drill their own hole as they are driven, eliminating the need for a pre-drilled hole.
Types:
- Type A (hexagonal washer head): For metal-to-metal (purlin to roof sheet)
- Type C (pan head): For fibre cement cladding
- Type K (large washer): For thicker insulation sandwich panels
Coating: Zinc plated with EPDM washer for weather seal. Stainless for coastal applications.
Purlins Bolts and Cleat Bolts
Standard M12 or M16 Grade 8.8 bolts for connecting purlins to primary rafters, and cleats to columns. These are regular hex bolts — the "roofing" designation refers only to the application.
Category 4 — Formwork and Concrete
Tie Rods and Form Ties
Thread rod Grade 4.8 or 8.8 in 15mm or 20mm diameter, used as formwork tie bolts. The rod passes through plywood faces; plastic cones create the break-off point inside the concrete wall. After stripping, the cone is removed and the hole is patched.
Bar Chairs and Spacers
While technically not fasteners, rebar spacers maintain cover for rebar. Where rebar is joined by screw coupler (rebar splice), the coupler and rebar thread is a precision connection requiring matching tolerances.
Common Site Mistakes and How to Avoid Them
Mistake 1: Wrong anchor installation. Most wedge anchor failures are due to installation error — insufficient hole depth, dirty holes, undertorqued. Always follow the manufacturer's installation instruction for every anchor type.
Mistake 2: Using non-HDG nuts with HDG bolts. This strips the zinc coating from bolt threads during installation. Always use matched HDG nuts (tapped oversize) with HDG bolts.
Mistake 3: Substituting lower grade. Grade 4.6 bolts look identical to Grade 8.8 from a distance. The grade is marked on the bolt head — verify before installation. Substituting lower grades in structural connections is dangerous.
Mistake 4: No torque control on HSFG bolts. HSFG connections depend on specific preload. Tightening by feel or with an impact wrench without torque verification will under-clamp or over-clamp the joint.
Mistake 5: Ignoring edge distance for anchors. Anchor loads dramatically reduce near concrete edges. Consult the anchor design data (typically in ETA approval documents) for minimum edge distances and reduction factors.
Contact PGS Fasteners for construction fastener supply with technical support for your site specification requirements.