Home/Standards compared/Tie spacing
Scaffold tie spacing and the 4:1 rule compared
Quick answer: OSHA ties above a 4:1 height-to-base ratio, then every 20 ft (26 ft on wider scaffolds) up and 30 ft across. TG20 follows its compliance sheets, with tie lines usually 4.0 m apart. Saudi Aramco CSM: every 8 m up and 9 m across, from 4 × the base.
Side by side
Each value with the document it comes from.
| Requirement | OSHA 1926 Subpart L USA | BS EN 12811-1 · TG20 UK and Europe | Saudi Aramco CSM · GI 8.001 Saudi Aramco sites |
|---|---|---|---|
| When ties are needed | Height-to-base over 4:1Supported scaffolds above this ratio must be held by guys, ties or braces.29 CFR 1926.451(c)(1) | As the TG20 sheet showsTie pattern and tie duty come from the TG20 compliance sheet for that set-up; anything outside it needs a specific design.NASC TG20:13 Operational Guide (check TG20:21) | Height over 4 × the minimum baseHeight to the top planked level more than four times the smallest base dimension (3× for mobile scaffolds).CSM II-2 §2.5.8 C |
| First tie level | At the 4:1 heightAt the horizontal member closest to four times the base width, above or below it.29 CFR 1926.451(c)(1)(ii) | As the TG20 sheet showsNASC TG20:13 Operational Guide (check TG20:21) | Lift closest to 4 × baseThe lowest tie level goes at the lift closest to four times the minimum base dimension.CSM II-2 §2.5.8 D |
| Vertical tie spacing | 20 ft (6.1 m) or 26 ft (7.9 m)20 ft for scaffolds 3 ft wide or less, 26 ft for wider ones. The top tie must sit within the 4:1 height of the top.29 CFR 1926.451(c)(1)(ii) | Usually 4.0 m between tie linesTG20 sheets typically limit tie lines to 4.0 m apart, so lifts taller than 2 m can mean ties at every lift.NASC TG20:13 Operational Guide 6.5, 7.5 (check TG20:21) | 8 m (4 lifts) or lessTop tie level as close to the top as practical.CSM II-2 §2.5.8 D |
| Horizontal tie spacing | 30 ft (9.1 m) or less29 CFR 1926.451(c)(1)(ii) | As the TG20 sheet showsSheeting, netting or brick guards change the tie pattern; use the matching sheet.NASC TG20:13 Operational Guide 6.24, 6.25 (check TG20:21) | 9 m or less, ties at both endsMeasured from one end.CSM II-2 §2.5.8 D |
| Rakers and outriggers | — | — | Rakers 65°–75°; outriggers past 1/4 of heightRaker angle above horizontal not less than 65° and not more than 75°. Outrigger frames extend the base to more than a quarter of the scaffold height.CSM II-2 §2.5.8 F, G |
Summary for learning, checked on 24 October 2026. Values as written in the documents named, as used in the AL-YASSIN question banks. TG20 values are from TG20:13; check TG20:21. Verify against the latest edition and your project's own rules before you use any figure. AL-YASSIN is independent and is not endorsed by OSHA, BSI, NASC or Saudi Aramco. — means the document does not give it as one figure here.
Mistakes we see in our exams
- Putting the first OSHA tie exactly at 4 × the base width when there is no member there. It goes at the horizontal member closest to that height, above or below.
- Spacing OSHA ties at 5 bays of 7 ft: that is 35 ft, over the 30 ft limit.
- Mixing up the Saudi Aramco limits: 8 m is vertical, 9 m is horizontal.
- Keeping alternate-lift ties on 3.0 m lifts. Two lifts make 6.0 m, over the usual 4.0 m TG20 tie-line spacing, so every lift needs ties.
- Adding sheeting or netting without moving to the matching TG20 sheet and its extra ties.
Test yourself, free
More comparisons
Questions
What is the 4 to 1 rule for scaffolding?
Under OSHA 29 CFR 1926.451(c)(1), a supported scaffold whose height is more than four times its minimum base width must be restrained by guys, ties or braces. Saudi Aramco CSM II-2 §2.5.8 C uses the same 4× trigger (3× for mobile scaffolds). Verify against the latest editions.
How far apart are scaffold ties under OSHA?
Vertically every 20 ft or less for scaffolds 3 ft wide or less, every 26 ft or less for wider ones, and horizontally every 30 ft or less, with the top tie within the 4:1 height of the top. 29 CFR 1926.451(c)(1)(ii). Verify against the current eCFR.
How far apart are scaffold ties on Saudi Aramco sites?
CSM II-2 §2.5.8 D: vertically every 8 m (4 lifts) or less and horizontally no more than 9 m, with ties at both ends. Verify against the latest edition.
Does TG20 give a tie spacing?
TG20 gives tie patterns on its compliance sheets for each scaffold set-up. Tie lines are typically no more than 4.0 m apart vertically. Outside a sheet, the scaffold needs a specific design. Check TG20:21.