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Topic: Finding roof studs (Read 914 times) previous topic - next topic

Finding roof studs

I'm starting to think about how I'm going to mount the solar racks to the roof of my GV. I'm leaning towards using Iron Ridge XR100 Rails with their Q-Base mounts. My goal would be to fasten as many of the Q base mounts to a roof stud as possible. I have two questions:

1) Any tips or tricks for finding the aluminum studs? I brought a nice stud finder up on the roof with me and they seem to be spaced 23"-26" apart but the readings weren't exactly consistent so I'm looking for a better way to confirm than just drilling small pilot holes with a cobalt bit.

2) What would your preference be for attaching said rails to the studs? Self tapping metal screws?

And to clarify: I'm going to elevate 8 of the panels pictured below above all the other hardware on my roof. It'll look like one big long sheet of 81" wide solar panels.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Finding roof studs

Reply #1 –
I would be inclined to use full length runners, probably square tube, secured in place with 3M VHB double sided tape then some #14 stainless steel hex washer head sheet metal screws through the runner,  1" min longer than thickness of runner into each perpendicular roof framing member..  Prior to this I would have my uprights, precut to length, tig welded to the bottom runner and the alum angle above which would receive the panels.  I would have at least one diagonal welded in on each corner as well.

Owned and operated a hurricane shutter business on the coast for years, and this is similar to how they would be mounted.  With the elevated panels there's going to be more than cat 1 hurricane force on this assembly, every day.  Don't know anything about typical solar panel mounting other than a lot of concessions to deal with standing seam, shingle, tile roofs which I doubt would be ideal for this custom installation. 

Driving 65 mph, meeting a semi pushing 70 mile headwind at you.......do the math. Lots of uplift pressure from what is essentially a crude wing mounted above.
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Finding roof studs

Reply #2 –
I can see a lot of advantages to this mounting style, easy cable management, you'll take a ton of heat load off the roof and have excellent cooling under the panels.  Could probably even gain some advantage from bifacial panels as well. 
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Finding roof studs

Reply #3 –
Chuck, I can't use tape to adhere the mounts to roof. The previous owner had some kind of aftermarket coating put on the roof that isn't really a paint. It's more like a roll-on membrane that doesn't adhere to the underlying fiberglass everywhere, it's flexible. It's almost like a really hard wrap so I'm gonna have to drill through it to get to something truly solid.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Finding roof studs

Reply #4 –
Look on top of the coach early in the morning when the dew is still on the roof you may see where the top studs are.No joke
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Finding roof studs

Reply #5 –
Quote from: Elliott –
Chuck, I can't use tape to adhere the mounts to roof. The previous owner had some kind of aftermarket coating put on the roof that isn't really a paint. It's more like a roll-on membrane that doesn't adhere to the underlying fiberglass everywhere, it's flexible. It's almost like a really hard wrap so I'm gonna have to drill through it to get to something truly solid.

Ah.  That does complicate things. Eliminates the belt but you still got the suspenders.  The withdrawal on the #14 screws is substantial, though.  These are deep coarse threads.  So, probably a good reason to use a good heavy aluminum tube along the roof, it will help ensure that the zipper effect of isolated fasteners won't happen.  Foretravel used a good structural tube in the roof frame. 

As far as locating the framing, seems like a good stud finder would readily locate the square tube framing.  Perhaps an upgrade of finders is in order.  Or, following John44's suggestion, there is a temp differential that shows up in dew, might be a good reason to get that IR camera for your phone.  That should definitely do it.  There have been roof framing diagrams posted in the files section, don't know if there's one for a GV.

PM me if you need help sourcing aluminum extrusions. 
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Finding roof studs

Reply #6 –
I mounted 6 large panels to my roof. I used 2x3" aluminum channels to mount to. They are glued 5200 adhesive and through bolted to the inside of the MH with long 1/4" SS bolts and nuts. I used a Bosch stud finder to locate frame.
I mounted the Solar panels to the 2x3" aluminum box beams with door hinges bolted through the box beams. This way I can easily tilt the panels if I want to and I can raise a panel and prop it up  so I can maintain the roof under it or give me easy access for walking the roof. I can also quickly remove a panel by just pounding out the hinge pins. I'm able to have 4"+ of air under the panels for heat dissipation.

I found the stud sensor to be iffy on locating the roof structure. A magnet seems to be able to pickup on the beams showing some strength. The old standby of watching for the dew to form and showing off the inner studs always seems to work.
When  I through bolted I used beams that were located along the curve in the roof. This way the through studs would exit in the upper cabinets inside the coach, easy to reach for install and the hardware is lost inside the cabinet.
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: Finding roof studs

Reply #7 –
early morning dew worked on my 96 also.
On my 99 I got a hold of foretravel, and they sent me the diagram. The morning dew didn't work on this one due to the roof being sprayed with bed linner.
Now 1999 U320 36' with ISM/M11
600 amps hours of lithium ion batteries.
Jeep gladiator tow vehicle for exploring.

