For Architects & GCs

Working With 4C:
Who Does What in Off-Site Construction

The question we hear most from architects and general contractors: if 4C builds the walls in a factory, what’s left for us? The short answer is almost everything you do today. Here’s how the work splits, phase by phase, on a real project.

The 4C team and the homeowners at the Escondido Residence, a steel-framed home built with off-site 4C SAFE wall panels

Off-site construction doesn’t replace your project team. Someone still designs the building, someone still engineers it, and someone still grades the site, pours the slab, runs the trades and finishes the house. What changes is where the frame and envelope are built, and when the decisions behind them get made.

At 4C, our scope is the structural frame and envelope: exterior wall panels, interior partitions, and roof and floor framing. We build them in our Hayward factory and install them with our own crew. Everything else stays with the team you already trust.

By the 4C team · October 27, 2026 · 10 min read

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The short version

Architects keep the design and the client. Decisions just move earlier.
Engineers of record keep the structural design and review our panel drawings.
General contractors keep the site, the foundation, the trades and the schedule. Framing becomes one delivered scope.
4C configures, manufactures, delivers and installs the frame and envelope, then supports it after closeout.

On this page: What 4C does · Who does what · Phase by phase · From model to factory · For architects · For GCs · Decide early · Escondido · Our network · FAQ

What 4C does, and what stays with your team

Think of a 4C project as one coordinated scope inside a normal project. The work that usually means framing crews, lumber deliveries and several trades on site for weeks becomes labeled, factory-built components that arrive in installation order.

4C’s scope: converting the design into 4C components, coordinating panel drawings with the architect and engineer, manufacturing exterior wall panels (framing, insulation, sheathing and a weather-resistant barrier in one panel), interior partitions, and roof and floor framing, then delivering and installing them, with warranty and support for the installed system.
Stays with the project team: the building design and client relationship, structural design by the engineer of record, site work and grading, foundations, mechanical, electrical and plumbing, window installation, roofing, interior and exterior finishes, and the overall construction schedule.

Where the two meet (windows, roofing, utility penetrations, the connection to the foundation) we treat the work as coordinated interfaces. They’re drawn and agreed before anything is built, not left for the field.

Who does what: roles on a 4C project

Here’s how responsibilities usually split when 4C supplies and installs the frame and envelope. Every project is set up a little differently, and we confirm the split in writing at the start.

Role	Responsible for	Decides early, with 4C
Owner or developer	Goals, budget, site and the project team	System choice (4C SAFE™ steel or 4C ECO™ wood) and the overall schedule
Architect	Building design, design intent and the client relationship	Window and door openings, wall layout, finishes and exterior details
Structural engineer (engineer of record)	Structural design values and calculations for the project	Review of panel and connection drawings, and the foundation connections
MEP engineer and trades	Mechanical, electrical and plumbing design and installation	Where pipes, ducts and wiring pass through walls and roof framing
4C	Panel configuration, coordinated drawings, manufacturing, delivery, installation and warranty of the 4C scope	Production slot, delivery sequence and installation plan
General contractor	Site, foundation, following trades, finishes and the overall schedule	Foundation readiness, truck access, staging and the telehandler route
Building department	Plan review and inspections, as on any project	Nothing special: 4C documentation is available for plan review

Phase by Phase

Who leads each phase

4C projects follow our six-phase process. The lead changes as the project moves from drawings to the site.

Design

Lead: architect. 4C advises on system fit and configures the design into components.

Coordination

Lead: 4C, with the architect, engineer of record, MEP, GC and the building department.

Manufacturing

Lead: 4C, in Hayward. At the same time, the GC prepares the site and foundation.

Delivery

Lead: 4C, sequenced to the GC’s site access, staging and foundation schedule.

Installation

Lead: 4C crew for the frame and envelope. The GC lines up the following trades.

Warranty

GC finishes the building; 4C supports the installed system after closeout.

From Revit model to factory: how a design becomes panels

Here’s what that coordination looks like on a real house. Below is the Escondido Residence, designed by Megan Campbell of Campbell Architects, after our team broke her design into 4C components. Nothing about the architecture changed. What the model adds is a manufacturing answer for every wall, opening and connection.

One model, three layers. Roof and floor framing, interior partitions and exterior wall panels are modeled separately, so each can be checked and built on its own schedule.
Every panel has a number. Our configurator, a Revit plugin, gives each panel its own bill of materials and production sequence, and every panel leaves the factory with a serial number and a label for its place on site.
Openings come from the design, not a catalog. Headers and the short walls above and below windows are made to order, so the architect picks the window sizes and most of the wall stays standard.

