How to Make Benches Out of 2x4s

Picnic table benches are fairly easy woodworking projects.

You can make benches out of 2-inch by 4-inch boards (2x4s) without a lot of carpentry skills by using carriage bolts and wood screws to join wood surfaces. The benches will be made in the style of a picnic table. They can be made from cedar or pressure-treated 2x4s, ideal for outdoor use, or they can be made from common Douglas fir lumber and finished in a protective stain or painted, giving them a durable finish that should last for years.

Things You'll Need

• 8 - 2 inch by 4-inch by 8-foot boards (2x4s)
• Circular saw
• Carpenter's file
• Carpenter's square
• 80 to 100 grit sandpaper
• Drill and 1/2-inch drill bit and auger bit
• 2 1/2-inch galvanized drywall screws
• 3 1/2-inch by 1/2-inch galvanized carriage bolts
• 1/2-inch washers and nuts

Instructions

1. Cut four of your 8-foot 2x4s in half. Note that standard, stud-length 2x4s, might be a little longer than 8-feet, requiring you to trim one end to make each half identical in length, or cut a center line taking into account the exact measurement of the 2x4 studs. Cut more studs if you want to want wider bench seats or if you want to make more than two benches, 4 feet wide.

2. File the edges where you cut the lumber with a coarse wood file, rolling the edge over to match the radius on the edges of your lumber. For a finer detail, you can follow up with 80 or 100 grit sandpaper.

3. Lay four of your 4-foot pieces side-to-side on your work bench. Space the pieces so there is a 1/4-inch gap between each. The gap will allow rainwater to drain through the bench-top. You can use the width of a pencil to gauge your gaps, rubber tile spacers or cut 1/4-inch slats on a table saws for spacers.

4. Check the ends with a carpenter's square or T-square; the ends should be perpendicular to the edge of the outside 2x4.

5. Measure across the 2x4s and cut two cross-braces for each bench to to that length. Standard 2x4s are milled down to 3 1/2 inches wide. So, if your bench is four boards across with 1/4-inch gaps your 2x4 cross-brace will be 1-foot, 2 3/4-inches long.

6. Mark a perpendicular line 6 inches from each end of the bench to position your cross-brace. Glue the cross-brace inside the line. With a counter-sink and drill bit, drill pilot holes through the cross member -- one in each seat board. Drill a 2 1/2 inch galvanized drywall screw into each pilot hole. Make sure you do not countersink the screw beyond flush with the cross-braces as they can protrude through the seat. Allow your glue to dry.

7. Lay two lengths of 2x4s, 32-inches long (one-third the length of a stud), side by side on your work bench. Mark the center of the 2x4s at 16 inches. Drill a hole 1/2-inch in diameter. It may be easier to use an auger-style drill bit than the more traditional twist-bit for a large hole like this.

8. Place a carriage bolt 3 1/2 inches long through both holes with the 2x4s stacked on top of one another. Place a washer over the threaded end of the carriage bolt, then a 1/2-inch nut and snug the nut, finger-tight. Make two of these leg assemblies for each bench.

9. Draw a rectangle on your work bench the width or your bench-top and whatever height you would like your bench to be. 28 inches is a common seat height, but you can adjust the height to your preference. Draw a center line showing half the height of the rectangle.

10. Lay your two bolted legs along the height of your rectangle and open them into an X-pattern until the edges align with the corners of your rectangle and the center of the X (the carriage bolt) is touching your center line. Mark the four edges of your legs where they intersect the corners of your rectangle, then make a cut-line using your straightedge. Cu your leg-ends with your circular saw. Round over the edges or your cut marks with your file.

11. Apply glue to the ends of your legs and one side of each cross-member on the underside of your bench-seat. Set the glued leg-ends perpendicular on the underside of the bench, snug to the cross member. Drill two pilot holes per leg with your countersink bit. They should pass through the legs into the side of the cross member. Drill a 2 1/2-inch galvanized drywall screw into each hole.

12. Turn the bench right-side up. Measure the outside distance from one set of legs to the other. Cut two 2x4s to this length to be used as lateral braces.

13. Hold one of your lateral braces on the outside of the lower legs, tight to the joint of the X. Drill two pilot holes through the ends of the brace into the bench-legs and fasten with glue and galvanized screws. Add the second brace to the the outside lower leg on the opposite side of the bench.

Tips & Warnings

• If you buy pre-dried lumber, it is less likely to warp in the weather.

• Circular saws require safety instruction before operating.

References

• Redwood Bridges: How to Build a Picnic Table and 6 Benches
• "This Old House" Magazine: How to Build a Picnic Table: Jennifer Stimpson