Room Additions in Orange County & Los Angeles

When the house is the right house but there isn't enough of it, an addition gives you more space without moving. IA Builders is a licensed general contractor based in Culver City, building room additions and second-story additions for homeowners across Orange County and Los Angeles.

Types of home additions

Single-room additions

A new bedroom, family room, home office or larger kitchen, built out from the existing house on a new foundation.

Primary suite additions

A bedroom with its own bathroom and closet, often the most valuable addition for a family that has outgrown a two- or three-bedroom house.

Second-story additions

Building up instead of out. A second story keeps the yard intact and can nearly double the living space, but it's the most involved type of addition: the existing foundation and walls have to carry the new load, often with structural upgrades, and the project needs a new stair and careful planning around the roof.

Bump-outs

Small additions of a few feet to enlarge a kitchen, bathroom or living room. They still need a foundation and permits, but they change the feel of a room for less than a full room addition.

If what you need is a separate place for a family member or a tenant, an ADU or garage conversion may fit better than an addition.

Making the addition look like it was always there

The best additions are the ones you can't spot from the street. That means matching the existing roof pitch and materials, siding or stucco, window style and floor heights, and extending the existing heating, cooling, plumbing and electrical properly instead of tacking on separate systems. When an addition goes with a larger update to the house, we can plan both together; see whole-home remodeling.

What an addition involves

1. Feasibility. Every city sets limits on how much of the lot can be built on, how tall a house can be, and how close it can be to the property lines. Coastal and hillside lots, historic districts and HOA communities add their own rules. We check what's allowed on your lot before design starts.
2. Design and engineering. Architectural plans, structural engineering, energy calculations, and a soils report where required.
3. Permits. Submittal to the city, plan-check corrections, and any design review, coastal-zone or HOA approval that applies.
4. Foundation and framing. New footings or slab, framing tied into the existing structure, and roofing.
5. Systems and finishes. Plumbing, electrical and HVAC extended into the new space, then insulation, drywall, flooring, trim and paint matched to the rest of the house.
6. Final inspection and walkthrough.

What affects the cost

• Size of the addition, and whether it includes a bathroom or kitchen
• Ground-floor addition or second story (second stories usually need structural upgrades below)
• Foundation type and soil conditions
• Whether the electrical panel and HVAC system can carry the added space
• How closely finishes need to match the existing house
• Design review, coastal or HOA requirements

Frequently asked questions

Do I need permits for a room addition?

Yes. Every addition needs a building permit, plans and inspections, and many need planning approval too. We handle the submittals and coordinate the engineering.

Should I add on or build an ADU?

It depends on how you'll use the space. An addition expands your own home; an ADU is a separate unit with its own kitchen and entrance that can house family or a tenant. On some lots the rules favor one over the other. We'll talk through both at the feasibility stage.

Can I stay in the house during an addition?

Often yes for ground-floor additions, since most of the work happens outside the existing walls until the final tie-in. Second-story additions usually require moving out for part of the project, because the roof comes off.

How long does a room addition take?

Design and permitting often take as long as construction. Ground-floor additions are faster to build than second stories. We give you a schedule once we know the scope and your city's review process.

How much do I pay upfront?

California caps the down payment on a home improvement contract at $1,000 or 10% of the contract price, whichever is less. The rest is paid on the schedule written into your contract, and any change to price or scope needs a signed written change order.

Last reviewed October 2026