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About

A strip foundation (or trench footing) is a continuous strip of concrete used to support load-bearing walls. Accurate estimation of materials is financially critical; under-ordering ready-mix concrete results in expensive "short load" fees and cold joints, while over-ordering eats into the project margin. This tool calculates the exact volume required based on perimeter, width, and depth, accounting for a user-defined waste factor. It simultaneously calculates the linear footage of rebar required (based on the number of bars per trench) and generates a cost estimate using regional material price averages.

foundation calculator concrete cost strip footing construction estimator rebar calculator

Formulas

The volume V is derived from the total perimeter P, width W, and depth D:

V = P × W × D

Total Rebar Length Lrebar depends on the number of longitudinal bars (n):

Lrebar = P × n × 1.1 (overlap)

Reference Data

MaterialTypical UnitApprox. Cost (US)Waste Factor rec.
Ready-Mix Concreteyd3$125 - 1505 - 10%
Pre-Mix Bags (60lb)Bag$4.5010%
Rebar (#4, 1/2")ft$0.605%
Lumber (2x10)ft$1.50Reusable

Frequently Asked Questions

As a rule of thumb, if your project requires more than 1.5 cubic yards of concrete (approx 65 bags of 80lb mix), ordering a ready-mix truck is more consistent and labor-efficient, despite the delivery fee.
It varies strictly by local building codes and the frost line. In the US, it is typically at least 12 inches below the frost line to prevent heaving. Always consult a structural engineer.
For trenches dug directly into earth (earth-formed), add 10-15% as the ground is uneven. For formwork (wood-formed), 5-8% is usually sufficient for spillage.