After the Set What Still Has to Happen Before You Can Move In?
The crane is gone.
The modules are sitting on the foundation, or the panels have been erected and the house finally looks like a house.
It is tempting to think the project is almost over.
Sometimes it is.
Sometimes there is still a surprising amount of work between 'the house is standing' and 'you can legally move in.'
That last stretch is where prefab projects can become confusing because factory completion, site construction, utility work, inspections, corrections, and final approvals all converge.
The set is a major milestone.
It is not a certificate of occupancy.
First: What Does 'Set' Actually Mean?
For a volumetric modular project, the set usually means the modules have been lifted from their transport carriers and placed onto the permanent foundation.
For a panelized project, there may not be one dramatic set day. Wall, floor, and roof panels may be erected over several days until the shell is standing.
In either case, the building can look much more complete than it legally or functionally is.
A volumetric module may arrive with finished drywall, cabinets, flooring, fixtures, and windows. A panelized building may suddenly have walls and a roof.
But the remaining work may still include:
Permanent structural connections.
Module-to-module or panel connections.
Foundation anchorage.
Roof completion.
Weatherproofing.
Exterior closure pieces.
Electrical connections.
Plumbing connections.
HVAC commissioning.
Utility service.
Site drainage.
Stairs, porches, decks, and landings.
Fire and life-safety work.
Required testing.
Local inspections.
Correction work.
Final inspection and occupancy approval.
The exact list depends on the product, plans, site, jurisdiction, and scope of work.
California's Factory Approval Does Not Finish the Local Permit
This is one of the most important distinctions in a California Factory-Built Housing project.
HCD's Factory-Built Housing program regulates and approves the factory-built portion through HCD-certified third-party agencies. An HCD insignia tells the local building official that the factory-built unit or component was inspected and approved under the applicable approved plans.
But HCD expressly states that installation of factory-built housing and FBH building components is subject to inspection by the local building department.
In other words, the local inspector is not being asked to reopen the walls and re-inspect factory work that was properly approved and insigniaed.
The local jurisdiction still has a very real job:
Confirm the approved factory-built product is what arrived.
Verify the HCD insignia where applicable.
Inspect foundation and site-built work.
Inspect installation and assembly.
Inspect field connections.
Inspect site-installed systems.
Inspect local code and permit requirements outside the factory scope.
Approve post-installation alterations when applicable.
Complete the project's required inspections before occupancy.
Factory approval and local approval are complementary, not interchangeable.
Protect the HCD Insignia and Approval Documents
For qualifying California FBH units and building components offered for sale to first users, HCD requires the insignia to be affixed before shipment.
Do not casually remove, cover, lose, or damage those identifiers before the local building department has accepted the factory-built work.
Keep the project records organized:
HCD-approved or DAA-approved plans supplied for the project.
Insignia information.
Manufacturer installation instructions.
Structural connection details.
Engineering and calculations.
Local approved permit set.
Inspection records.
Change documentation.
The more factory work is concealed, the more important the approval documentation becomes.
The Modules Still Have to Become One Building
Volumetric modules arrive as separate structural units.
After placement, they must be connected according to the approved structural and installation details.
That may include:
Module-to-module structural connections.
Bolting, welding, straps, clips, or proprietary connectors.
Foundation anchorage.
Marriage-line connections.
Roof connections.
Shear-transfer details.
Seismic connections.
Connections at floors and ceilings.
In California, seismic design makes these connections particularly important.
The fact that two modules appear to be touching does not mean the structural installation is complete.
The set puts the pieces in position. The approved connections make them a building.
Panelized Buildings Have Their Own Connection Work
Panelized construction trades the enormous module connections for many smaller assembly connections.
Depending on the system, field work may include:
Panel-to-foundation connections.
Wall-to-wall connections.
Wall-to-floor connections.
Floor diaphragm connections.
Roof panel or truss connections.
Shear connections.
Hold-downs.
Blocking.
Straps and hardware.
Field-installed structural members.
Some systems are highly engineered and proprietary.
Do not let an erection crew improvise simply because the panels fit together visually.
The installation drawings are part of the construction system.
