How To Build A Slide In Truck Camper
So how do you actually build a slide in truck camper?
I definitely have ideas, but since I haven’t actually built one, and there are only a handful of articles and videos online explaining the construction process, I can mostly only extrapolate from my own experience and research to suggest how you might go about it.
If you’re building from scratch…
Based on what I’ve seen online, you’re essentially going to create a camper shape whose front and back walls are “T-shaped”, and you’ll panel around that basic shape. The most common approach seems to be to simply lay plywood boards across the truck bed rails that are wide enough to extend outwards 4-8 inches and inwards far enough to pass the wheel well risers. Once you have that essential measurement, you just build two walls upwards from the outer edges, two walls downwards from the inner edges, put a floor on the bottom, and a roof on top! The thickness of your panels and how you attach them together will be part of your design strategy in which you’ll probably want to minimize weight and bulk, while making the lower section sturdy enough to support some weight from inside while on jacks and support the weight of the camper above when set on the ground or on saw horses or cinder blocks for long-term storage.
As previously mentioned, another way to think of it is that you’re making a camper top and connecting it to a “floor box”. That’s what I would have to do if I ever wanted to convert my bolt-on camper to a slide-in design, and it’s an approach you might use if you wanted build the top and bottom from different materials, ex. plywood on the bottom and aluminum framing on top.
If I was converting my own home built truck camper into a slide on, here’s what I THINK I would do:
STEP 1: Install jacks. Otherwise I’d have no good way to get it off the truck. While I think it would technically be possible to retrofit a hanging floor box while the camper is still on the truck, I think it would be a lot easier to work if I could get under it easily. Now regarding jacks — in order to use them easily, your attachment points on the corners of the camper need to be wider than the body of the truck. Since my camper walls are built flush with the truck bed rails — I’d need to build out my corners by 4 to 6 inches so the jacks can hang past the bulge in the truck body. I suppose I would use lengths of 4×4 post at the corners to build them out and then bolt the jack posts to those. (Though I would also think about some way to maybe insert temporary horizontal supports that would function like handles, a la “the Ark of the Covenant”.)
STEP 2: Install rails. I’d need to create a structure to hang the floor box from the walls, so I would run two 2×4 rails on edge just from the bottom of the front wall to the back wall just inside the wheel well risers.
STEP 3: Make the floor box. There are plenty of ways to make a plywood box that hangs from the 2×4 rails. Since the back end of the box is actually the back wall / door opening, essentially you’re talking about just 2 long side panels and the floor (and a front panel, if different from the camper’s front wall) which will “hang” from rails above. You’ll need to consider how much extra framing you’ll need based on the weight of the camper that it occasionally needs to support from below. A tradeoff to consider is that the thickness of the walls and floor framing — if any — will impact your internal space, ex. If you were to attempt a typical “floor joist” design, you’d lose a lot of internal height.
To deal with that you actually could “hang” the floor panel from “joists” above the floor (like a ceiling) but they would then be in your way, inviting you to trip over them. Fortunately in this case, the floor in a slide-on is usually pretty narrow — just 2 to 3 feet wide — and if you expect only to be walking on it when it’s sitting in the truck bed, you really don’t need much floor support at all, other than to make sure it stays put. I think what I would do is use a “floor rail” to which the box sides and the floor are attached, screwing the floor panel into it from below (making sure to angle your screws to make them more difficult to pull out under load). And of course if you need to support a really heavy camper, you might find it appropriate to build the box walls with an actual framed-wall structure — though it does seem intuitively like a well-made plywood box should be able to support quite bit of weight.
STEP 4: Panel the top “box flaps” to make a bench … (or bed or whatever you like).
STEP 5: Insulate the floor box. Note that styrofoam boards can assist with the structure and fit much more neatly. Whether you attach them from the inside or outside is up to you.
STEP 6: What about the back wall? One seemingly universal feature of slide-ins is the pronounced "T-shaped" rear. But since the wheel wells are probably nowhere near the tailgate, it's possible to use a rear wall that encloses the entire tailgate area with no leftover space cut out of the sides, and it will still fit in the truck. Doing this would give you lots of enclosed area under the bench that can be used for temporary storage and can help you out with insulation by keeping the weather out of the under-bench area. So in my case, I would just leave the back wall exactly as it is (like a facade wall), rather than cutting it to match the shape of the floor.
Are we done??
That seems easier than I expected, so I probably missed something! But I think it captures the basic elements unique to a demountable camper -- a floor box attached to the bottom of the camper and jacks. Other than those features, construction should be pretty similar to how you would make any other. It does need to hang over the rails a bit -- at least 4 to 6 inches, depending how much bulge you have in the bed walls -- so you'll lose a little bit of aerodynamic efficiency as a result (according to my calculations, in the area of 10% worse). And the floor box and jacks will add in the area of 100-150 pounds.
Of course, I would love to hear from anyone who has actually built a slide in truck camper! Photos and videos would be especially helpful.
Meanwhile, be sure to view any other videos I've collected in this category that might give you the inspiration you need.
Credit: The background photo for the article's "featured image" is from an interesting video by The Motorhome Channel which you can watch within my other post here: Homemade Slide In Truck Camper (Demountable)