I built three sets of TRIPLE BUNK BEDS. The many (grand)kids love them. They have plywood "floors" instead of springs and single bed size mattresses fit perfectly.
They are substantial, fairly heavy and SOLID.
The plans came from "
Bunk Beds Unlimited, Tallahassee Florida". I believe the plans cost $10.00, ordered on line. Plans are copyrighted so I will not share them
For one set of beds, you will need 10 2x6x8s, 12 2x4x12s, 6 2x2x8s and 3 4x8 sheets of 3/4" plywood. Hardware requirements are listed, as well.
You'll need power drill, bench saw, good hand tools/wrenches and if possible, a planer, to "dresses up" the wood.