# Modular and Prefabricated Construction

## Prefabrication Types

### Hierarchy of Prefabrication
| Level | Description | Example |
|-------|-------------|---------|
| Component | Individual parts | Trusses, precast panels |
| Panel | 2D assemblies | Wall panels, floor cassettes |
| Volumetric | 3D modules | Bathroom pods, rooms |
| Whole building | Complete structure | Modular buildings |

### Construction Methods
| Method | Off-site Work | On-site Work |
|--------|---------------|--------------|
| Stick-built | 0% | 100% |
| Panelized | 20-40% | 60-80% |
| Modular | 60-90% | 10-40% |
| Manufactured | 95%+ | 5% |

---

## Modular Construction

### Module Types
| Type | Typical Size | Application |
|------|--------------|-------------|
| Bathroom pod | 8' × 12' × 9' | Hotels, multifamily |
| Corridor module | 14' × 60' × 12' | Hotels, healthcare |
| Corner module | 14' × 28' × 12' | Apartments |
| MEP module | Varies | Mechanical rooms |
| Stair module | 12' × 16' × varies | All buildings |

### Module Dimensions
| Constraint | Maximum | Reason |
|------------|---------|--------|
| Width | 14'-16' | Highway transport |
| Height | 13'-6" | Overpass clearance |
| Length | 60'-70' | Turning radius |
| Weight | 50,000-80,000 lbs | Crane capacity |

### Structural Systems
| System | Application |
|--------|-------------|
| Corner-supported | Stacked modules |
| Wall-bearing | Traditional layout |
| Chassis | Relocatable units |
| Hybrid | Mix with site-built |

### Module-to-Module Connections
| Location | Connection Type |
|----------|-----------------|
| Vertical | Steel plates, bolts |
| Horizontal | Marriage wall clips |
| Diaphragm | Floor ties, plates |
| Lateral | Tie rods, clips |

---

## Panelized Construction

### Wall Panel Types
| Type | Framing | Finish |
|------|---------|--------|
| Open panel | Framing only | Site-applied |
| Closed panel | Framing + sheathing | Site-applied |
| Insulated panel | Full assembly | Pre-finished |
| SIP | Foam core | Pre-finished |

### Floor Panel Types
| Type | Structure | Ceiling |
|------|-----------|---------|
| Floor cassette | Joists + subfloor | Site-applied |
| CLT panel | Solid wood | Pre-finished option |
| Hollow-core | Precast concrete | Pre-finished |

### Roof Panel Types
| Type | Structure | Application |
|------|-----------|-------------|
| Truss + sheathing | Wood truss | Residential |
| SIP | Foam + OSB | Residential |
| CLT | Solid wood | Commercial |

### Panel Dimensions
| Panel Type | Width | Length | Weight |
|------------|-------|--------|--------|
| Wall panel | 4'-8' | Up to 60' | 15-30 psf |
| Floor cassette | 8'-12' | Up to 40' | 20-40 psf |
| SIP | 4' | Up to 24' | 3-5 psf |

---

## Bathroom and MEP Pods

### Bathroom Pod Types
| Type | Size | Application |
|------|------|-------------|
| Full bathroom | 8' × 10' | Hotels, apartments |
| Three-quarter | 6' × 8' | Multifamily |
| Half bath | 5' × 6' | Commercial |
| ADA | 8' × 12' | All buildings |

### Pod Construction
| Component | Material |
|-----------|----------|
| Floor | Steel pan, waterproof |
| Walls | Light gauge steel, FRP |
| Ceiling | Moisture-resistant drywall |
| Fixtures | Pre-installed |
| MEP rough | Pre-installed |

### MEP Considerations
| System | Pod Provision |
|--------|---------------|
| Plumbing | Stubbed for connection |
| Electrical | Junction boxes |
| Ventilation | Duct connections |
| Fire sprinkler | Stub-outs |

### Pod Benefits
| Factor | Advantage |
|--------|-----------|
| Quality | Factory-controlled |
| Schedule | Parallel path |
| Labor | Skilled factory workers |
| Consistency | Identical units |
| Waste | 30-50% reduction |

