A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Home Addition Contractor Across San Lorenzo
Putting an addition on a San Lorenzo home usually runs $180,000 to $420,000 depending on scope, and the biggest variable isn’t square footage. It’s whether your contractor knows what’s under your slab and above your roofline. Most mid-century tract homes here sit on post-tensioned concrete, and any plumber or builder who cuts into that foundation without X-ray scanning first can compromise the entire structure in about ten seconds. That’s a $60,000 mistake on a $250,000 project. We’re Lodgewick ADU San Francisco, and our Home Addition Contractor team has been working on exactly these homes since 2010. Call (707) 760-0502 for a written, line-item quote before any work starts.
Why Lodgewick ADU San Francisco Is San Lorenzo’s Preferred Home Addition Contractor Company
San Lorenzo homeowners don’t ask us for a sales pitch. They ask us whether we’ve handled post-tensioned slabs, whether we know the setback rules on Via Manzanas versus Bockman Road, and whether our price today is the price at rough inspection. The answers are yes, yes, and yes, in writing. Our crews work Home Addition Contractor in San Lorenzo jobs every month, which means we already know the building department’s expectations for shear wall documentation on second-story additions and which inspectors want to see X-ray scan reports before signing off on garage slab trenching. That familiarity saves you weeks and prevents the red-tag stops that happen when an out-of-town crew shows up with plans that ignore San Lorenzo’s parking and setback requirements. The work carries the 365-Day Done Right Promise: if something isn’t right within a year, we come back and fix it. That’s in writing, on every project, before the first tool comes off the truck. And when you call (707) 760-0502, a live person answers. Every time.
Garage Addition Contractors in San Lorenzo
Garage Addition Contractors working in San Lorenzo confront a specific housing stock: single-story ranch homes from the 1940s through 1960s, built on flat, tight lots with attached garages. Converting or expanding that garage into living space typically runs $95,000 to $220,000 in this market. The price depends on whether you’re keeping the existing slab, cutting into it for a bathroom, or building over the garage as a second story. On many San Lorenzo properties, the only way to add real square footage is up, and that means the existing foundation and roof truss condition dictate the entire structural approach. A garage-to-studio conversion where the slab stays intact and plumbing runs along the wall instead of through the concrete is fundamentally different from a garage addition with a full bath, where trenching triggers post-tension cable X-ray work. We’re a licensed, insured, bonded contractor, and every quote includes the scanning, permits, and structural engineering needed to pass inspection the first time.
Over-Garage Second Story Additions
When the lot won’t allow a side expansion, the standard answer in San Lorenzo is building up. Over-garage additions on these homes usually land between $160,000 and $280,000. The existing garage headers, foundation capacity, and roof trusses often need reinforcement before vertical construction begins, and the plans must document compliance with local wind-load requirements. We’ll show you exactly what gets reinforced, in writing, before you commit.
Post-Tensioned Slab Trenching for Garage Baths
San Lorenzo’s post-tensioned slabs make adding a bathroom inside a converted garage a high-stakes job. Before any saw touches concrete, we X-ray scan to map the cable grid. A single severed cable can fail the entire foundation, and the repair cost dwarfs the scan fee. Our quotes include the scan line item so you’re not surprised by it later, and the report goes into your permit package.
Bathroom Addition Contractor in San Lorenzo
Bathroom Addition Contractor work in San Lorenzo is disproportionately slab-cut work. These ranches were built with one or one-and-a-half baths, and homeowners adding a second or third bath almost always need new drain lines through a post-tensioned foundation. A bathroom addition in San Lorenzo typically runs $48,000 to $95,000 depending on whether you’re converting a closet, bumping out a wall, or going into converted garage space. The spread isn’t about fixtures. It’s about what’s under the floor and how far the new drain line has to travel. On Via Manzanas, our crew recently completed a garage-to-studio ADU where the slab was post-tensioned. Before trenching for the new bathroom drain, we brought in a concrete X-ray scanner to map the cable layout and avoid a catastrophic cut. The structural design was upgraded to meet the required 85 mph wind exposure, and every shear wall and roof tie-down detail was documented for the inspector. That’s how we do every bathroom addition here.
Bump-Out Bath Additions
When you only need forty square feet and the lot allows it, a bump-out bath addition can work well on a San Lorenzo ranch. Expect $55,000 to $85,000 for a full bath bump-out with foundation work, framing, roofing, plumbing, electrical, and finishes. The foundation line where the bump-out meets the original slab needs careful detailing to prevent differential settlement, especially in the wet winter months when soil moisture shifts.
Second-Story Bath Additions
Adding a bathroom on a new second story over the original house or garage changes how the whole structure resists wind and seismic loads. These projects generally fall between $70,000 and $120,000 for the bath portion within a larger second-story addition. The answer isn’t always to add shear wall everywhere; sometimes it’s a post-and-beam system that redistributes the load. We’ll show you the engineering, not just the tile selection.
