How We Built DIY Bunk Beds for Our Happijac System

The Happijac lift mechanism is great – it raises and lowers reliably and the hardware is solid. But the sleeping surfaces it came with weren’t working for a family of six living full time on the road. The couches on the bottom were uncomfortable as beds, and one queen mattress up top doesn’t sleep four kids.

We wanted the garage to function as a real bedroom. That meant a proper lower bunk platform to replace the couches, and a wider upper frame that could actually fit two kids side by side. Construction lumber from Home Depot, a few boxes of screws, a tube of construction adhesive, and four sheets of plywood. That’s it.

We used RevolutionPly 5mm Poplar Plywood (4 ft x 8 ft sheets) from Lowe’s – or something similar. It’s lightweight, sands well, and holds a finish. We bought 4 sheets total and cut them with minimal waste:

• Sheet 1 – lower bunk top surface, piece 1: trimmed to 48in x 90in
• Sheet 2 – lower bunk top surface, piece 2: cut to 22in x 90in / scrap (26in x 90in) cut down to 15in x 90in for upper bunk extension top surface
• Sheet 3 – lower bunk bottom surface, piece 1: trimmed to 48in x 90in
• Sheet 4 – lower bunk bottom surface, piece 2: cut to 22in x 90in / scrap (26in x 90in) cut down to 15in x 90in for upper bunk extension bottom surface

The lower bunk top and bottom surfaces are each pieced from two cuts (48in + 22in = 70in). The upper bunk extension top and bottom surfaces come entirely from the leftover scrap. Four sheets, nothing wasted.

Note on stability: We reused the two fold-down Happijac couch supports that were originally part of the couch installation. These sit in the middle of the lower bunk and support the platform when it’s down. If your Happijac setup still has those supports, don’t remove them – they’re doing real work.

Note on mounting: We didn’t need additional brackets for the top bunk – the original Happijac side brackets supported the frame well once we extended it. Don’t over-engineer it. If your Happijac hardware is solid, trust it.

We assembled both frames outside the RV first – that’s the only way to do it with any amount of working room. Both builds are essentially the same concept: a 2×2 outer rectangle with 2×2 cross supports spaced evenly inside, screwed together with 3in wood screws and locked in with construction adhesive at the joints.

Lower bunk: Build the complete frame first – the outer 2×2 rectangle with all five 87in cross slats spaced evenly inside, everything screwed together and locked in with construction adhesive. Use scrap pieces to add short center blocks along the center line between each slat – offset them slightly from each other so you can get a screw in easily. Add diagonal corner braces at all four corners from scrap as well. Once the frame is fully built, fasten the plywood skins to both faces – bottom first, then top – piecing the two cuts (48×90 and 22×90) together on each face. Finally, fasten the three 70in support pieces to the outside bottom of the plywood, running front to back perpendicular to the internal slats. The 1×4 face board fastens along the front visible edge to finish things off. The two Happijac couch supports in the middle do the rest of the stability work when the bunk is down.

Upper bunk: We started from the existing Happijac frame and extended it 15 inches using 2×2 rails and cross supports. The scrap plywood from the lower bunk cuts sheathes the top and bottom of the extension. The 1×3 face board runs the full 75in length to clean up the front edge. The 1×2 rails keep the mattresses from shifting while we’re rolling down the road.

Both builds are pretty forgiving. Measure twice, cut once, and get everything square before you lock it in with adhesive.

We were well under $200 for both builds combined, and the whole thing took about a day and a half – with plenty of kid helpers along the way.

This is construction lumber in a moving vehicle. It will flex slightly. That’s expected and fine. What you’re building is a functional, safe sleeping surface that travels – not a showpiece. The 2×2 slat system on the lower bunk gives just enough flex to be comfortable while staying solid enough to not feel like a trampoline.

After miles and miles of road, both bunks have held up exactly the way we hoped.

If you have a Happijac system and you’re trying to figure out what to actually put on it, this build is a solid starting point. It’s not complicated, it’s not expensive, and it works.

And if you’re into the whole RV life / roadschooling thing, come hang out with us – we’re @milemarkersandmemories on Instagram and we document the whole journey.