Concrete Footings Calculator
Calculate concrete volumes for strip footings, pad foundations, and circular post holes. Essential for extensions, outbuildings, decks, and fence projects.
Foundation Concrete Guide
Foundation Depth Requirements
UK building regulations require strip foundations to be at least 150mm wide and the depth of any concrete specified by the structural engineer. For typical domestic extensions: 450mm wide × 300mm deep in stable ground, deeper in clay or shrinkable soils. Always consult building control for foundations near trees.
Concrete Grade
Strip footings: GEN3 (equivalent to C20/25). Pad footings: RC28/35. Post holes: GEN1 or even just rapid-set postcrete. For reinforced concrete (RC) work, always use the specified grade — not general purpose bags.
When to Order Ready-Mix
For volumes over 0.5m³, ready-mixed concrete is usually more economical and gives better consistency. Minimum ready-mix orders are typically 0.5–1m³. Below this, bagged rapid-set concrete is more practical and avoids minimum load charges.
Safety and Regulations
Most structural and electrical DIY work in England and Wales must comply with Building Regulations and is notifiable to local Building Control. Work that is not notifiable (like-for-like replacements, cosmetic changes) can be done without notification. Notifiable work done without approval is technically illegal and can cause problems when selling the property. Electrical work in most rooms requires a Part P competent person or Building Control inspection. Gas work must always be performed by a
Recommended for this calculator