---

## Design Considerations

### Module Planning
| Factor | Consideration |
|--------|---------------|
| Transportation | Width limits layout |
| Stacking | Align verticals |
| Connections | Accessible joints |
| MEP | Vertical risers |
| Finishes | Protect for transport |

### Grid Optimization
| Dimension | Recommendation |
|-----------|----------------|
| Module width | 12'-14' typical |
| Module length | 30'-60' typical |
| Corridor module | 8' clear width |
| Unit depth | 24'-36' typical |

### Structural Layout
| Principle | Application |
|-----------|-------------|
| Stacking | Align load-bearing walls |
| Symmetry | Balanced loading |
| Corner support | Primary connection |
| Redundancy | Multiple paths |

### Interface Zones
| Interface | Requirement |
|-----------|-------------|
| Marriage walls | Fire separation, sound |
| Floor gaps | Expansion, tolerance |
| Vertical chases | Aligned through building |
| Corridor | Continuous finishes |

---

## Transportation and Logistics

### Transport Modes
| Mode | Module Size | Distance |
|------|-------------|----------|
| Truck (standard) | 12' × 60' | Any |
| Truck (oversized) | 16' × 70' | Permitted routes |
| Barge | Unlimited | Water access |
| Rail | Width limited | Rail access |

### Permit Requirements
| Dimension | Permit Level |
|-----------|--------------|
| < 8'-6" wide | None |
| 8'-6" to 12' | Standard oversized |
| 12' to 14' | Escort required |
| > 14' | Police escort, route survey |

### Site Logistics
| Requirement | Consideration |
|-------------|---------------|
| Crane access | 150-ton typical |
| Staging area | 20,000+ SF |
| Access road | Width, turning |
| Overhead | Power lines, structures |

### Protection During Transport
| Element | Protection |
|---------|------------|
| Windows | Plywood covers |
| Finishes | Plastic wrap |
| Corners | Steel protectors |
| MEP | Secure loose items |

---

## Factory Production

### Factory Layout
| Area | Function |
|------|----------|
| Material storage | Raw materials |
| Framing station | Structure assembly |
| MEP rough | System installation |
| Insulation | Thermal envelope |
| Finish | Interior completion |
| QC | Inspection |
| Staging | Ready for ship |

### Production Rate
| Building Type | Modules/Week |
|---------------|--------------|
| Small factory | 2-5 |
| Medium factory | 10-25 |
| Large factory | 50+ |

### Quality Control
| Stage | Inspection |
|-------|------------|
| Materials | Incoming QC |
| Framing | Dimensional check |
| MEP rough | Pressure test, inspection |
| Insulation | R-value, coverage |
| Finish | Visual inspection |
| Final | Third-party review |

### Factory Certifications
| Certification | Scope |
|---------------|-------|
| ICC Plant certification | Building code |
| HUD | Manufactured housing |
| State approval | Varies by state |
| ISO 9001 | Quality management |

---

## Code Compliance

### IBC Classification
| Type | Application |
|------|-------------|
| Modular building | IBC as site-built |
| Manufactured housing | HUD code |
| Temporary structure | Limited duration |

### Third-Party Inspection
| Level | Inspection |
|-------|------------|
| Factory | In-plant inspection |
| Transport | Delivery verification |
| Set | Foundation, connections |
| Final | Complete building |

### Documentation
| Document | Purpose |
|----------|---------|
| Approved plans | Factory and set drawings |
| Insignia | State/local approval |
| Inspection reports | Verification of work |
| As-builts | Final documentation |

### Fire Separation
| Condition | Requirement |
|-----------|-------------|
| Between units | 1-hour minimum |
| Corridors | Per occupancy |
| Marriage walls | Fire-stopping |
| Penetrations | Fire-stopping |

---

## MEP Integration

### Plumbing
| Strategy | Description |
|----------|-------------|
| Vertical alignment | Stack risers |
| Pod-based | Bathroom pods |
| Point of connection | Standardized locations |
| Testing | Factory pressure test |

