About

Foundation stability is the single most critical factor in construction, determining the longevity and safety of a structure. Unlike traditional concrete ribbons or pads, screw piles offer a versatile solution for challenging soil conditions, slopes, or projects requiring speed. However, the integrity of a screw pile foundation relies entirely on the correct distribution of load.

This tool is designed for contractors, engineers, and DIY builders to estimate the precise quantity and layout of piles needed. By analyzing the building footprint (Rectangle or L-Shape), total structural weight, and specific pile diameter capacities, it calculates the minimum number of support points required to prevent settling or structural failure. It strictly adheres to industry standards regarding maximum span distances to ensure floor joists remain rigid.

Formulas

The calculation of screw piles involves two primary checks: Load Capacity and Maximum Span.

1. Load Requirement:
N_load = W_totalC_pile

2. Perimeter Spacing:
N_perimeter = PS_max

Where N is the number of piles, W_total is the total weight of the structure (dead + live loads), C_pile is the bearing capacity of a single pile, P is the perimeter length, and S_max is the maximum allowed spacing between piles (typically 2.5m).

Reference Data

Pile Diameter (mm)	Blade Diameter (mm)	Typical Bearing Capacity (Tons)	Common Application
57 mm	200 mm	0.8 - 1.2 Tons	Light fencing, decking, signposts
76 mm	250 mm	1.5 - 2.5 Tons	Gazebos, sheds, small timber cabins
89 mm	300 mm	3.0 - 5.0 Tons	Residential framing, brick veneers, large decks
108 mm	350 mm	6.0 - 8.0 Tons	Heavy timber homes, modular houses, industrial masts
133 mm	350-450 mm	8.0 - 12.0 Tons	Commercial foundations, bridges, heavy load bearing
159 mm	500 mm	15.0+ Tons	Industrial hangars, significant infrastructure
Spacing Limit	N/A	Max 2.5m - 3.0m	To prevent timber/joist sagging

Frequently Asked Questions

For a precise calculation, an engineer sums the dead loads (materials) and live loads (occupancy/snow/wind). A general rule of thumb for estimation: Light timber frame = 150 kg/m²; Log cabin = 250-300 kg/m²; Brick/Block = 600+ kg/m². Don't forget to add 20-30% safety margin.

The spacing is usually dictated by the spanning capability of your floor beams (joists). Standard practice suggests a maximum span of 2.5 to 3 meters (approx. 8-10 feet). Exceeding this can cause the floor to bounce or sag, even if the piles can hold the weight.

Absolutely. The values in the table assume standard dense clay or loam. In sandy or loose soil, the bearing capacity drops significantly, potentially requiring deeper piles or larger blade diameters. Marshy or peat soils may require pile extensions to reach stable ground.

Small diameters (57mm, 76mm) can often be installed manually with a leverage bar. Diameters of 89mm and above typically require hydraulic machinery (excavator attachments) to ensure sufficient torque and vertical alignment.

L-shaped foundations introduce a re-entrant corner (internal corner) which often carries higher loads from roof valleys. The calculation must ensure a pile is placed exactly at this intersection, and spacing is calculated along all six sides of the perimeter.