Service Area · Los Angeles County
General Contractor in Topanga, CA
New homes, fire rebuilds, ADUs and additions on Topanga's steep canyon lots, planned around septic systems, coastal zone rules and Los Angeles County permitting in the Santa Monica Mountains.
- Licensed California general contractor
- Custom homes, ADUs & additions
- Permits with LA County Public Works
- Written, line-item estimates
Topanga, CA
Building and Remodeling in Topanga
Simply Construction acts as the general contractor in Topanga for owners building or rebuilding on the steep, wooded lots of the Santa Monica Mountains. Topanga is unincorporated Los Angeles County, so permits come from LA County Public Works Building and Safety and LA County Regional Planning, and parts of the canyon also sit in the California Coastal Zone.
Building here means handling several site constraints at once: narrow canyon roads, septic systems, unstable slopes, protected habitat and a very high fire hazard. We plan for each of them before the design is locked, and we run the project, permits through final inspection, as a licensed California general contractor.
Local Knowledge
Building in Topanga Canyon
Topanga follows Topanga Creek and Topanga Canyon Boulevard through the Santa Monica Mountains, with communities such as Fernwood and the Old Topanga Canyon Road area, and with Topanga State Park and Red Rock Canyon Park surrounding much of it. Homes range from small older cabins to owner-built houses and newer homes engineered for the slope. Many sit at the end of narrow, winding roads where delivery trucks, concrete pumps and fire engines all have limited room.
Most Topanga homes are not on a public sewer, so onsite wastewater systems reviewed by LA County Environmental Health set real limits on bedrooms and additions. Where a property falls in the coastal zone, the county's Santa Monica Mountains Local Coastal Program applies, with its own habitat protections and coastal development permit process. Native oaks are protected under county rules as well.
Fire is the constant. The January 2025 Palisades Fire burned 23,448 acres across Pacific Palisades, parts of Malibu and parts of Topanga, and new homes in the canyon need LA County Fire approval of a fuel modification plan along with wildfire-resistant construction.
Services
Construction & Remodeling Services in Topanga
From ground-up homes to kitchens, here is how each of our services applies to Topanga properties.
Custom Home Building in Topanga
A custom home in Topanga starts with the land: a geotechnical investigation of the slope, a septic feasibility study, a fuel modification plan for LA County Fire and, in the coastal zone, the Local Coastal Program's habitat and permit rules. Once those constraints are mapped, the architect designs the house into the space that remains. We coordinate that consultant team and the county's plan check, plan a build that works on narrow access roads, and include the rooftop solar every new home needs under Title 24.
ADU Construction in Topanga
Topanga lots can support an ADU, but the septic system usually decides how. An added unit may need a larger or new onsite wastewater system approved by LA County Environmental Health, and steep terrain limits where a structure can go. Under state rules, a unit under 750 square feet carries no impact fees, which helps on a site where engineering already adds cost. In the coastal zone, the Local Coastal Program's limits on habitat and development area also apply, so the unit is sited with both in mind.
Garage Conversions in Topanga
A garage conversion is one of the more practical ways to add a unit in Topanga, because it reuses a structure that already has a building pad and access. The garage becomes an ADU or studio without new grading, and the state waives replacement parking for a garage converted to an ADU. The main questions are septic capacity for the new bathroom and kitchen, fire-safe upgrades to an older structure, and whether the garage sits on a sound foundation.
Room Additions in Topanga
Room additions in Topanga are shaped by the hillside and the septic system. A new bedroom can trigger a septic review, and footings on a slope follow the geotechnical engineer's design, often with deepened foundations or caissons. In the coastal zone, an addition may need a coastal development permit depending on its size and location. We check these early so the addition's footprint, cost and schedule reflect the real site.
Second-Story Additions in Topanga
Building up rather than out avoids new grading and habitat encroachment on a Topanga lot, which makes a second story worth a look. A house built decades ago needs a structural review of its foundation and framing before anything goes on top, and older owner-built additions may need to be documented first. County height limits and, in the coastal zone, the Local Coastal Program's scenic protections shape how tall the addition can be.
Garage Construction in Topanga
New garages in Topanga are often cut into the hillside, with retaining walls forming part of the structure. Engineering, grading permits and drainage design are part of the scope, and the driveway has to satisfy LA County Fire access requirements. We schedule concrete and material deliveries around traffic on Topanga Canyon Boulevard and the narrow side roads, and we build with ignition-resistant materials from slab to roof.
Whole-House Remodeling in Topanga
Many Topanga homes were built or expanded in stages, some without a clear permit record, and a whole-house remodel is the time to bring the structure, wiring, plumbing and septic up to date. We begin with an investigation of what is there, including any unpermitted work that needs to be legalized or removed. Replacing roofing, siding, vents and windows with fire-resistant materials is usually part of the plan.
