Enclosing a utility trailer means not only making a safe and secure covering, but also doing it within a determined budget. No matter the size of the trailer, whether it's 1.8 or 4.8 m (6 feet or 16 feet) long, there are two obvious options for enclosure: hard or soft. A hard cover of wood is relatively easy to make with a few hand tools. A metal shell is also possible, but requires metal working tools. A soft cover of canvas, vinyl or plastic not only will keep the trailer contents dry, but can be versatile for different uses.
If building a wood enclosure for the utility trailer, it must be secure going down the road. The last thing an operator needs is for the enclosure to come loose or, worse, come off in a high headwind on the motorway.
Create a frame using 60 cm by 60 cm (2 by 2 foot) pieces and secure them to the trailer floor with angle brackets. Space the vertical supports every 45 cm (18 inches). Attach horizontal pieces every 60 cm (24 inches) from bottom to top. Use woodscrews over nails for this procedure. Connect the two sides, front and rear with transverse 5 cm by 10 cm (2 inch by 4 inch) studs. Cover with 9 mm (3/8 inch) plywood cut to size. Again, attach with screws. Seal all joints with caulk and thin strips of aluminium flashing. Install a door where convenient.
Contact a marine supply shop for a waterproof material large enough to enclose the wooden frame. Reinforce the edges with grommets at a maximum of every 30 cm (12 inches). Cover the wooden frame with the cut-to-size fabric and secure with line to the trailer frame at every grommet. The advantage of the cloth enclosure is that it can be removed in the event any outsize tall or wide items need to be loaded on the trailer.
Although involving more work than maybe a home hobby craftsman wants to perform, a third option for enclosing the utility trailer is using metal. Complete the wooden frame as described above. Using corrugated galvanised sheeting, install with panhead screws around the frame and the roof. The corrugated galvanised sheets can be overlapped to ensure a good seal. Apply a layer of caulk between each seam to make the trailer water tight. The advantage of the metal frame is, once painted, it will stand up to weather for much longer than any other material. The disadvantage is the interior of the trailer may be insufferably hot in high summer.