Home Additions in Ventura County & Los Angeles

Room additions with RnD Builders generally run $450 per square foot and up. Smaller additions can approach $650 per square foot, while larger ones often come in lower per square foot, so the total depends on size, finishes and site conditions. Foundation type, roofline, plumbing and heating and cooling extensions all affect the final price, and your written estimate confirms the exact number.

A 20x20 home addition covers 400 square feet. At $450 per square foot and up, a standard 20x20 addition is roughly $180,000 and up in total. The price depends on the type of room, materials and finishes. We give you a detailed written estimate up front so you can see what is included.

A 20x20 master suite with a bedroom, walk-in closet and private bathroom starts at roughly $180,000 and can go higher depending on finishes and site conditions. The bathroom is usually the most expensive part because of plumbing rough-in, tile, fixtures and ventilation. Smaller suites can approach $650 per square foot, and your written estimate confirms the exact price.

Simple room additions might take about 3 months, while adding a second story can take a year or longer. The build phase is the longest part of the project, and design, plans and permit approval happen before it. Your project manager gives you a timeline and updates it if anything affects the finish date.

In many cases, yes. A second-story addition depends on whether your existing foundation and framing can support the new level, so we evaluate the structure first and bring in engineering where needed. It is a larger project with a longer timeline and a higher price than a ground-level room addition.

Yes. Home additions generally require a building permit, and electrical, plumbing and structural work may need separate permits depending on your design and city. RnD Builders drafts the plans, handles the permit process and manages the inspections for you.

No, most homeowners can stay in their home. Certain stages may affect access to specific rooms. A larger project such as a second floor may require more adjustment to your routine. Your project manager guides you through each phase and helps you plan around any disruptions.

Construction is completed in phases, from design and permitting to foundation work, framing, mechanical installations and finishing touches. Your project manager keeps you informed with regular check-ins, explains what is happening on site, outlines the next steps and answers your questions.

In many cases minor changes can be made depending on where we are in construction. Your project manager walks you through what is possible and explains how any adjustment affects the scope, timeline and cost. Changes are agreed in writing before they are added to the contract.

We set up dust barriers, floor coverings and designated work zones to keep debris contained. We tidy the site regularly so the rest of your home stays safe and comfortable. If you have specific concerns, tell your project manager and we will plan around them.

Yes. California requires a contractor license for any project that needs a building permit or totals $1,000 or more in labor and materials. An addition needs a permit. RnD Builders is a licensed general contractor, and you can verify any license on the CSLB website before you hire.

Your written estimate lists the scope and each selection. We review what could change the job, such as soil, existing wiring or hidden structural conditions. If something changes, you approve it in writing before it is added. Our promise is a project completed in line with the budget agreed in your contract.

It often does. More living space, an extra bedroom or a new suite appeals to many buyers. The space can serve as an office, guest room or, where local rules allow, a rental. The return depends on your market and the quality of the work, so we do not promise a specific amount.

Ventura County is our main focus, such as Thousand Oaks, Newbury Park, Camarillo, Santa Rosa Valley, Oxnard, Ventura, Simi Valley and Moorpark. We also build home additions across Los Angeles County, including Westlake Village, Calabasas, Agoura Hills, Malibu, Woodland Hills, West Hills, Chatsworth, Northridge, Porter Ranch, Santa Clarita, Valencia, Pacific Palisades, Pasadena, Altadena and the South Bay. Ask us if you are not sure we cover your address.