Safe/professional way to transport lumber with just a roof rack

Question

I'm doing some home improvement, and have the necessary skills, tools, etc, for the job. There is one thing I'm lacking: a large pickup truck for transporting lumber. A buddy of mine used to have one, but he had to trade it in for an SUV to get the kids to/from school, sports, etc.

I have a fairly large SUV, and can buy an aftermarket cross-bar roof rack. I've tied down some mid-sized items in the past while camping, but I'm a bit concerned about how I'm going to transfer a few large items from Home Depot:

A 5/8" thick x 4' wide x 8' long MDF particle board.
16 2x4's, each at 6' long.

I think I'll have to do two trips. The planned setup is documented below (pardon the obscene number of pictures), and I plan to essentially run web ratchet straps (with band protectors where it comes in contact with the wood) to hold down the load to the cross-bars, and then an extra 20' web ratchet strap along the length of the load to act as a fail-safe. I'll have to drive maybe 20 minutes at highway speeds, and am concerned, especially in the case of the MDF board, of the payload catching too much wind drag and being pulled off the roof (ie: acting as a big parachute).

Does the setup below look sound? I'm not comfortable enough with my knot-tying skills to go with a hitch in place of the web ratchets, unless there are some dead easy knots I could use in place of the ratchets. I do not want to pose any risk at all to other drivers, so if I need to invest in additional hardware to secure the lumber, that's fine with me.

Also, if I can find a working approach for the lumber project above, I also need to transport a glass door plus frame about 400km at highway speeds, and was wondering if it would be viable to fix it down to a large piece of plywood similar to what I'm doing above.

Thank you for your help!

My Car

My Car with roof rack with cross-bars installed

My car with 4'x8' MDF board on the roof rack

4 web ratchet straps in a pair of X formations to hold down the board to the cross-bars

A pair of 20' web ratchets used as a fail-safe, in case the board slides to the rear of the vehicle

Second trip, 16 2"x4"x6' boards on my roof rack

3 ratchets for holding the bundle together, 4 in X patterns to secure it to the cross-bars, and a 20' ratchet along the length of the bundle as a fail-safe

Update

I'm getting a pair of stainless steel tow hooks installed on my vehicle tomorrow. The current little hook on the rear of my vehicle doesn't have a large opening, and the one on the front is a joke, as it just screws on, so it's easy to steal. The new ones will be bolted on the vehicle without the bolts being exposed.

I'll continue using my roof rack with the advised ratchet configuration to secure them (ie: the pen-and-paper plus elastic example in the accepted answer), and using a large 27' ratchet wrapped around the length of the load, and secured to the rear and front tow hooks (with thick protectors where it touches the car chassis) to keep the front of the planks from flapping upwards and either snapping off or acting as a parachute. Plus, it gives some extra security in case the friction from the other ratchets isn't enough. Thanks everyone!

