What is a pile layout plan?

A pile layout plan (also called a piling plan) is the structural drawing on which every foundation pile of a building is set out, with a number, the pile type, the exact position and the design length for each one. It is the drawing the piling crew sets out from, and the record against which the finished work is checked.

What it shows

A complete pile layout plan normally contains:

• A plan of pile positions, dimensioned from a fixed grid or from the building lines
• Pile numbering, running consistently and logically per building section so every pile is traceable
• Pile type and size for each pile (for example a 250 × 250 mm precast concrete pile, a tube pile, a grouted or screw pile)
• Design length and toe level, derived from the cone penetration tests
• Calculated bearing capacity per pile type, and the distinction between compression and tension piles
• Pile cut-off level relative to datum or site level
• Driving sequence, important for displacement piles so that piles already installed are not heaved
• Locations of the cone penetration tests and a reference to the geotechnical report
• Tolerances for position and verticality

Why accuracy matters

A pile in the wrong place cannot simply be moved. If it deviates too far, eccentricity results: the load no longer sits over the pile axis, which introduces additional moments in the ground beam or pile cap. The engineer then has to check it and sometimes specifies an extra pile or a heavier cap. For that reason, actual positions are surveyed after driving and recorded on an as-built pile layout plan.

Practical points

• Check the plan in advance for clashes with cables, service runs, drainage and existing foundations.
• Watch the minimum centre-to-centre spacing; piles too close together reduce group capacity.
• Agree who does the setting out and survey and what tolerance applies — a classic source of argument afterwards.
• Keep the driving records with the pile layout plan; they are the later evidence of what is actually in the ground.

Related terms

• Pile foundation
• Driven pile
• Bearing capacity of a driven pile
• Ground beam
• Detail drawing

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