Summary
Tower scaffolds are the most common access equipment for small trades: decorators, plasterers, electricians and roofers on low eaves. They're also involved in a steady stream of HSE-reported accidents, and overloading is a recurring factor, together with missing guardrails, unlocked castors and towers built on soft ground. Overloading rarely means the platform snaps. More often a tower gets top-heavy with blocks or plasterboard, overturns when pushed, or sinks on one leg into a lawn and tips.
Most tradespeople never do the sums. They assume "it's a tower, it'll take it". This page sets out the numbers you need to check before loading a platform: the platform load class, the manufacturer's SWL, leg and castor loads, and ground bearing pressure. It also covers the loads that catch people out: stacked materials, side loads from drilling or pulling, and wind.
A key misconception is that the BS EN 1004 class figure (2.0 kN/m²) is a capacity you can fill to. It's a design test load for the platform. The instruction manual's SWL (per platform and per tower) and the configuration you've built (height, stabilisers, ballast) set your real limits. If the figures differ, always work to the lower one.
Key Facts
- BS EN 1004-1:2020 — European standard for mobile access and working towers made of prefabricated elements, up to 8m platform height outdoors and 12m indoors (free-standing).
- Load class 3 — 2.0 kN/m² uniformly distributed load on the working platform. Most trade towers are class 3.
- Load class 2 — 1.5 kN/m². Some lightweight "DIY-grade" or narrow towers.
- Concentrated load test — platforms must resist a point load of about 1.5 kN over a 500 × 500mm area.
- Manufacturer's SWL — commonly quoted per platform (often around 225–275 kg for a standard 2.5m deck) and as a total tower SWL, varying with configuration. This is the figure you work to.
- Worker allowance — allow 100 kg per person including PPE and hand tools as a planning figure.
- Only one working platform loaded at a time unless the manual allows otherwise. Intermediate platforms are for rest and access.
- Height-to-base ratio — set by the manufacturer for each configuration using stabilisers or outriggers. Never build higher than the manual's table for the base you've used.
- Ballast — required by some configurations, especially outdoors and free-standing. The amount and position are specified in the manual and must be secured.
- Wind — PASMA guidance: stop work in winds above about Beaufort force 4 (around 17 mph). Follow the manual for tying in or dismantling in stronger winds.
- Castor brakes — must be locked whenever anyone is on the tower. Never move a tower with people or materials on it.
- Work at Height Regulations 2005, Reg 12 — inspect after assembly in any position, after any event that could affect stability, and at suitable intervals. A written report is required for towers where a person could fall 2m or more.
- BS 1139-6:2014 — covered towers outside the scope of BS EN 1004 (for example linked, cantilever or large-deck configurations); withdrawn by BSI in January 2022 without replacement, so rely on the manufacturer's engineered design for such builds.
Quick Reference Table
Got your quantities? squote builds the full quote with labour, materials and markup.
Try squote free →| Item | Typical value | Notes |
|---|---|---|
| Platform design load (class 3) | 2.0 kN/m² (≈ 200 kg/m²) | Test load, not an operating target |
| Platform SWL (manufacturer) | Often 225–275 kg per deck | Always check the manual |
| Worker allowance | 100 kg each | Includes PPE and hand tools |
| Plasterboard 12.5mm, 2.4 × 1.2m | ≈ 22–25 kg per sheet | Heavier for moisture/fire boards |
| 25 kg bag (plaster, adhesive) | 25 kg | |
| Concrete block (dense, 100mm) | ≈ 18–20 kg | Lightweight aerated block ≈ 7–9 kg |
| Double-width tower self-weight, 4m platform | ≈ 150–220 kg | Configuration dependent |
| Double-width tower self-weight, 6m platform | ≈ 220–320 kg | Plus ballast if required |
| Leg load uneven distribution factor | × 1.5 | Planning allowance for off-centre loads |
| Free-standing max platform height (EN 1004) | 8m outdoors / 12m indoors | Manual may set lower limits |
Indicative allowable ground bearing pressures (for planning only; get a competent assessment for doubtful ground):
| Ground | Indicative allowable bearing (kN/m²) |
|---|---|
| Soft clay, wet lawn, made ground | 25–50 |
| Firm clay, dry lawn | 75–150 |
| Loose sand | 50–100 |
| Compacted hardcore / MOT Type 1 | 150–300 |
| Block paving on sound sub-base | 200+ (check for voids and edges) |
| Reinforced concrete slab | Usually not critical (check suspended floors) |
Detailed Guidance
Step 1: Platform load check
Add up everything that will be on the working platform at the same time:
Platform load = (number of workers × 100 kg) + materials + tools and equipment
Compare it with:
- Manufacturer's platform SWL — this governs.
