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Grillage Foundation Material Calculator

Calculate concrete volume, formwork area, and reinforcement steel weights for grillage foundations. Generates cross-section diagrams and BOQ estimations.

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Category Foundation & Concrete
Beam Dimensions
Longitudinal Reinforcement
Transverse (Stirrups) & Waste
Dynamic Cross Section
Total Concrete
0.00 m3
Total Steel
0.00 kg
Formwork Area
0.00 m2
Binding Wire
0.00 kg
Longitudinal Weight: 0 kg
Stirrup Weight: 0 kg
Stirrup Cut Length: 0 m
Total Stirrups: 0 pcs
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About

Grillage foundations transfer heavy structural loads from columns to a wider soil area or pile caps. Accurate material estimation for these reinforced concrete beams is critical for project cost control and logistics. Errors in quantification often lead to concrete overage charges or steel shortages during critical pour phases.

This tool computes the precise material requirements for foundation beams based on geometric parameters and reinforcement detailing. It calculates the net concrete volume, surface area for formwork shuttering, and the total weight of steel reinforcement. The calculation distinguishes between longitudinal bars and transverse stirrups, accounting for specific diameters and spacing. It applies configurable waste factors to accommodate site losses and lap splices, ensuring the final Bill of Quantities reflects realistic site conditions.

foundation calculator rebar weight concrete volume civil engineering construction estimation

Formulas

The calculation of materials relies on geometric derivation from the beam cross-section and length.

1. Concrete Volume:

V=L×W×D×(1+waste)

Where L is total length, W is width, and D is depth.

2. Formwork Area:

Aform=(2×D×L)+(W×D×2)

Note: This assumes formwork on sides and ends, excluding the bottom (blinding) and top.

3. Stirrup Cutting Length:

Lst=2(W+D)−8cov+hook_len

Where cov is the concrete cover.

Reference Data

Rebar Size (mm)Unit Weight kg/mCross Section mm2Common Application
60.22228.3Stirrups / Ligatures
80.39550.3Stirrups / Light Mesh
100.61778.5Stirrups / Slab Main
120.888113.1Light Beam Main
161.580201.1Column / Beam Main
202.469314.2Heavy Foundation Main
253.853490.9Pile Caps / Heavy Beams
326.313804.2Mega Structures
409.8651256.6Bridge Piers

Frequently Asked Questions

For concrete, a waste factor of 3% to 5% is standard to account for spillages and uneven excavation. For steel reinforcement, 5% to 10% is typically added to cover cutting waste and rolling margins, though this can vary based on bar optimization strategies.
The base calculation determines theoretical weight based on linear length. To account for laps (splices) in long beams where bar lengths exceed standard stock (usually 12m), you should adjust the "Steel Waste" percentage upwards. A standard lap length is often 50 times the bar diameter.
Binding wire is not calculated by geometry but by empirical ratio. This tool uses a standard industry constant of approximately 10kg to 12kg of binding wire per metric ton of reinforcement steel (approx 1% to 1.2%).
Reinforcement must not touch the formwork or soil to prevent corrosion. The "cover" is the distance between the outer concrete surface and the steel. The stirrup dimensions are reduced by twice the cover on each axis (top/bottom and left/right).
Yes, provided the pile cap is rectangular or square in section. The logic for volume and reinforcement density remains valid, though complex pile cap shapes might require separate calculations for varying depths.