Have you checked your car's owners manual for roof rack weight limits? Some vehicles have less capacity than you might think, like 100 lbs or even lower. For example, Ford recommends no more than 100 lbs on the roof rack for the Ford Explorer. Sixteen 6' 2x4's would be close to 150 lbs. A friend tried to haul too much lumber on the roof of his car (he had 6 sheets of 5/8" plywood) - he hit a big bump in the road on the way home and the roof dropped down by 3"... the insurance company ended up totaling his car. — Johnny, Dec 10 '15 at 04:45
@Johnny Thank you for the heads-up. My vehicle can support up to 150lbs, so I should be good. :) — Cloud, Dec 10 '15 at 05:03
@Johnny: wow I am extremely surprised that 6 sheets of plywood damaged the car. That's only 300 lbs. Government safety tests require the roof to withstand 2.5x the weight of the car to get anything better than a "poor" rating. — Hank, Dec 10 '15 at 05:09
@HenryJackson - Yeah, so was he... though he was around 3 times the 100lb recommended limit and it was a pretty big bump. The roof didn't collapse all the way, so it may still have been able to support the weight of the car without collapsing further. This roof crush standard doc says that the roof is allowed to deform up to 5" under a static load of 1.5x the weight of the car. — Johnny, Dec 10 '15 at 05:17
If you have an SUV, and the seats fold down, you should be able to carry the 2x lumber of most any length inside the vehicle rather than on the roof. I've hauled 16' 1x5 decking via my Honda Pilot (yes, it hangs out the back window, of course). — DA01, Dec 10 '15 at 05:20
You've thought about it, which is more than many people do! One thing to be wary of when transporting sheet materials on the roof is to make sure the front can't rise up -- at common driving speeds the lift caused by a board tilted up at the front can have a significant effect on handling (not so much braking as steering) — Chris H, Dec 10 '15 at 09:08
Further to the comments about "rising up"... I'd throw a strap around the roof (and through the passenger compartment), in case the factory racks are unable to control the lift you might get at higher speeds. But short term van rental or delivery are much better options. — Aloysius Defenestrate, Dec 10 '15 at 13:45
Good question, and some good answers. I would encourage you to learn how to tie a Trucker Hitch, which is the knot used to tie a load to a vehicle. It looks complicated but when you break it down it is quite simple; a loop on the standing part allows you to make an impromptu pulley to tighten the line with advantage, and the knot is secured with two simple half hitches. People often think that knots are more complicated than they are; knowing which simple knot to use for a given task is a useful skill. — Eric Lippert, Dec 10 '15 at 16:05
You're probably already done hauling this load, but I don't understand why 6' boards need to go on the roof? I haul 10' boards inside my Outback all the time. I also just transported a 4x8 1/4" hardboard panel on the roof rack last weekend with just two 12' lashing straps wrapped all around the panel and then through the door openings. Oh, and sticking to back roads under 35mph helped, too. — paulmz, Dec 10 '15 at 17:48
@paulmz I considered hauling with the load inside the vehicle, but even with it tied down, the boards were slowly drifting backwards, and I was relying 100% on frictional force with no normal force to act as a failsafe. I come from an engineering background (medical science, computers, etc), but this isn't my forte, and I didn't want to risk endangering other drivers if I'm not 100% certain about what I'm doing. — Cloud, Dec 10 '15 at 18:33
@ Everyone: thank you for the additional comments and suggestions. This has been a very enlightening discussion. — Cloud, Dec 10 '15 at 18:34
I'm the one out there in the parking lot with my circular saw and my cut list.. "I can't fit this in there!" — Raystafarian, Dec 10 '15 at 19:14
I've hauled 2x4s in sedans, 4x8s in minivans, and a miter saw (in box) a 30-gallon garbage can and all sorts of other random stuff in a 2-door fastback (all at the same time). /trying but failing to point out how little utility there is an an SUV — FreeMan, Dec 11 '15 at 20:26

score 29 · Answer 1 · answered Dec 10 '15 at 04:54

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Almost all of the Home Depots that I do business with have short term rental trucks available right in their parking lots for very reasonable rates. Call in and reserve one for a particular time. Drive to the Home Depot in your car and park it in the lot. Go inside and checkout the truck. Then drive it up and load all of your materials and head home with it to unload. Take back the truck, check in and head away in your own car.

This is a lot safer option than risking some accident resulting from wood items sliding or flying off the roof of your vehicle.

answered Dec 10 '15 at 04:54

Michael Karas

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a huge savings in time (one trip, not having to tie it all down, etc.)

