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Top-Rated Addition to existing structure builders in Simi Valley - Updated Nov 2026

Avatar for HA My Design, Inc.
HA My Design, Inc.
5.0(
379
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

Super Service Award Winner

In business since 2011

Free estimates

Customers say: True professional

"I recently worked with HA My Design to build an ADU, and I could not be happier with the results. Golan and his crew were always on time and worked hard to ensure the project was completed within budget. The quality of their work was excellent, and they were quick and efficient. I highly recommend HA My Design for anyone looking to build an ADU. Their one-stop-shop showroom, covering 5000 square feet, made selecting finishes a breeze. I will definitely refer them to friends and family!"
After
Kitchen Remodel+Fireplace
Complete Home Renovation
Complete Kitchen Remodel
Complete Kitchen Remodel

+526

Response time1 day
Response rate100%
2 neighbors recently requested a quote
Avatar for So Cal Builders & Design Inc
So Cal Builders & Design Inc
4.6(
310
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved (Corporate)

Super Service Award Winner

In business since 1982

Free estimates

Warranties offered

"After several long years of designing and permitting our home remodel during the pandemic, we were searching for a good contractor to build out our remodel and second story addition. Avi and David were wonderful; very thorough in explaining the process, answering all of our questions, and settling on a price that was reasonable and within our budget. During the building process, David was very responsive, available, and receptive to changes and last minute decisions made along the way. The project took longer than anticipated and there were some unexpected setbacks, but David and Avi worked quickly to fix issues and keep the project moving forward. At the end of the project they were very responsible about making sure we were satisfied with every last detail before completing the project. Our new home is beautiful and we're very happy with how it turned out, thanks to David and all the crews at So Cal Builders."
Completely renovating both the guest and master bathrooms. In the master bathroom, we're installing a spacious walk-in shower featuring dual black-finished shower heads, elegant floating benches, and marble wall tiles. Meanwhile, the guest bathroom will have a sleek built-in tub and stylish hexagon tiles.
This project involved adding a new master bathroom to the existing house. The shower features sleek white subway tiles complemented by striking black fixtures and shower door hardware. The bathroom floor is adorned with elegant white marble tiles, providing a seamless and luxurious finish. A white shaker vanity topped with a white marble countertop completes the space, creating a clean and sophisticated look.
Experience a whole new level of indoor-outdoor living with the Torres Residence Backyard Remodel. This project highlights the addition of a kitchen sliding door, seamlessly merging your interior and exterior spaces
We remodeled the current kitchen, incorporating the addition of a new sliding door to establish a seamless indoor-outdoor living area
New pool with Baja bench and spa. New pavers, aluminum patio cover and built-in BBQ in the backyard

+563

42 neighbors recently requested a quote
Recommended by83%of homeowners
Avatar for KN Remodeling & Supplies Inc
KN Remodeling & Supplies Inc
4.8(
63
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

In business since 2012

Free estimates

Warranties offered

"We just finished a four bedroom/ three bathroom full remodel in Santa Monica. We are very happy with the end result. Nathan, who is the owner, was very involved in all phases of the job. Nathan got the job done on time. The workmanship and attention to detail was great. He had good communication and relationship with his team. Whenever we had a concern or question, Nathan was easy to get a hold of and handled it quickly. We were worried about the process of a remodel with all the stories you hear about bad experiences. But Nathan made this so easy on us and we would definitely use him for any future projects."
Additional Photos
Additional Photos
Additional Photos
Additional Photos
Additional Photos

+48

Response time8 hrs
Response rate100%
5 neighbors recently requested a quote
Avatar for YB Builders Group Inc.
YB Builders Group Inc.
5.0(
13
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

In business since 2025

Free estimates

Credit card accepted

"We recently had our kitchen remodeled, and the entire experience exceeded our expectations. From the initial consultation to the final installation, the team was professional, punctual, and paid incredible attention to every detail. They kept the work area clean, communicated with us throughout the project, and delivered exactly what they promised."
Bathroom Remodel
Master bathroom
Master bathroom
Master bedroom
Kitchen Remodel

+74

52 neighbors recently requested a quote
Avatar for Trig Builders, Inc.
Trig Builders, Inc.
4.9(
37
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

In business since 2004

Free estimates

Warranties offered

"We needed to do a kitchen remodel for a while now so we did a massive research online and by asking friends and family in our area. After meeting with all of them and explaining to them what are we looking for, what we want to do and mainly what is our budget. We received estimates from all the contractors that we met and we selected Trig Builders because Yossi was the most competitively priced and the referrals that we got on him and his company were very positive. Yossi and the workers were very easy people to work and to deal with and Yossi designed the kitchen exactly the way we wanted it with some nice additions of things that we didn’t think we will get. His suggestions about the new kitchen layout, where and what materials to buy were very helpful. Also, his advises and recommendation on where to buy the cabinets, lightings, plumbing and appliances saved us a lot of money. The end result of the new kitchen was perfect and one of the things that added a huge plus before we hired them was the warranty that included in the price of the work that they did."
Addition in Diamond Bar
Addition in Diamond Bar
Addition in Diamond Bar
Addition in Diamond Bar
Addition in Diamond Bar

+15

Response time7 hrs
Recommended by87%of homeowners
Avatar for Imperial Remodeling Inc
Imperial Remodeling Inc
4.6(
128
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

