Methodology

This page explains how the BasementCalcs calculators are derived and verified — and why they need no ongoing maintenance to stay correct.

1. Timeless math, stable conventions

Every tool computes from a closed-form formula: piers or straps = ceil(length ÷ spacing); wall area = perimeter × height; concrete/gravel volume = area × (thickness ÷ 12) ÷ 27 cubic yards; material quantity = area ÷ coverage × (1 + overlap/waste); project cost = quantity × your unit price + labor; price per sq ft = your total ÷ area; loan payment = P·r ÷ (1 − (1+r)⁻ⁿ). The only baked-in numbers are stable conventions — 27 cubic feet in a cubic yard; typical pier spacing ~6–8 ft; strap spacing ~4 ft; vapor-barrier overlap ~6–12 in; drain-tile slope ~1%. These do not drift, so the statements stay true over time.

2. No prices, no feeds

There is deliberately no material price, no labor-rate table, no regional cost index, no live loan rate and no product catalog. Every cost tool works on the prices you enter from your own quotes and bills ($/pier, $/linear ft, $/sq ft, $/cu yd, $/roll, $/gallon, per-unit price, labor $/hour, APR). That is why the site is correct regardless of what materials, labor or interest rates do.

3. Numeric self-check

Every formula is asserted against a worked example with known numbers (for instance: a 120 ft affected run at 6 ft spacing needs 20 piers; a 120 ft × 8 ft exterior wall is 960 sq ft; a 400 sq ft, 4-inch slab is 4.94 cubic yards of concrete; $25,000 at 9% over 60 months is ≈ $518.96/month). A release gate runs all of these and fails on any mismatch, so "verification" here is mathematical correctness plus accurate conventions — not a time-based check.

4. Estimate, not a bid or engineering design

The spacing, coverage, overlap and allocation values are labeled planning bands — a starting point, not an engineering spec, and the cost-per-sq-ft bands are explicitly not a price index. Every cost result is a planning estimate: get itemized written quotes from licensed contractors, and treat foundation movement, structural, excavation and electrical scope as licensed-engineer, licensed-pro, permit-and-inspection work. The financing and ROI tools are illustrative math on your figures, not financial advice, and home value protected is never guaranteed. We make no mold, radon or air-quality health claims.