Mighty Buildings Garage Conversion ADU Nationwide

Mighty Buildings Garage Conversion ADU: The San Bernardino Owner’s Guide

We stock and install Mighty Buildings-compatible replacement components for garage conversion ADUs in San Bernardino, with most installed repairs running $2,800-$6,400 depending on the subsystem and whether the original panel connections need re-certification. Most parts are on our truck or available within 24 hours through our Dvele and Cover supplier network. Homeowners usually notice the failure first as a climate-control alarm or a panel seam gap after a Santa Ana wind cycle, not as a sudden collapse.

Call (909) 359-6463

Which Mighty Buildings Models This Applies To

Mighty Buildings produces two shell systems relevant to garage conversions in San Bernardino: the standard Mighty House series (typically 350-700 sq ft for garage footprints) and the larger Mighty House Duo, which occasionally gets spec’d for double-garage sites near the University District. The critical identifier is the 12-digit production label inside the utility chase, not the marketing name. That label tells us whether your unit shipped with the first-generation MEP chase (pre-2022, rectangular junction box) or the revised circular-hub version that handles San Bernardino’s 105°F summer load differently.

We specify OEM Mighty Buildings panels when the original fire-resistance rating must stay intact for your certificate of occupancy. For non-structural components - exterior trim, gasket systems, flashing transitions - we often source equivalent-grade material from Cover’s compatible line, which carries the same ASTM E84 rating at roughly 30% less lead time. The gotcha: mixing first-gen and second-gen chase components voids the thermal bridging warranty. We check that serial prefix before quoting.

Signs Your Mighty Buildings Garage Conversion ADU Is Failing

• Panel seam separation at the roof-wall junction. The 3D-printed composite expands differently than traditional stick framing, and San Bernardino’s 40-degree daily temperature swings in spring accelerate the fatigue. You’ll see a hairline crack in the exterior finish or feel a draft at the interior corner.
• HVAC mini-split short-cycling or failure to hold setpoint. Mighty Buildings units ship with a dedicated load calculation based on sealed-envelope performance. If a panel gasket degrades, the system was never sized for that leakage. The compressor runs constantly, then faults.
• Moisture staining on the interior face of exterior panels. The composite shell is hydrophobic, but the proprietary gasket at penetrations isn’t. Failed gaskets let irrigation or rare driving rain wick behind the finish. We see this most on north-facing walls in the Del Rosa neighborhood where sprinklers hit the same spot daily.
• Electrical arc-fault tripping with no load attached. The pre-wired chase uses compression fittings that can loosen in transit from the factory to your slab. Intermittent trips, especially after seismic activity, usually trace to a single loose junction.
• Slab settlement visible at the threshold. Garage conversions in San Bernardino often rest on the original 4-inch garage slab without a stem wall. If that slab wasn’t post-tensioned (most pre-1990 garages aren’t), differential settlement cracks the panel-to-sill seal. The door sticks before you notice the gap.

Replacement Cost & What’s Included

For San Bernardino garage conversion ADUs with Mighty Buildings shells, component replacement typically runs:

• Panel gasket and seal restoration: $2,800-$4,200
• MEP chase junction repair or replacement: $3,600-$5,800
• Single panel replacement (OEM, fire-rated): $4,800-$8,200
• Slab-edge remediation with sill seal replacement: $5,200-$9,400

The range reflects three variables: whether we need to match a discontinued finish texture, whether the city requires a re-inspection of the modified envelope (San Bernardino does for panel swaps over 32 sq ft), and whether your original slab needs a moisture barrier retrofit we couldn’t see until demobilization. Under Haven Standard Clause 1, the written price you receive before work starts locks that scope. Clause 5 prohibits change orders for conditions we should have identified in our site documentation, which we share with you as a photo record before quoting.

Every Mighty Buildings repair carries our 365-Day Done Right Promise on workmanship, plus the manufacturer’s remaining material warranty where OEM parts apply.

DIY or Call Us?

An owner can safely check three things: the production label location (inside the utility chase, left side), the GFCI test button function, and whether the exterior stains align with sprinkler or drainage patterns. Document what you find with photos; we use those during triage.

What you should not attempt: panel removal (the composite is structural and the lifting sequence matters), electrical chase disassembly (240V pre-wired runs with factory compression fittings), or gasket replacement behind the finish layer. The fire-resistance rating is assembly-dependent; one wrong sealant choice and your certificate of occupancy is void. We’ve re-permitted three San Bernardino conversions where well-meaning owners used big-box caulk and the inspector flagged it.

Call (909) 359-6463 and we’ll walk through what you’ve observed. If it sounds like a truck-roll situation, we’ll schedule a documented site visit.

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