# Foundation Types - Selection and Details

## Decision Logic

### Foundation Selection
```
What is the soil condition?
  Good bearing (3000+ psf) → Spread footings OK
  Poor/expansive soil → Deep foundations or mat
  High water table → Raised slab or piles

Is it in a flood zone?
  VE Zone → Piles or columns required
  AE Zone → Elevate to BFE, slab OK if engineered
  X Zone → No special requirements

What is the building type?
  Residential 1-2 story → Slab, crawl, or basement
  Commercial → Spread footings, mat, or deep
  High-rise → Deep foundations (piles, caissons)

What is the climate?
  Frost line deep → Footings below frost line
  Florida → No frost, shallow footings OK
```

---

## Slab-on-Grade Foundations

### Type SOG-1: Monolithic Slab (Florida Standard)
**Use when:** Residential, good soil, no flood concern
```
Components:
- 4" concrete slab (3000 psi)
- 6x6 W2.9xW2.9 WWF or fiber mesh
- 6 mil vapor barrier
- 4" compacted fill (crusite/sand)
- Compacted subgrade

Thickened Edge (Integral Footing):
- 12" wide x 18" deep at perimeter
- 2-#4 rebar continuous
- Extend 12" min beyond slab edge
```
**Bearing Capacity Required:** 1500 psf minimum
**Thickness:** 4" slab + 18" edge = 22" total depth

### Type SOG-2: Slab with Turn-Down Footing
**Use when:** Interior load-bearing walls, heavier loads
```
Components:
- 4" concrete slab
- Turn-down footings at interior walls
- 12" wide x 12" deep (typical)
- 2-#4 rebar continuous
- Vapor barrier
- Compacted fill
```

### Type SOG-3: Elevated Slab (Flood Zone)
**Use when:** AE flood zone, elevate to BFE
```
Components:
- 4" concrete slab at elevated level
- CMU stem wall to BFE height
- Spread footing below stem wall
- Flood vents in stem wall
- Fill within stem walls
```
**Note:** Enclosed area below BFE requires flood vents

### Type SOG-4: Post-Tensioned Slab
**Use when:** Expansive soil, large spans, crack control
```
Components:
- 4" to 5" concrete slab
- Post-tension cables @ 48" O.C. both ways
- Perimeter beam (varies by engineer)
- Interior beams at loads
- Vapor barrier
- Compacted fill
```
**Note:** Requires structural engineer design

---

## Crawl Space Foundations

### Type CS-1: Standard Crawl Space
**Use when:** Sloped sites, access needed below floor, termite-prone areas
```
Components:
- Wood or steel floor framing
- Foundation wall (CMU or poured)
- Spread footing below wall
- Piers at interior bearing points
- Vapor barrier on ground (6 mil)
- Access opening (18"x24" min)
```
**Minimum Clearance:**
- 18" below floor joists
- 12" below beams

**Ventilation Required:**
- 1 SF per 150 SF crawl area
- Or mechanical ventilation

### Type CS-2: Conditioned Crawl Space
**Use when:** HVAC in crawl, humid climate
```
Components:
- Same as CS-1, but:
- Insulation at perimeter walls (not floor)
- No vents to outside
- Vapor barrier sealed to walls
- Dehumidification or HVAC supply
```

---

## Basement Foundations

### Type BF-1: Full Basement
**Use when:** Below-grade living space, cold climates
```
Components:
- 8" or 10" concrete walls
- Horizontal rebar @ 24" O.C.
- Vertical rebar @ 48" O.C.
- Spread footing (16" x 8" typical)
- 4" slab on grade inside
- Waterproofing on exterior
- Drainage board
- Perimeter drain to sump or daylight
```
**Wall Reinforcement:** Varies with height and soil

### Type BF-2: Walkout Basement
**Use when:** Sloped site, daylight on one side
```
Same as BF-1, but:
- One or more walls partially exposed
- Step footings following grade
- Waterproofing on buried portions only
```

---

## Deep Foundations

### Type DF-1: Driven Piles
**Use when:** Poor soil, high loads, flood zones
```
Types:
- Timber piles (30-40' typical)
- Concrete piles (precast)
- Steel H-piles

Components:
- Pile cap (grade beam connecting piles)
- Minimum 3 piles per cap (typical)
- Structural slab or framing above
```
**Note:** Requires geotechnical engineer and testing

### Type DF-2: Helical Piers
**Use when:** Limited access, lighter loads, retrofit
```
Components:
- Helical steel pier (8"-14" helix)
- Driven to refusal or specified torque
- Pile cap or bracket connection
- Structural connection above
```
**Capacity:** 20-75 kips typical per pier

### Type DF-3: Drilled Shafts (Caissons)
**Use when:** Very high loads, rock bearing
```
Components:
- Drilled hole (24"-72" diameter)
- Reinforcing cage
- Concrete fill
- Bell at bottom (if in clay)
```
**Note:** Requires structural and geotech design

---

## Florida-Specific Foundation Issues

### High Water Table
When water table is high:
- Use waterproof concrete mix
- Consider elevated slab
- Dewatering during construction
- Sump pump for crawl/basement

### Expansive Soil
When expansive clay present:
- Post-tensioned slab
- Deep foundations
- Void forms under grade beams
- Moisture barriers

### Termite Protection
All Florida foundations require:
- Soil treatment (termiticide)
- Or physical barrier
- Or bait system
- Inspection access at perimeter

### Flood Zone Construction
| Zone | Foundation Options |
|------|---------------------|
| AE | Elevated slab, crawl with vents, piles |
| VE | Open piles or columns ONLY |
| X | Any type |

---

## Foundation Details to Include in CDs

### Plans
- Overall foundation plan
- Footing sizes and reinforcement
- Slab thickness and reinforcement
- Expansion/control joint locations
- Termite treatment note

### Sections
- Typical footing section
- Slab edge/perimeter detail
- Interior footing section
- Step footing (if applicable)

### Schedules
- Footing schedule (if multiple types)
- Pier/column schedule
- Reinforcement schedule

### Notes
```
FOUNDATION NOTES:
1. ALL CONCRETE 3000 PSI MIN (4000 PSI FOR EXPOSURE)
2. REINFORCEMENT: GRADE 60 DEFORMED BARS
3. COVER: 3" TO EARTH, 2" TO FORMS
4. SOIL BEARING: VERIFY WITH GEOTECH REPORT
5. CONTRACTOR TO NOTIFY ARCHITECT OF ANY SOIL
   CONDITIONS DIFFERENT FROM GEOTECH REPORT
6. TERMITE TREATMENT PER FBC CHAPTER 26
7. VAPOR BARRIER: 6 MIL POLYETHYLENE
```