Temporary Bracing Has to Become Permanent Stability
During delivery and erection, modules or panels may rely on temporary bracing.
That bracing cannot simply disappear because the building looks upright.
The permanent structural system needs to be completed before temporary supports are removed when the approved installation sequence requires them.
This is especially important with:
Tall walls.
Large openings.
Roof assemblies.
Hillside construction.
High-wind locations.
Panelized systems erected over multiple days.
The manufacturer's erection sequence and structural plans should govern.
The Roof May Still Need Significant Work
A prefab home can arrive with much of the roof complete, but transportation often requires the roof to be shipped in sections or in a lowered configuration.
After the set, roof work may include:
Hinged roof sections raised into position.
Ridge connections.
Roof panel installation.
Trusses or rafters installed onsite.
Roofing at module joints.
Flashing.
Underlayment repairs.
Gutters and downspouts.
Penetration flashing.
Final weather sealing.
A panelized home may require even more roof work onsite.
The project should have a specific plan for getting the structure weather-tight quickly.
Weatherproofing Is a Critical Post-Set Job
The building has just been transported, lifted, connected, and opened at marriage lines or panel joints.
Now the exterior envelope has to become continuous.
Pay particular attention to:
Roof joints.
Wall joints.
Windows near module or panel seams.
Door openings.
Flashing.
Weather-resistive barrier transitions.
Siding closure strips.
Foundation transitions.
Deck and porch connections.
Utility penetrations.
Water does not care whether a leak originated in the factory or in the field.
Someone needs clear responsibility for every transition between factory work and site work.
Marriage Lines Need More Than Trim
Where volumetric modules meet, the visible finish work can make the seam disappear.
But before the trim goes on, there may be structural, fire, acoustic, mechanical, electrical, plumbing, insulation, air-sealing, and weatherproofing work at the marriage line.
Depending on the design, crews may need to complete:
Drywall or finish patches.
Flooring transitions.
Ceiling joints.
Cabinet or countertop connections.
Interior trim.
Exterior siding.
Roofing.
Insulation.
Air sealing.
A beautiful trim strip should be the last step, not a substitute for completing the hidden connection work.
Plumbing Has to Cross From Factory to Site
A factory can install a great deal of plumbing before delivery.
But the house still has to connect to the property.
Post-set plumbing may include:
Connecting module plumbing across marriage lines.
Connecting the building drain to sewer or septic.
Connecting domestic water.
Connecting water heater systems.
Pressure testing.
Completing vents.
Installing field fixtures or appliances.
Insulating exposed piping where required.
Correcting transportation-related leaks.
On rural properties, the house may be ready before the well or septic system is ready.
That still means the project is not ready for occupancy.
Septic Can Be Its Own Project
For rural prefab projects, septic work deserves to be treated as a separate critical path.
The home may be manufactured quickly while the site still needs:
Septic permits.
Tank installation.
Dispersal field installation.
Pumps or controls.
Electrical connections.
Inspection.
Testing or certification required by the local agency.
Final grading and protection of the system.
Heavy delivery and crane equipment also need to stay off septic tanks, piping, and dispersal areas.
A finished house without an approved wastewater system is still not a finished project.
Well Water May Need More Than a Pipe Connection
A private well project can involve more than connecting a water line.
Depending on the jurisdiction and project, remaining work may include:
Pump and pressure system.
Electrical service to the well.
Storage tanks.
Treatment equipment.
Water quality testing.
Flow or yield documentation.
Backflow or cross-connection requirements.
Local environmental-health signoff.
These requirements vary considerably by county and by project.
They should be identified during feasibility and permitting rather than discovered after the house arrives.
Electrical Work Does Not End at the Factory Panel
The factory may install branch circuits, receptacles, lighting, and even electrical panels.
Site work may still include:
Module-to-module electrical connections.
Service equipment.
Meter installation.
Utility connection.
Grounding and bonding.
Exterior disconnects.
Site lighting.
EV equipment if included.
Solar or battery connections if included.
Field-installed appliances and equipment.
Required testing and inspection.
The utility company has its own process, and that process does not necessarily move at the same speed as the building permit.
Utility Company Timing Can Surprise You
A house can pass substantial portions of its building inspection and still be waiting for permanent power.
