DIY Enclosed Trailers

Protect your cargo from the elements by building a trailer enclosure.

If you need to enclose your utility trailer to conceal and protect your cargo, a homemade plywood trailer container may be a solution. Most utility trailers have stake mounts welded along the front, rear and sides of the frame. You can build a plywood box with 1-by-4 extensions that will mount the box to the trailer frame. An enclosed trailer container, sealed with silicone, can protect your cargo from the elements, and conceal your cargo from view.

Things You'll Need

• Utility trailer, 40- by 48-inch frame, with stake mounts
• 1 plywood board, 3/4-inch thick, 40 inches by 48 inches
• 1 plywood board, 3/4-inch thick, 40 inches by 54 inches
• 2 plywood boards, 3/4-inch thick, 48 inches square
• 2 plywood boards, 3/4-inch thick, 38 1/2 inches by 48 inches
• 80 feet of 1-by-4 board length
• 10 stainless steel angles, 2 inches by 2 inches by 3 1/2 inches
• 4 stainless steel rotating hasp hinges
• 72 lag machine screw, washers, and nuts, 3/8-inch diameter, 1 3/4 inches long
• 96 wood screws, Phillips head, 1/4-inch diameter, 1 inch long
• Power drill and a 3/8-inch bit
• Socket wrench and socket set
• Screw gun, Phillips head bit
• Circular saw
• Tape measure
• Wood glue
• Silicone sealant
• Safety goggles

Instructions

Preparation

1. Locate your trailer's stake mounts along the inside of the frame. There should be two mounts per side. Measure and note the width, from the inside edges, of the side, front and rear stake mount pairs. The side stake mount widths should be the equal, as the front and rear widths should also be.

2. Measure the stake mount insertion depth. This depth should measure between three and five inches, and will allow vertical 1-by-4 boards to mount to the trailer's frame.

3. Cut six 1-by-4 boards to a length matching the side stake mount widths. Then, cut six 1-by-4 boards to a length matching the front and rear stake mount widths. These boards will mount horizontally to the plywood walls.

4. Cut eight 1-by-4 boards, each to a combined length of four feet, plus the insertion depth of the stake mounts. The final length of each board should measure between 51 and 53 inches. These boards will mount vertically to the plywood walls.

5. Frame the side walls of the trailer box. Lay the two 48-inch-square plywood boards on a flat surface. Place the horizontal 1-by-4 boards, cut to the side stake mount width, at the top, middle and bottom of the plywood. These 1-by-4's should be oriented horizontally in the center of the plywood board. Fasten these boards to the plywood with a screw gun, using two wood screws per end.

6. Lay two vertical 1-by-4 boards along either side of the horizontal boards mounted to each side wall. Allow the excess length of the vertical boards to extend past the bottom of the plywood. Fasten the vertical boards with a screw gun, using two wood screws, each at the top, middle and bottom. The 1-by-4 framing on both side walls should resemble a step ladder, with legs extending out from the bottom of the boards.

7. Frame the 38 1/2- by 48-inch front and rear walls of the trailer box using the same procedure as the side wall assembly. Mount the horizontal 1-by-4's -- cut to the width of the front and rear stake mounts -- at the top, middle and bottom center of each plywood board. Mount vertical 1-by-4's along each side of the horizontal boards. Fasten all the boards using wood screws and a screw gun.

Assembly

1. Fit the 40- by 48-inch plywood board to the bottom of the trailer frame. Fasten the board to the bolt holes of the frame by drilling 3/8-inch holes in the board, and fastening lag screws with a socket wrench.

2. Mount the front and side walls to the trailer. Insert the vertical 1-by-4 leg extensions of each board, into the stake mounts of the trailer. The 1-by-4 framing should face into the trailer.

3. Fasten the two front corners of the trailer, where the side walls and front wall meet. Apply a line of glue along both vertical edges of the front wall. Drill 3/8-inch screw holes to accommodate two steel angles, equally spaced, along each front corner. The angles should sandwich the edges of the front wall between the ends of side walls. Fasten the steel angles using lag screws and a socket wrench.

4. Apply a line of glue along the top edges of the three walls. Place the 40- by 54-inch plywood ceiling board on top of the three-sided trailer box. Allow the excess 54-inch length to extend past the rear of the trailer. Secure the ceiling to the front and side walls by fastening two equally spaced steel angles per edge -- six angles in all. Drill 3/8-inch screw holes to accommodate the steel angles, and fasten the angles using lag screws and a socket wrench. The ceiling should be tightly fastened atop the front and side walls.

5. Mount the rear wall in the rear stake mounts. Fasten two, equally-spaced rotating hasp hinges along each rear corner of the box. To do this, attach the hinge component of the hasp to the side wall edges, and the rotating cylinder component to the rear wall. Drill 3/8-inch screw holes to accommodate the hinges and cylinders. Fasten the components with lag screws and a socket wrench. The hasp hinges should latch over the cylinders, which rotate to lock the hasps in place. This will secure the rear wall when driving, and allow for quick removal when loading.

6. Apply silicone sealant along the front corner edges and around all lag screws, to weatherproof the front of the trailer. The ceiling overhang should deter water runoff into the rear of the trailer.

Tips & Warnings

• To further weatherproof your trailer box, install waterproof rubber bushing around the outer edges of the rear wall, using screws and a screw gun.

References

• WM8C's Ham Links and Amateur Radio Site: Building a Covered Trailer For Hauling
• Harbor Freight Tools: Mini-Trailer Assembly and Operation Instructions

Resources

• Read this Article in Spanish