Beam Selection for Residential Construction

Intermediate Level

How to choose the right beam type — dimensional lumber, LVL, glulam, PSL, steel, or flitch plate — for headers, girders, and long-span applications in residential framing.

Materials Needed

Note

All beam sizing must be performed or verified by a licensed structural engineer. Manufacturer span tables cover simple cases but cannot account for complex load paths, point loads, or unusual conditions.

Note

When comparing beam options, always compare total installed cost — not just material price. A $200 LVL with $50 in hangers may be cheaper than a $150 steel beam that requires $300 in bearing plates and fireproofing.

Note

Local codes may have specific requirements for beam types in certain applications. Always verify with your building department before purchasing materials.

Beam Selection Decision Framework

Selecting the right beam starts with three questions: What load must it carry? What span must it cover? What depth is available? The answers narrow the field to one or two beam types that meet structural requirements within practical constraints.

Step 1: Determine the Load

Calculate the tributary area — the floor, roof, or wall area supported by the beam. Multiply by the applicable design loads: 40 psf live + 10–20 psf dead for floors (IRC Table R301.5), 20–30 psf live + 15 psf dead for roofs. Add any point loads from posts or beams above. This gives you the total uniform load (plf) or point load (lbs) the beam must carry.

Step 2: Check Span Tables

For loads under 500 plf and spans under 20 feet, manufacturer span tables (Weyerhaeuser, Louisiana-Pacific, Boise Cascade) will identify suitable LVL or glulam sizes. For heavier loads or longer spans, you will need engineered calculations from a structural professional.

Step 3: Select the Beam Type

Dimensional lumber (doubled or tripled 2×10/2×12) works for short spans under 8 feet and light loads — window and door headers in non-bearing walls. LVL is the workhorse for spans of 8–24 feet. Glulam excels for exposed beams and very long spans. PSL handles heavy column loads and posts. Steel is the last resort when wood cannot meet depth or load constraints.

Step 4: Verify Connections

Every beam needs a complete load path from the supported structure, through the beam, to the foundation. Specify bearing plates, hangers (Simpson LUS/HUS), or welded connections as appropriate. Minimum bearing length is 1.5" on wood, 3" on masonry. Steel beams typically require 4"+ bearing on concrete piers with 1/2" bearing plates.