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Has anyone ever built their own rooftop luggage or cargo box? Answered

I have had a couple and for 2 & 300.00 bucks or more, there's really not much to them. It's just a hollow hinged plastic box, made to be a little aerodynamic and strapped to an existing luggage rack. I find it hard to believe that a home made version couldn't be created as sturdy if not sturdier, hold more and last longer. I was thinking maybe pvc, conduit, or even wood framed. Just curious. Thanks in advance for any helpful input.




OK, I just did build a box for the top of our Toyota Sienna van. Is about 3' x 3' x 12" and quite aerodynamic too. Its made of wood and aluminum, so before I finish it, I will take it apart, show you the construction ( it only cost me $6.00 using scrap material from my shop).

I got into XC skiing this year and have been putting the skis in the Jeep with me so far. Kinda stinks when the melting snow falls off onto my arm while I'm trying to drive. Also seems like they would be deadly the way the end is up near my head in the event of certain types of accidents.

Been brainstorming a PVC pipe "box" for each ski that will attach to my old school Con-ferr roof rack. I'm thinking a glue capped 3in. pipe with an offset transition on the end with a screw on cap should account for weather, weight, the ski tips and curve, aerodynamics, and painted black, blend in with the rack.

I'm sure some kind of DIY project could be made, BUT, I would be concerned with a few factors;
  • The combined weight of the box and contents doesn't exceed safe limits, and create a dangerously top heavy load. (Commercial units specify a maximum weight of items, and therefore make the boxes a lightweight plastic, to allow for more storage weight).
  • The box can safely be secured to the vehicle (without rubbing or causing other damage).
  • The box can safely be secured and not come loose while traveling down a highway.
  • The aerodynamics are well thought out so that fuel costs don't dramatically rise (due to wind drag).
And the last, and maybe most important factor, is that you are allowed to do this. It would be counterproductive to make some kind of DIY storage box for your vehicle, and get pulled over by the Department of Transportation, and either fined, or forced to remove everything on the side of a busy highway (which can happen if they feel your load is unsafe). 

I'm also looking for information about this, surprised I can't find any examples. Commercial boxes seem to run about $300-$500 which seems like big money for some molded plastic.

I've already got a factory-installed roof-rack which gives me secure mounting points, so wondering why I can't just build something simple myself.

For sake of argument say a large box in the range of 6'x3'x1.5' (i.e. 27cuft which is probably bigger than I actually need; the bigger commerical ones run about 18-20cuft).

That would be about 63sqft of sheeting material. 3/4" plywood seems like overkill to me (tho I'm only thinking about putting lightweight but bulky stuff in the box), so say you built with 1/4" (marine?) ply with 1"sq internal frame, then you'd be around 50lb or so (at 3lb/sqft-in for plywood), plus some clamps and waterproofing (spar varnish?). Maybe double the weight of a commercial version? Hard to believe I couldn't secure that safely to my roofrack for hwy speeds?

Are there really laws about what you're allowed on the roof of your car? I see lots of crazy stuff people have tied up there which looks completely unsafe but never see anyone pulled over for it.

Its the Department of Transportation versus the police that you have to worry about, but even with them it depends on who you get. If your build looks professional (which can be easy enough to do), you can get away with not having to buy a commercially made container; but if you leave it more on the "rustic" side, you can easily get pulled over for an inspection (which can either be a time waster, or a ticket if they deem it unsafe). That being said, I think its more than possible to make something, especially since you have the mounting brackets.

Obviously you want to make sure the load doesn't get top heavy for your vehicle, and so if the items are more lightweight but bulky, you could do this a few ways.

The way I would make the cargo box is with fiberglass. Its strong and lightweight, easy enough to work with and fairly inexpensive. You simply buy the fiberglass sheets and resin, and like making paper mache, you cover a mold until you have the shape and its set. The mold can be made out of styrofoam, cardboard or even plywood if you have some scrap sheets. You may need to use some plastic sheeting over the mold to act as a release agent, but having built a fiberglass boat, I can tell you that making a rooftop cargo box would be rather easy.

So once you have the 2 halves made and dry, you can trim/sand until its perfect and finish it off with a coat of marine paint. A seal can easily be made with some rubber, and then just drill out the holes for the mounting brackets, add a couple hinges and a latch to keep it closed.

IMO, that's your best bet, and will be much lighter than plywood, and obviously weather proof. :-)

I did years ago when I had a roof rack. I used 3/8" plywood and cut down 2x4's to build an open box that I covered with a tarp. For mounts, I used bolts and large washers to pinch into the slots of the roof rack rails. It made it for over 3500 miles round trip and lasted outside for a good 7+ years before I got rid of it. Thing was, it was heavy. Much more so than a manufactured one. If you factor in the extra weight, you'll actually save money (in gasoline) by using a store bought shell. Pick your trade off.


Hey Qa,

there has got to be a way to stay lightweight and still keep durability and strength.

And canucks,
you have got to relax, we're just brainstorming here. Anyway, I have yet to meet a very creative rule follower.

Thanks guys

Canucksgirl is only looking out for your best interests. And it is true that certain things are better off left to the professionally maunfactured products, especially where safety and liability are concerned.

In my particular case, the cartop carrier was needed to haul a bunch of bulky stuff - not heavy - that would not fit in the station wagon with 7 people and all their stuff. Standard carriers were way too small (and still are for what we needed) and cost a ton more. My carrier had corner braces that fit between all 4 rails (the 2 sides and the 2 cross pieces) - tightly - and then there were 4 sets of bolts and washers that went through the bottom and the largest washers fit into the rail slots and clamped them tight. Then, after loading, tying the load with a bunch of rope in a net fashion (via holes along the top of the wood) and covering with the tarp, the whole thing was tied around the racks with rope. If they had tried to pick up this box with a big claw under the ends, it would have ripped the roof up or at least pulled the roof racks out of the roof (if the wood didn't fail at the claws!). It wasn't very aerodynamic, but it worked well for what I needed. Fully loaded, the old '86 Caprice Estate got between 17-18 mpg on that trip with a worn out engine.

For your own edification, you would need to engineer a good, high strength frame (I would prefer some sort of ChromeMoly tubing as opposed aluminum, aluminum is just too soft for mounting points) and mounting system that could be wrapped in something to keep the wind and weather out/off of the cargo. You also would need to be sure that the cargo could not escape the carrier. Keep it sort of teardrop shaped for lower wind resistance and make it as professional looking as possible. I will give that advice, but it is up to the individual to take responsibility for their build and anything that happens during the use of the product.