Components

| Part | Function | Material | |------|----------|----------| | Top chord | Carries roof sheathing, transfers load to panel points | 2×4 or 2×6 SPF | | Bottom chord | Tension tie, carries ceiling load | 2×4 or 2×6 SPF | | Web members | Diagonal + vertical bracing between chords | 2×4 SPF | | Panel points | Nodes where members intersect | Metal connector plates (MPC) | | Heel | Junction of top and bottom chord at bearing | Critical for height/insulation | | Peak | Apex where top chords meet | MPC gusset | | Bearing point | Where truss sits on wall/beam | Min 1.5" bearing required |

Common Residential Truss Types

Fink (W-Pattern) — Most Common

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• Span: Up to 40–50'

• Best for: Standard residential roofs, no attic use

• Depth: Shallow (economic use of material)

• Why it's #1: Best strength-to-weight ratio, cheapest to fabricate

• ML Systems use: Primary truss type spanning between steel beams

Howe

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• Span: Up to 60'

• Best for: Heavy snow loads, clay tile roofing

• Verticals in compression, diagonals in tension (opposite of Pratt)

• ML Systems use: When snow load > 35 PSF or heavy roofing material

Scissors

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• Span: Up to 30–35'

• Best for: Cathedral/vaulted ceilings

• Bottom chord slopes up (typically 1/2 of top chord pitch)

• Caution: Higher horizontal thrust at bearings — needs robust connection

• ML Systems use: Living room feature ceiling over steel beam

Attic Truss

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• Span: Up to 30' (limited by room inside)

• Best for: Habitable attic space in Cycle 2

• Live load increases to 30 PSF for habitable space

• ML Systems use: Cycle 2 expansion — room within truss

Mono (Single Slope)

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• Span: Up to 30'

• Best for: Shed roofs, additions, clerestory windows

• Single bearing point at high end, roller at low end

• ML Systems use: Lean-to additions, covered entries

Hip Truss Set

• Not a single truss — a SET of progressively shorter trusses

• Standard truss at center, stepping trusses reduce toward corners

• Hip jack trusses transfer load to hip girder truss

• More complex framing, but better wind resistance (lower profile at corners)

Truss Spacing

| Spacing | Tributary Width | Common Use | |---------|-----------------|------------| | 24" o.c. | 2.0 ft | Standard residential (default) | | 16" o.c. | 1.33 ft | Heavy loads, long spans, tile roofs | | 48" o.c. | 4.0 ft | Engineered trusses, heavy top/bottom chords |

ML Systems default: 24" o.c. wood trusses spanning between steel beams

Span Capacity (Fink Truss, 24" o.c.)

| Truss Depth | Dead Load 10 PSF | Dead + Snow 30 PSF | Dead + Snow 40 PSF | |-------------|-------------------|---------------------|---------------------| | 12" | 28' | 24' | 22' | | 18" | 36' | 32' | 28' | | 24" | 42' | 38' | 34' | | 30" | 48' | 44' | 40' |

Values approximate — actual capacity depends on lumber grade, MPC rating, and specific geometry. Always per engineer's design.

Critical for ML Systems: With 20' bay spacing, trusses span 20' between steel beams — well within capacity for any standard truss depth. This is the clear-span advantage of the hybrid system.

Truss-to-Steel Beam Connections

Bearing on Top of Steel Beam

╱ Truss ╲ ╱─────────╲ │ bearing │ ═══════════════ ← Steel beam top flange W12×26

• Truss sits directly on beam top flange

• Wood nailer plate (2× PT) lag-bolted to beam flange

• Truss toe-nailed or hurricane-tied to nailer

• Advantage: Simple, allows full truss depth above beam

• Disadvantage: Adds truss depth to overall building height

Hung from Steel Beam (Joist Hanger)

═══════════════ ← Steel beam ┌─ hanger ─┐ │ ╱ ╲ │ │ ╱truss╲ │

• Welded or bolted joist hanger on beam web

• Simpson HUS or custom steel hanger

• Advantage: Flush ceiling — truss bottom chord aligns with beam bottom flange

• Disadvantage: Requires field-bolted hanger (DfD compatible) or shop-welded (not DfD)

ML Systems Preferred Detail

Top-bearing with bolted nailer plate:

Hurricane Ties — Uplift Resistance

Simpson Connectors for ML Systems

| Connector | Capacity (Uplift) | Use | |-----------|-------------------|-----| | H2.5A | 475 lbs | Light wind zones, truss to plate | | H10 | 1,100 lbs | Standard — RI wind zones | | H10A | 1,130 lbs | Skewed installation option | | LSTA | 1,175 lbs | Strap tie over truss, both sides | | HDU | 3,000+ lbs | Holdown — column to foundation |

RI Wind Uplift Requirement

Uplift per connector = (Wind uplift PSF × tributary area) − (0.6 × Dead load) Example: 20 PSF uplift × (2' × 10') = 400 lbs gross 0.6 × (12 PSF × 2' × 10') = 144 lbs counteracting Net uplift = 400 − 144 = 256 lbs → H2.5A adequate Coastal RI: Higher wind → H10 or LSTA required

Continuous Load Path (Roof to Foundation)

Roof sheathing → Ring-shank nails → Truss top chord ↓ Hurricane tie (H10) → Truss to nailer plate ↓ Nailer plate → Through-bolts → Steel beam flange ↓ Beam end-plate → A325 bolts → Column flange (moment connection) ↓ Column base plate → Anchor bolts → Grade beam ↓ Grade beam → Rebar → Spread footing → Soil