Scaffolding Load Capacity Calculator

How this scaffolding load capacity calculator works

This scaffolding load capacity calculator estimates the maximum uniform live load that one rectangular scaffolding bay can safely support, based on:

• the allowable compressive load in each scaffold leg,
• the bay plan dimensions (length and width),
• how many levels are loaded at the same time, and
• the rated capacity of the planks or decking.

It compares two limits:

1. Leg capacity limit – how much load the legs (standards) can carry in compression when several levels are loaded.
2. Platform capacity limit – how much load the planks or deck can support per square metre without excessive deflection or failure.

The governing allowable live load is the smaller of these two capacities. The calculator focuses on uniformly distributed live loads such as workers, tools and stored materials, not on localized, impact or wind loads.

Key formulas used in the calculator

For a rectangular bay with four legs, bay length L and bay width B, the platform area is:

A = L × B

Let:

• P_leg = allowable axial load on one leg (kN)
• N_leg = number of legs supporting the bay (usually 4)
• n = number of levels that are simultaneously loaded
• A = plan area of the bay (m²)
• q_plank = plank or deck rating (kN/m²)

The leg-governed uniform live load intensity is:

q_leg = (P_leg × N_leg) / (n × A)

The plank-governed intensity is simply the plank rating:

q_plank

The calculator then takes the minimum of these two intensities:

q_allow = min(q_leg, q_plank)

Finally, the total allowable live load on the bay is:

W = q_allow × A

The same relationships can be written in MathML for clarity:

How to use the scaffolding load capacity calculator

Use the inputs above to represent one typical scaffolding bay:

• Allowable load per leg (kN) – Take this from the scaffold manufacturer's leg or standard capacity tables. Use the value appropriate to the bay height, bracing arrangement and leg spacing. This should be a factored allowable load, not the ultimate capacity.
• Bay length (m) – Centre-to-centre spacing of standards in the longitudinal direction (along the building face).
• Bay width (m) – Centre-to-centre spacing of standards in the transverse direction (distance from building to outer rail).
• Loaded levels – Count how many working or storage platforms may be fully or heavily loaded at the same time. If in doubt, assume more levels loaded rather than fewer.
• Plank rating (kN/m²) – Distributed load rating of the platform boards or deck, typically from decking manufacturer data or scaffolding design tables. Ensure units are kN/m².

After entering these values and running the calculation, the tool will report:

• the allowable live load intensity in kN/m², and
• the corresponding total live load in kN for the whole bay.

Interpreting the results

The calculated allowable live load intensity, q_allow, represents the maximum average live load that should be applied to the platform area of the bay under the given assumptions. To use it in the field:

• Compare the total bay load W with the estimated combined weight of workers, tools, and stored materials in that bay.
• Remember that 1 kN is approximately equal to 100 kg of mass (9.81 m/s²). A 2.0 kN/m² rating roughly corresponds to about 200 kg/m².
• Limit stacking of heavy materials (e.g., bricks, blocks, tiles) so the total estimated load stays well below the calculated limit.
• If multiple bays share loads (for example, materials spanning across transoms), use the most conservative bay as a guide and comply with the manufacturer's loading diagrams.

If the result is governed by leg capacity (q_allow = q_leg):

• Adding more simultaneously loaded levels will further reduce the allowable load per level.
• Better bracing, shorter leg height, or tighter bay spacing (per manufacturer guidance) may increase leg capacity, but must be verified by a competent designer.

If the result is governed by plank capacity (q_allow = q_plank):

• Stronger planks or closer plank supports may allow higher platform loads.
• Do not exceed the plank rating even if the legs appear to have spare capacity.

Worked example: single scaffolding bay

Consider a simple scaffolding bay with the following properties:

• Allowable load per leg, P_leg = 20 kN
• Number of legs, N_leg = 4
• Bay length, L = 2.5 m
• Bay width, B = 1.3 m
• Loaded levels, n = 1
• Plank rating, q_plank = 2.0 kN/m²

1. Compute the platform area:

A = L × B = 2.5 × 1.3 = 3.25 m²

2. Compute leg-governed intensity:

q_leg = (P_leg × N_leg) / (n × A)

q_leg = (20 × 4) / (1 × 3.25) ≈ 80 / 3.25 ≈ 24.6 kN/m²

3. Compare with plank rating:

q_plank = 2.0 kN/m²

4. Governing allowable intensity:

q_allow = min(24.6, 2.0) = 2.0 kN/m²

5. Total allowable load on the bay:

W = q_allow × A = 2.0 × 3.25 = 6.5 kN

Thus, this bay should be limited to an average live load of 2.0 kN/m², or a total of 6.5 kN. In mass terms, this is roughly equivalent to 650 kg of combined workers, tools, and materials, spread reasonably evenly over the platform.

If two levels are loaded simultaneously (n = 2), the leg-based intensity halves to about 12.3 kN/m², but the planks still govern at 2.0 kN/m². Only when the plank rating exceeds the leg-based intensity would the legs become the controlling factor.

Comparison: leg capacity vs plank capacity

The table below highlights how the two main limits differ conceptually.

Assumptions and limitations

This calculator uses a deliberately simplified model suitable for preliminary planning, not for final scaffolding design. The main assumptions and limitations are:

• Uniform loading – Loads are assumed to be spread reasonably evenly over the bay. Highly concentrated loads (e.g., a stack of bricks in one corner) can exceed local capacities even if the average load appears acceptable.
• Four-leg rectangular bay – The equations assume one standard at each corner. Special arrangements (cantilevers, inside boards only, truss-out scaffolds, etc.) are not covered.
• Adequate bracing and ties – The legs are assumed to be fully braced and tied in accordance with the manufacturer's instructions and relevant standards so that they act in pure compression. Inadequate bracing drastically reduces actual leg capacity.
• Level, sound foundations – The calculation assumes that baseplates, sole boards and soil or slab can resist reactions without significant settlement or punching. Uneven settlement can cause load redistribution, overloading some legs beyond their assumed capacity.
• No wind, impact or seismic effects – Only static vertical live loads are considered. Wind loads on sheeting or debris netting, impact from dropped materials, and dynamic actions from moving equipment are outside the scope of this tool.
• Standard scaffolding components – It is assumed that all tubes, couplers, planks and boards are in good condition, correctly assembled, and used in the way their manufacturer intends. Corrosion, damage or incorrect assembly can reduce capacity.
• Manufacturer data governs – Actual capacities must always come from the manufacturer's design manuals or tables for the specific system, bay dimensions, and configuration. This calculator does not replace those documents.
• Regulatory compliance – National and local regulations (e.g., OSHA, EN 12811, AS/NZS standards) may impose additional load categories, partial factors, and checks that are not captured here.

Safety notes and professional use

This calculator is intended for competent persons who already understand basic scaffolding behaviour and need a quick sense-check on leg and platform loads. It can help with:

• planning where to stack materials such as bricks, blocks or boards,
• deciding how many levels can be used for heavy storage at one time, and
• comparing alternative bay sizes or plank ratings.

However, it is not a full design tool. Before erecting, modifying or heavily loading any scaffold:

• consult the scaffold system manufacturer's design guide or capacity tables,
• ensure all design and checks are carried out or approved by a competent engineer or scaffolding designer, and
• comply with all applicable regulations and site-specific safety requirements.

Never rely solely on a simplified calculator when human safety is involved. Treat the outputs as indicative values to support, not replace, professional judgement.