Since my wife and I are staring down kid #3, I figured it was about time to make a bunk bed so we can do the big bedroom shuffle before our new baby arrives. You may have noticed this bunk bed in the background of another project I did in conjunction -- Smart LED Lights, so I thought I might share some of my design and build experience on Instructables.
This project definitely falls in the "Practical" category, though I can never make a purely practical project, it still needs to be aesthetically pleasing, structurally sound, durable, and something that I feel proud of. This is the domain where the vast majority of my project time goes. Sure you could buy something cheaper or get it done faster -- but there's something about well made furniture that makes me happy.
Step 1: Concepting
I'll often spend weeks in this step depending on how focused I am on the design. I start by gathering all the requirements, the things the furniture needs to do to meet it's basic purpose. For this bunk bed, it needed to house two twin mattresses, fit under an 8 foot ceiling (with a ceiling fan -- important if you don't want to make your kids sleep with helmets to keep from getting thwacked by a fan blade at night), have a safe ladder, prevent sleepy kids from falling overboard (again very important if as a parent you like sleep, which surprise surprise, I do), and be structurally sound so it doesn't fall apart (or creak in my book).
With the basic requirements in place, it already sets a lot of the design parameters, the basic interior dimensions are fixed due to mattress size, the height is limited to a maximum, and you already know you want a reasonably shallow ladder angle and most of the crappy bed rail hardware is out.
Now I sit back and day dream what I want it to look like. This is really the fun part where you get to start to think through the shape, curves, or unique features you want to add. If I have a lot of driving or traveling, I work through a lot of the details quickly. I have a very spatial mind, so I can turn the design around in my head and look for problems or if I like the form long before I put pen to paper or finger to mouse. It's often helpful to look for inspiration, for me it's often thumbing through Houzz, LumberJocks, or any other magazines to see what you like about various designs before selecting your own.
Once I've got it pretty well formed in my mind, I start sketching. Like all engineers, there's something soothing about graph paper, it's kinda like a comfort blanket. I don't focus on making good sketches, just enough to get some ideas on paper and throw on some dimensions. Once I have most of the basic form and critical dimensions outline, I'll move onto the virtual design.
Step 2: Virtual Design
Now that you've turned the design around in your head for a while, it's time to put pen to paper. By the time you get to the virtual design phase, you should have at least 60% of it figured out, virtual design really comes in handy for documenting, getting the proper proportions, and finalizing the details.
Pick your favorite 3D modeling software and get started. For me, that's Sketchup, currently maintained by Trimble Navigation -- which for me is conflicting since I work for a company that is a competitor to Trimble in some markets, I feel a little dirty using it.... but it's also free.
Note: Most of the time when you start up a new model they automatically throw in creeper lady for references on size -- sometimes I leave her in , sometimes I get to creeped out and delete her. She ALWAYS faces you, I think that the part that weirds me out. So delete her if you're unnerved, which happened for this bunk bed model.
For the model I've attached, there's very little joinery information in it because I was planning to use my festool domino joiner, which simplifies the joinery since you can just butt two pieces together, then do a floating tenons.
I won't cover how to use SketchUp, but it's pretty similar to any of your other major CAD packages and there is already a wealth of information on those online.
As far as the design, I like to use curves to lighten up the structure and make it look less like it's made in a factory. There's a slight asian inspiration to the design, mostly in the curves of the rails to keep kids from falling out. I love the contrast between maple and walnut, and seeing how walnut is both softer (read easier to dent) and more expensive than hard maple, I usually like to use walnut as the accent wood. You'll notice the only significant change I made between the SketchUp model and the actual bed is the angle of the ladder. I realized when I held a piece of wood at the angle I had previously chosen that it was a little to steep considering my kids ages (3.5 and 1.5). The beds were designed as two separate units that could be separated in the future.
I also debated for some time how to join the bed rails with the head/foot board, as I said earlier, I didn't want any creaking, and most of the commercially available bed hardware are pretty good at making creaky or flimsy joints -- so I went with a 6" through bolt with a nut sitting in a slot in the rail.
I've attached the SketchUp model in case you want to use it. If you do happen to make one, let me know, I'd be interested to see the results.
Step 3: Let's Make Some Sawdust!
Well before you can make sawdust, you'll need to buy some wood. If you plan to use hardwoods (which I recommend) you'll need to find a good supplier -- you could try to buy it all from a big box store, but they usually don't have enough stock widths or species to be useful. If you happen to be in the upper Midwest, Liberty Hardwoods is GREAT! I've bought wood for nearly all my projects from them and had really good results. If you've never purchased non-structural lumber, it's a bit daunting at first. They use all sorts of archaic words that are really quite ridiculous, but if you want to fit in with the woodworking crowd, you'll have to learn to translate their vernacular. If you haven't heard someone say "four quarter" or 4/4 stock before -- the "Art of Manliness" has a great blog post on that.