DA01

Dec 10 '15 at 05:18

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This is the safest, most professional way to do it. Using the proper type of vehicle, is the way a pro would do it. NOTE: Most building supply places will deliver, though there may be a small fee, and possibly a minimum order size. – Tester101 Dec 10 '15 at 12:58

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Not only that, but the cost of a roof rack is easily 5-10 times more expensive than a one day truck rental. If you have an SUV and need to haul lumber often a trailer would be a better option than a roof rack. For infrequent use, though, truck rental is a better option. – Adam Davis Dec 10 '15 at 15:03

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@DA01 - Most big boxes around me have either 1 or 2 trucks. They are always due back "any minute". My guys have waited around for hours and nothing. Also when returning the truck you often have one guy that checks all trucks out and you have to find him and hope he is available. The extra time added to renting the truck is 15 minutes if everything goes perfect plus the extra round trip to house. And hours on the high end with an average of probably 30-40 mins plus extra driving. Yes hauling on roof is stupid but this doesn't save time at all. – DMoore Dec 10 '15 at 19:28

@DA01 renting the truck does not cut down on the number of trips though. Either 2 trips to move the lumber with the car or 2 trips to move it with the truck with 1 being used to move the lumber and the other being used to return the truck. – Brad Dec 10 '15 at 19:52

You might have a project though where you have 40 2x4 studs, 13 4x8 sheets of drywall, 9 ten foot long metal drywall edging/corners, 4 gallons of primer/paint, two 5 gallon buckets of drywall mud and 16 packages of laminate flooring and those two trips to use the truck will look pretty sweet. – Michael Karas Dec 10 '15 at 20:37

Ed Plunkett · Accepted Answer · 2015-12-10T20:11:17.240

You didn't mention how you're using the ratchet straps, but from your concern about slipping, I think it's possible that you could be using them to better advantage. So I apologize if this is what you're already planning to do, but just on the off chance it isn't...

For the MDF, you want the straps going over the edge of the MDF and running straight down to the load boar, so the force is all pulling straight downward. The way to do that is one strap per load bar, in a loop, with the joined hooks and the ratchet mechanism on the same side of the loop. In the following sophisticated CAD rendering, the Sharpie represents one load bar, the Post-It Notes represents one end of the MDF, and the rubber band represents the looped ratchet strap:

This approach will clamp a low, flat load very securely in place. With the straps snug you shouldn't be able to budge it at all. Nevertheless, stop to inspect the load carefully after five minutes and regularly thereafter, and you're right to worry about the parachute effect.

If you're not comfortable with what the load is doing on the highway, hit the hazards and slow down. If people can't pass, pull over every few minutes.

To make the loop, you join the hooks by putting each hook through the eye part of the opposing hook; under tension, that'll be secure:

That ought to work for the door too, but a glass door be a lot heavier than the MDF, and assuming the edges are plastic or aluminum or finished wood, it'll likely be smoother (i.e. less friction against the straps). Finally, it's a much longer drive. So I'd want at least one strap securing the front of the door to something under your front bumper, for insurance against sliding back under acceleration. And then another to the rear, to guard against hard braking.

I can't say for sure how you would secure those end straps without seeing the door. If the door is mounted in a frame, you could loop them around the lintel and sill parts of the frame. To avoid contact between the hook and the frame, tie a figure-8 loop in the strap two feet from the hook, run the hook end through the door frame, and hook it onto the loop. You may need a pair of extra long straps for that part. You'll need to keep the strap under tension for this to be secure, and remember that the rear one may be out of view so you'll have to get out and inspect it regularly. Also if the rear end of the door overhangs the rear bumper, as it probably will, then the rear strap can't resist forward movement except in a disaster where the whole door comes completely free. Then you're just hoping to slow it down a bit. So if a forward movement will slacken both end straps, you must keep a close watch on the front strap for slackening.

And here's how I'd put a strap around a bundle of 2x4s on top of the MDF. The loop clamps them together and also grabs them to prevent sliding back. Note that the loop is arranged so the strap crosses at the top, not the bottom. That method would work with sheet goods as well.

I would also consider renting a U-Haul 5x8 utility trailer for the door.

Using a trailer for the lumber also would be safer, much easier, just as secure, not much more expensive, but infinitely less fun. I hear there are some weird people who don't think securing large things with ratchet straps is fun. But that's just weird.

