Home additions and construction
Plan a home addition, from drawings to final inspection
An addition changes the size of the house itself, so it starts on paper long before anyone digs. Tell us how much space you need and where you picture it, and we call you back to talk through the steps, the kind of licensed contractor it takes, and the questions worth asking. There is no charge for the request.
What counts as a home addition?
An addition is any project that adds enclosed floor area to the building. The common kinds are:
- A room addition on the ground floor: a bedroom, a family room, a larger primary suite.
- A second story added over part or all of a one-story house.
- A bump-out: a few feet pushed out from one wall to enlarge a kitchen, a bath or a dining area.
- A garage conversion, which turns existing space into living space instead of building new walls. It is not new area, but it goes through the same planning, structural and permit questions.
Each one ties new framing into the old house: a new foundation meets the existing one, a new roof meets the old roofline, and walls are opened to connect rooms. That joint between new and existing is where most of the planning goes.
Why does an addition start with drawings?
Because the city reviews the plan before it allows the work, and the plan has to answer questions a contractor cannot settle on site. How far the addition may sit from the property lines, how tall it may be, and how much of the lot it may cover are zoning questions set by your city's planning department. How it stands up is a structural question: footings, beams over new openings, and for a second story, whether the existing foundation and walls can carry the extra load.
Most additions involve a designer or architect for the floor plan and elevations, and a structural engineer for foundations, beams and lateral bracing. Some contractors offer design and build under one contract; others build from plans you bring. Either way works, as long as you know who is responsible for the drawings being complete and accepted by the city.
Older homes add their own questions: the condition of the existing foundation, the capacity of the electrical panel for new rooms, and whether the heating and cooling system can serve more space. Those are good to raise at the first site visit.
What permits does a home addition need?
Plan on a building permit, a review of the drawings and inspections as the work goes up, and confirm the details with your city's building department. Each Bay Area city runs its own planning and building departments with their own submittal lists. In Dallas, the city's residential permit page keeps a separate checklist for residential additions and takes applications through DallasNow; in Fort Worth, the contractor pulling the permit must be registered with the city. Ask your city's building department for its own list before the drawings are final.
Plan check can take several rounds of comments and corrections, so the permit stage is often a real part of the timeline, not a formality. Ask whether the contractor or your designer will handle submittal and corrections, and write that into the agreement.
Which contractor license does an addition need?
An addition brings together foundation, framing, roofing, windows, insulation, drywall, plumbing and electrical, which is the kind of multi-trade work the B, General Building license exists for. CSLB's B classification description lets a general building contractor take a prime contract that involves at least two unrelated trades besides framing or carpentry, and use licensed specialty subcontractors.
The B-2, Residential Remodeling license is a different thing. Its CSLB description excludes structural changes to footings, foundations, load-bearing walls and roof structures, which an addition almost always needs. For an addition, look for a B license on the CSLB lookup. Our license check guide shows how to read the result.
Is a garage conversion or backyard unit an ADU?
It can be. When the new space is a separate living unit with its own kitchen and bath, it may count as an accessory dwelling unit rather than an addition, and the city decides which. California's Department of Housing and Community Development explains ADUs, junior ADUs and the state rules behind local ordinances on its accessory dwelling units page, which also links its ADU Handbook. Tell us on the request whether you want an extra room for the household or a separate unit, because the planning path is different.
What to have ready before you call
- What the new space is for, and roughly how large you picture it.
- Where it would go: the back, the side, above the garage, or upstairs.
- Any plans or drawings you already have, including old permit drawings of the house if you can find them.
- Your lot size and anything you know about the property lines, easements or a homeowners association.
- Photos of the outside wall or roof where the addition would join the house.
- Whether the household will live in the home during construction.
Questions to ask an addition contractor
- Do you hold a B license, and which trades do you subcontract?
- Will you work from my architect's plans, or do you provide design and engineering?
- Who submits the plans, answers plan check comments and schedules inspections?
- How does the contract handle surprises found when the old wall or foundation is opened?
- How will the house be closed against weather while the roof is open?
- How are payments tied to finished stages of work?
California limits the deposit to 10 percent of the price or $1,000, whichever is less, and requires changes in writing. The full list of what the contract must say is in our contract guide and on CSLB's contracts page.
What we do, and what we don't
We take your addition request free and get back to you by phone or email to talk over the space you need, the kind of licensed contractor and design help it takes, and what to ask them. We are not a general contractor or a designer. We hold no contractor's license, draw no plans, pull no permits and build nothing, and we do not give prices, promise schedules or vouch for anyone. Check each contractor's license on CSLB's site before you sign.
Tell us about the project
A short note is enough. We call or email you back about it; the request is free and you owe nothing for it.
Home addition questions people ask
Can we live in the house while an addition is built?
Often yes for a ground-floor addition, since the new rooms stay closed off until the final connection. A second story is harder, because the roof comes off and the work happens overhead. Ask the contractor how they protect the occupied rooms and which stages would require you to move out.
Do I need a survey of my lot before designing an addition?
When the addition comes close to a property line, a survey is the reliable way to know where that line is, because fences are not always on it. The city's planning department can tell you the setbacks for your zone, and your designer can tell you whether a survey is needed for your plan.
Who pays for the engineer and the permit fees?
That depends on the agreement. Some contractors include design, engineering and permit fees in a design-build contract; others expect you to hire the designer and pay the city directly. Write down which costs are in the contract and which are yours, so nothing is assumed.
Sources: CSLB, B General Building Contractor; CSLB, B-2 Residential Remodeling Contractor; CSLB, Contracts and Binding Agreements; City of Dallas, Residential Permits; City of Fort Worth, Contractor Registration; California Department of Housing and Community Development, Accessory Dwelling Units.