# Ceiling Joist



## rackman (Oct 17, 2008)

Hey guys I'm an installer of garage overhead storage, I was wondering what is the easiest way to tell if a ceiling has 2x6 or 2x4 joist when there is no access into the area. I have only run into this situation once, so I am tring to find out before I even install what joist's our installed. The reason why I ask is that our load rating changes when we install into a 2x4 joist all are rating are for 2x6 joist, so any help will be greatly appreciated.

Thanks
Shane


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## mdshunk (Mar 13, 2005)

Poke a small hole next to a joist. Insert a wire with a small "L" on the end. Slide it up along the joist, spin it sideways, and pull down to catch the top of the joist. Mark the wire. Bring it back out and measure. 

If you're dealing w/trusses, chances are pretty good it's not rated for the type of duty you propose, no matter what size the bottom chord is.


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## loneframer (Feb 13, 2009)

mdshunk said:


> Poke a small hole next to a joist. Insert a wire with a small "L" on the end. Slide it up along the joist, spin it sideways, and pull down to catch the top of the joist. Mark the wire. Bring it back out and measure.
> 
> If you're dealing w/trusses, chances are pretty good it's not rated for the type of duty you propose, no matter what size the bottom chord is.


 Exacly right.


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## dkillianjr (Aug 28, 2006)

mdshunk said:


> Poke a small hole next to a joist. Insert a wire with a small "L" on the end. Slide it up along the joist, spin it sideways, and pull down to catch the top of the joist. Mark the wire. Bring it back out and measure.
> 
> If you're dealing w/trusses, chances are pretty good it's not rated for the type of duty you propose, no matter what size the bottom chord is.


Nice trick MD, :thumbup: Its one of those simple things that you just dont think of!



Dave


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## rackman (Oct 17, 2008)

My manufactors say that it's rated for so much weight and as long as the customer/home owner does not exceed that limit then it's ok. The weakest part is obviously the truss, Here is what are spec's say.

*WARNING, DO NOT EXCEED THESE WEIGHT LIMITS *
* 4? x 8? Frame 600 lbs. 3? x 6? Frame 400 lbs. *
* 3? x 8? Frame 550 lbs. 2? x 6? Frame 400 lbs. *
* 2? x 8? Frame 450 lbs. 4? x 4? Frame 300 lbs. *
* 4? x 6? Frame 500 lbs. *
*
These weight limits are based on a framed garage with a minimum of 2 x 6" (standard lumber) ceiling joists at 24" or less on-center. For truss framed garage ceiling structures, 2 x 4" (bottom truss cord) is okay. The racks themselves are structurally rated to double the above limits. However, the weakest point in the entire system is the garage ceiling joists and rafter system. 

Thanks for the tip I was thinking that myself just not sure if there was a different way.*


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## RobertCDF (Aug 18, 2005)

I like MDs idea the best but here is another one for the hell of it.

You could get a 6" long 1/8" drill bit by the time you chuck it it will be around 5.5" if the drill breaks through before you bury then its a 2x4.


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## Warren (Feb 19, 2005)

Question: How will he know if its trusses or rafters/joists? This will make a difference.


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## mdshunk (Mar 13, 2005)

Warren said:


> Question: How will he know if its trusses or rafters/joists? This will make a difference.


A man might say that if he is unable to sort this out for himself, he sure picked an interesting line of work.


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## scuba (Feb 26, 2008)

It's interesting that you have a load table when you have no idea what the truss calculations are.

It's just a guess on your part.

Greg


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## rackman (Oct 17, 2008)

Are load ratings are for the rack only not the joist, this has been tested by the manufactors the racks themselves areracted for more. I don't know how they determine the rating I just hit center of stud a let the customer know what the ratings are. 

"A man might say that if he is unable to sort this out for himself, he sure picked an interesting line of work." 

I have never ran into this cituation before so as with anything it's a learning process, every ceiling is different.


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## D.Foster (Sep 13, 2008)

Being that "every ceiling is different" i guess that MD was correct, in that you have chosen an interesting line of work. Seeing how you have to attach alot of stuff to ceilings.


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## TempestV (Feb 3, 2007)

Are you saying that you worked on a house where there wasn't an access hole in order to get into the attic space above the garage?

I would think that you would want to talk with the engineer of the trusses before hanging 600 pounds off the bottom cord.


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## scuba (Feb 26, 2008)

TempestV said:


> Are you saying that you worked on a house where there wasn't an access hole in order to get into the attic space above the garage?
> 
> I would think that you would want to talk with the engineer of the trusses before hanging 600 pounds off the bottom cord.


 Thanks Tempest
That was my point also. Sounds like he is setting up a homeowner to load a truss when he doesn't know what the truss is rated for. Sounds like a liability.

Greg


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## knucklehead (Mar 2, 2009)

I don't see how it would make any difference . If is a truss with 2x4 joist it would have webbing in the middle somewhere to make it as stong as a 2x6 without any webbing.


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