Thank you. I appreciate all the answers provided here. I was originally going to go with the suggestion to rent a truck from HomeDepot, but a severe language barrier prevented me from successfully renting the vehicle. I found a Home Hardware with similar products much closer to me (10 minutes of driving down back roads rather than 25 minutes on the highway). I used 2x ratchets in the clamping configuration you suggested against the crossbars, and it held much better. I then ran a pair of 27' dual S-hook ratchets in the loop configuration you provided, and hooked it under the vehicle. Thanks! — Cloud, Dec 10 '15 at 14:45
It was quite interesting to see your answer while I was browsing the store. Perfect timing. I was originally going to go to town with excess ratchets, but the loop configuration you provided gives a lot more grip. — Cloud, Dec 10 '15 at 15:09
This is probably the best LOW-TECH answer I have seen in a long time. Great desktop representations! — paulmz, Dec 10 '15 at 17:44
Hahah, yeah. The post-it diagrams give it that Richard Feynman seat-of-your-pants master engineer touch. — Cloud, Dec 11 '15 at 04:14
@Dogbert If I could be the Richard Feynman of ratchet straps, I would be a happy man indeed. — Ed Plunkett, Dec 13 '15 at 23:39
@EdPlunkett It was more of a compliment along the lines of being such a clever engineer, you can explain in layman terms with very simple examples, and your audience understands.. — Cloud, Dec 14 '15 at 02:35
You are truly a master in your field if you understand it so well that you can explain it in terms that a layman can understand. Big props for a great question and answer! — Kristopher, Feb 22 '17 at 20:11

score 8 · Answer 3 · answered Dec 10 '15 at 04:30

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I think you're overthinking this. I carry all kinds of lumber on my roof rack all the time.

The 2x4s are no problem at all. Just strap them down tight, one at the front bar and one at the back bar.

Sheets goods are harder. Your drawing is completely not to scale and I think you will be surprised how big 4x8 is when you get it up there. However as long as your bars are wider than 4 ft it again won't be a problem.

I would do it all in one trip. In fact the 2x4s will help keep the MDF from flopping around. 2 or 3 straps should be enough.

answered Dec 10 '15 at 04:30

Hank

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You are correct on the drawing not being to scale, as it was a quick sketch with OO Draw, since I don't have AutoCAD installed on this machine. Assuming I have 52" wide roof rack bars, I only have about two inches of clearance on each side of the roof rack. Would two large ratchets really produce enough grip/friction to hold donw the 4'x8' and the 2x4 boards? It seems that I'm relying solely on that friction to keep the sheet from sliding backwards and off of my vehicle. There's no "normal force" that locks it to the bars. – Cloud Dec 10 '15 at 04:48
@Dogbert - The way bigger problem with plywood or MDF sheets on the roof is that it acts as an air foil and can produce a large amount of lift even at moderate driving speeds. – Michael Karas Dec 10 '15 at 04:57
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@MichaelKaras: that's why I suggested putting the 2x4s on top. They will keep the sheet from lifting up. – Hank Dec 10 '15 at 05:00
Thank you Henry. Still, even with the 2x4s on top, is the grip from the extra weight and the straps enough to prevent the MDF sheet from gradually sliding backwards? It just doesn't seem like the ratchets are generating much downward force when I simulate if with some planks on my workbench: I can still grab and slide them without too much difficulty. Maybe I'm not clamping down with the ratchets properly. – Cloud Dec 10 '15 at 05:03
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I agree with Henry Jackson about the 2x4s helping to hold down the plywood. It's not just their weight, they also change the angle of the straps, which greatly increased their clamping force. You're right, they aren't generating much clamping force because they are at a nearly 90 degree angle to the sheet. Adding the 2x4s in the right way changes that to 60 or 70 degrees. – Joel Keene Dec 10 '15 at 05:30
@Dogbert: I don't really know what to tell you other than I carry dimensional lumber (and furniture, boats, etc.) on my roof all the time. I've never had an issue. I usually use ropes since they're more versatile but you should be able to generate at least as much force with a ratchet. If you are not comfortable with this then you can rent a trailer or put the lumbar inside your car but it's totally doable. If you do put stuff on the roof and are nervous about it I recommend spending a few minutes driving around the parking lot abruptly and then checking to make sure nothing has loosened. – Hank Dec 10 '15 at 17:31

