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Scaffold standards compared
Guardrails, ties, inspection, load classes and platforms under OSHA 1926 Subpart L, BS EN 12811-1 and TG20 and the Saudi Aramco Construction Safety Manual, side by side, each value with its reference.
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13 requirements scaffold people ask about most.
| Requirement | OSHA 1926 Subpart L USA | BS EN 12811-1 · TG20 UK and Europe | Saudi Aramco CSM · GI 8.001 Saudi Aramco sites |
|---|---|---|---|
| Top guardrail height | 38–45 in (0.97–1.2 m)Supported scaffolds made or placed in service after 1 Jan 2000. May be higher when conditions warrant, if every other guardrail rule is met.29 CFR 1926.451(g)(4)(ii) | At least 1.0 m (never below 950 mm)Top surface of the principal guardrail above the working level, along its whole length. UK law: at least 950 mm.BS EN 12811-1:2003 5.5.2; Work at Height Regulations 2005 Sch. 2 | 0.95–1.15 m (38–45 in)Top edge of the toprail above the platform.CSM II-2 §2.5.4 B |
| Midrail or intermediate protection | About midwayMidrail roughly halfway between the top edge and the platform. Crossbracing can count as the midrail only where the braces cross 20–30 in above the platform.29 CFR 1926.451(g)(4)(iv), (g)(4)(xv) | No gap over 470 mmIntermediate protection so that no unprotected gap is more than 470 mm.Work at Height Regulations 2005 Sch. 2 para 3 | About halfway, inside the uprightsMidrail about halfway up; toprails and midrails fixed to the inside of the uprights, which stand no more than 2.5 m apart unless the system maker allows more.CSM II-2 §2.5.4, §2.5.4 D |
| Toe board | At least 3-1/2 in (9 cm)Measured from its top edge to the walking surface, with no more than 1/4 in clearance underneath.29 CFR 1926.451(h)(4)(ii) | At least 150 mmTop of the toe board above the next working level. Overlaying the deck reduces it: check again.BS EN 12811-1:2003 5.5.4 | At least 100 mmNo more than 6 mm above the platform; wood at least 25 mm thick, clamped along the outer edge.CSM II-2 §2.5.5 B |
| When edge protection is needed | More than 10 ft (3.1 m)Each worker more than 10 ft above a lower level needs guardrails or personal fall arrest.29 CFR 1926.451(g)(1) | Any height that could injureThere is no minimum height in UK law: the rules apply wherever a person could fall a distance liable to cause injury.Work at Height Regulations 2005 reg. 2 | 1.8 m (6 ft) or moreGuardrails on all open sides and ends where people could fall 1.8 m or more.CSM II-2 §2.5.4 A |
| 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 |
| 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 |
| How often | Before each work shiftAnd after anything that could affect the structure, such as a storm or an impact. A night shift is a new shift.29 CFR 1926.451(f)(3) | Before first use, then every 7 daysAnd after any alteration or event that could affect safety, such as high wind. The 7-day count restarts after an alteration.Work at Height Regulations 2005 reg. 12; NASC TG20:13 Operational Guide 18.3 | At least every 2 weeksScaffold tags are valid for two weeks at most; re-inspect with the field checklist within each two-week period.GI 8.001 §9.3.2, §9.4.3, §9.8 |
| Who inspects | A competent personSomeone able to spot the hazards and authorised to correct them on the spot.29 CFR 1926.450(b), 1926.451(f)(3) | A competent personThe result is recorded in an inspection report.Work at Height Regulations 2005 reg. 12 | Supervisor; certified Inspector over 6 mOver 6 m the Supervisor hands the signed tag to a certified Inspector, who inspects, signs, dates and inserts it.GI 8.001 (2025) §9.3.3, §9.4 |
| Duty or load class | Light 25 · medium 50 · heavy 75 lb/ft²About 1.2 · 2.4 · 3.6 kN/m². Guidance in the non-mandatory Appendix A.29 CFR 1926 Subpart L, Appendix A (1)(c) | Classes 1–6: 0.75 · 1.5 · 2.0 · 3.0 · 4.5 · 6.0 kN/m²TG20 covers classes 1 to 4; classes 5 and 6 need a specific design.BS EN 12811-1:2003 6.1.3 Table 3; NASC TG20:13 Operational Guide 6.2 | Light 120 · medium 240 kg/m²25 · 50 lb/ft². Above 240 kg/m² the scaffold is special duty.CSM II-2 §2.5.1 E |
| Minimum platform width | 18 in (46 cm)12 in (30 cm) for ladder jack, top plate bracket, roof bracket and pump jack scaffolds.29 CFR 1926.451(b)(2) | Width classes W06 to W24W06 is 0.6 m to under 0.9 m of clear width; only 30 mm of the toe board counts. At least 600 mm clear between standards.BS EN 12811-1:2003 5.2, Table 1 | — |
| Plank or board overhang | At least 6 in; at most 12 inPast the support centreline, unless cleated or hooked. Up to 18 in when the platform is longer than 10 ft.29 CFR 1926.451(b)(4), (b)(5) | At least 50 mm; at most 4 × board thicknessAbout 150 mm for 38 mm boards.NASC TG20:13 Design Guide 2.1.8.3, Table 2.4 (check TG20:21) | At least 150 mm; at most 300 mmPast the end bearer centreline, unless cleated or restrained.CSM II-2 §2.5.6 G–H |
| When proper access is needed | Platform more than 2 ft (0.6 m) above or belowLadder, stair tower, ramp or similar. Cross braces are never access.29 CFR 1926.451(e)(1) | — | Platform more than 0.6 m above or belowLandings at the top and at least every 9 m of ladder height; ladder 1 m above the landing.CSM II-2 §2.5.7 A, §2.5.6 V; CSM II-3 §3.4.3 |
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.
Why the numbers differ
OSHA writes minimum legal requirements for US workplaces in feet and inches. BS EN 12811-1 is a European performance standard, and in the UK the TG20 guide turns it into ready-made tube-and-fitting designs, while the Work at Height Regulations set the legal floor. Saudi Aramco writes its own Construction Safety Manual and General Instruction 8.001 for work on its sites, often stricter or more specific than the others. On a project, the strictest rule that applies to you wins, and the contract decides which documents apply.
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Questions
Which scaffold standard is the strictest?
It depends on the requirement. For example, Saudi Aramco needs guardrails from 1.8 m, OSHA from more than 10 ft (3.1 m), and UK law at any height that could cause injury. Compare each requirement, and follow the strictest one that applies to your project. Verify against the latest editions.
Can I use TG20 on an OSHA or Saudi Aramco project?
Only where the project allows it and the local rules are also met. A design to one document does not automatically satisfy another; check every requirement in the table against the documents your contract names.
Is this page an official interpretation?
No. It is an independent summary for learning, made by AL-YASSIN, and is not endorsed by OSHA, BSI, NASC or Saudi Aramco. Always verify against the latest edition of each document.