ADUs & Home Additions
Ground-up Accessory Dwelling Units and home additions, foundation through finish, fully permitted. Active ADU portfolio across Alhambra.
Request a Free EstimateQuality. Integrity. Craftsmanship.
Trustworthy Construction for Your Home
Expert construction and remodeling services delivered with quality, integrity, and care.
- Licensed & Insured
- Free Estimates
- On-Time & On-Budget
- Quality Craftsmanship
- Satisfaction Guaranteed
Credentials & Compliance
California CSLBLicense #1108418
Better Business BureauAccredited business standards
Bonded & InsuredGeneral liability + workers comp
About Us
Expert Construction. Deep-Rooted in Community.
OSEM Construction is a family-owned general contractor with over 10 years of work across San Marino, Alhambra, and greater Los Angeles. We handle the whole build, from rebar tied for the slab to the final coat of paint, with the same crew you meet on day one.
The philosophy is in the tagline our family put on the business card: A better living. A better space to come home to, a better process to get there, and a better record of permitted, inspection-passed work behind every project we hand off.
- Family Owned & Operated
- Permitted & Inspected Work
- Foundation to Finish
- Licensed CSLB #1108418
Our Process
How It Works
Four clear stages, every one documented. You know the schedule, the permits, and the next milestone before we move to it.
- 01
Initial Planning Session
We walk the project with you, lock down the scope, and put together a written estimate with realistic milestones.
- 02
Secure All Required Permits
We pull every permit your scope requires and schedule the inspections, so the work is documented and code-compliant from day one.
- 03
Verify Delivery of Approved Materials
Materials are reviewed against the spec before they hit the jobsite. Nothing gets installed that does not match what you signed off on.
- 04
Maintenance & Handoff
Final walkthrough, punch list, and a clear handoff packet covering warranties, finish specs, and the maintenance schedule.
Ready to put your project on paper?
Request a Free EstimateReliable. Trusted. Skilled.
Built on track record, not marketing.
Every claim below is something we can point at on the jobsite. The portfolio, the permits, and the license number are the receipts.
10+ years
Hands-on construction across the San Gabriel Valley
Foundation to finish
One licensed crew owns every phase of the build
CSLB #1108418
Licensed California general contractor, bonded and insured
Our Services
Foundation to finish for homes, businesses, and apartments.
One licensed crew, one accountable point of contact, and a written scope for every line of work. Homes · Businesses · Apartments.
Bathroom Remodeling
Marble counters, custom double-vanity carpentry, subway and hex tile, tub-to-finish work. Completed projects across San Marino.
Request a Free EstimateInterior Renovation
Drywall, paint, finish carpentry, custom fireplace surrounds, and flooring upgrades. Before-and-after transformations on residential interiors.
Request a Free EstimateFoundations & Concrete
Foundation prep, rebar layout, slab pours, and existing-structure underpinning. Inspection-passed foundation work on recent jobs.
Request a Free EstimateFraming & Structural Carpentry
Wood framing for additions, ADUs, and structural remodels. Rough framing through inspection signoff with rough plumbing and electrical in place.
Request a Free EstimateCommercial Build-Outs
Light-commercial interior remodels for offices and small businesses. Flooring, paint, finish carpentry, and ceiling refresh.
Request a Free EstimateWhy Choose Us
A licensed crew, a clear schedule, and a clean handoff.
Reliable & Timely
On-time delivery and crew accountability from foundation through finish, with milestones you can hold us to.
Customized Solutions
Every project is unique. We tailor scope, finishes, and sequencing to the way your household or business actually works.
Licensed & Insured
Fully licensed under CSLB #1108418 and insured. Permitted work, passed inspections, and clean documentation throughout.
Transparent Pricing
Written estimates that line-item the work. No vague allowances, no mid-project surprise invoices, no padded change orders.
Our Projects
San Marino · Alhambra · LAReal homes. Real ADUs. Real receipts.
