A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted Room Addition Contractor Nationwide
A room addition contractor in Los Angeles handles the design, permitting, framing, and finishing of new living space attached to your existing home. Most full-size room additions run between $80,000 and $220,000, while simpler bump-outs and prefab options can start around $55,000. At Benson ADU Builders, we put that price in writing before the first tool leaves the truck, and we stand behind the finished space with a 365-Day Done Right Promise. Call (903) 568-7222 for a free estimate.
Troy Eastman leads our team with a simple rule: no verbal estimates, no disappearing until demo day, no change orders that show up after the walls are framed. You’ll know who’s on your property because every technician is background-checked and arrives in uniform. You’ll know what you’re paying because the price is confirmed before work starts. And you’ll know what happens if something isn’t right: we come back and make it right, covered by a written guarantee on every project.
Written by Troy Eastman, Owner at Benson ADU Builders, building home additions nationwide since 2006.
Sunroom Builders
Sunroom Builders construct glass-heavy living spaces that connect your home to natural light without the full cost of a traditional room addition. A prefab sunroom typically runs $30,000 to $75,000, while a site-built sunroom with insulated glass and climate control lands between $70,000 and $130,000. We build both, and we’ll show you the difference in writing before you commit to either.
Prefab Sunroom Kits Versus Site-Built
Prefab sunroom panels arrive pre-cut and pre-glazed, which trims weeks off the build and reduces labor cost. Site-built sunrooms give you more control over dimensions and glass performance but take longer to frame and finish. We walk you through both options with actual material samples, not a brochure.
Climate Considerations That Change the Price
If your sunroom needs to handle snow load or extreme heat, the glazing spec changes and so does the budget. We factor your local climate into the written estimate so the glass performs in August and January alike. A sunroom that bakes in summer or leaks in winter is a design failure, not a luxury.
Room Additions
Room additions are attached living spaces built onto the existing footprint of your home, from a single bedroom bump-out to a full primary suite. Expect to budget $200 to $450 per square foot depending on finishes, foundation work, and whether the roofline ties into the existing structure or stands on its own. Benson ADU Builders prices the project in writing, so the square-foot math is visible from the first conversation.
Foundation and Roofline Decisions
The two biggest cost drivers on any room addition are what’s under the floor and what’s over your head. A slab-on-grade addition costs less than one requiring new footings or pier work, and tying into an existing roof costs less than building a separate ridge. We review both with you before the estimate is finalized.
Matching Existing Finishes
New space should look like it grew there, not like it was bolted on. We match siding, trim, flooring, and paint to your existing home and document that in the scope of work. If a material is discontinued, we tell you and give you alternatives before demo day, never after.
Modular Home Addition
A Modular Home Addition is a room or wing built off-site in sections, delivered by truck, and set onto a prepared foundation. Because the modules are constructed indoors, weather delays shrink and framing tolerances tighten, with most projects running $90,000 to $180,000 all-in. We’re authorized to build with Dvele and Plant Prefab, two modular brands homeowners can research and verify independently.
How Modular Delivery Works
The modules arrive on a flatbed and a crane sets them onto the foundation, usually in a single day. Site crews then handle the marriage line, utility connections, and interior finish work. You’ll see a written schedule before the crane is booked, and you’ll get real-time tracking as the modules move from factory to your property.
Why Modular Framing Stays Tight
Factory-built modules are framed on jigs, which means fewer gaps, squarer corners, and better insulation continuity than field framing often delivers. Dvele and Plant Prefab both publish their build specs, and we’re happy to walk you through them. If modular isn’t right for your site, we’ll say so and show you a site-built comparison instead.
Home Addition Plans
Home Addition Plans are the architectural drawings and permit documents that define every dimension, material, and structural connection on your project before construction starts. Plan costs typically run $3,000 to $8,000, though complex additions with structural engineering can reach $12,000. At Benson ADU Builders, plans are never an upsell, they’re the first deliverable, and the price is confirmed before a designer opens a file.
What a Good Plan Set Includes
Floor plans, elevations, foundation details, electrical layouts, and a written scope of work are the minimum. If your addition touches a load-bearing wall or alters the roofline, structural calculations must be stamped by a licensed engineer. We coordinate that for you and keep you copied on every revision.
