Mighty Buildings ADU Design & Permitting Nationwide

Mighty Buildings ADU Design & Permitting: The Chino Owner’s Guide

Mighty Buildings ADU design and permitting in Chino typically runs $8,500-$14,500 for the full permit set and design coordination, with most projects moving to plan check within 2-3 weeks of our first site visit. We stock the documentation templates, structural calcs, and city-specific submittal packages that Mighty Buildings units require, and we coordinate directly with Mighty Buildings’ engineering team on your behalf. Most Chino owners find us after their prefab unit has arrived or is in production and they realize the city’s planning department wants a site-specific drainage plan or a revised setback calculation that wasn’t in the factory package.

Call (909) 323-1107

Which Mighty Buildings Models This Applies To

We handle design and permitting for the full Mighty Buildings product line: the M1 one-bedroom (480 sq ft), M2 two-bedroom (700 sq ft), and the studio configurations. Each ships with a factory engineering package, but that package is generic to California Title 24, not to your specific Chino lot. The serial plate on your unit, usually found on the electrical panel door or the mechanical chase exterior, tells us which revision of the structural drawings we’re working with. Rev A through Rev D have different foundation anchorage details, and Rev D onward requires the enhanced shear-wall schedule that Chino’s building department started enforcing after the 2022 code cycle.

OEM versus aftermarket isn’t a parts question here, it’s a documentation question. Mighty Buildings provides the factory sealed engineering, but they do not provide the site plan, the Soils-7 geology review for Chino’s expansive clay, or the utility service load letter that Southern California Edison wants for any ADU over 400 amps. We source those in-house. If your contractor is telling you to “just get the permit yourself,” what they mean is they don’t want to absorb the risk of a plan-check revision. We do, under the same contract that covers your build.

Signs Your Mighty Buildings ADU Design & Permitting Is Failing

• City rejected your submittal for “incomplete site drainage.” Mighty Buildings’ standard package assumes a flat lot with no existing structures within 10 feet. Chino’s older neighborhoods near Central Avenue and the areas south of the 60 often have zero-lot-line conditions or historic drainage easements that the factory drawings don’t address. We remap your stormwater path to the street or an approved infiltration pit.
• Your contractor stopped work and said “the permit’s wrong.” This usually means the foundation detail on the permit set doesn’t match what your grading contractor actually poured. The document either says it or it doesn’t. We catch that mismatch before concrete, not after, by walking the site with the grading plan in hand.
• SoCal Edison won’t release the meter without a “verified load calculation.” Mighty Buildings’ electrical package lists the unit’s demand load, but Edison wants the combined service calculation for your main house plus the ADU. We provide that letter, stamped by our electrical engineer, as part of the permit set.
• Chino Planning flagged a “conflict with the General Plan.” Certain corridors, including portions of Pipeline Avenue and the area near Chino Airport, have height restrictions or design review overlays that standard factory packages ignore. We run the zoning check before the first submittal, not after the rejection.
• Your lender won’t fund until they see a “permit to construct.” Construction loans for prefab units often require the full permit set, not just the factory engineering. We package everything the underwriter needs, including the fire department access letter and the school fee calculation, in one binder.

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Replacement Cost & What’s Included

Mighty Buildings ADU design and permitting in Chino runs $8,500-$14,500 all-in, depending on whether your lot needs a Soils-7 report, a drainage redesign, or a utility service upgrade. That range covers our site survey, the full permit set including structural, electrical, plumbing, and energy compliance drawings, all city submittals, and responses to plan-check comments through permit issuance. We don’t charge separately for revision rounds. Under Haven Standard Clause 1, you receive a written price before any work starts, and under Clause 5, that scope is locked at signing.

What’s not in that range: the city’s permit fees themselves, which Chino bills directly and which typically run $2,800-$4,200 for detached ADUs under 750 square feet. We itemize that separately so you know exactly what goes to the city and what comes to us. Our 365-Day Done Right Promise covers the permit set: if Chino rejects for an error in our documentation, we fix it at our cost.

DIY or Call Us?

An owner can safely check three things before calling: confirm your Mighty Buildings serial number and revision, pull your property’s Assessor Parcel Number from the San Bernardino County site, and verify your lot’s zoning on Chino’s online GIS. What goes wrong fast: treating the factory engineering package as a permit-ready submittal. It isn’t. The structural calcs are real, but they’re not tied to your foundation, your soils, your utility service, or your city’s specific plan-check checklist.

We’ve seen owners lose six weeks and $3,000 in re-submittal fees because they filed the factory drawings without a site-specific drainage plan. Chino’s building department is thorough, not hostile, but they don’t coach you through corrections. We do. Call (909) 323-1107 and we’ll review what you have, no charge, and tell you exactly what’s missing.

FAQs