Types of Fasteners Used in Construction
Construction uses five main fastener families: foundation bolts cast into concrete, anchor fasteners drilled into it, structural bolts for steelwork, threaded rods for services, and screws for roofing and interiors.
Foundation bolts
Foundation bolts (J, L, hook or rag bolts) are cast into concrete when it is poured. They hold down steel columns, machinery, tanks and towers, and are made to the length and bend shown on the structural drawing.
Anchor fasteners
When the concrete is already set, fixings are drilled in instead. Wedge anchors carry the heaviest loads in solid concrete, sleeve anchors suit brick and block, drop-in anchors sit flush in ceilings for hangers, and chemical anchors bond studs or rebar with resin close to edges.
Structural bolts
Steel frames, PEB buildings and bridges are bolted with high tensile structural bolt sets: heavy hex bolts with matching nuts and hardened washers. High strength friction grip (HSFG) bolts are tightened to a high preload so the joint works by friction.
Threaded rods and hangers
Building services such as ducts, pipes, sprinklers and cable trays hang from threaded rods fixed to the slab with drop-in anchors, joined with coupling nuts and supported on strut channels and clamps.
Screws for roofing and interiors
- Self drilling and roofing screws fix metal sheets to purlins
- Drywall screws fix gypsum boards to studs
- Wall plugs and frame fixings hold doors, windows and fixtures in masonry
Choosing for Chennai conditions
Chennai's humid, coastal climate corrodes plain steel quickly. Use hot dip galvanized fasteners for outdoor steelwork and SS 316 for anything exposed to sea air.
