Understanding Board Types
Choose the right decking material for your climate.
- Pressure Treated Economical, requires maintenance.
- Composite Low maintenance, stable dimensions.
- Cedar Natural resistance, attractive grain.
- Hardwood Durable, premium appearance.
Board Spacing Engineering
- Thermal Expansion Coefficient: 1.9-2.3×10⁻⁵ in/°F. Temperature range: -20 to 120°F. Maximum movement: 1/8" per 12'. Seasonal variation: ±1/16". Stress relief gap: 1/8" min.
- Moisture Management Equilibrium MC: 12-19%. Fiber saturation: 25-30%. Shrinkage coefficient: 0.002 in/in/%MC. Ventilation gap: 1/4" min. Drainage slope: 1/8" per foot.
- Load Distribution Edge distance: 1/4" min. End gap: 1/8-1/4". Fastener spacing: 12-16" O.C. Point load spread: 45°. Surface deflection: L/360 max.
Material Performance
- Wood Properties Tangential movement: 6-12%. Radial movement: 3-6%. Density variation: 10-15%. Grain angle: 0-15°. Surface texture: 60-80 grit. Checking limit: 1/8" width.
- Composite Behavior Linear expansion: 0.1-0.2%. Water absorption: <1%. Creep deformation: <0.2% at 1000hrs. Thermal conductivity: 0.15-0.20 W/m·K. R-value: 0.9-1.2 per inch.
- PVC Characteristics Thermal expansion: 2.5-3.0×10⁻⁵ in/°F. Flexural modulus: 400,000 psi. Impact resistance: >4 ft·lb/in. Heat deflection: 160-180°F. UV stability: <3% change/year.
Installation Standards
- Gap Specifications Side gap: 1/8-3/16". End gap: 1/8-1/4". Perimeter gap: 1/4-3/8". Structure gap: 1/2". Transition gap: 3/8". Feature gaps: 1/4" min.
- Fastening Systems Screw withdrawal: 400-600 lbs. Edge distance: 3/4-1". Predrilling: 90% of fastener dia. Countersink: 1/16-1/8". Torque setting: 16-18 in·lbs.
- Quality Control Spacing tolerance: ±1/32". Alignment variation: 1/8" max in 20'. Fastener depth: flush to -1/16". Surface flatness: 1/8" in 6'. Level variation: 1/4" in 10'.
Spacing Factors
Climate
Affects wood expansion/contraction.
Material
Different materials need different gaps.
Pattern
Layout affects material needs.
Installation
Fastener type impacts spacing.