Build a twin over full mattress bunk bed with standard lumber

I built this bed to fit into a dormer that is only 73" wide; a standard mattress length is 75". I saw this similar design at a furniture store for more money than I have to give. This design can be adapted to standard or custom lengths. I ordered foam mattresses that I shortened to fit with an electric knife.

To start, send the kids away for the weekend; this is a huge project that took about 20 hours for my wife and me to complete. Hand-pick the best boards at the lumber store, straight and as few knots as possible; also make sure all edges are good. If you have a router, routing boards before assembly makes the bed look much more furniture-like.








Tools Needed:

• Circular Saw
• Drill and Bits
• Countersinking Bit
• Ratchet and Socket Set
• Hammer
• Wood Chisel
• Tape Measure
• Square
• Level
• Chalk Line or something to make lines on plywood.
• Sander
• Router (Not necessary, but makes it nicer.)
• Paint Brush

Materials:

• 11 – 8' 2x6s
• 8 – 8' 1x4s
• 5 – 8' 2x2s
• 2 – Sheets of 3/4" Plywood (I spent $5 more for the fancy birch kind.)
• 20 – 3.5" Lag Screws and Washers
• 6 – 2" Lags Screws and Washers
• 1 Box of 100, #8 All Purpose 2" Screws (Don't use sheet rock screws, they're too brittle.)
• 4 – 2" L-Brackets
• Wood Glue
• Wood Filler Putty
• Painters Caulking
• Semi-Gloss Paint

These materials came to around $150.

Step 1: Build the A-frame End Pieces

Cut the back legs (2x6s) to a height of 6', then lay out the cross pieces and the diagonal front leg on the floor to line things up. The three 2x6 cross braces have lengths of 36.75", 39", and 54" from top to bottom.

My front leg was about 72", but it will vary depending on the angle you set; use a square and a long board or laser to mark the length and cut points (see picture.)

Once everything is laid out and marked, cut the front leg ends and attach the pieces with several 2" screws. For extra strength notch the boards with a circular saw and a chisel; use wood glue and several countersunk 2" screws to attach the pieces. My notches are .5" deep, make some test cuts on scrap wood to make sure the depth is right. Notching the legs makes it very strong, notching just the cross braces makes it strong enough; leaving out the notches would result in a less stiff frame. If notching the legs, use a router or chisel to square the curve left behind by the circular saw.

Step 2: Build the Mattress Platform

Twin Mattress is 39"x75"
Full Mattress is 54"x75"

Cut four 2x6 boards to mattress length, 75" for normal size; mine are 68" because of the narrow dormer I'm squeezing it into. Cut four 2x2s to the same length and attach them on the 2x6s to form a lip for the plywood to rest on; use the 2" screws every 6" across the 2x2. Pre-drill all holes to keep the wood from splitting.

Make a 2" thick template out of scrap 2x6 to evenly drill the holes for the 3.5" lag screws that connect the A-frame to the 2x6 mattress boards (see picture in gallery.) Drill through the legs, and then use the template to drill into the 2x6 ends. Measuring to the bottom of each 2x6, the lower bunk boards are 12" off the floor, the upper bunk boards are 20" from the top.


Across the middle on the bottom bunk, add a 2x2 for extra support under the plywood; attach it with the 3.5" lag screws.
In the photo you can see I messed up on the back mattress support; I didn't angle the front leg enough when calculating the mattress width, so the 2x6 had to be lowered to fit the plywood and mattress.

Cut the two sheets of 3/4" plywood to make mattress supports as shown in the diagram in the photo gallery. These should lay onto the 2x2 supports. On the upper bunk I added a 2x2 rib under each sheet with four countersunk screws to stiffen it up a little.

Step 3: Build the Ladder and Railing

The ladder rails should be about the same length as the front diagonal legs on the A-frames. I used 1x4 boards here and cut the ends to the same angle as the front legs; mine were about 18 or 108 degrees depending on how you look at it. Use a piece of scrap wood with the angled cut to mark the stair cuts in the railing; use a circular saw to cut 1/4" deep notches to receive the step boards. I made each step 9" apart and 15" wide for a total of seven steps. I used four 2" screws with pre-drilled holes to attach each step. L-brackets attach the ladder to the bed.

The front rails are attached with 2" lag screws on the frame side; regular screws attach the other side to the ladder. Two 1x4 back rails on top and one 1x4 back rail on the bottom are attached with 2" lag screws. Make the spacing between the rails 4" or less to keep little heads safe. Note: My pictures don't show the back 1x4 rail on the bottom bunk.

Step 4: Paint and Finish Details

You can fill screw holes and sand everything at this point or as you finished each step above.
Clean the dust with a damp rag; use rubbing alcohol to clean stamps and other marks on the wood. Use painter's caulking to fill in seams and spaces on the ladder and wherever else that needs tidying up. Prime, paint, and order the mattresses. My wife used an electric knife to shorten the foam mattress to fit our shorted bed frame, it worked very well. She also added stencil floral graphics on the front of the bed.

Optional Step: Build under-bed storage drawers; that's for another day.

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