I designed a two-story indoor rabbit hutch with a ramp for our bunny to go up and down. One really great feature of my design is the grates are very easily removed for easy access. I designed it in Fusion360 with almost everything parametrically driven, so if you have/download Fusion360 you can change the dimensions to be whatever works for your house. There's a section on that further below. The instructions in this tutorial are for my build, which was 61.5'' x 16.5'' x 33.75''.

Supplies

I used kiln dried white pine for my lumber because it is known to be safe for rabbits. There's a lot of stuff on the internet about pine phenols being bad for rabbits, so be safe and get the kiln dried stuff. For the floors I used baltic birch plywood - birch is also rabbit safe (and ours tends to lick the floors)

All of my lumber were 1x4s, except for the ramp which was a 1x8.

1 pine 1x4, 61.5'' long (slotted roof). This will be ripped in half (length-wise), so try to get straight pieces.

4 pine 1x4s, 60'' long (slotted pieces for front/back). These will also be ripped in half.

4 pine 1x4s, 16.5'' long (slotted pieces for sides). These will also be ripped in half.

8 pine 1x4s, 15.5'' long (first floor columns).

8 pine 1x4s, 15.75'' long (second floor columns).

2 pine 1x4s, 15.00'' long (short sides of roof).

1 piece of .5'' birch plywood, at least 60''x30''. This will be cut in half for each floor. Ideally you'll have a little more than 30'' to accommodate the width of your blade, as each floor is 15'' wide.

1 pine 1x8, 25'' long (the ramp).

1 5/16'' wooden dowel. I think these typically come in 4' lengths, that should be plenty.

#8 X 1 1/4'' screws and #8 X 1 1/2'' screws

#6 X 1 1/4'' screws

24 14-inch grate panels, I bought these ones

Tools

Table saw, router table (with 5/16'' router), drill press, handheld drill, and potentially other types of saws like saber saw or circular saw to make a few parts easier.

Step 1: Alter the Design (Optional)

If you've never used Fusion360, this is a great opportunity to get acquainted with it - it's a fantastic piece of software free for hobbyists. Even if you don't want to change any of the dimensions of the build, having the 3D model to refer to is incredibly useful when constructing the hutch. You can download it here, and you can register the trial as a hobbyist for a full license. Once you have the software, you can download the CAD for this design here as a Fusion360 Archive. You can then upload that file into Fusion360 using the Upload button on the left hand side.

Once you've opened it, click on the Modify dropdown, and hit Change Parameters. I tried to Star the parameters that people would be most likely to change. The two most important parameters are "num_grates_length" and "num_grates_width", as they will determine the length and width of your cage. Each grate is 14 inches square, so that is the length added by incrementing either of those numbers. As you change those values, you can see how the "cage_length" and "cage_width" parameters are affected. The only thing I wouldn't change is the height, as that wasn't designed to be changed. That said, it wouldn't be very hard to take the design and make a single-story unit. Lastly, this is my first parametrically driven design, so there may be some unexpected bugs with certain changes. Overall it seems to work though.

Step 2: Fusion360 Tips to Help Your Build

Downloading Fusion360 isn't required for this build, but I wanted to give a few tips if you've never used the program that will help you with your build. First, if you click on an edge of the design, in the bottom right it will tell you the length of that edge. I find that very helpful so I know quickly and easily what length to cut a piece. Just be careful to see that the edge you picked isn't interrupted by other lines, so you get the full dimension. Also if you click on any piece/line/sketch, Fusion will highlight on the left which component your selection is part of. This is very useful if you want to A) Hide the component to see other parts better or B) Change something yourself. You can hide the component by hitting the Lightbulb next to the component name.

Step 3: Preparing Your Wood

First you'll want to cut your pieces down to the sizes mentioned in step 1, or to the sizes Fusion360 shows after you've made your changes. For the pieces I mentioned will be ripped in half, I recommend doing this on a tablesaw - so you can set your fence distance and do all the pieces you need at once. Next, take those pieces to your router table and route one side with a 5/16'' router bit, going 5/8'' deep into the wood. Make sure you're routing in the center of the wood. Do some test pieces if you have to.

