Temporary Support Design Calculator

Inputs

All loads are in kN and meters. Adjust defaults to suit your project.

Fields marked * are required.

Loads

Defines slab pressure used for prop and beam checks.

Slab thickness (mm) *

Concrete density (kN/m³) *

Wet concrete factor (-) *

Formwork load (kN/m²) *

Construction live load (kN/m²) *

Impact factor (-) *

Load factor (-) *

Use your project’s safety factor or code load factor.

Prop layout

Defines tributary area per support element.

Spacing X (m) *

Spacing Y (m) *

Position factor (-) *

Use 1.0 interior, 0.5 edge, 0.25 corner, or custom.

Total supported area (m²) *

Allowable prop capacity (kN) *

Use manufacturer tables for the chosen extension and bracing.

Beam check (optional)

Quick check for a simply supported beam under uniform load.

Enable beam check

Beam span L (m)

Tributary width to beam (m)

Material model

Elastic modulus E (MPa)

Allowable bending stress (MPa)

Deflection limit ratio (L/n)

Timber width b (mm)

Timber depth h (mm)

Allowable shear stress (MPa)

Section modulus S (mm³)

Use your profile property table.

Second moment I (mm⁴)

Effective shear area Av (mm²)

Optional. Provide to enable shear check.

Allowable shear stress (MPa)

Beam checks assume simple supports and uniform load. If you have multiple spans, point loads, cantilevers, or heavy rebar stacks, perform a detailed analysis.

Example data

Sample scenario for quick testing. Adjust values for your project.

Case	Slab (mm)	q_live (kN/m²)	Spacing (m)	Prop capacity (kN)	Expected outcome
Interior slab bay	200	2.5	1.5 × 1.5	30	Typically PASS with defaults
Heavier pour	250	3.0	1.5 × 1.5	30	May be near limit
Wider spacing	200	2.5	2.0 × 2.0	30	Often FAIL; reduce spacing

Formula used

This calculator applies common preliminary shoring and beam-check relationships.

Concrete load: q_conc = t · γ · k_wet (kN/m²), where t is slab thickness (m).
Service pressure: q_svc = (q_conc + q_form + q_live) · k_impact.
Design pressure: q_d = q_svc · k_LF.
Prop tributary area: A = s_x · s_y · k_pos.
Prop design load: P = q_d · A.
Beam UDL line load: w = q_d · b (kN/m).
Simple span UDL: M = wL²/8, V = wL/2.
Bending stress: f_b = M/S.
Deflection: Δ = 5wL⁴/(384EI). Allowable is L/n.

How to use this calculator

Enter slab thickness, concrete density, and the wet factor.
Set formwork and construction live loads for your method.
Choose an impact factor and a safety or load factor.
Enter prop spacing in both directions and position factor.
Provide allowable prop capacity from manufacturer data.
Optionally enable beam check and enter beam properties.
Press Calculate, then download CSV or PDF for records.

Tip: If results fail, reduce spacing, increase capacity, add beams, or lower construction loading assumptions after verifying site requirements.

Technical guidance for temporary support design

This article explains how the calculator inputs influence safe shoring decisions.

1) Understand the design pressure you are applying

The calculator builds a slab design pressure from concrete self-weight, formwork allowance, and construction live load. For example, a 200 mm slab with density 24 kN/m³ produces about 4.8 kN/m² before wet and impact factors. Always confirm whether your pour includes heavy reinforcement congestion, pump line loads, or localized material stacks.

2) Use realistic construction live load and impact factors

Construction live load commonly ranges from 1.5 to 3.0 kN/m² depending on access, placing method, and expected worker density. Impact factors between 1.05 and 1.25 are typical when concrete placement and equipment movement are controlled. Select values consistent with your site method statement and inspection regime.

3) Convert spacing into tributary load per prop

Prop load is determined by tributary area, calculated as A = s_x·s_y·k_pos. Interior supports use k_pos=1.0, edges 0.5, and corners 0.25, reflecting reduced tributary share. If utilization exceeds 1.0, reduce spacing, raise capacity, or add secondary beams to share the load.

4) Interpret utilization and recommended spacing outputs

Utilization is P/P_allow. Values above 0.85 indicate limited reserve and deserve closer review. The calculator also reports the maximum tributary area and a recommended square spacing that matches the allowable prop capacity at the computed design pressure. Treat this as a planning value and adjust for openings and irregular grids.

5) Use the beam check to validate walers and bearers

When enabled, the beam module checks a simply supported member under uniform load from the same design pressure. It reports moment, shear, bending stress, and deflection against an L/n limit. For steel, provide section properties (S and I), and enter effective shear area (Av) if you want a direct shear stress check. Always verify connections, bracing, base plates, and manufacturer capacities for the actual extension and braced height.

FAQs

1) What does the position factor mean?

It reduces tributary area for edge and corner supports. Interior uses 1.0, edge 0.5, and corner 0.25. Use a custom value if your framing or boundaries change the load share.

2) Which prop capacity should I enter?

Use manufacturer allowable capacity for the actual extension, bracing, and eccentricity conditions. If you only have ultimate ratings, convert them to allowable using your project’s safety basis.

3) Why can a result fail even with strong props?

Spacing may create a large tributary area, increasing load per prop. Reduce spacing, add intermediate members, or reassess design pressure assumptions to bring utilization to 1.0 or less.

4) Is the beam check suitable for multi-span shores?

No. It assumes a single simply supported span with uniform load. For continuous members, cantilevers, point loads, or scaffold decks, perform a proper structural analysis and confirm support reactions.

5) What deflection limit should I use?

Common temporary works limits include L/360 for serviceability, but requirements vary. Use a limit that controls formwork tolerance, concrete finish expectations, and any imposed alignment constraints.

6) Can I use this for wall formwork or lateral loads?

This version focuses on vertical slab support and a simple beam check. Wall formwork needs lateral pressure models, tie spacing, walers, and kicker checks. Use dedicated wall-form design methods.

7) How should I document assumptions for approvals?

Record slab thickness, load components, factors, spacing grid, capacities, and inspection controls. Use the CSV or PDF outputs, attach manufacturer tables, and include sketches showing bays, edges, and openings.