Revit model of the Escondido Residence roof and floor framing, configured into 4C components

Revit model of the Escondido Residence interior partition framing, configured into 4C components

Revit model of the Escondido Residence exterior wall panels, each 4C panel shown with its openings

Roof + floor framing

The Escondido roof and floor framing, modeled as its own layer: trusses or joists, connections and hardware, checked before production.

Interior partitions

Interior walls coordinated with the plumbing, duct and electrical pathways, so the openings for them are planned in the factory.

Exterior wall panels

Every exterior panel with its window and door openings, numbered and labeled for its place on site.

The panel layout

Here is the same house as a 4C panel layout: Campbell Architects’ floor plan with every panel drawn and tagged on top. Each tag along the exterior walls is one 4C panel, named by its type and size, and the interior partitions are numbered the same way. It’s the link between the architect’s plan and the panels we build. Click the drawing to see every tag.

4C panel layout for the Escondido Residence: the floor plan with every exterior wall panel and interior partition tagged by type and size — 4C panel layout over the Campbell Architects floor plan. Tap or click to enlarge.

For architects: your design, decided earlier

You don’t design around our system. Bring any architectural design, and our team converts it into defined components, builds a coordinated digital model and produces the panel drawings for the permit and construction sets. You review and approve them. The design and the client relationship stay with you.

The real change is timing. In a factory, a window opening, a plumbing vent or a connection detail is built into the panel weeks before anyone is on site. Decisions that often get settled in the field have to be made and drawn during design. In return, they stay made: at Escondido, every window and door opening fit with zero field adjustments.

Best time to call us: schematic design or early design development, before the permit set is finished. More on how we work with design teams on our architects and designers page.

For general contractors: one scope instead of several

For a GC, 4C works like a framing subcontractor that arrives with the insulation, sheathing and weather barrier already on the wall. Instead of separate suppliers and crews, you get one procurement line and one installation sequence. Components arrive pre-labeled and in the order our crew needs them, and staging requirements are set out in the installation plan.

Heavy equipment is not always required, but a reach forklift (telehandler) is our preferred method for handling and installation. We plan equipment and staging around each site with you.

You still own the site, the foundation, the following trades and the schedule. What you gain is a frame and envelope that goes up in days, so the trades behind it can start sooner. More on our builders and general contractors page.

4C crew standing an exterior wall panel by hand on the foundation slab at Borrego Springs, with panel stacks staged behind them — Borrego Springs: setting a wall panel by hand.

Aerial view of the Borrego Springs site with labeled 4C panels staged on the slab and the first walls standing — Borrego Springs: labeled panels staged on the slab.

4C crew guiding a wall panel with a large opening into place at the Escondido Residence as a telehandler lowers it — Escondido: a panel set with a telehandler.

4C crew member sealing the exterior face of the wall panels at the Escondido Residence, with roof framing overhead — Escondido: sealing the panel face on site.

Decisions to settle before production

Most of the friction on a panelized project comes from decisions made too late. These are the ones we work through with the team during coordination:

System choice. 4C SAFE™ (steel framing, 1-hour and 2-hour fire-rated assemblies, suited to wildfire zones) or 4C ECO™ (wood framing for Type V construction).
Openings. Final window and door sizes and locations, since rough openings are built into the panels.
Penetrations. Where plumbing, ducts and electrical pass through walls and roof framing.
Foundation connections. Anchor locations agreed between the engineer of record, the GC and 4C before the slab is poured.
Window, cladding and roof interfaces. How windows, flashing, cladding and roofing tie into the panels and their weather-resistant barrier.
Site logistics. Truck access, staging space and the telehandler route, especially on tight or hillside lots.
Schedule. The foundation-ready date, which sets the production slot and the delivery date.

A real example: Escondido

The Escondido Residence, a 1,894 sq ft home on a steep hillside pad in San Diego County, shows how the split works in practice:

Architect of record: Megan Campbell of Campbell Architects, who designed the home to work with the slope and hold the reservoir view.
Engineer of record: M-Integrated, our structural engineering partner, which produced the calculations and construction documents the panels were built to.
Site, foundation, MEP and finishes: Palm Coast Design Build, with windows and doors by All Weather Architectural Aluminum.
Frame and envelope: 4C, with 4C SAFE™ steel-framed panels engineered, manufactured and installed as one package.

Because everyone agreed on the design intent early, Palm Coast’s grading and site package and our structural submittal moved through the County on parallel tracks instead of waiting on each other. Delivery was sequenced with Palm Coast’s site team, panel by panel, so nothing reached the ridge-top pad before there was a place to put it.

The result: by the end of Day 2, about 75% of the exterior walls were standing. By Day 3, the wall package was complete and the crew had moved on to roof framing and interior partitions.

