How to Screw 2X4s Together

Lumber is strong, but there are times when one 2-by-4 board just won't cut it. Screwing two together will allow the boards to support much more weight. However, it is not simply a matter of lining the boards up, jamming some screws in and calling it a day. The boards will eventually separate if only screws are used to attach them. Wood glue is recommended to help ensure a more permanent bond.

Drill
Screws
Lumber
Polyvinyl acetate glue
Clamps
Screwdriver/screw gun
Shop rag

Instructions

- 1
  Lay one 2-by-4 board on a work bench or other flat surface. Coat the top of the board with polyvinyl acetate (PVA) glue. Place the second 2-by-4 board on top of the glued surface. PVA glue will remain wet for less than 10 minutes, so the boards must be positioned before then. Remove any excess glue with a wet rag.
- 2
  Affix clamps to the boards. Allow the PVA glue to dry according to product directions. Drill one pilot hole for each screw. Pilot holes will allow the screws to penetrate the lumber and prevent splitting and cracking. Each hole should be approximately 3 inches deep. This is to ensure that it will penetrate into the bottom board.
- 3
  Drive a screw into each of the previously drilled holes. The screws will form an additional mechanical bond between the two boards. Use galvanized metal screws for outdoor applications as the galvanized coating provides corrosion resistance. Non-coated screws, such as drywall screws, can be used for interior applications.

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