Kitchen Remodeling in Topanga
Topanga kitchens often sit in houses shaped by the canyon, with compact footprints, split levels and views into the trees. We rework layouts within those limits, add storage, upgrade electrical service and ventilation, and replace older gas lines where needed. On a septic system a kitchen remodel rarely changes the load much, though a garbage disposal can, so fixtures are chosen with the system in mind.
Bathroom Remodeling in Topanga
Adding or enlarging a bathroom in Topanga often calls for a septic review, since the system's design is tied to the home's bedrooms and fixtures. We handle that evaluation, then build with proper waterproofing, outside-vented fans and water-efficient fixtures. On split-level and hillside houses, plumbing runs and access for tile and materials are planned before demolition so the job does not stall halfway.
Fire Rebuilds in Topanga
The 2025 Palisades Fire reached parts of Topanga, and emergency orders issued after the January fires let owners rebuild the same type of structure in the same location at up to 110 percent of the original footprint and height with streamlined review. We manage Topanga rebuilds through LA County Public Works, coordinating county fire, septic and, in the coastal zone, coastal review together. The new home is built with ignition-resistant construction, and construction access is planned around the canyon's roads.
Junior ADUs (JADU) in Topanga
A junior ADU works well in Topanga because it creates a separate suite inside the existing house without grading or new habitat impacts. It is limited to 500 square feet, must include at least an efficiency kitchen, and since it stays within the home's walls, it avoids most of the site issues a detached unit raises. If the JADU adds a bedroom, the septic system still has to be evaluated by the county.
SB 9 Lot Splits & Duplexes in Topanga
SB 9 is a hard fit for most Topanga lots. The law covers cities and urbanized unincorporated areas only, parcels in a Very High Fire Hazard Severity Zone are excluded unless they adopt the state's fire mitigation measures, a designation that covers much of the canyon. Steep lots, septic limits and coastal zone rules add further barriers. We can review a specific parcel, but most Topanga owners get more from an ADU or a junior ADU.
Patios, Decks & Outdoor Living in Topanga
In Topanga, outdoor space is often built as decks projecting off the slope or terraces held by retaining walls. In a very high fire hazard area, decking must be ignition-resistant or noncombustible, and structures near the house must respect the approved fuel modification plan. We also work around protected oaks, which limit where footings and hardscape can go, and we design drainage so runoff does not undermine the slope.
Why Choose Us
Why Topanga Homeowners Choose Simply Construction
Licensed, Bonded and Easy to Verify
Simply Construction inc. is a licensed California general contractor, CSLB [CSLB LICENSE # PLACEHOLDER]. State law requires a license for any job of $1,000 or more in labor and materials, and anyone can check a contractor's license, bond and workers' compensation status on the CSLB website in about a minute. We encourage every Topanga homeowner to do exactly that before signing with anyone, including us.
Permits Handled With LA County Public Works
Most delays on large residential projects start at the permit counter. We prepare the drawing set, coordinate structural and Title 24 energy calculations, answer plan-check comments and schedule inspections with LA County Public Works, so you are not the one chasing corrections. For ADUs, state law requires the agency to act on a complete application within 60 days, and a complete, well-coordinated submittal is what starts that clock.
Written, Line-Item Estimates
Before you commit, you receive a written estimate that breaks the project into its real parts: design and engineering, permit and utility fees, foundation, framing, systems, finishes and site work. Allowances are named and priced, so you can see where your selections move the budget. If the scope changes, the numbers change on paper first, never as a surprise on the final invoice.
Nearby Service Areas
We Also Build Near Topanga
FAQ
Building in Topanga: Common Questions
Who handles building permits in Topanga?
Topanga is unincorporated, so LA County Public Works Building and Safety issues building permits and LA County Regional Planning handles zoning and, in the coastal zone, coastal development permits under the Santa Monica Mountains Local Coastal Program. LA County Fire reviews fuel modification and access, and county Environmental Health reviews septic systems. We coordinate those reviews for you.
Can I rebuild in Topanga after the Palisades Fire?
For most lots, yes. Emergency orders issued after the January 2025 fires allow like-for-like rebuilds, meaning the same type of structure in the same location at up to 110 percent of the original footprint and height, with streamlined review. The rebuild still needs county permits, current wildfire construction standards and a septic review. We can help you weigh a like-for-like rebuild against a redesigned home.
Why does septic matter so much for Topanga projects?
Most homes in the canyon rely on onsite wastewater systems, and each system's design is tied to how many bedrooms and fixtures the house has. Adding a bedroom, an ADU or a bathroom can require LA County to confirm the system can handle the load, or require a new system. Steep slopes and soil conditions limit where leach fields can go, so septic planning comes first.
Start Your Project
Start Your Topanga Project
Tell us what you are planning. We will visit the property, talk through options and costs, and send a written, line-item estimate.
Licensed California General Contractor · CSLB [CSLB LICENSE # PLACEHOLDER]