Permits and Plan Revisions
Most additions require a building permit, and plan reviewers frequently send back revision requests. We handle the back-and-forth and track the status in real time so you’re never wondering where the project stands. If a revision changes the price, you’ll see it in writing before we resubmit anything.
In Law Suite Builders
In Law Suite Builders construct self-contained living quarters attached to or adjacent to the main home, with their own entrance, bathroom, and kitchenette. A finished in-law suite typically runs $120,000 to $250,000 depending on square footage and whether full kitchen plumbing is included. We build them for aging parents, adult children, and rental income landlords alike, with the same written-price guarantee as every other Benson project.
Private Entrance and Sound Separation
An in-law suite only works if it feels like its own home, not a spare room with a toilet. That means a dedicated exterior door, a fire-rated separation wall, and insulation designed to keep conversations from traveling through the studs. We spec all three in the plan set and verify the sound ratings before drywall goes up.
Kitchenette Versus Full Kitchen
The difference between a kitchenette and a full kitchen is mostly about ventilation and gas line work. A kitchenette with a microwave, sink, and compact refrigerator keeps the budget closer to $120,000. A full kitchen with a range hood, oven, and dishwasher pushes the project toward the top of the range, and we’ll show you both line-item options before you choose.
ADU Conversion
An ADU Conversion transforms an existing structure, usually a garage, basement, or workshop, into a legal accessory dwelling unit. Conversions typically run $90,000 to $200,000 depending on what’s already there: a finished garage with drywall and electrical costs far less to convert than a bare shell. Benson ADU Builders handles the entire conversion, from structural review to final inspection, and we author builds with Mighty Buildings and Boxabl when a panelized approach fits the site.
Garage Conversion Starting Points
Most garages already have a slab, framing, and a roof, which is why garage conversions are usually the cheapest path to an ADU. The unknowns are the foundation depth, the electrical service size, and whether the slab needs insulation cut in. We assess all three during the estimate visit and line-item the costs before you sign anything.
When a Panelized ADU Makes More Sense
If your existing structure has foundation issues or the ceiling is too low for legal habitation, converting it can cost more than starting fresh with a panelized unit. Boxabl and Mighty Buildings deliver precision-cut panels that assemble quickly and meet current energy codes out of the box. We’ll run the comparison honestly and show you both numbers.
Brands We Service
We build with Dvele and Plant Prefab when a project calls for modular precision and factory-controlled framing tolerances. Both brands publish their material specs and build standards, so homeowners can verify exactly what’s going into their addition before we ever break ground. Our crews are trained on their connection details and panel layouts, which means fewer field surprises during set day.
For panelized and rapidly deployable builds, we’re authorized to work with Mighty Buildings and Boxabl. These systems cut framing time dramatically while meeting current energy and fire codes. Whether you have a specific brand in mind or you’re comparing all four side by side, we can help you choose without pushing a single take-it-or-leave-it product.
Signs You Need a Pro Right Now
- Cracks that move or widen. A hairline crack in drywall is cosmetic. A crack that grows month over month suggests foundation movement or a failing header. Because room additions tie into existing structure, an unstable foundation means the new space inherits the problem.
- Doors or windows suddenly sticking. When a door that closed fine last year starts binding at the top corner, the framing has shifted. That’s a structural conversation, not a sanding job.
- Water stains on ceilings or exterior walls. Stains mean water is already inside the envelope. Adding square footage without fixing the intrusion point just gives the moisture more places to hide, and mold doesn’t wait for a change order.
- Floors that slope or bounce. A floor that flexes underfoot points to undersized joists or failing piers. New space attached to that framing will sag with it, and the fix gets more expensive every month it’s ignored.
- Electrical panels that trip under normal load. Every addition adds circuits, and an overloaded panel can’t legally or safely supply them. If your breakers trip when the microwave and space heater run together, the addition needs a service upgrade, not just a new outlet.
Our Process, Step by Step
- 1
Written estimate and site review. We walk the property, measure the existing structure, and identify any foundation, framing, or utility issues before we quote a dollar figure. You leave the first meeting with a written price range, not a verbal ballpark.
- 2
Plans and permits. Our design team drafts the addition plans and submits them for permit review. You’re copied on every submission and every reviewer comment, so there’s no black box between handshake and groundbreaking.
- 3
Material selection and brand confirmation. We show you actual samples from Dvele, Plant Prefab, Mighty Buildings, Boxabl, and James Hardie cladding where they apply. Every material is confirmed in writing before it’s ordered, so the price can’t drift after the fact.