A working portfolio from the San Gabriel Valley, mixed in-progress and finished. Foundation pours, framing inspections, tile installs, and final paint, all photographed on the jobsite.
Bathroom Remodel
Finished marble double-vanity bathroom in a San Marino home
Interior Renovation
Painted-brick fireplace with a floating wood mantel after interior remodel
Bathroom Remodel
Marble tub deck with hexagonal floor tile in a San Marino bathroom
Foundation
Rebar-laid foundation slab ready for concrete pour, inspection passed in Alhambra
Commercial
Light commercial office build-out with new wood-look flooring and fresh paint
Framing
Interior framing with window light after passing structural inspection
Electrical
New electrical sub-panel installation in a San Marino remodel
Interior Renovation
Interior renovation with skim-coat paint and finished flooring
Exteriors
Finished textured stucco exterior wall
Bathroom Remodel
Custom marble double-sink vanity with white cabinetry in a San Marino bathroom
Interior Renovation
Finished interior with wood-look flooring and floor-to-ceiling glass doors
ADU Build
Wood-frame ADU interior with floor joists, roof rafters, and slab in place
Recent Projects
A closer look at four recent builds.
Short case notes on what the scope was, what we ran into, and how the project landed. Photos are from the actual jobsite, not stock.
San Marino, CAFull bath, marble + custom carpentry
San Marino Bathroom Remodel
A full bathroom rebuild with custom double-vanity carpentry, honed marble countertops, and a paneled tub deck. Tile, plumbing rough-ins, and finish trim all completed in-house.
View Project- Alhambra, CA
Ground-up accessory dwelling unit
Alhambra ADU Build
Permitted ADU from foundation through framing, weatherproofing, and rough mechanical, electrical, and plumbing. Inspection signoffs at every stage on a tight residential lot.
View Project 
Los Angeles, CAExisting-structure underpinning
LA Garage Underpin
Underpinning an existing detached garage to support a planned conversion. Hand-dug pier sections, rebar tied per the structural engineer's plan, and inspection-passed pours.
View Project- Los Angeles, CA
Light commercial remodel
Commercial Office Refresh
Worn carpet and dated finishes pulled out, replaced with durable wood-look flooring, refreshed ceiling, and a clean repaint. Open during business hours by phasing the build.
View Project
Talk to a Contractor
Our team is here to answer your questions and help you get started on turning your vision into reality.
Our Service Areas
Serving the families of the San Gabriel Valley.
Active projects across San Marino, Alhambra, and greater Los Angeles. If your address is nearby and not on the list below, give us a call. We almost certainly cover it.
- San Marino, CA
- Alhambra, CA
- Los Angeles, CA
- Pasadena, CA
- South Pasadena, CA
- Arcadia, CA
- Monterey Park, CA
- San Gabriel, CA
Still Not Sure?
Frequently Asked Questions
Common questions from homeowners and property owners across the San Gabriel Valley.
What types of construction and renovation services do you offer?
We work as a full-service general contractor. That covers ADUs and home additions, bathroom and full-interior remodels, foundations and concrete, framing and structural carpentry, and light commercial build-outs. Foundation through finish, with one crew accountable for the whole scope.
How long does it take to complete a project?
Timelines depend on scope, permits, and material lead times. A bathroom remodel typically runs four to six weeks once demo starts. A ground-up ADU usually runs four to seven months from foundation through finish. You get a written milestone schedule with your estimate, so the timeline is on paper before we break ground.
Are your projects permitted and inspected?
Yes. We pull permits for every scope that requires them and schedule the inspections. Recent projects across the San Gabriel Valley have passed foundation, rough plumbing, rough electrical, and framing inspections on the first walkthrough.
Do you provide free estimates?
Yes. The first planning session and the written estimate are free. We walk the project with you, confirm the scope, and put numbers and milestones on paper so you can compare apples to apples before signing anything.