- Class 3 area capacity — 200 kg/m² × deck area, as a sense-check only.
Example: plasterer boarding a ceiling from a double-width tower
| Item | Weight |
|---|---|
| 2 workers × 100 kg | 200 kg |
| 3 sheets 12.5mm board × 24 kg | 72 kg |
| Screw gun, scrim, sundries | 10 kg |
| Total platform load | 282 kg |
If the manual gives a platform SWL of 275 kg, this is over the limit. Take two sheets up at a time, or have one person work from the platform while the other feeds boards from below. Small adjustments like this are what the calculation is for.
Step 2: Tower and leg load check
Total load = tower self-weight + ballast + platform load(s)
Leg load (planning) = Total load ÷ 4 × 1.5
The 1.5 factor allows for people and materials being off-centre, which concentrates load on one or two legs.
Example: 6m platform, double-width tower
| Item | Weight |
|---|---|
| Tower self-weight | 280 kg |
| Ballast (per manual) | 0 kg (stabilisers fitted) |
| Platform load (revised) | 258 kg |
| Total | 538 kg ≈ 5.28 kN |
| Leg load = 5.28 ÷ 4 × 1.5 | ≈ 1.98 kN (≈ 202 kg) |
Compare that with the castor or baseplate rating in the manual. Most trade castors are rated well above 2 kN, but check the figure, especially for adjustable legs extended near their maximum.
Step 3: Ground bearing check
Ground pressure (kN/m²) = Leg load (kN) ÷ Bearing area (m²)
Continuing the example:
| Bearing | Area | Pressure | On soft lawn (25–50 kN/m²) |
|---|---|---|---|
| Castor/baseplate only (≈ 150 × 150mm) | 0.0225 m² | 88 kN/m² | Fails — likely to sink |
| Sole board 450 × 225mm | 0.101 m² | 19.6 kN/m² | Passes |
| Sole board 600 × 225mm | 0.135 m² | 14.7 kN/m² | Passes, with margin |
On soft or uneven ground, sole boards are not optional. Watch for:
- Drain covers, manholes and cellar lights. Never stand a leg on them.
- Block paving edges and recently backfilled trenches.
- Suspended timber floors indoors. A loaded tower on four small castors can overload joists. Spread loads with boards across several joists.
- Slopes. Use the adjustable legs within their range; never pack under castors with bricks or offcuts.
Step 4: Stability, side loads and wind
Vertical load is only half the picture. Towers overturn from horizontal forces:
- Pulling or pushing (drilling into walls, prising, hauling materials up on a rope) creates a side load at platform height.
- Wind acting on the tower, on sheet materials and on debris netting or sheeting. Sheeting a tower greatly increases the wind load and is usually prohibited unless the manual covers it.
- Leaning ladders against a tower, or bridging between towers. Never do either.
Controls:
- Fit stabilisers or outriggers as per the manual for the height built.
- Add ballast where the manual requires it, and secure it so it can't be removed.
- Tie the tower to the structure where the manual or the conditions require.
- Hoist materials inside the base footprint where possible, and never hoist heavy items with a rope over the guardrail unless the manual permits it.
- Stop work in winds above the PASMA/manufacturer limit, and never leave a tower free-standing outdoors overnight without checking the forecast and the manual.
