Mighty Buildings Site Prep & Utilities: The Los Angeles Owner’s Guide
If your Mighty Buildings ADU is sitting on a failing foundation pad, has shifted out of level, or the utility trenching wasn’t done right the first time, we handle it. Site prep and utilities typically run $8,500 – $22,000 installed in Los Angeles depending on scope: foundation pad repair, new trenching for water/sewer/electrical, grading, and compaction. Most owners discover the problem the same way: doors that no longer close square, a slab crack that widens after rain, or a PG&E or LADWP hookup that got red-tagged.
We’re an independent contractor, not affiliated with Mighty Buildings, but we install, prep, and repair sites for their panels every month. If your site work is failing, the panel system above it will follow. Here’s what you need to know before you spend a dollar.
Key Takeaways
- Mighty Buildings panels are light, but they still need a properly engineered foundation. Site prep failures show up as panel misalignment first.
- Los Angeles hillside lots, expansive clay soil, and seismic requirements change what “site prep” means. A flat pad in Reseda is not the same job as a slope in Mount Washington.
- We stock the utility conduit, meter bases, trenching specs, and foundation repair materials we need on our trucks, so we don’t run back and forth to supply yards on your dime.
- Every price goes in writing before we dig. No change orders because “we found something.” We quote for what we find during the walk, not after the trench is open.
Which Mighty Buildings Models This Applies To
Mighty Buildings manufactures panelized ADU kits in a few core series, and the site work underneath them matters for every one. We handle site prep for the Mighty Mod, Mighty House, and any custom Mighty Buildings panel assembly. The panels themselves are fiber-reinforced polymer composite, not wood framing, which means the panels don’t rot or warp, but they also don’t forgive a foundation that’s off by even an inch. When a slab settles unevenly or piers weren’t set deep enough, the panel seams open up and you’ll see it at the corners first.
Here’s the compatibility gotcha most owners don’t know: Mighty Buildings panels rely on precise anchor-bolt placement. If the original foundation contractor used the wrong bolt layout or undersized the bolts, replacing the part does nothing until the site work is corrected. We pull the original foundation plan, verify anchor bolt spacing on-site, and match the repair to the panel series you have. If you’re unsure which model you own, check the serial plate on the interior of the main wall panel near the electrical panel. The series name is printed there, and we can identify it from a photo if you text it over.
Signs Your Mighty Buildings Site Prep & Utilities Is Failing
- Doors and windows bind or no longer latch. This is almost always slab settlement or pier movement. Composite panels don’t sag on their own, but they shift when the ground below them moves.
- Water pools near the foundation after rain. Los Angeles gets concentrated rain events, not steady drizzle. If your drainage or grading wasn’t sloped correctly, water collects against the pad and accelerates settlement. We fix the grade, not just the symptom.
- Cracks in the slab wider than a quarter-inch. Hairline cracks are common and usually cosmetic. A widening crack with vertical displacement means the soil underneath is moving. That’s a compaction or pier-depth problem.
- Utility trench lines sinking or collapsing. If your electrical conduit or water line trench was backfilled without proper compaction, you’ll see a visible depression running from the street or main house to the ADU. The utility line itself may still work, but the trench is slowly crushing it.
- Red tags or failed inspections from LADWP or SoCalGas. When the original trench depth was too shallow, or the conduit separated, the utility won’t energize the line. We re-trench to code depth, install new conduit, and get the inspection re-booked.
Replacement Cost & What’s Included
In Los Angeles, here’s what we typically see for Mighty Buildings-related site repair work, installed and permitted:
- Minor grading and drainage correction: $2,500 – $5,500. Includes re-sloping, compacting, and drainage swale or French drain as needed.
- Foundation pad repair (localized slab section): $4,000 – $9,000. Cutting out and repouring a settled section, then re-anchoring the panels.
- Full utility re-trench (water, sewer, electrical): $6,000 – $14,000 depending on run length and depth. Includes new conduit, backfill with compaction, and inspection coordination.
- Complete site prep for a new Mighty Buildings unit: $12,000 – $22,000. Full grading, compaction, slab or pier foundation, utility stubs, and panel-ready anchor bolt layout.
Every quote includes parts, labor, disposal, and the permit inspection. We write it down before we start, and the 365-Day Done Right Promise covers the work for a full year in writing. If a covered repair fails within that year, we come back on our second visit at no charge.
DIY or Call Us?
You can check a few things yourself without risk: take photos of any new cracks, mark the date, and watch whether they widen over a few weeks. Check that downspouts discharge at least three feet from the foundation. Walk the utility trench line and photograph any depressions. That’s useful information for us to have before we arrive.
What you shouldn’t do is attempt to dig out a utility trench or re-level a slab yourself. Utility lines in Los Angeles are buried at specific code depths, and hitting a live electrical or gas line while digging is a fast way to a serious injury. Slab and pier work also requires permits and inspections. One call to (903) 568-7222 gets you a straight answer and a free estimate. We’ll tell you what we’d do, what it’ll cost, and put it in writing before anything gets dug.
FAQs
A properly engineered and compacted site should last the life of the structure. In Los Angeles, the main threat is expansive clay soil that swells with winter rain and shrinks in summer drought, so the key is soil compaction and drainage done right the first time. We build for that movement, not against it.
Yes, in most cases. We can cut out and repour a localized settled section, then re-anchor the Mighty Buildings panels to the new concrete, as long as the failure is isolated. If the entire pad was poured without compaction underneath, full replacement is sometimes the only honest fix. We’ll tell you which one you’re facing and why. Call (903) 568-7222 for an exact quote, estimates are free.
A typical utility trench repair or localized pad fix takes three to five working days from first dig to inspection. Full site prep for a new Mighty Buildings unit usually runs two to three weeks including permit sign-off. We’ll give you a start date and a daily update once we’re on site.
We keep standard anchor bolts, panel-ready form hardware, utility conduit, meter bases, and compaction equipment on our trucks. For site-specific material like engineered slab rebar or specialty retaining components, we order ahead so it’s on site the day we start. No waiting on materials once the job is underway.
Need a straight answer about your Mighty Buildings site prep or utilities in Los Angeles? Call (903) 568-7222 and ask for a free estimate. Every promise goes in writing before a single shovel turns.
Written by Troy Eastman, Owner & Lead Builder, Benson ADU Builders at Benson ADU Builders, serving Los Angeles and nearby areas.