Utility work can involve:
Service applications.
Engineering.
Transformer capacity review.
Trenching.
Conduit.
Easements.
Meter location approval.
Utility inspections.
Scheduling the final connection.
If new service or an upgrade is required, start that process early.
Do not assume that because the prefab manufacturer can produce a house in a few months, the utility can energize it on the same schedule.
HVAC Has to Be Connected and Commissioned
Heating and cooling equipment may be factory-installed, site-installed, or divided between the two.
After the set, crews may need to:
Connect refrigerant lines.
Connect duct sections.
Install exterior heat-pump equipment.
Complete condensate drainage.
Connect controls.
Install ventilation equipment.
Balance or test systems.
Start up and commission equipment.
A thermostat lighting up is not necessarily proof that the system has been properly commissioned.
California Energy Requirements Still Have a Finish Line
California residential projects may have energy-code documentation, field-verification, testing, or compliance items that continue into the final phase.
The exact requirements depend on the approved energy documents and project scope.
Do not treat the energy report as something that mattered only during plan check.
Before the project reaches final inspection, confirm that all required field verification, testing, certificates, equipment documentation, and compliance steps shown in the approved project documents have actually been completed.
Ventilation and Indoor-Air Requirements Need to Work
Modern homes are intentionally tighter than older buildings.
That makes mechanical ventilation and exhaust systems important.
Depending on the approved plans, final work may involve:
Whole-building ventilation.
Bathroom exhaust.
Kitchen exhaust.
Controls.
Duct completion.
Required airflow verification.
Equipment labeling or documentation.
Factory installation can make these systems look finished long before they have been connected, tested, or verified onsite.
Fire Sprinklers May Need Field Connections
If the project requires residential fire sprinklers, portions of the system may be installed in the factory while other work is completed onsite.
Remaining work can include:
Connections between modules.
Connection to the water supply.
Backflow or other required devices.
Pump or storage systems where applicable.
Testing.
Inspection.
Correction of damaged heads or piping.
Rural water supply can make this more complicated than the sprinkler piping inside the house itself.
Wildfire Areas Add Site Requirements
In California wildfire-prone areas, the building itself is only part of the fire-safety picture.
Depending on the project and jurisdiction, remaining requirements may involve:
Fire apparatus access.
Driveway width and grade.
Turnarounds.
Address visibility.
Water supply.
Vegetation or defensible-space requirements.
Exterior ignition-resistant construction details.
Fire-department inspection or signoff.
A factory-built house does not bypass site-specific wildfire requirements.
Stairs, Landings, Decks, and Porches Are Often Site-Built
Many prefab renderings show a finished porch, deck, or entry.
That does not mean it is included in the factory scope.
Site-built work frequently includes:
Entry stairs.
Landings.
Guardrails.
Handrails.
Decks.
Porches.
Ramps.
Exterior platforms.
Connections between finished floor elevation and grade.
These elements can be required for safe and code-compliant access before occupancy.
They also need foundations, structural details, inspections, and sometimes separate engineering.
Accessibility Requirements May Affect the Finish Work
Depending on the project type and applicable requirements, site work may need to complete accessible routes, landings, thresholds, parking, ramps, or other accessibility features.
Even in projects where extensive accessibility requirements do not apply, the actual finished grade and entry condition must match the approved plans.
A door that is installed perfectly at the factory can still end up with a noncompliant landing if the site work is wrong.
The Ground Around the House Still Matters
One of the easiest mistakes is focusing so intensely on the house that the site is treated as an afterthought.
Final site work may include:
Positive drainage away from the foundation.
Swales.
Drainage structures.
Retaining walls.
Erosion control.
Final grading.
Driveways.
Walkways.
Required paving.
Site restoration.
Protection of septic and utilities.
A completed building surrounded by unfinished drainage problems may not be ready for final approval - and may be at risk during the first major storm.
Stormwater and Erosion Work May Continue After the Set
Construction disturbs soil.
Depending on the project, permit conditions may require erosion-control measures to remain in place until the site is stabilized.
Do not remove wattles, inlet protection, temporary drainage, or other measures simply because the modules have arrived.
