To build a loft bed, gather the materials, measure the mattress, create a frame, and assemble the platform. Finally, prime and paint the loft bed.
Gather two-by-fours, 5-inch lag bolts, 3-inch pan-head steel screws, metal connectors and 3/4-inch plywood. Also gather 2-inch deck screws, 1/4-inch birch plywood, oriented strand board and a 1- by 8-inch poplar drill.
Measure the mattress, adding 2 inches on each side for sheets and blankets and 2 feet to the length to make a sitting platform. Create the top frame by attaching one two-by-four to the end wall and one to the side wall. Place lag bolts through the boards and into the wall studs. Attach the front board to the other side by hammering pan-head screws through the boards into the wall rails.
Make a column to support the loft platform. Attach two two-by-fours at a 90-degree angle to the outer unattached corner. Place metal connectors every 12 inches to support the top deck of the platform. Cut the plywood to size, and attach it to the top of the frame with deck screws. Attach oriented strand board to the back wall to close in the end under the loft.
Attach two-by-fours to the wall horizontally and oriented strand board at the end at the desired step heights. Cut pieces of oriented strand board for the steps, and secure them to the two-by-fours. Attach pieces of poplar to create a safety rail. Finally, prime the loft, let it dry, and add semi-gloss paint.