score 6 · Answer 4 · answered Dec 10 '15 at 06:04

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The MDF might be a problem. When driving at any appreciable speed the sheet will catch air and try to sail up and away. This is compounded by the air that is pushed up and over your hood and windshield, right up into the MDF.

I had two sheets of particle board that broke off where the straps were holding them down. It wasn't a clean break :)

I would recommend the $20 Home Depot truck rental, if available. (kudos to Michael Karas)

If you do need to do this on your car:

Use the 2x4's on top of the MDF for support.
Try to shift the whole sheet farther back than you normally would. This will reduce the overhang over your hood.
Try to tie it on in a way that holds the front edge of the sheet down. Don't let it start to lift up.
Drive slowly!

Good luck.

answered Dec 10 '15 at 06:04

bitsmack

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When carrying kayaks and canoes, you absolutely have to tie them down at the front and back, otherwise they're very likely to lift up and rip away from the roof rack. I'd suggest sheets of MDF or ply would be worse! As @bitsmack suggests, use the 4x2 battens slightly longer than the sheets on top to keep the whole arrangement stiffer, and tie them down to the front & rear bumpers. And drive slowly! – rcoup Dec 11 '15 at 11:46
Appreciable speed meaning 50-65mph on a highway? Or even just 35 mph on surface streets? – stannius Oct 27 '16 at 16:38
@stannius I can't really say. If you use 2x4's on the top and tie the front and back edges to your bumpers it'll be pretty solid. When I lost the particle board sheets they were only strapped to the roof rack and I didn't try to hold the leading edges down. It was around 30-35 mph when they broke. – bitsmack Oct 27 '16 at 18:04
The only real safe speed to avoid the airflow under sheet goods on the roof of a vehicle is less than about 10 miles per hour. Even at that speed if there is any actual wind blowing it can become dangerous. – Michael Karas Jul 02 '20 at 18:08

score 2 · Answer 5 · answered Dec 11 '20 at 15:34

Anybody who has ever sailed even a small sailboat knows the amount of force in even a light breeze can be incredible. I would be very hesitant to ever put any sheet goods on a roof rack as the lifting forces can be significant, working to pull your rack off. Yes, you can tie the front and back down but if it isn’t done perfectly you are asking for trouble.

The Home Depot rental truck is a great suggestion for the occasional or on-off project. If you find you need it more than a few times a year consider the folding trailers that Harbor Freight sells. They are pretty cheap and fold/store upright and can easily fit in even a crowded garage. They have 1200 and 1700 pound models available and either will cost less than a Thule roof rack and fit full size sheet goods. I bought one after I sold my pickup and can’t believe everything I’ve hauled with that thing using nothing more than a VW Sedan. Like everything at HF, there are many online guides on doing a few simple mods to vastly improve the usability of the thing. I would consider it to be light or at best medium duty but if you use it within limits mine has been an incredible value.

score 1 · Answer 6 · answered Dec 10 '21 at 05:45

I haul stuff ALL THE TIME on my standard dodge Durango roof rack. With some common sense the right amount of straps and some ingenuity anything is safely possible. I'm a roofer and I haul ladders, lumber, plywood, metal roofing panels the list goes on and on. I've hauled 16 12 inch wide 24 foot 22 Guage roofing panels with a stinger made of 2x4 and drove 62 miles at 75+ mph the whole way. With will and common sense anything is possible.......lots of common sense..... better pick up an extra bucket just in case.

Safe/professional way to transport lumber with just a roof rack

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6 Answers6