The end of vertical construction is not necessarily the end of site compliance.
Addressing Can Hold Up More Than You Expect
Emergency responders, utilities, inspectors, and delivery services all need to identify the property.
Some jurisdictions require address numbers to be installed before final approval.
Rural projects may have additional addressing or road-sign requirements.
It is a tiny line item compared with a house.
It is also exactly the kind of tiny line item that can appear on a final correction list.
Smoke and Carbon-Monoxide Alarms Still Need Final Verification
Alarms may be factory-installed, but final installation conditions still matter.
Connections, power, interconnection, locations, and operation should match the approved requirements.
Transportation can also loosen or damage devices.
Test them before the inspector does.
Appliances and Fixtures Need to Be Finished, Not Merely Delivered
Depending on the project and inspection sequence, final work may include:
Connecting ranges or cooktops.
Installing dishwashers.
Connecting water heaters.
Installing plumbing fixtures.
Completing garbage disposals.
Securing appliances.
Installing required anti-tip devices.
Completing exhaust connections.
Clarify which appliances are part of the permitted construction and which are simply owner furnishings.
Transportation Damage Becomes a Punch-List Issue
Even a well-built factory home has just traveled down public roads and been lifted through the air.
Inspect promptly for:
Drywall cracks.
Broken tile.
Flooring damage.
Cabinet movement.
Window or door misalignment.
Roof or siding damage.
Plumbing leaks.
Loose fixtures.
Finish scratches.
Damaged exterior trim.
Document damage with photographs before repairs obscure what happened.
Then determine who is contractually responsible: manufacturer, transporter, set crew, general contractor, installer, or another party.
Do the Punch List Before Everyone Leaves
The best time to identify responsibility is while the relevant contractors are still mobilized.
Create a written punch list organized by party.
For each item, record:
Location.
Problem.
Photograph.
Responsible party.
Required correction.
Date reported.
Completion status.
A vague list saying 'fix drywall' is much less useful than a room-by-room record.
Expect Corrections
An inspection correction is not automatically evidence that the prefab system failed.
Construction projects routinely generate corrections.
The important questions are:
What failed?
Was it factory work, installation work, or site work?
Who is responsible?
Does the correction require manufacturer involvement?
Does it affect concealed work?
Does it require revised plans or engineering?
Who requests the reinspection?
Resolve responsibility quickly so a small correction does not stall the whole project.
Be Careful With Post-Installation Changes
Once the factory-built unit has been installed, changes are not simply a matter of cutting into whatever is convenient.
HCD states that alterations to FBH after installation require approval from the local building department.
That matters because an apparently simple field change may affect:
Structure.
Fire resistance.
Electrical systems.
Plumbing.
Energy compliance.
Factory-approved assemblies.
Coordinate changes with the building official and design professionals as required before modifying approved work.
Final Inspection Is Not Just an Interior Walk-Through
By final inspection, the inspector may be looking at the entire permitted project, not merely whether the inside of the house looks complete.
That can include:
Outstanding correction notices.
Site work.
Required clearances.
Stairs and guards.
Utility connections.
Drainage.
Fire requirements.
Energy documentation.
Mechanical systems.
Electrical systems.
Plumbing.
Addressing.
Permit conditions.
Required agency signoffs.
This is why a project can look completely move-in ready and still not be ready for final approval.
Other Agencies May Need to Sign Off
The building department may not be the only agency involved.
Depending on the property, final approval may depend on work or signoff involving:
Environmental health.
Fire department or fire district.
Public works.
Planning.
Water district.
Sewer district.
Utility provider.
Floodplain administrator.
Other local agencies.
Your permit conditions and approved plans should tell you which approvals apply.
Track them before the final building inspection rather than discovering a missing signoff at the end.
Do Not Move In Just Because the House Looks Finished
This is worth saying plainly.
Furniture in the living room does not make a house legally occupiable.
Before occupancy, confirm the local jurisdiction has issued whatever final approval, certificate of occupancy, temporary certificate, or equivalent authorization is required for that project.
The terminology and procedure can vary by jurisdiction and permit type.
