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Calculate beam spans, load capacity, deflection, and sizing for wood beams. Determine if your beam is safe for the intended load and get material requirements with cost estimates.
Total span: 0.00 ft (0.0 inches)
Built-up beam dimensions: 3.00" × 7.25"
Enter beam span above to calculate capacity
Your load: 50 lbs/ft
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A structural beam is a horizontal load-bearing member that transfers loads from above to vertical supports (posts, columns, or walls). Beams must resist both bending stress and deflection under load.
Common beam types include:
Where b = width (inches), h = depth (inches)
Where w = load (lbs/ft), L = span (inches)
Actual bending stress must be less than allowable stress for the wood species
Deflection must be less than L/360 for floors, L/240 for roofs
Maximum spans for built-up beams under 50 lbs/ft residential load:
| Beam Size | Single Ply | Double Ply | Triple Ply |
|---|---|---|---|
| 2x6 | 6' | 8' 6" | 10' 6" |
| 2x8 | 7' 6" | 11' 0" | 13' 6" |
| 2x10 | 9' 0" | 13' 6" | 16' 6" |
| 2x12 | 10' 6" | 15' 6" | 19' 0" |
| 4x8 | 11' 0" | 15' 6" | 19' 0" |
| 4x10 | 13' 6" | 19' 0" | 23' 6" |
| 4x12 | 15' 6" | 22' 0" | 27' 0" |
Note: These are approximate values. Always consult local building codes and a structural engineer for critical applications.
Deflection is how much a beam sags under load. Even if a beam is strong enough not to break, excessive deflection can cause:
L/360 means a 12-foot span can deflect max 0.4 inches (12×12÷360)
Beams must have adequate bearing on posts or walls. Minimum bearing lengths:
| Support Type | Min. Bearing |
|---|---|
| Wood post | 3.5 inches |
| Steel post | 3.0 inches |
| Masonry wall | 4.0 inches |
Nail each ply with 10d nails at 16" o.c. staggered pattern
Use structural post caps for uplift resistance
Install blocking or bridging to prevent rotation
For a typical 50 lbs/ft residential floor load, a double 2x10 or triple 2x8 Douglas Fir beam works for a 12-foot span. Always verify with local codes and consider actual loads.
Yes, built-up beams made from 2x lumber nailed together are common and code-approved. They're easier to handle and install than solid beams, though engineered beams like LVL may span farther.
A single 2x8 Douglas Fir can span about 7.5 feet for residential floors. A double 2x8 extends to 11 feet, and triple to 13.5 feet. Actual capacity depends on wood species, grade, and load.
Beams are primary load-bearing members that support joists. Joists are smaller members spaced 12-24 inches apart that support floor or roof decking and transfer loads to beams.
For critical applications, large spans, heavy loads, or when required by local codes, yes. This calculator provides estimates but doesn't replace professional structural analysis for important projects.
LVL (Laminated Veneer Lumber) is engineered wood made from thin wood veneers glued together. It's stronger and more consistent than solid lumber, ideal for long spans, heavy loads, or when you need smaller beam depths.
Add dead load (weight of structure: 10-15 lbs/ft²) and live load (occupancy: 40 lbs/ft² for residential floors). Multiply by the tributary width (half the joist span on each side) to get lbs per linear foot.
Notching and drilling significantly reduce beam capacity. If necessary, notches should be in the outer thirds only, no deeper than 1/6 the beam depth. Holes should be centered vertically, away from supports. Consult codes first.
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