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From where the base plates bear to the top of the scaffold.
Measure from the ground the base plates or casters stand on — the low end, on a slope — to the top of the scaffold. Whether the top means the highest working platform or the top of the guardrails above it is set by the manufacturer's instructions for the scaffold in question; measuring to the top of the rails gives the taller figure and the more ties.
The smallest dimension of the scaffold's base, with outrigger supports counted where they are fitted.
OSHA reads the 4:1 ratio against the base width "including outrigger supports, if used". For a frame scaffold it is the width across the frame; outriggers widen it only when they are fitted and bearing. The narrower the base, the lower down the scaffold the first tie comes, and a scaffold 3 feet (0.91 m) wide or less takes its ties at the closer vertical interval.
The run of scaffold along the building, end to end.
Ties go at each end of the run and at no more than 30 feet (9.1 m) apart along it, measured from one end — so a run just over a multiple of that interval takes one more column of ties than a run just under it.
The vertical spacing of the ledgers or frame bearers that ties are fixed at.
The rule places ties "at locations of horizontal members", so every tie level lands on a multiple of this spacing — the lift height of a tube-and-fitting scaffold, or the frame height of a frame scaffold. The vertical interval in the rule is a maximum, so the levels use as many whole lifts as fit inside it.
Ties, guys or braces under OSHA's default pattern
8 ties
The scaffold stands 9.8 times as tall as its base is wide, past the 4:1 at which OSHA's rule requires a supported scaffold to be guyed, tied or braced. The count is 2 levels of ties up the face at 4 positions along it: the first level at the horizontal member closest to four base widths, the rest at the widest interval the rule allows for this width until the highest is within four base widths of the top, and along the face a position at each end and at no more than 30 feet (9.1 m) apart. It is the rule's default pattern and a minimum; the manufacturer's recommendations may replace it.
- Height at which the rule starts (4 × the base width)
- 20 ft
- Height to base width ratio
- 9.8 :1
- First tie level, at the horizontal member closest to that height
- 19.5 ft
- Tie levels up the face
- 2 levels
- Vertical interval between tie levels
- 26 ft
- Largest vertical interval the rule allows at this width
- 26 ft
- Highest tie level
- 45.5 ft
- Scaffold standing above the highest tie
- 3.5 ft
- Tie positions along the face
- 4 positions
They open the calculator with your figures already in it
Scaffold Tie Count Calculator (OSHA 1926.451): 8 ties — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- 29 CFR 1926.451(c)(1): supported scaffolds with a height to base width (including outrigger supports, if used) ratio of more than four to one (4:1) shall be restrained from tipping by guying, tying, bracing, or equivalent means
- 29 CFR 1926.451(c)(1)(ii): guys, ties and braces go according to the scaffold manufacturer's recommendations or at the closest horizontal member to the 4:1 height, repeated vertically at horizontal members every 20 feet (6.1 m) or less for scaffolds 3 feet (0.91 m) wide or less and every 26 feet (7.9 m) or less for wider ones; the top one no further than the 4:1 height from the top; at each end and at horizontal intervals not exceeding 30 feet (9.1 m), measured from one end
Inputs used
- Scaffold Height
- 49 ft
- Narrowest Base Width, Including Outriggers
- 5 ft
- Scaffold Length Along the Face
- 79 ft
- Height Between Horizontal Members
- 6.5 ft
Intermediate steps
- Height at which the rule starts (4 × the base width)
- 20 ft
- Height to base width ratio
- 9.8 :1
- First tie level, at the horizontal member closest to that height
- 19.5 ft
- Tie levels up the face
- 2 levels
- Vertical interval between tie levels
- 26 ft
- Largest vertical interval the rule allows at this width
- 26 ft
- Highest tie level
- 45.5 ft
- Scaffold standing above the highest tie
- 3.5 ft
- Tie positions along the face
- 4 positions
Confidence note: The scaffold stands 9.8 times as tall as its base is wide, past the 4:1 at which OSHA's rule requires a supported scaffold to be guyed, tied or braced. The count is 2 levels of ties up the face at 4 positions along it: the first level at the horizontal member closest to four base widths, the rest at the widest interval the rule allows for this width until the highest is within four base widths of the top, and along the face a position at each end and at no more than 30 feet (9.1 m) apart. It is the rule's default pattern and a minimum; the manufacturer's recommendations may replace it.
What this calculation does not cover
- It applies the default pattern of 29 CFR 1926.451(c)(1)(ii). The same paragraph lets ties follow the scaffold manufacturer's recommendations instead, and a scaffold designed by a qualified person follows its design.
- Ties are counted, not designed. What force each must carry, and whether its anchor holds in the wall behind it, belong to the scaffold's design — a tie into soft brick or failed pointing restrains nothing.
- Sheeted, netted or encapsulated scaffolds, and those carrying a hoist, a loading bay or signage, take wind and loads the default pattern does not allow for, and are tied to a design.
- In the UK the tie pattern of a tube-and-fitting scaffold comes from the NASC's TG20 guidance or from a design. This page follows OSHA's rule only and reproduces neither.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-21 · v1.0.0
Regulatory standards & verification citations2
- 29 CFR 1926.451(c)(1): supported scaffolds with a height to base width (including outrigger supports, if used) ratio of more than four to one (4:1) shall be restrained from tipping by guying, tying, bracing, or equivalent means
- 29 CFR 1926.451(c)(1)(ii): guys, ties and braces go according to the scaffold manufacturer's recommendations or at the closest horizontal member to the 4:1 height, repeated vertically at horizontal members every 20 feet (6.1 m) or less for scaffolds 3 feet (0.91 m) wide or less and every 26 feet (7.9 m) or less for wider ones; the top one no further than the 4:1 height from the top; at each end and at horizontal intervals not exceeding 30 feet (9.1 m), measured from one end
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