The person who decides the project is legally ready for occupancy is not the delivery driver, factory salesperson, set crew, or homeowner. It is the authority having jurisdiction through its final approval process.
A Temporary Certificate Is Not the Same as Being Done
Some jurisdictions may allow temporary occupancy when specified remaining items do not prevent safe occupancy.
If a temporary approval is available, understand:
What work remains.
The deadline for completion.
What inspections remain.
Whether financial security is required.
What restrictions apply.
Temporary occupancy can be useful.
It should not become an excuse for unresolved construction to linger indefinitely.
Lender Final Draws May Have Their Own Requirements
If the project is financed with a construction loan, the lender may have a separate completion process.
That may include:
Draw inspections.
Lien releases.
Final invoices.
Certificate of occupancy or final permit evidence.
Insurance documentation.
Completion certificates.
Passing the building inspection and satisfying the lender are related but separate administrative steps.
Insurance Needs to Transition Too
Construction-phase coverage and completed-home coverage are not necessarily the same.
Before occupancy, coordinate with the insurance carrier so there is no gap as the project transitions from construction to an occupied residence.
Prefab classification can also matter to insurers, so make sure the carrier understands what was actually built rather than relying on a vague label such as 'modular.'
Know When the Warranty Clock Starts
Prefab projects can involve multiple warranties with different start dates.
There may be separate warranties for:
Factory construction.
Installation.
Transportation.
Site construction.
Roofing.
Windows.
HVAC equipment.
Appliances.
Other products.
Some may begin at shipment, some at installation, some at substantial completion, and some at owner acceptance.
Collect the documents and record the dates.
Do not wait until a problem occurs to discover that nobody knows which warranty applies.
Get the Closeout Documents
Before everyone considers the project finished, collect the records you may need later.
Depending on the project, that can include:
Final approved plans.
Revised or as-built information where required.
Inspection record.
Final approval or certificate of occupancy.
HCD/FBH documentation.
Manufacturer manuals.
Equipment manuals.
Warranty documents.
Energy-compliance records.
Testing and commissioning records.
Subcontractor information.
Lien releases.
Utility information.
Septic and well records.
Paint, flooring, roofing, siding, and finish specifications.
Future-you will be very grateful.
Who Is Managing the Last Mile?
This is where the responsibility matrix from earlier in the prefab process becomes essential.
Someone has to coordinate:
Manufacturer.
Set or erection crew.
General contractor.
Electrician.
Plumber.
HVAC contractor.
Foundation contractor.
Utility company.
Septic contractor.
Well contractor.
Roofing and weatherproofing crews.
Inspectors.
Other agencies.
If the answer is 'the homeowner will figure it out,' understand what that means.
CSLB states that an owner-builder who signs the permit assumes responsibility for the project, including permits, inspections, supervision, scheduling, and correction of work that does not pass inspection.
The gap between factory and occupancy needs an actual project manager, whether that is a licensed general contractor or an owner-builder who knowingly accepts that role.
The Owner-Builder Trap
Prefab marketing can make owner-building sound easier than it is.
The factory may say it handles the house.
The foundation contractor handles the foundation.
The set crew handles the set.
The electrician handles electricity.
The plumber handles plumbing.
Individually, all of those statements may be true.
But who handles the spaces between those scopes?
Who notices that the electrician is waiting for a utility decision the manufacturer assumed was already resolved?
Who schedules the inspection before work is concealed?
Who gets the revised detail when the field condition does not match the plan?
Who owns the correction?
That coordination is general-contracting work.
Do not accidentally become the project's general contractor simply because nobody put that role in the factory quote.
A Better Definition of 'Turnkey'
If a prefab company uses the word turnkey, ask them to define it in writing.
Does turnkey include:
Permits?
Foundation?
Grading?
Delivery?
Crane?
Set?
Structural connections?
Roof completion?
Utility trenching?
Utility company fees?
Electrical service?
Water and sewer or septic connection?
HVAC commissioning?
Stairs and landings?
Decks?
Fire requirements?
Energy testing?
Inspections?
Corrections?
Final approval?
Certificate of occupancy?
If the answer to half of those questions is 'by owner,' it may still be a perfectly good product.
