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Joist & Beam Calculators | Free Construction Calculators

Calculate joist spans, beam capacity, spacing, and load limits

Joist Span Calculator

Calculate maximum joist span

Beam Span Calculator

Calculate maximum beam span

Joist Spacing Calculator

Calculate optimal joist spacing

Load Capacity Calculator

Calculate safe load capacity

About Joists and Beams

Joists and beams are fundamental structural elements in building construction. Joists are horizontal framing members that support floors and ceilings, while beams carry larger loads and support joists. Proper sizing ensures structural integrity and code compliance.

Key Structural Concepts

Span: The distance between supports for a joist or beam
Spacing: The on-center distance between parallel joists
Live Load: Temporary loads from people, furniture, snow
Dead Load: Permanent loads from the structure itself
Deflection: How much a member bends under load

Common Lumber Species

Douglas Fir-Larch: Strong, widely available, good for structural use
Southern Pine: High strength, dense, commonly used in the South
Hem-Fir: Moderate strength, good workability
Spruce-Pine-Fir: Lower strength, economical option

Lumber Grades

Select Structural: Highest grade, fewest defects, strongest
No. 1: High quality, suitable for most structural applications
No. 2: Most common grade, good balance of cost and strength
No. 3: Lower grade, suitable for shorter spans and lighter loads

Typical Load Values

Residential floors: 40 psf live load, 10 psf dead load
Commercial floors: 50-100 psf live load depending on use
Residential attics: 20 psf live load (limited storage)
Roof loads: 20-40 psf depending on snow and roofing materials

Deflection Limits

L/360: Standard for floors with plaster ceilings
L/240: Common for roof rafters and commercial floors
L/180: Heavy commercial or industrial applications
Lower ratios mean stiffer members with less deflection

Best Practices

Always verify calculations with local building codes and span tables
Consider deflection as well as strength when sizing members
Account for point loads like walls or heavy equipment
Use appropriate lumber grade for the application
Consult a structural engineer for critical or unusual loads
Consider long-term effects like creep and moisture content

Professional Review Required

These calculators provide preliminary estimates for planning purposes. All structural designs should be reviewed and approved by a licensed professional engineer or architect before construction. Local building codes and site-specific conditions may require different sizing.