# MEP Coordination for Architects

## Ceiling Space Requirements

### Typical Ceiling Cavity Depths
| Building Type | Min Depth | Notes |
|---------------|-----------|-------|
| Residential | 6"-12" | HVAC in attic usually |
| Small commercial | 12"-18" | VAV or split systems |
| Office building | 18"-24" | Ductwork + lighting |
| Healthcare | 24"-36" | Heavy MEP, access needed |
| Laboratory | 36"-48" | Intensive services |

### Coordination Order (Top to Bottom)
1. Structure (beams, joists, deck)
2. Fire sprinkler mains
3. Large ducts (supply mains)
4. Plumbing (drain lines slope)
5. Medium ducts (branches)
6. Electrical conduit/cable tray
7. Small ducts (diffuser connections)
8. Sprinkler branch lines
9. Ceiling grid

---

## Ductwork Sizing Reference

### Duct Velocity Guidelines
| Application | Velocity (fpm) |
|-------------|----------------|
| Residential | 600-900 |
| Commercial (low velocity) | 1,000-1,500 |
| Commercial (high velocity) | 1,500-2,500 |
| Industrial | 2,000-4,000 |

### Duct Size vs. CFM (Approximate)
| Duct Size | CFM @ 1000 fpm |
|-----------|----------------|
| 6" round | 200 |
| 8" round | 350 |
| 10" round | 550 |
| 12" round | 800 |
| 14" round | 1,100 |
| 16" round | 1,400 |
| 12"x8" rect | 650 |
| 18"x12" rect | 1,500 |
| 24"x12" rect | 2,000 |
| 24"x18" rect | 3,000 |

### Main Duct Sizing Rule of Thumb
```
1 CFM per SF of conditioned space
400 SF/ton of cooling

Example: 2,000 SF office
- CFM needed: 2,000 CFM
- Tonnage: 5 tons (2,000/400)
- Main duct: ~18"x18" or 20" round
```

---

## Plumbing Coordination

### Pipe Sizes
| Fixture | Min Supply | Min Drain |
|---------|------------|-----------|
| Lavatory | 1/2" | 1-1/4" |
| Toilet | 1/2" | 3" (4" main) |
| Shower | 1/2" | 2" |
| Bathtub | 1/2" | 1-1/2" |
| Kitchen sink | 1/2" | 1-1/2" or 2" |
| Dishwasher | 1/2" | 2" (via disposal) |
| Clothes washer | 1/2" | 2" |
| Floor drain | N/A | 2" min |

### Drain Slope Requirements
| Pipe Size | Min Slope |
|-----------|-----------|
| 2-1/2" or smaller | 1/4" per foot |
| 3" or larger | 1/8" per foot |

### Wall Thickness for Plumbing
| Pipe Size | Min Wall Thickness |
|-----------|---------------------|
| 1-1/2" or 2" drain | 2x4 wall (3-1/2") |
| 3" drain | 2x6 wall (5-1/2") |
| 4" drain (toilet) | 2x6 wall or furr-out |

### Plumbing Chase Sizes
| Fixture Stack | Min Chase Size |
|---------------|----------------|
| Single lav | 12" x 8" |
| Toilet | 12" x 12" |
| Kitchen + Lav | 18" x 12" |
| Multi-story wet stack | 24" x 18" |

---

## Electrical Coordination

### Panel Clearances (NEC)
- 36" clear in front (30" for 150V or less)
- 30" wide working space
- 78" headroom (6'-6")
- No storage in working space

### Electrical Room Sizing
| Building Size | Room Size |
|---------------|-----------|
| Small commercial (5,000 SF) | 8' x 10' |
| Medium commercial (20,000 SF) | 10' x 15' |
| Large commercial (50,000+ SF) | 12' x 20' or larger |

### Outlet Spacing (Residential)
- 12' max between outlets (6' from any point)
- Within 2' of doorway
- Countertops: every 4' max, within 2' of edge
- Bathrooms: 1 per sink within 3'
- Outdoors: front and back, accessible

### Lighting Power Density (IECC)
| Space Type | Max W/SF |
|------------|----------|
| Office (open) | 0.98 |
| Office (enclosed) | 1.11 |
| Conference | 1.23 |
| Retail | 1.26 |
| Classroom | 1.24 |
| Corridor | 0.66 |
| Restroom | 0.98 |
| Warehouse | 0.60 |