It just is not turnkey in the way most homeowners hear that word.
The Last-Mile Budget
Before ordering the house, create a budget category specifically for everything between set day and occupancy.
Possible costs include:
Set completion.
Field structural work.
Roofing.
Exterior closures.
Interior marriage-line finishes.
Electrical.
Plumbing.
HVAC.
Utilities.
Septic or sewer.
Well or water.
Fire requirements.
Decks and stairs.
Grading and drainage.
Testing.
Reinspection.
Punch-list repairs.
Temporary facilities or weather protection.
Do not assume these costs are miscellaneous.
On some projects they are a major portion of the total development budget.
The Last-Mile Schedule
Build the schedule the same way.
Instead of ending the project schedule at 'set day,' continue through:
Dry-in/weatherproofing.
Structural completion.
MEP connections.
Utility activation.
Site work.
Required testing.
Agency signoffs.
Punch list.
Building inspections.
Corrections.
Reinspection.
Final approval.
Occupancy.
This gives you a much more realistic answer to the question homeowners actually care about:
When can I live there?
A Practical Post-Set Checklist
Immediately after the set or erection:
Photograph the building and any visible damage.
Confirm temporary weather protection.
Confirm structural bracing and connection sequence.
Protect HCD insignias and approval documentation.
Verify who is responsible for security and site protection.
Before closing walls, roofs, or connection areas:
Complete required structural connections.
Complete concealed MEP connections.
Complete insulation and air sealing.
Obtain required inspections before concealment.
Resolve field conflicts with approved details.
Before final inspection:
Finish roofing and weatherproofing.
Complete utilities.
Complete HVAC and ventilation.
Complete plumbing and electrical.
Complete stairs, landings, guards, and handrails.
Complete required fire work.
Complete grading and drainage.
Complete septic/well requirements where applicable.
Complete energy testing/documentation.
Resolve punch-list and inspection corrections.
Obtain other agency signoffs.
Before moving in:
Confirm final inspection approval.
Confirm occupancy authorization required by the jurisdiction.
Transition insurance.
Complete lender closeout if applicable.
Collect warranties and closeout documents.
Record warranty start dates and responsible contacts.
The Bottom Line
Prefab can make the construction of the building dramatically faster.
It does not eliminate development.
The property still needs foundations, utilities, access, drainage, inspections, site work, and final approval.
The more complete the house looks when it arrives, the easier it is to underestimate what remains.
That is why I would never evaluate a prefab project by asking only:
How long does it take to build the house?
I would ask:
How long does it take to get from permit issuance to legal occupancy on this property?
That is the schedule that matters.
The crane leaving is exciting.
The final inspection is the finish line.
Looking Ahead
Next: Final Inspection: What Can Still Hold Up Occupancy?
We will look specifically at the small and not-so-small issues that can derail the final inspection: missing agency signoffs, incomplete site work, energy documentation, stairs and guards, utility problems, fire requirements, unapproved field changes, unresolved corrections, and the paperwork that can keep a physically finished home from being legally occupiable.
If you are evaluating a California prefab, modular, panelized, manufactured, tiny-home, ADU, or SFR project, Buchanan Land Use Consulting can help evaluate the permitting, site, access, and development side before you commit to the product.
Continue Reading
Previous: Volumetric Modular vs. Panelized: Which Kind of Prefab Actually Makes Sense for Your Property?
Next: Final Inspection: What Can Still Hold Up Occupancy?
California References
California Department of Housing and Community Development (HCD), Factory-Built Housing - www.hcd.ca.gov/building-standards/fbh
HCD, Factory-Built Housing: Inspections and Fees - www.hcd.ca.gov/building-standards/fbh/inspections
HCD, Factory-Built Insignia - www.hcd.ca.gov/building-standards/fbh/insignia
HCD, Factory-Built Housing Handbook for Local Enforcement Agencies, Builders, and the General Public (HCD FBH 314).
California Contractors State License Board (CSLB), Owner-Builder Responsibilities - www.cslb.ca.gov/Consumers/Know_Risks_Of_Owner_-_Builder/The_Responsibilities_Of_An_Owner_-_Builder.aspx