I've included a picture of my order sheet, which has the species, thickness, and number of board feet of each type that I needed. I won't go through each specific operation that needs to happen, because I'm assuming you already know something about woodworking and can figure out most of the steps, but if not "The Wood Whisperer" is a great resource to get started with. Mark Spagnolo is both an entertaining and informative (and my inner nerd feels a special bond, and if for any reason he ever reads this, he will probably be totally creeped out. So this aside never happened).
I usually have Liberty Hardwoods straight line rip one edge and rough plane to +1/16 the final dimension. Once you have the wood in your shop, give it a couple days to acclimate to the humidity in your particular environment. Then plane down each board to it's final thickness (unless you need to do a glue up to get a particular width, like for the walnut panels). Cut to rough length and rough width and let it sit another couple days to make sure it doesn't warp any as it reaches equilibrium again. Finally cut down all the pieces to final width and length. Since I used a domino joiner XL, I didn't have to add any extra length for tenons but if you don't have that luxury make sure you add that length before cutting to final length.
I left the walnut thicker than its final thickness until after I glued it up. That way any gluing misalignment can be hidden after final planing. I then used a router table and large panel raising bit to get a centered tongue on the panel. I sanded the panels a lot to get rid of all the sharp edges (I received a lot of "feedback" from my wife on a coffee table I built that has left pretty sweet dents in both my kids heads after biffing it good into the table edges).
Next cut some grooves in the frames for panels, I used 3/8 of an inch, and cut them on the table saw with a dado blade. You can of course use your favorite technique to make the groove, but for me the table saw was fastest. I just cut the groove all the way through, and glued back in some fillers for the panels outside the panel area.
Now you can start gluing up the assemblies. Fill the grooves with "caulk backer rod" to keep the panels from rattling, and make sure to only glue a small section in the middle of the panels to the frame to make sure the panels have room to expand and contract. Work your way outward with larger assemblies, if possible cutting the joinery as you go so that everything lines up. Unlike machining metal, it's more important to get the relative dimensions right and the fit right than the absolute dimension correct.
Once you have the headboards all glued up, you can start on the bed rails. They're formed from two different pieces of wood, a large 8/4 board for the main support and a smaller board with cut-outs for the mattress support that will be glued to the main 8/4 board. I marked out the 5" x 3/4" slots, cut out the bulk of the waste with a bandsaw, then finished up with a dado blade to square everything up and get the final thickness right. Then glue them to the main board and hand plane everything flush.
I ordered my hardware from McMaster-Carr, arguably the best hardware site out there.
I cut the 316 SS bar stock down to 1" x 1" squares, and tapped a hole in each one. Then using my domino joiner, I cut a slot in the bed rails to slide in the giant nut. To align everything, I first put a couple dominos into the end of each bed rail and headboard, clamped it all together. Then I counterbore for the bolt head and drilled a hole through the headboard and into the bed rail. Then I used the little jig to estimate where to put the nut. Once you have that, all you need to do is drill a hole in tops of one bed and the bottoms of the other. Then cut a 4" pin from the 1/2" shaft stock to use for aligning the beds and keeping them from falling off each other. Then cut the aluminum stock to width and length, drill and countersink the holes, then bend it using a sheet bender or press. I just happened to know someone with a press... which helped a lot. You could probably make do with some enthusiasm and a vise too.
For the ladder I cut a dado for each stair so it would be very resistant to vertical loads, then screwed, glued, and capped all the holes with walnut.
For the anti-kid-roll-out-of-bed-and-disturb-your-sleep supports, I cut the pieces of out walnut and then just face glued them to two pieces of hard maple. Then I drilled some holes in the maple for 5/16"-18 button head screws. Then I held the supports up to the bed rails, clamped them down, and transferred the center of the holes to the bed rails. I used the threaded inserts to create threads on the bed rail side. That way they're removable in the future.
Step 4: The Boring Part - But Important None the Less: Sanding and Finishing
Now hopefully you've been sanding as you go since there are a lot of places that are difficult to sand. Give it all one more sanding, start at 100 grit then sand everything again with 150 grit. I usually don't sand any more than that. I like to spray my finishes, and have switched over to all water based finishes. My favorite is General Finishes Polyurethane Water Based Topcoat. It's easy to apply, cleanup, and gives a great clear finish. I like my furniture to let the beauty of the wood show through rather than covering it with stain. So it works great for me. If you've never sprayed before, the Earlex 5500 works great and is quite affordable. My boy Mark has a great intro to spray finishing on theWoodWhisperer.com. You'll need to sand between coats, which I usually do with 220 grit after the first coat and 600 before the final coat (usually 3-4 coats).
Boom you're done.
Hope you enjoyed it!