Scaffold Ties, Guying & Bracing
A tall scaffold is like a thin tower. Without ties to the building and proper bracing it can sway, rack and tip over, even without much load. Ties and braces are structural parts, not optional extras, and collapses often follow the removal of ties for convenience.
- Scaffold Erectors
- Masons
- Painters
- Competent Persons
The 4-to-1 rule
OSHA (29 CFR 1926.451(c)(1)) says supported scaffolds with a height-to-base-width ratio of more than 4 to 1 must be restrained from tipping by guying, tying, bracing or equivalent means. For example, a scaffold with a base 5 feet wide needs restraint above 20 feet of height. Where you measure the base width (the outside dimension of the posts, including outriggers if they are properly built and used) matters. Follow the design.
- Vertical spacing: guys, ties and braces must be installed at the closest horizontal member to the 4:1 height and repeated vertically at intervals not more than 20 feet for scaffolds less than 3 feet wide, and 26 feet for scaffolds wider than 3 feet.
- Top tie: the top guy, tie or brace of a completed scaffold must be no further than the 4:1 height from the top.
- Horizontal spacing: ties are installed at each end of the scaffold and at intervals not exceeding 30 feet, measured from one end toward the other.
- Manufacturer's instructions or an engineer's design may require closer spacing, especially with netting, sheeting, signs or high wind.
Types of restraint
| Method | What it does | Notes |
|---|---|---|
| Wall ties (rigid ties) | Tubes or couplers connecting the scaffold to the building structure | Resist pulling in and pushing out. Best where the wall is sound |
| Through ties and reveal ties | Tie through a window opening or pressed in a reveal | Must use the right tubes and not rely on window frames; check the structure |
| Anchor ties | Eyebolts or masonry anchors in the wall with a tube or wire | Pull-test anchors; use anchors rated for the substrate |
| Guy wires or ropes | Cables from the scaffold to ground anchors or structure | Only where designed. Must resist tipping loads, not just hold tension by hand |
| Outriggers and counterweights | Extend the base so the scaffold resists tipping | Must be designed and used as the manufacturer says; ballast only if engineered |
Bracing
- Cross bracing on frame scaffolds, and facade and longitudinal diagonal bracing on tube and coupler and system scaffolds, keeps the structure from racking sideways. Follow the maker's pattern.
- Install bracing as the scaffold rises, level by level, with proper pins, locks or couplers fully engaged. See Frame Scaffolds, System Scaffolds and Tube & Coupler Scaffolds.
- Never use cross braces as a ladder or as guardrails unless designed to meet both roles.
- Plumb and level the scaffold: bent frames or twisted bracing reduce strength.
Common ties mistakes
- Ties on weak items: gutters, downpipes, window frames, signs, parapets and thin cladding that can't take the load.
- Removing a tie to paint, clean or install a window, and not replacing it. If a tie must be moved, install a substitute first or have the competent person approve and engineer it.
- Too few ties or the wrong spacing, especially after adding sheeting or banners that catch wind.
- Ties that can only push or pull, not both, where both are needed.
- Loose or damaged anchors, unrated expansion bolts, wrong drill sizes and cracked masonry.
- Ties that tie two scaffolds together or to unstable structures.
- Forgetting ties during dismantling: take down ties only as the scaffold is taken down level by level.
Wind and sheeting
- Wind loads increase greatly when scaffolds are covered with netting, tarps, signs or shrink wrap, acting like a sail. Add ties and have an engineer review the design. See Scaffold Weather.
- Stop work and clear the scaffold in high winds and storms, and check ties before returning.
Competent person duties
- Check ties and braces before every shift and after storms, impacts or changes. Look for loose, bent, missing or pulled ties.
- Make sure ties are pull-tested to the design load where required, and keep records.
- Tag scaffolds that are unsafe and keep people off until fixed. See Scaffold Tags.
- Train erectors and users that ties and braces stay put and who to call about a conflict. Use a scaffold design or plan for complex scaffolds.
Scaffold ties checklist
- The scaffold is tied at the 4:1 height and the required spacing
- Ties are on sound structure with rated anchors and are pull-tested
- Bracing is complete and installed as the scaffold rises
- No tie or brace was removed without approval and replacement
- Netting and signs were considered in the design, and ties are inspected before each shift
Standards & references
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