Step 5: Moving a loaded tower
Never. Clear all people and materials, check the route for overhead obstructions (especially power lines: see scaffolding near overhead lines), check for slopes, holes and kerbs, then push at the base, never from the platform. Re-level, re-lock the castors and re-inspect before going back up.
Worked example: decorator on a gable end
- Single-width tower, 5.2m platform, outdoors on a dry lawn
- Self-weight from manual: 165 kg; stabilisers fitted; no ballast required
- Platform SWL from manual: 225 kg
- Platform load: 1 worker (100 kg) + 2 × 10L masonry paint (≈ 26 kg) + roller, brushes, kettle (6 kg) = 132 kg → passes
- Total load: 165 + 132 = 297 kg ≈ 2.91 kN
- Leg load: 2.91 ÷ 4 × 1.5 = 1.09 kN
- Ground pressure with 450 × 225mm sole boards: 1.09 ÷ 0.101 = 10.8 kN/m² → fine on dry lawn
- Wind check: forecast gusts 22 mph → above Beaufort 4. Postpone the outdoor tower work.
The load sums pass but the job still stops. The calculation is only one part of the assessment.
Frequently Asked Questions
Can I put a 2.0 kN/m² load on every platform of the tower?
No. The class 3 figure is the platform's design test load. Towers are designed for one working platform loaded at a time, with intermediate platforms for access and rest. The manufacturer's total tower SWL is usually far less than "2.0 kN/m² × every deck".
Who can build a tower scaffold?
Anyone competent. In practice that means trained, typically through a PASMA course, and working from the manufacturer's instruction manual. The method of assembly matters as much as the loads: use the "3T" (through the trap) or advance guardrail method so you're never standing on an unguarded platform.
Do I need a written inspection for a tower?
Under the Work at Height Regulations 2005 (Reg 12 and Schedule 7), a tower from which someone could fall 2m or more needs an inspection after assembly and at suitable intervals, recorded in writing. In practice that means a tag or inspection record at least every 7 days, and after any event that could affect stability (moving it, high winds, alterations). See scaffold inspection.
Can I mix components from different tower brands?
No. Mixing components invalidates the manufacturer's design and testing. Frames, braces, platforms and stabilisers must all be from the same system as specified in the manual, and damaged parts must be removed from use.
How heavy are typical loads I might forget?
Buckets of wet plaster (≈ 30–40 kg each), a full box of tiles (≈ 20–25 kg), a large SDS drill plus case (≈ 10 kg), a 110V transformer (≈ 15 kg), and wet rendering materials. Always count everything that's on the deck at the same time, not just what you're about to lift.
Regulations & Standards
Work at Height Regulations 2005 (SI 2005/735) — Reg 8 and Schedule 3 (requirements for working platforms, including stability and loading), Reg 12 (inspection), Schedule 7 (inspection report contents)
BS EN 1004-1:2020 — mobile access and working towers made of prefabricated elements: materials, dimensions, design loads, safety and performance requirements
BS EN 1004-2 — rules and guidelines for the preparation of an instruction manual
BS 1139-6:2014 — specification for prefabricated tower scaffolds outside the scope of BS EN 1004 (withdrawn by BSI in January 2022 without replacement; still referenced by PASMA and manufacturers for linked, cantilever and large-deck configurations)
BS EN 12811-1:2003 — temporary works equipment: scaffolds, performance requirements and general design (load classes)
Provision and Use of Work Equipment Regulations 1998 (SI 1998/2306) — suitability, maintenance and inspection of work equipment
HSE information sheet CIS10 — tower scaffolds
PASMA Code of Practice for Mobile Access Towers
Tower scaffolds (CIS10) — HSE
Working at height — HSE
Work at Height Regulations 2005 — legislation.gov.uk
BS EN 1004-1:2020 — BSI Knowledge
mobile tower scaffold — tower scaffold types, assembly and safe use
scaffold loading limits — load classes and limits for tube-and-fitting and system scaffolds
working at height regulations — legal duties under WAHR 2005
scaffold inspection — inspection intervals and records
scaffolding near overhead lines — clearances when moving or erecting near power lines