Home Addition Cost Calculator

Home Addition Checklist: Plan Your Project Step by Step

Home Addition Checklist

Guide

A practical home addition checklist: budget, design, permits, contractor bids, and build — in the order to do them.

Start with the decision, not the drawing.

Write down what the addition must do: an extra bedroom, a larger kitchen, a home office, or a suite for family. A clear brief keeps the design, the budget, and the bids comparable. If the brief is vague, every contractor will price a different project, and the bids cannot be compared fairly.

Set a budget range before you fall in love with a finish.

Run the calculator with a realistic size and a Standard finish first, then test Economy and Premium to see the spread. Add a 10–20% contingency outside the central estimate. A budget that only works if everything goes perfectly is not a budget; it is a hope.

Check what the lot and the existing house will allow.

Confirm setbacks, height limits, lot coverage, and access before paying for detailed drawings. Check how the new work will tie into the roof, structure, wiring, plumbing, and heating. The cheapest time to find a problem is before it is drawn.

Get three itemised bids.

Ask each builder for the same scope, separated into structure, foundation, features, and allowances, with a schedule and a payment plan. Compare scope first and price second. A bid that omits work is not cheaper; it is incomplete.

Plan for living through the build.

Agree dust, noise, access, storage, and working hours in writing, and plan where daily life moves while the work is underway. Small agreements made early prevent most friction during the build.

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Home addition cost calculator · Addition cost hub

Planning estimate only, based on 2026 cost data. It is not a quote. Get itemised bids from licensed local contractors before building, and set aside a 10–20% contingency for permits, design fees, and site surprises.