Overhead view of the Escondido foundation slab with the first steel framing on the hillside pad — Site and foundation: Palm Coast Design Build.

Aerial view of off-site built 4C SAFE wall panels rising on the Escondido foundation, with a telehandler staged on site — Frame and envelope: 4C, set with a telehandler.

4C team member checking installed wall panels against the digital model on a laptop inside the Escondido Residence frame — Coordination on site: checking each panel against the model.

The finished Escondido Residence exterior with its carport on the hillside — Finished home, designed by Campbell Architects.

The full story of that build, including the County review, is in Escondido: what we learned building a fire-resilient home on a hillside.

Thank you to the network that makes this work

None of this happens alone. Every 4C project is a team effort, and we’re grateful to the architects, engineers, builders and suppliers who bet on a new way of building with us, often before there was a finished house to point to:

Architects: Megan Campbell and Campbell Architects, for Escondido; Skripchenko Architects, for the Altadena rebuild designs; Gensler, for adapting the Miami Affordable Teacher Housing project to the 4C system; and Büttner Reis Dias, part of our architect network for fire-rebuild work in Los Angeles.
Engineering: M-Integrated, our primary engineering partner, who turn each design into the structural calculations our panels are built to.
Building: Palm Coast Design Build, whose site team at Escondido handled the grading, foundation and finishes around our panels.
Windows and doors: All Weather Architectural Aluminum.
Our installation crews, who set every panel at Borrego Springs and Escondido.
The homeowners at Borrego Springs and Escondido, who trusted a new system with their homes.

The network keeps growing

We want more architects in it. That’s why, on November 18, we’re hosting the AIA San Francisco Custom Residential Architects Network (CRAN) at our Hayward factory: part of our push to bring more architects into the 4C network. Visitors walk the production line, see a full-size building we built inside the factory (half steel, half wood) and earn 1 AIA LU|HSW. Bay Area architects can still reserve a spot, and the background is in our CRAN tour announcement.

Not in the Bay Area, or can’t make the date? Send us a project. A quick look at your drawings is the easiest way to see how your design would translate into 4C panels.

You don’t need to start at phase one

Some projects come to us with permits in hand, an engineer already engaged or a GC already on board. That’s fine. We can pick up at the phase your project needs, coordinate with the team you have and deliver the frame and envelope into your schedule.

Wherever you start, the earlier we see the drawings, the more we can help. For a broader comparison of panels with modular and conventional framing, see Panelized vs. Modular vs. Stick-Built, and for how the panels are built, our manufacturing page.

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FAQ

Working with 4C: common questions

What is off-site construction?

Off-site construction means building parts of a structure in a factory and installing them on site. With 4C, that means the frame and envelope: exterior wall panels with framing, insulation, sheathing and a weather-resistant barrier built in, plus interior partitions and roof and floor framing. Foundations, mechanical, electrical and plumbing, and finishes are still done on site by the project team.

Does 4C replace the general contractor?

No. 4C manufactures and installs the structural frame and envelope components: exterior wall panels, interior partitions, and roof and floor framing. The general contractor still runs the site and the overall schedule, and handles site work, foundations, mechanical, electrical and plumbing, and finishes. Window installation, roofing and other work outside the agreed 4C scope stay with the project team as coordinated interfaces.

Is 4C a framing subcontractor?

In practice, 4C works like a framing subcontractor that also delivers the insulation, sheathing and weather barrier on the same panels. The GC gets one procurement line and one installation sequence for the frame and envelope instead of several suppliers and crews.

Can I use my own architect and engineer with 4C?

Yes. The architect keeps the design and the client relationship, and the engineer of record keeps the structural design. 4C converts the approved design into factory components and coordinates the panel drawings with both teams. No redesign is required.

When should the architect bring 4C into a project?

As early as possible, ideally in schematic design or early design development, before the permit set is finished. Openings, penetrations and connections are built into the panels in the factory, so the earlier they are settled with 4C, the fewer changes there are later.

What does the GC need to have ready before the panels arrive?

A finished foundation that matches the coordinated drawings, clear truck access, a staging area and room for the telehandler (reach forklift) that sets the panels. Delivery dates are tied to foundation readiness, so the slab schedule and the production schedule are planned together.

Can the design change after manufacturing starts?

Changes are possible before manufacturing and costly after, because the panels are built to the coordinated drawings. That is why the key decisions are made with the architect, engineer and GC during design and coordination.

Do I have to use 4C for every phase?

No. If you already have permits, your own engineer or your own GC lined up, you don’t need to start at phase one. We’ll talk through which phases your project needs us to run.

Have a project and a team in place?

Send us the drawings. We’ll show you how they translate into 4C components, who does what and which decisions to make early.