### Electrical
| Strategy | Description |
|----------|-------------|
| Modular panels | Pre-wired |
| Quick connects | Module-to-module |
| Raceways | Accessible locations |
| Data/low voltage | Separate pathway |

### HVAC
| Strategy | Description |
|----------|-------------|
| Packaged units | Factory installed |
| Split systems | Condenser on grade |
| VRF | Distributed approach |
| Ductwork | In-module, connect at set |

### Fire Protection
| Strategy | Description |
|----------|-------------|
| Dry system in module | Charged on-site |
| Flexible connections | Module joints |
| Head locations | Pre-determined |

---

## Schedule Benefits

### Timeline Comparison
| Phase | Traditional | Modular |
|-------|-------------|---------|
| Design | 6-9 months | 4-6 months |
| Permits | 2-4 months | 2-4 months |
| Site work | 3-6 months | 3-6 months |
| Structure | 6-12 months | 2-4 months |
| MEP/finish | 6-9 months | Included |
| **Total** | **24-36 months** | **12-20 months** |

### Parallel Work Streams
```
Traditional:
Site → Foundation → Structure → MEP → Finish

Modular:
Site → Foundation ─┬─ Set ─┬─ Connect → CO
Factory Production ─┘      └─────────┘
```

### Weather Independence
| Phase | Site Exposure |
|-------|---------------|
| Factory | None |
| Transport | 1 day |
| Set | 1-2 days |
| Connections | Interior work |

---

## Cost Factors

### Cost Comparison
| Factor | Modular | Traditional |
|--------|---------|-------------|
| Material | +5-10% | Baseline |
| Labor | -20-40% | Baseline |
| Schedule | -30-50% | Baseline |
| Financing | -10-20% | Baseline |
| **Total** | -10-20% | Baseline |

### Premium Items
| Item | Cost Impact |
|------|-------------|
| Transport | $5,000-15,000/module |
| Crane | $5,000-20,000/day |
| Factory overhead | 10-15% |
| Engineering | +10-20% |

### Savings Sources
| Source | Savings |
|--------|---------|
| Labor productivity | 20-30% |
| Material waste | 5-10% |
| Schedule reduction | 10-20% |
| Weather delays | 5-10% |
| Quality/rework | 5-10% |

---

## Project Delivery

### Procurement Methods
| Method | Description |
|--------|-------------|
| Design-Bid-Build | Traditional, less common |
| Design-Build | Preferred for modular |
| CMAR | Early contractor involvement |
| Integrated | Owner, designer, builder team |

### Early Design Decisions
| Decision | Timing |
|----------|--------|
| Modular approach | Concept phase |
| Module dimensions | Schematic |
| Factory selection | Design development |
| Transport route | DD/CD |

### Contract Considerations
| Issue | Approach |
|-------|----------|
| Scope split | Clear factory vs. site |
| Responsibility | Connections, tolerances |
| Insurance | Factory and transport |
| Payment | Progress-based |

### Risk Allocation
| Risk | Party |
|------|-------|
| Factory delays | Manufacturer |
| Transport damage | Carrier/manufacturer |
| Setting damage | GC |
| Connections | GC |
| Design coordination | Designer |

---

## Building Types

### Ideal for Modular
| Type | Reason |
|------|--------|
| Hotels | Repetitive units |
| Multifamily | Repetitive units |
| Student housing | Speed, repetition |
| Healthcare | Bathroom pods |
| Schools | Classroom modules |
| Data centers | MEP-intensive |

### Challenging for Modular
| Type | Challenge |
|------|-----------|
| Custom homes | Limited repetition |
| High-rise | Logistics, structure |
| Irregular plans | Custom modules |
| Remote sites | Transport cost |

### Hybrid Applications
| Approach | Description |
|----------|-------------|
| Podium + modular | Concrete base, modules above |
| Core + modular | Site-built core, module units |
| Pods only | Bathroom/MEP pods in traditional |
| Panelized + modules | Panels for custom, modules for repetitive |