- 4
Construction with real-time tracking. Uniformed, background-checked technicians handle every phase, and you get updated progress with photos throughout the build. You’ll always know who’s on site and what got done that day.
- 5
Final walkthrough and 365-Day Done Right Promise. Before we call the project complete, we walk the space with you and test every outlet, window, door, and fixture. If anything isn’t right within a full year, we come back and make it right, backed by a written guarantee on every project.
How Much Does Room Addition Contractor Cost?
A typical room addition runs $200 to $450 per square foot, which puts a 400-square-foot addition between $80,000 and $180,000. Sunrooms land lower, often $30,000 to $75,000 for prefab kits and $70,000 to $130,000 for site-built versions. Modular additions from brands like Dvele or Plant Prefab usually fall between $90,000 and $180,000. In-law suites with full kitchens start around $120,000 and can reach $250,000 depending on plumbing, ventilation, and finish level. ADU conversions vary the most, from $90,000 for a finished garage with existing electrical to $200,000 for a bare shell that needs new utilities, insulation, and fenestration.
What moves the price: foundation type, roofline complexity, kitchen versus kitchenette, finish material grade, and whether the electrical panel needs an upgrade. The best way to avoid overpaying is to get a written line-item estimate before work starts and refuse any contractor who won’t put the number in writing. Our free estimate includes the full scope of work, the material allowances, the permit fees, and the labor cost, so you can compare apples to apples. Call (903) 568-7222 to schedule yours.
Where We Work
Benson ADU Builders serves homeowners and businesses across the United States through local crews, including our Room Addition Contractor in Huntington Park, each independently owned and operated under The Relay Visibility Guarantee. Our team comes to you with background-checked technicians, real-time project tracking, and written pricing no matter where your property sits. We coordinate permits, materials, and scheduling through a single point of contact so the process feels the same in every market we serve.
Frequently Asked Questions About Room Addition Contractor
A room addition contractor is a licensed builder who manages the design, permitting, framing, and finishing of new attached living space. Benson ADU Builders specializes in room additions, ADU conversions, in-law suites, and modular additions, and every project gets a written price before work starts. You’ll know the full scope, the material list, and the total cost from the first conversation.
Most room additions take 3 to 6 months from permit submission to final walkthrough, with modular and panelized options running closer to 2 to 4 months. Site-built additions take longer because framing, roofing, and finishing happen outdoors and on-site. We provide a written schedule before work starts and real-time tracking throughout the build.
Room additions typically run $200 to $450 per square foot, or $80,000 to $180,000 for a 400-square-foot project. Sunrooms, modular additions, in-law suites, and ADU conversions each have their own ranges, all detailed in the pricing section above. Call (903) 568-7222 for a written, line-item estimate for your specific project.
Yes, we’re authorized to build with Dvele, Mighty Buildings, Boxabl, and Plant Prefab, and we can service and add onto homes that already use these systems. Our crews are trained on the connection details and panel layouts for each brand. If you have a different modular or prefab system, we can evaluate it and let you know what’s possible.
A live person answers every call 24/7, and we can schedule an assessment for urgent foundation, water intrusion, or failing framing issues. If a structural problem is actively affecting the safety of your home, we’ll prioritize the visit. Call (903) 568-7222 and you’ll speak to a person, not a voicemail loop.
If any part of your addition isn’t done right within a full year, we make it right at no cost. That includes framing, finishes, doors, windows, electrical, plumbing, and any covered repair that fails. If a covered repair fails after we’ve addressed it once, you get a free second visit, all in writing.
Have a rough idea of the room’s purpose, the square footage you’re considering, and any existing structural issues you’ve noticed, like cracks, sloping floors, or sticking doors. We’ll handle the measurements, the site review, and the written scope of work. You don’t need plans or permits before we arrive, just a list of what matters most to you.
Schedule Your Room Addition Contractor Service Today
Call (903) 568-7222 to schedule your free estimate. You’ll get a written price, a clear scope of work, and a timeline before you commit to anything. Our team is available 24/7, and every project carries the 365-Day Done Right Promise in writing. Let’s plan your addition the right way, with the numbers on the table from day one.
Written by Troy Eastman, Owner at Benson ADU Builders, building room additions with written pricing since 2006.
