Built a free side-by-side California ADU cost ledger (800 vs 400 sq ft)
I needed a way to compare California ADU scopes without collapsing everything into one average cost per square foot, so I shipped a free side-by-side ledger at https://everylineitem.com/compare/. It walks a six-phase line-item ledger, and the page server-renders a default of a detached 800 sq ft build next to a 400 sq ft one so the cost cliff is visible immediately. Figures come from public sources (HCD, local permit context, NAHB framing) — no paywalled RSMeans. If you are weighing two ADU sizes before you hire anyone, the compare view is open.
The side-by-side view targets a real decision. Have any users actually changed their ADU size or scope after seeing the line-item comparison?
The side-by-side view makes sense here because cost per square foot hides the part people actually need to see.
For an ADU, a 400 sq ft build is not simply “half” of an 800 sq ft build. Design, permitting, utility work, site prep and some inspection costs do not scale neatly, so the smaller option can look cheaper in total while being much worse per usable foot.
I reckon the most useful addition would be a “fixed vs size-sensitive” label on each line item. That would help someone understand whether the cliff is coming from real construction scope, local fees, or costs they would pay almost regardless of size.