A stair bunk bed is an ideal piece of furniture for small children sleeping in a small bedroom. The stairs allow kids to easily climb into bed without the risk of falling posed by a ladder. The bunk bed structure doubles the amount of sleeping space in a bedroom. If only one child sleeps in the room, the extra space can be used for a desk or a play area.
Ask the timber yard where you buy your wood to cut it to your desired lengths. Many will do this for free and sand down the rough edges. If they won't help you, you can cut the wood yourself. Measure twice and cut once.
Construct the platform frame around the plywood slab. Use 12.5 cm (5 inch) bolts to secure two 2.2 m (7 foot 4 inch) boards and two 1.2 m (4 foot) boards together in a rectangle. Stand the wood on the 5 cm (2 inch) sides and connect two bolts in each corner. Bolt five more 1.2 m (4 foot) boards at equal intervals inside the rectangular frame. These boards should lay flat on the 10 cm (4 inch) sides. Nail the 1.8 cm (3/4 inch) plywood slab to the top of the supports.
Place the bed frame on its longer side and line up two 10 by 10 cm (4 by 4 inch) timber posts beneath it. The top of the posts should extend 60 cm (2 feet) beyond the top of the frame. Use bolts to attach the posts to the frame. Attach two more posts on the other side of the frame in the same way. Stand the frame on its legs and make sure that it is level.
Support the bunk bed structure with cross beams. Use bolts to attach a 2 m (6 foot 8 inch) 5 by 10 cm (2 by 4 inch) board between the two posts on the long side that will be against the wall. Place this cross beam along the floor. Attach another one halfway between the floor and the mattress frame. Attach 1.2 m (4 foot) long 5 by 10 cm (2 by 4 inch) boards in the same way on both short sides.
Connect security rails between the parts of the posts that rise above the bed frame. Bolt two 2 m (6 foot 8 inch) 5 by 10 cm (2 by 4 inch) boards between the posts on the long side that will go against the wall. Bolt two 1.2 m (4 foot) railings between the bed posts on both of the short sides. Attach a 60 cm (2 foot) vertical support 60 cm (2 feet) away from one of the railings on the open side. This will be where the staircase will go. Bolt two 1.5 m (5 foot) railings between the vertical post and the support on the side of the 1.5 m (5 foot) gap.
Build the staircase. Make sure the ends of the staircase rails are cut at 45 degree angles in opposite directions so that they will lay flat on the ground and bed frame. Attach six 60 cm (20 inch) steps at 30 cm (1 foot) intervals between the two 2 m (8 foot 6 inch staircase rails. Make sure that they are angled properly. Stand the staircase against the bunk bed and bolt it to the frame at the opening in the security rails.