---

## HVAC Equipment Space

### Rooftop Unit (RTU) Sizing
| Tonnage | Approximate Size | Weight |
|---------|------------------|--------|
| 5 ton | 6' x 4' | 800 lbs |
| 10 ton | 8' x 5' | 1,500 lbs |
| 15 ton | 10' x 6' | 2,200 lbs |
| 25 ton | 12' x 8' | 3,500 lbs |

### Air Handler Unit (AHU) Room
| Tonnage | Min Room Size |
|---------|---------------|
| 5-10 ton | 10' x 12' x 10' H |
| 15-25 ton | 12' x 16' x 12' H |
| 30-50 ton | 16' x 24' x 14' H |

### Mechanical Room Checklist
- [ ] Equipment clearance (36" min service)
- [ ] Door size (equipment removal)
- [ ] Floor drain
- [ ] Ventilation (combustion air if gas)
- [ ] Sound isolation
- [ ] Vibration isolation
- [ ] Access for maintenance

---

## Fire Protection

### Sprinkler Coverage
| Hazard | Max Area/Head |
|--------|---------------|
| Light hazard | 225 SF |
| Ordinary hazard | 130 SF |
| High hazard | 90 SF |

### Sprinkler Head Clearance
- 1" to 12" below ceiling (standard pendant)
- 18" clearance below sprinklers
- 24" from!"walls (typical)

### Fire Riser Room
- 6' x 6' minimum (8' x 8' preferred)
- Floor drain
- Wall-mounted backflow preventer at 24-36"
- Exterior access preferred
- Not in residential units

---

## Coordination Clash Prevention

### Common Conflicts

| Conflict | Prevention |
|----------|------------|
| Duct vs beam | Route ducts between beams, use flat oval |
| Sprinkler vs light | Coordinate ceiling layout early |
| Plumbing vs structure | Locate chases at non-bearing walls |
| Electrical vs duct | Cable tray below ductwork |
| Diffuser vs beam | Flex duct to avoid beams |

### Ceiling Coordination Drawing
Show on RCP:
- Ceiling grid layout
- Light fixtures (centered in tiles)
- Diffusers (centered in tiles)
- Sprinkler heads (centered in tiles)
- Access panels
- Speakers/AV
- Exit signs
- Smoke detectors

### Bulkhead/Soffit Solutions
When main ducts don't fit:
- Drop ceiling in corridors
- Create architectural soffit
- Expose structure and run above
- Use smaller high-velocity ducts

---

## Mechanical Space Requirements

### Residential
| System | Space Needed |
|--------|--------------|
| Furnace/AH (closet) | 3' x 3' min |
| Water heater | 2' x 2' min + clearance |
| Condensing unit | 3' x 3' exterior |

### Commercial
| Equipment | Location | Space |
|-----------|----------|-------|
| RTU | Roof | Per unit + 4' service |
| Chiller | Mechanical room | Per unit + 5' service |
| Boiler | Mechanical room | Per unit + 4' service |
| Cooling tower | Roof or grade | Per unit + 5' service |
| VAV boxes | Above ceiling | 18" min clearance |

### Electrical Rooms
| Service | Room Size |
|---------|-----------|
| 200A residential | Panel in garage |
| 400A small commercial | 8' x 8' |
| 800A medium | 10' x 12' |
| 1200A+ | 12' x 16' + transformer |

---

## Access Requirements

### Access Panels
| Equipment | Panel Size |
|-----------|------------|
| VAV box | 24" x 24" min |
| Fire damper | 12" x 12" or 16" x 16" |
| Valve/cleanout | 12" x 12" min |
| Electrical junction | 12" x 12" min |

### Accessible Ceiling Types
| Ceiling | Access Level |
|---------|--------------|
| ACT (lay-in) | Full access |
| Tegular | Full access |
| Drywall | Limited (access panels) |
| Wood slat | Limited (removable sections) |
| Metal panel | Varies (clips vs screws) |

---

## MEP Coordination Process

### Design Phase Milestones
1. **SD**: Establish major equipment locations
2. **DD**: Size mains, locate risers and shafts
3. **CD (50%)**: Full routing, clash detection
4. **CD (90%)**: Resolve all clashes
5. **CD (100%)**: Coordinated composite drawings

### Coordination Meetings
- Weekly during CD phase
- All disciplines present
- Review 3D model/overlays
- Document decisions
- Assign responsibility for conflicts

### Submittal Coordination
Review MEP submittals for:
- Equipment dimensions match drawings
- Clearance requirements
- Weight (structural impact)
- Electrical requirements
- Duct/pipe connections
