Built-up Girder or Beam
How to nail 2x joist lumber into a beam of almost any length, for pier foundation beams, girders and headers.
While this is not an engineered beam and may not be approved by all inspectors, a careful builder can construct a strong and durable built-up beam of almost any length using 2x joist lumber. A three joist beam is shown above. To use standard metal hardware such as post brackets, hangers and post caps, 1/2" plywood can be used as shims. For greater strength use four 2x’s as it will be close to the same strength as a solid 6x beam.
Laying out and nailing the beam
Layout such a beam from straight solid lumber of reasonable length. You can build such a beam in place with major joints falling on the support piers. Typical spacing for nails is 20d galvanized 32" o/c in a “W” pattern with 2 nails over each other at splices.
The nails pin the joists together and get them to work as a single unit much like a LVL beam (but not as pretty or with the guaranteed and tested strength of the LVL). PT lumber can be used for exposed conditions. Be sure to use compatible fasteners such as stainless steel or hot-dip galvanized nails.
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Before you size anything: Check with a table of IRC allowed spans for sizing headers and girders. This page describes common building practice, not engineering for your site, and your building department has the final say.
Where to go from here
- Download the same detail as a PDF: built-up girder or beam.
- See where these beams sit: pier and beam foundations, with footing sizes for mild and cold climates.
- Read how building codes and permits work when you build from stock plans.
- Ask about beams and spans in our discussion forum.