You'll also want to prepare your dowel holes on the columns. I tried to position them as best I could in the design, but you might want to measure out in real life where those dowels could go that won't coincide with the grates (though it's not the end of the world if they fit inside a grate hole). The dowels keep the grates from sliding, but are easy to remove if you want to access the cage or your bunny. I recommend using Forstner bits on a drill press set to a depth roughly halfway through the 1x4. It's also not really necessary to have 2 on each piece. Note that the position of the dowels will be different on the sides of the cage vs on the front/back/top. Once you have one piece with the holes, you can use these to mark the holes on the equivalent pieces. Now would also be a good time to chop your wooden dowels into 1-inch pieces.

Step 4: First Floor Assembly

Start with your first floor, screwing your column pieces into the plywood from the bottom. I recommend placing the columns on your plywood, drawing the outline around the column, then mark where your drill holes should be. Drill your holes (with countersinks), then flip the plywood over. Clamp your columns to the plywood (columns should be pointing to the ground), drill pilot holes through the holes you already made and into the column pieces. Then put your screw through both pieces. Do this for each column and you should end up with something that looks like the first picture.

Next attach your routed pieces straight to the columns. You want to try to avoid screwing into the laminate of the plywood, but you can add one or two screws along the bottom for support. Be sure not to screw through the channel you routed. Also make sure the top pieces come up .5'' above the columns, because your second floor will be sitting inside that channel. You should end up with something that looks like photo 2.

You'll find that in the corners where the routed pieces meet, you'll have to cut out a piece to allow your grates to slide freely in both directions. I used a sabre-saw, but do it however you want. The design maintains a little nub, but that will probably break off. Feel free to saw it off completely as seen in the last picture.

Step 5: Second Floor Assembly

Cut out a hole in your second piece of plywood with the saw of your choice. My hole dimensions were 7 1/4''x15''. Then the second floor is made exactly the same as the first, except your routed pieces on the bottom are being screwed in just above the plywood base (instead of flush with it as on the first floor). You can see that in the first picture. Likewise, make sure the routed pieces on the top come up .75 inches above the tops of the column pieces - that's where the roof will fit in to place.

Depending on the dimensions of your cage, you may want some cross-bracing underneath the plywood for support. I just put a Forstner hole right underneath the plywood and use a small piece of dowel for support.

Adding the roof is pretty basic, just screw the wide pieces to the top floor so you have a snug fit (see photo 3), then attach the routed pieces on either side (see photo 4).

Step 6: The Ramp

The ramp is just a single piece of kiln dried pine 1x8. The length will depend on the angle you want in your cage. Personally, I wasn't sure about the best angle to put the ramp. I didn't want the ramp to take up too much space, but I also didn't want it too steep for a bunny to climb up or down. I read online it could be as steep as 45 degrees, so I went with that, but in retrospect I probably would have decreased the angle a little bit. Our bunny can get up and down fine, but it's more like a hop up and a hop down. I also added little steps on the ramp not included in the design, just from some offcuts. Note I put the ramp off to the side because we have a cage in front of this hutch, and I needed to make sure the ramp wasn't going to inhibit our bunny from jumping out of the cage into the hutch. I also added a reinforcement under the ramp, but I don't know if that is totally necessary. Our ramp comes up a little passed the top plywood to rest on it. We originally had a lip on the second floor to screw the top of the ramp into, but decided it wasn't needed. By not having fasteners connecting the ramp and the second floor, the top and bottom floors can be detached without removing any screws.

Step 7: Making It Comfy

The build is done! The last thing left to do is making it a comfy place for your rabbit. We put down cotton rugs and towels (avoid synthetic materials) and attached them by clipping them to the routed lips around the cage. Unfortunately that means the grates have a hard time sliding, but the bottom is still easily accessible as is the roof. Most rabbit owners have their tried-and-true techniques and know what their rabbit likes, so get creative and make the space comfortable for your bunny however you see fit. Throw some cardboard in there, some rags, toys, whatever! Our bunny did start chewing the corners of the columns, so I attached some aluminum L-bar (you can see in the picture) to each corner, but you can find your own solution if your bunny starts chewing their hutch.

Lastly I'd recommend still having a plastic cage accessible in the front where your rabbit can go to the bathroom, or at the very least a plastic container inside your hutch. Wood is much less resilient than plastic for such things.

I hope this guide was helpful to some people out there, please comment to let me know what you think or if you make it!