Trusted Brands We Service in San Lorenzo
We don’t push a single prefab system on every lot. The right choice depends on your existing structure, your setback constraints, and what you can actually build under San Lorenzo’s current code. That’s why we work hands-on with brands like Boxabl and Plant Prefab for compact, code-compliant ADU builds where speed and consistency matter, and we use Tuff Shed and James Hardie materials where a traditional stick-built addition makes more sense. We know which of these products carry wind-load ratings that satisfy the local building department, and which ones don’t. Our team can walk you through the differences in person, and we stock common James Hardie siding profiles and trim locally so a San Lorenzo job doesn’t stall waiting on materials from out of state. Call (707) 760-0502 and ask us which system fits your lot.
Common Home Addition Contractor Problems We See in San Lorenzo Homes
- Cutting into a post-tensioned slab without X-ray scanning. A cable cut severs the structural integrity of the whole foundation. Contractors unfamiliar with San Lorenzo’s 1940s to 1960s housing stock make this mistake because most other cities don’t require the scan.
- Using garage conversion plans that ignore San Lorenzo’s setback and parking rules. When a converted garage triggers a second-story or over-garage addition, the original off-street parking often has to be replaced. Missing this detail gets a project red-tagged mid-build.
- Failing to document wind-load compliance in the final permit package. San Lorenzo requires 85 mph wind exposure compliance on additions. Without the shear wall and tie-down documentation in your permit file, an insurance claim after a winter storm can get denied because you can’t prove the work met code.
- Underestimating drainage needs on flat lots. San Lorenzo’s cool, wet winters put real water against slab edges and addition foundations. Skipping proper drainage and moisture management rots sill plates and causes slab-edge cracking within a few seasons.
Pricing for Home Addition Contractor in San Lorenzo, CA
Here are real numbers for San Lorenzo’s market. A simple garage-to-studio conversion on an intact slab starts around $95,000. A one-bathroom addition runs $48,000 to $95,000. A full over-garage second-story addition lands between $160,000 and $280,000. A whole-home addition with multiple rooms typically runs $180,000 to $420,000. The difference between the low and high ends comes down to foundation work, structural reinforcement, wind-load documentation, and whether the slab requires X-ray scanning before plumbing cuts. We give you a written price before any work starts, every single time, and that price doesn’t change at the door. Call (707) 760-0502 to schedule a free estimate with a written, line-item quote.
We Also Serve Cities Near San Lorenzo
Our crews work daily in San Leandro, Oakland, Hayward, and Moraga, where the housing stock shifts from slab ranches to hillside foundations and the code requirements change with it. If you’re outside San Lorenzo proper, call us anyway. We’ll tell you straight whether your lot falls within our service area and what the first site visit looks like. The phone number is the same either way: (707) 760-0502.
Serving San Lorenzo, CA - Our Local Coverage Area
We’re based in the San Lorenzo area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About Home Addition Contractor in San Lorenzo
San Lorenzo additions must be designed to meet an 85 mph wind exposure requirement. That affects shear wall placement, roof tie-downs, and the documentation we file with your permit package. A cheap quote that skips this engineering won’t pass inspection and can leave you without proof of compliance for insurance. Call (707) 760-0502 for a written quote that includes the wind-load calcs.
If your home was built between the 1940s and 1960s, yes, almost certainly. Most San Lorenzo slabs are post-tensioned, and cutting into one without scanning can sever a cable and compromise the foundation. We include the scan in every quote where trenching is planned, and the report goes into the permit file.
Setback and parking requirements often mean the original off-street parking space must be replaced or reconfigured when a garage conversion triggers a second-story addition over it. San Lorenzo’s planning department enforces this strictly, and missing it in your plans gets the project stopped. We handle the parking and setback review during design, before you’ve committed any construction money.
A home addition triggers a reassessment of the newly added square footage under California Proposition 13, so yes, your property tax base will increase by the assessed value of the addition. The exact amount depends on the county assessor’s valuation. We’re not tax advisors, but we’ll give you the square footage and permit records you need to plan for it. Call (707) 760-0502 for a free estimate on the build itself.
The permit package plus the final inspection approval records from Alameda County document compliance. Specifically, your file needs the structural engineer’s wind-load calculations, shear wall schedules, roof tie-down details, and the signed final inspection card. We assemble all of this and give you a copy at project close. It’s part of the 365-Day Done Right Promise, in writing.
Call (707) 760-0502 today to schedule your free estimate. A live person answers, every time.
Written by Russ Delmar, Owner at Lodgewick ADU San Francisco, serving San Lorenzo since 2010.
