Strip Foundation Calculator

A strip foundation is a continuous band of concrete laid under load-bearing walls to spread a building's weight across the ground — and the Strip Foundation Calculator estimates all the materials you need before breaking ground. Enter your foundation length, width, and height, then select your concrete grade and reinforcement details to get the concrete volume, concrete weight, and foundation base area. Optionally include reinforcement specs (main bar diameter, stirrup diameter, and spacing) and formwork to also calculate main reinforcement weight, stirrup steel weight, and formwork area required.

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Total perimeter length of the strip foundation

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Width of the foundation strip

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Total height including below and above ground portions

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Results

Concrete Volume Required

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Total Concrete Weight

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Foundation Base Area

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Main Reinforcement Weight

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Stirrup Steel Weight

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Formwork Area Required

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Frequently Asked Questions

What is a strip foundation and when should it be used?

A strip foundation is a continuous concrete foundation that runs along the entire length of a wall. It's used when the load-bearing capacity of the soil is sufficient and provides continuous support for walls. It's ideal for most residential construction and light to medium commercial buildings.

How do I determine the correct width for my strip foundation?

Foundation width depends on the load from the structure and soil bearing capacity. Generally, residential foundations range from 450mm to 900mm wide. The width should distribute the load so that soil pressure stays within safe limits, typically calculated by a structural engineer.

What concrete grade should I use for strip foundations?

For most residential strip foundations, M20 or M25 grade concrete is suitable. M25 is commonly used as it provides good strength and durability. For heavy loads or poor soil conditions, higher grades like M30 may be required.

How much reinforcement is needed in a strip foundation?

Minimum reinforcement is typically 0.12% of the cross-sectional area for main bars and 0.08% for distribution bars. Common practice uses 12mm or 16mm main bars with 8mm stirrups spaced at 150-200mm centers, but this should be confirmed by structural calculations.

What is the minimum concrete cover required for strip foundations?

Minimum concrete cover is typically 40-50mm for foundations in contact with soil. This protects the reinforcement from corrosion and ensures proper bond. In aggressive soil conditions, cover may need to be increased to 75mm or more.

How deep should a strip foundation be?

Foundation depth depends on soil type, frost line, and local building codes. Minimum depth is usually 450mm below ground level, but can range from 600mm to 1200mm or more depending on soil conditions and structural requirements.

What's the difference between strip foundations and pad foundations?

Strip foundations are continuous and support walls along their entire length, while pad foundations are isolated square or rectangular foundations that support individual columns or posts. Strip foundations are more suitable for wall-bearing structures.

How do I calculate formwork requirements for strip foundations?

Formwork area equals the exposed surface area of concrete that needs temporary support during pouring. This includes both sides of the foundation plus any exposed ends. The calculator determines this based on foundation dimensions and typical construction practices.