Plant Prefab New Detached ADU Nationwide

Plant Prefab New Detached ADU: The San Bernardino Owner’s Guide

We stock and install replacement parts for Plant Prefab new detached ADUs across San Bernardino, with most calls resolved same-day. Typical installed pricing runs $340-$1,200 for component-level repairs and $180,000-$280,000 for full unit replacement, depending on model series and site conditions. Most Plant Prefab owners first notice trouble when the unit’s MEP chase shows moisture staining near the roof-to-wall junction, or when the mini-split lineset pressure drops trigger the inverter lockout - both signs that the factory-sealed envelope has been compromised.

Call (909) 359-6463

Which Plant Prefab Models This Applies To

Plant Prefab’s current detached ADU lineup centers on the LivingHome 10 and LivingHome 16 series, with earlier RPA modules still in service across San Bernardino County. The critical compatibility marker is the four-digit manufacturing date stamped on the electrical panel door: units built before Q3 2021 use a 2×6 wall assembly with Rockwool continuous exterior insulation, while later production shifted to ZIP System R-sheathing with integrated taping. The roof-to-wall flashing detail changed between these runs, and the part numbers do not cross over.

For the MEP chase boot - the most common failure point we see in San Bernardino’s Santa Ana wind conditions - OEM specifies an EPDM compression seal with stainless draw-band. We also source a reinforced silicone aftermarket equivalent rated for 180°F continuous service, which outperforms OEM in high-UV exposure. The LivingHome 10 uses a single 4-inch chase; the 16 uses dual 4-inch chases or one 6-inch depending on HVAC spec. Check the chase collar diameter before ordering. The label is inside the chase, visible with a flashlight through the exterior louver.

Ellery ADU Studio San Bernardino is an independent service provider, not affiliated with Plant Prefab.

Signs Your Plant Prefab New Detached ADU Is Failing

• Moisture staining on interior ceiling panels near the chase penetration. The factory EPDM boot loses compression set after 6-10 years in San Bernardino’s heat-cycling climate. Once the seal gaps, wind-driven rain enters during Santa Ana events and tracks along the chase interior.
• Mini-split inverter displays error code E1 or flashes the outdoor unit LED three times. This indicates low refrigerant pressure. The lineset runs through the MEP chase, and a failed chase seal lets the insulation degrade, causing thermal loss at the flare joint and eventual pinhole leaks in the soft copper.
• Exterior louver rattles or detaches in wind gusts. The aluminum louver mounts to a PVC subframe that UV-degrades faster than the metal. The mounting tabs crack, and the louver becomes a projectile risk. We see this most on west-facing units in the Del Rosa and Arrowhead neighborhoods.
• Floor-level cold spots or condensation at the base of wall panels. The bottom plate gasket, a closed-cell foam strip compressed at factory assembly, settles over time. In Plant Prefab units with slab-on-grade installation, this creates a thermal bridge where conditioned air meets the concrete edge.
• Interior panel seams visible or “oil-canning” between fasteners. The magnesium oxide board facing expands differentially from the steel stud behind it. This is cosmetic until the facing cracks, but it signals that the panel’s vapor profile has shifted and the assembly is no longer performing to its designed permeance.

Replacement Cost & What’s Included

Component repairs for Plant Prefab detached ADUs in San Bernardino typically run $340-$1,200 installed, depending on which assembly fails and access conditions. A chase boot replacement with re-flashing and lineset pressure test lands at $680-$920. Full panel replacement, when the MEP chase has leaked long enough to degrade the wall cavity, ranges $4,200-$7,800 including temporary weather protection, cavity drying, and re-sealing to factory spec.

These are written prices, confirmed on site before work starts, per Haven Standard Clause 1. The scope locks at signing - no door-side additions. Our truck stocks LivingHome 10 and 16 chase boots, louver subframes, and bottom plate gasket material in standard widths. Work carries a 365-Day Done Right Promise: if the repair does not perform as specified, we return and correct it at no charge.

Full unit replacement, when repair is no longer economical, runs $180,000-$280,000 all-in: permit set through final inspection, site prep, utility tie-ins, and commissioning. Tell me the lot dimensions and I can give you a real number - not a range so wide it’s useless.

DIY or Call Us?

An owner can safely inspect the exterior louver condition and photograph any staining for documentation. Do not remove the louver itself - the subframe tabs are brittle and will crack if flexed cold.

Everything involving the MEP chase, refrigerant lineset, or roof-to-wall flashing requires licensed handling. The refrigerant charge in these units is R410A at pressures that can cause frostbite or eye injury. The roof edge is a fall hazard, and the factory flashing integrates with the ZIP System membrane in a way that improper peeling voids the wall warranty. We have repaired three San Bernardino owner-attempted fixes this year; each cost more than the original call would have.

Call (909) 359-6463 to schedule your free estimate. A live person answers, and we bring the correct Plant Prefab-compatible parts on the first trip.

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