Mighty Buildings ADU Site Prep & Utilities in Los Angeles: What to Know First
Site prep and utility work for a Mighty Buildings ADU in Los Angeles typically runs $35,000 to $85,000 depending on whether you need a full foundation, trenching, panel upgrades, or lateral replacements. We provide independent Mighty Buildings site prep and utilities as part of a single design-build contract with a written price before any work starts. Permits, drawings, and construction are one scope, one price, one responsible party.
This page is for homeowners who own or have ordered a Mighty Buildings unit and need the ground, power, water, gas, and drainage work done before or after delivery. We serve all of Los Angeles, from Silver Lake to West Adams to Sherman Oaks. Call (971) 497-2402 for a written estimate. We are an independent Mighty Buildings service provider, not a manufacturer-authorized installer.
How Mighty Buildings Products Affect Site Prep and Utilities
Mighty Buildings panels are factory-fabricated and arrive with mechanical connection points, load assumptions, and utility stub locations already fixed. That changes what happens on the ground, and it changes what goes wrong on this scope. Here are the patterns we see across Los Angeles:
- Foundation tolerance vs. panel fit. Mighty Buildings units assume a foundation flat within a tighter tolerance than typical site-built ADU framing. A slab poured to conventional residential flatness can leave gaps at panel joints that are visible and, over time, allow moisture. We check the spec before the concrete goes in and verify flatness with a laser after the pour.
- Electrical panel undersizing on mid-century lots. Many Los Angeles homes built between 1945 and 1975 have 100-amp service. A Mighty Buildings unit with electric heat, induction cooktop, and mini-split routinely pushes load over 100 amps combined with the main house. We quote the panel upgrade as part of the written price, not as a surprise change order mid-job.
- Plumbing lateral conflicts at the property line. Mighty Buildings ADUs connect to sewer through a new lateral or an existing line. On narrow Los Angeles lots, the connection point often sits under an alley or a slab driveway, and the city requires specific depth and cleanout locations. We pull the permit and coordinate the LADBS inspection so the lateral passes the first time.
- Gas line routing through panelized walls. If your unit includes a gas appliance, the stub location is set at the factory. We have seen cases where the site gas line routing didn’t match the panel penetration because the site plan shifted during permitting. We verify penetration locations against the approved drawings before trenching, so you do not cut into a $40,000 wall assembly later.
- Drainage and stormwater on steep Los Angeles hillsides. Units placed on a downslope require retaining and drainage control before delivery. Mighty Buildings panels are heavy, and the crane or placement equipment needs stable ground. We design the pad, retaining, and drainage as one scope so the unit does not sit in a bowl that collects water every winter rain.
Our Mighty Buildings ADU Site Prep & Utilities Process
We run this scope as a sequence, and every step corresponds to a line item you can see before signing.
- 1
Site walk and measurements. We check the actual utility stubs, property lines, existing grade, and the Mighty Buildings spec sheet. We confirm what the factory sent you against what the site will actually accept.
- 2
Written scope and price. Single document covering foundation, utilities, drainage, and any panel work. The price is written, per Haven Standard Clause 1, before any work begins.
- 3
Permit set and submittal. We produce the drawings and the utility plans and submit to LADBS. Our permit sets go through on the first round in most cases, which matters because every resubmittal adds weeks and inspection fees.
- 4
Groundwork and utilities. We coordinate the trenching, the lateral, the panel, the gas line, and the pad with the Mighty Buildings delivery sequence. The crane does not show up to a site that is not ready.
- 5
Backfill, compaction, and drainage. We bring the site to final grade, document with photos at each phase, and run water to confirm drainage takes it away from the unit.
- 6
Final inspection and photo record. You receive a documented photo record of what was built, what was connected, and what the inspector signed off on. That record is yours.
What Mighty Buildings ADU Site Prep & Utilities Costs in Los Angeles
Here are the line-item ranges we quote in Los Angeles, based on hundreds of ADU site packages we have priced since 2015:
- Foundation and slab: $18,000 to $35,000
- Electrical panel upgrade to 200 amps: $4,500 to $9,500
- Sewer lateral: $6,000 to $14,000 depending on depth and length
- Gas line extension: $2,500 to $6,500
- Drainage and grading: $5,000 to $15,000
- Trenching and utility stubs to the unit: $4,000 to $10,000
What moves the price: lot slope, soil type (expansive soils in South LA require different compaction), panel distance, whether you have an existing cleanout, and whether the city requires a separate water meter. We name every number before work begins. Call (971) 497-2402 and we will put it in writing.
Why Los Angeles Homeowners Call Ellery ADU Studio for Mighty Buildings Work
We have designed, permitted, and built over 900 ADUs since 2015, and every one of them started with a written price. The Mighty Buildings unit you ordered is a factory product. The site it sits on is not. Our job is to make the ground and the utilities match the spec, and to document everything so there is no ambiguity between what the factory promised and what the site required.
We also specify and coordinate Abodu, Cover, and Dvele systems. If you are still deciding between prefab manufacturers, we can walk you through the differences in foundation and utility requirements between them, because the numbers differ and the site work is where those differences show up first. Nadia Ellery founded this studio in Los Angeles, and the practice is built around one clause we repeat on every project: the drawing either satisfies the inspector or it doesn’t. Let’s make sure it does.
Under our 365-Day Done Right Promise, if the site work is not built to the permitted drawings, we make it right. In writing, before the project starts. Call (971) 497-2402 for a written estimate, or bring us another bid for a free second opinion.
FAQs
No. The Mighty Buildings warranty covers the factory-built panels and the unit assembly. The foundation, trenching, utility connections, and drainage are site work and fall outside the manufacturer’s warranty. That is why we quote and build this scope as a separate written contract with its own workmanship warranty.
Some parts yes, most parts no. Gas, water, and sewer lateral connections must tie into the unit’s fixed stub locations, so those are done after placement but must be designed and permitted before delivery. The foundation and pad, obviously, must be done before. We sequence the schedule so you never pay for a crew standing around waiting on delivery. Call (971) 497-2402 and we will map the sequence for your specific lot.
Most Mighty Buildings site packages in Los Angeles run 5 to 10 weeks from permit issuance to final inspection, depending on slope, panel upgrade, and DWP meter timing. LADBS plan check and DWP utility approval are often the longest leads, which is why we submit early and track both threads weekly. If you already have a written estimate from another firm, we can review it free and tell you whether the schedule and scope look realistic.
Yes. We pull all permits through LADBS under our license. That includes grading, sewer, electrical, and any required retaining or Soils reports. We do not start any work without a permit and we do not ask you to pull anything yourself.
No, unless we uncover a site condition that was invisible before excavation, such as a buried concrete foundation from a previous structure or an unmapped sewer line conflict. If that happens, we document it with photos, show you the line item, and get written approval before proceeding. No door-side upsells, no scope creep. That is Haven Standard Clause 5, and it is in every contract we write.
Written by Nadia Ellery, Principal, Ellery ADU Studio at Ellery ADU Studio, serving Los Angeles and nearby areas.