Scaffold tie (wall tie tube)

Hook-ended 48.3 mm tube linking the scaffold to an eye bolt in the wall, so wind and overturning forces pass into the building.

Also called: wall tie, tie tube, hook tie, scaffold anchor, wall anchor

A facade scaffold is narrow and tall. A freestanding line of frames 0.73 m deep and twelve metres high would go over in the first strong gust. The scaffold tie is what prevents that. It couples the uprights to the building and transfers wind and overturning forces through the eye bolt into the wall. Only with ties does a set of stacked frames become a stable scaffold.

Two force directions matter: perpendicular to the facade (tension and compression) and parallel to it. A single tie handles only the first. For forces along the wall there is the V-tie.

Design and lengths

The tie itself is a length of 48.3 mm steel tube; a hook welded on at the wall end engages in the eye of the bolt; at the scaffold the tube is clamped to the upright with a right-angle coupler.

• Short tie: about 0.4 to 0.5 m, one coupler on the inner upright. Takes forces perpendicular to the facade only.
• Long tie: spans the full scaffold width and is clamped to inner and outer upright with two couplers. Lengths up to around 1.5 m are common, more for large wall gaps. Bricklaying scaffolds of 1.00 or 1.09 m need correspondingly longer ties than narrow painting scaffolds.
• Tie with fork or claw: grips the deck profile of the frame and, depending on the system, saves a coupler.
• Hook position: inside or outside, depending on the space between wall and upright.

Fitting

1. Set out the anchor points from the tie pattern in the system instructions. Nets or sheeting raise the wind load and often call for a denser pattern.
2. Fix the eye bolt with a suitable plug in sound substrate, at the height of the later connection.
3. Insert the hook into the eye.
4. Clamp the tie to the inner upright as close to the node as possible – directly beneath the deck – and on long ties also to the outer upright.
5. Tighten the couplers to the specified torque, usually 50 Nm.
6. Install ties as the scaffold rises, not at the end. When dismantling they come out only after the lifts above have gone.

On frame scaffolds the tie sits under the deck profile of the frame; on modular scaffolds directly under the rosette that carries the working-level transoms.

Mistakes and used parts

• Wrong substrate: suitable anchor bases are reinforced concrete and structural masonry. Downpipes, window frames, snow guards or balcony railings are not.
• Wire or rope never replaces a tie.
• Distance from the node may deviate only within tight limits set by the instructions.
• Removing ties without authority: only the scaffold contractor may move or remove them. Missing ties are among the most frequent causes of scaffold collapses.
• Used: check the hook for opening and cracked welds, the tube for straightness and crushing. An opened hook slips out of the eye under load.

Our guide to ties and anchoring deals with patterns and pull-out tests. Used ties are listed under wall tie.