Super Service Award Winner

In business since 2006

Free estimates

Emergency services offered

"Fantastic. Not only is the end result superb but the process was as smooth and efficient as it could possibly have been. Gino consults you on everything, even after you’ve made the initial choice of cabinets, tile, countertop, scope of work, etc. He talks to you every day to update you. He has people working continuously, all organized so that no time is wasted. Once he started there was not a (week)day when his people weren’t working on my job, usually all day long. He has the work and teams organized and timed so that each one comes to your project as few days as possible, which reduces the cost. Gino is a stickler for detail, and getting everything exactly right, aesthetically and functionally, and the people he hires are very highly skilled with the same attitude. They’re also very clean. They sealed off the kitchen during the demolition so that the dust wouldn’t get to the rest of my open-plan condo. In construction they minimized particulate matter by doing all of the heavy cutting off-site. And they vacuumed the space every day before leaving! I’ve had contractors in several different cities and states and none came even close to this level of work, but it’s how remodeling should be! The price of my project was reasonable given the very high quality of the work, and the scope of work. Gino is very straight with you. The only costs that exceeded the estimate were due to my decisions to upgrade materials, or add a job to the project, and discovery of conditions in the existing structure that had to be upgraded (e.g., electrical). I’ve never been able to recommended a contractor before -- all the ones I’ve had have been so bad -- but I recommend Imperial Remodeling with two thumbs up."
Additional Photos
Additional Photos
Additional Photos
Additional Photos
Additional Photos

+185

Response time1 day
Recommended by89%of homeowners
Avatar for R Design, Inc.
R Design, Inc.
4.3(
31
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

In business since 2007

Free estimates

Small jobs welcome

"I hired Ramy and his team to help me build out some closets. He was very communicative and easy to work with. The team showed up on time, collaborated with me on the design, worked fast, were very respectful of the home the whole time, and cleaned up nicely. Highly recommend R Design for any contract work!"
 Joining dining room to kitche
 Cabinets, granite counter, marble/granite floor
 Bath tub wall tiling
 Restaurant previous counter
 Marble

+193

Response time1 day
Response rate99%
18 neighbors recently requested a quote
Avatar for Home Renew 360
Home Renew 360
4.7(
78
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved (Corporate)

In business since 2010

Free estimates

Warranties offered

"Had our roof replaced by the awesome team with Nathan behind the wheel. Very professional and no hidden costs, upgrades, etc. Very timely and up to standards. I cannot recommend them enough to anybody needing anything. In fact, we will be reaching out for future improvements on our small bungalow in LA. Also, be assured that they are not some "new to the game" company as there are a lot of them."
Roof in Huntington Beach
Asphalt Shingle Roof
Flat roof
Master Bathroom
Exterior Paint

+179

Response time8 hrs
Response rate100%
22 neighbors recently requested a quote
Avatar for KN Remodeling and Supplies, Inc.
KN Remodeling and Supplies, Inc.
4.6(
65
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

In business since 2002

Free estimates

Warranties offered

"After having remodeled our kitchen several years ago, we had KN remodel our master bathroom. Great guidance, from the construction stuff we don't understand to the aesthetic discussions we much appreciate. Done on time, and with great clarity around the billing. And the crew was great -- neat, thoughtful, on time, helpful. A big thumbs up."
kitchen remodel in Los Angeles and woodland hills
kitchen remodel in Los Angeles and woodland hills
kitchen remodel in Los Angeles and woodland hills
kitchen remodel in Los Angeles and woodland hills
kitchen remodel in Los Angeles and woodland hills

+128

Response time11 hrs
Response rate98%
Recommended by95%of homeowners
Avatar for McCormick Home Builders, Inc.
McCormick Home Builders, Inc.
4.7(
42
)
Addition to Existing Structure - Build

Serving Simi Valley, CA and surrounding areas

Approved

In business since 2017

Free estimates

Customers say: True professional

"We hired McCormick Home Builders to remodel our living room, and we are beyond pleased with the result. The team was professional, worked efficiently, and Aris design ideas made a huge difference. The room feels so much brighter and more spacious. This was the best decision we made for our home, and we were already planning our next remodel with them."
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+1

Response time6 hrs
Recommended by17%of homeowners
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FAQs for addition to existing structure building service projects in Simi Valley, CA

You can typically raise your roof by four to eight feet, depending on your home's structure and roof design. The exact amount depends on factors like roof slope and framing support. Raising the roof creates additional interior space, enhances natural light, and increases your home's value. Consult a professional to determine the feasible height increase for your home.

Yes, you need a building permit to raise your roof. Obtaining a building permit ensures your project complies with local building codes and safety regulations. A professional contractor can assist with the permit and inspection process and ensure all legal and safety requirements are met. Your contractor will be familiar with building codes in your area, which can differ between cities or states.

While it's possible to raise a flat roof, it requires extensive structural modifications. Flat roofs lack the attic space and support structures of pitched roofs, so raising them involves significant engineering to ensure safety and durability. This process can be complex and costly, so professional assessment is essential before undertaking a project of this magnitude.

The Simi Valley, CA homeowners’ guide to addition to existing structure building services

From average costs to expert advice, get all the answers you need to get your job done.