Re: Finding roof studs

Reply #8 –
I used a good stud finder on ours. It found the "studs" without a miss.

Used stainless screws into the aluminum and into the roof where there was no aluminum. The roof is .400" thick and the screws have held perfectly since 2008. See my old posts with photos of the mounts/brackets/wiring.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Finding roof studs

Reply #9 –
Get some rare earth magnets to search for the beams.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Finding roof studs

Reply #10 –
Yes! Strong ones.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Finding roof studs

Reply #12 –
Thanks all, there's some great advice here. I don't think the dew trick will work because of the weird flappy/loose roof coating over the fiberglass that I mentioned previously but an IR camera might just do the trick...and it gives me a reason to buy an IR camera  ;D

I'd love to do a continuous aluminum rail for the footings of the rack but I can't weld aluminum and trying to bolt one together sounds like a nightmare, so I'm leaning towards a combination of screwing into the studs and running a bunch into the wood roof with anchors. Once the anchors expand the fiber glass will also add support.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Finding roof studs

Reply #13 –
Most high quality stud finders locate conduit with a red light. The aluminum frame should trigger the conduit function.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Finding roof studs

Reply #14 –
Quote from: Elliott –
Thanks all, there's some great advice here. I don't think the dew trick will work because of the weird flappy/loose roof coating over the fiberglass that I mentioned previously but an IR camera might just do the trick...and it gives me a reason to buy an IR camera  ;D

I'd love to do a continuous aluminum rail for the footings of the rack but I can't weld aluminum and trying to bolt one together sounds like a nightmare, so I'm leaning towards a combination of screwing into the studs and running a bunch into the wood roof with anchors. Once the anchors expand the fiber glass will also add support.

There are many in the xscapers community with roof racks. I've seen a few with full angled aluminum along the roof and others that will just use angled aluminum as a bracket into the wood. As some have said, a magnet may work IF there are screws or nails into the aluminum frame. That may not be the best option. I hear ultrasonic stud finders are best.

What I used:
K2 cross rails
K2 Cross Rail 44-X 86" Mill | SanTan Solar
K2 connector
K2 Rail Connector Cross Rail 44-X Mill | SanTan Solar
k2 mid clamp
K2 Cross Rail Mid Clamp Silver 40-50mm | SanTan Solar
hidden end clamp
K2 Yeti Hidden End Clamp for Cross Rail 13mm Hex | SanTan Solar
Make sure you've got all nuts and bolts as well.

1 1/2" x 1/8" flat aluminum bar
1 1/2" x 1/8" angled aluminum

Self tapping screw with neoprene washer
https://www.homedepot.com/p/Everbilt-12-x-2-in-Flange-Hex-Head-Drive-Self-Drilling-Screw-with-Neoprene-Washer-1-lb-Box-53-Piece-116043/205142716

I believe Doug W uses Iron Ridge solar racks with aluminum angle and flat aluminum.

I've been using this for over a year now with minimal issues. I've had to go up and retorque once and will likely check again soon and put some lock-tite on the bolts. Ideally, I'd get rid of the roof airs and vents and have the panels a couple of inches off the roof instead of 9-10 inches off the roof. Winds still scare me when driving, but they haven't moved nor do they make noise. And yes, a solar rack does benefit from bifacial. I've seen 466 watts on one of my 390 watt panels.
1999 U320 WTFE #5586
2014 Subaru Forester 6sp
4000 watts of solar
650 aH @ 24v

Re: Finding roof studs

Reply #15 –
 That's some pretty good looking racking that Zach pointed to.  Too bad you're not around Scott, he could tig this thing up in a flash.  One final recommendation, though.  If possible use the #14 non drill point screws.  Since these are soft materials compared to steel, which is what the drill point screws are for, they will have much more holding power with larger diameter and deeper coarse self cut threads.  Sure you've thought of it but will need to make allowances for the roof angle you'll be mounting on so your upper mounts are correct distance side to side.

 Neat project, I'm envious, been wanting to install solar on my residential property, alas the way codes are here in San Antonio my proposed self installed $10K system has to go through a "certified solar contractor" and comes in at $36K.  Sheesh.  Not happenin.
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Finding roof studs

Reply #16 –
Leaving this here for posterity's sake. This is the space between roof studs according to my stud finder.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.
 

Re: Finding roof studs

Reply #17 –
So which spacings are used for the ACs and vents??
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD