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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Fri Jul 31, 2009 4:50 pm Post subject: |
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| CRT_Ben wrote: | | Person99 wrote: | | Belcherwm wrote: | Five years and no problems. Lagged into three joists.
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Both my 1208/2 and my 1200x were lag bolted into three joists. Total of about 5 years they hung there. I then build a nice black velvet covered "box" to go around the unistrut and hide it.
I will never cease to be amazed at the cluelessness of people that thing they need more than this. You could put one 1/2" lag bolt in the joist and hang on it until you die. Remember those goofy seats from the 70s suspended by 1 lag bolt that 190 pound men would sit in?!?!?
Even if you only use 4 lag bolts, depending upon exact placement, no 1 lag bolt will be holding more than 70 pounds (and chances are less). That is WAAAAAAY under the pull out rating. |
It's not ignorance of the rated capacity, it's a feeling of safety. It's easy to put in a few more lags and unless you go nuts drilling holes in the joists there's no harm done. So, one or two lags would hold up your projector, but would you do it that way? |
Oh, should have been clear, I was not railing against using 6 or 8 lag bolts (I used more than 4), I was railing against this concept the you have to put cross braces on the joists and do complicated things to "hang" it from those as opposed to lag bolts. There are and have been several who will not use lag bolts at all for fear the PJ will fall!
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A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Fri Jul 31, 2009 5:12 pm Post subject: |
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Yeah, I think many people really don't understand the strength of lag screws. I wasn't exaggerating when I said you could hang a car from 12 screws! Hell, as long as we're not talking Hummers, you could probably safely hang TWO of 'em. 
Lag screws are an extremely strong and safe way to hang a projector. With 12 screws you would probably pull down the ceiling before you pulled out the lags. 4-6 is plenty safe for any projector, and use more if you really want to.
If you don't want to bother with drilling holes and screwing in lags, then fine, hang the projector from cross-joist sleeper doodads. But it's not necessary for safety.
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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Fri Jul 31, 2009 6:07 pm Post subject: |
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I just found out that it is NOT below finished space. It's a two story house but this room is sorta off to the side, with it's own roof above it. Friend doesn't think he has crawlspace access, so I don't know if I'll be able to do the cross-framing idea (I just think that's easier).
Question is, what if it's only 2x4 framing up there? Is that sturdy enough?
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tri_joel
Joined: 03 Jul 2007
Posts: 646
Location: Northern Virginia
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| Posted: Fri Jul 31, 2009 6:51 pm Post subject: |
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Ben-
2 x 4 framing would not be enough, in my opinion. What type of roof is it? Gable? Flat? Something else? Can you see into the roof cavity from an adjoining attic?
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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Fri Jul 31, 2009 7:32 pm Post subject: |
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| tri_joel wrote: | Ben-
2 x 4 framing would not be enough, in my opinion. What type of roof is it? Gable? Flat? Something else? Can you see into the roof cavity from an adjoining attic? |
That's my gut feeling as well. If you penetrate 2" into a 2x4 I'd be afraid it could snap in half.
Ceiling mounting may not be necessary, in fact I think I've come up with a better solution for his space that involves building a small platform to hold the PJ above his current TV.
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RobertMfromLI
Joined: 29 Jun 2009
Posts: 114
Location: West Islip, NY
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| Posted: Fri Jul 31, 2009 10:09 pm Post subject: |
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| garyfritz wrote: | You can sink a very small-diameter nail or pin into the drywall to locate the joist precisely without cutting any holes.
But if you over-engineer enough, even a non-centered lag screw isn't that big a deal. I can't find the tables of load limits, but if I remember right a 3/8" lag screw in pine is rated for at least 300-500lbs or more -- meaning that any ONE lag screw is enough to support your entire projector. If you're hanging your projector from 4-6 lag screws, you've got so much more load-bearing capacity than you need that one sub-optimal screw isn't going to matter.
You should still try to center all of them. You just don't have to panic if one of them is off a little. |
While this is true, there are other factors that people do NOT take into account that are very important. For instance, if the ceiling is load bearing (yes, that includes roof joists, as they, in most climates, need to be able to support a large quantity of snow or ice), each hole you put into them can cause the joist to crack when weight is placed on the top side of that structure. This also often makes lag screw placement very important as if the screw is not dead center, the joist is more likely to crack.
The other thing to consider is the age of the structure. Very very old structures (100 year old houses for instance) will either have wood that has become softer (and is less likely to crack - but more likely to have a lag screw pull out) or much more brittle/dry wood - for instance any joists that are exposed to an attic or in a roof area (and thus more likely to crack).
And of course, the least likely, is that you happen to put a lag screw into a big knot in the wood... surefire way of ensuring the wood will crack.
These I know from my "days" (years) of commercial and residential construction - and numerous joists I have either had to replace or cistern.
-Rob
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dturco
Joined: 06 Feb 2009
Posts: 3778
Location: Eastern Shore Maryland
TV/Projector: Runco DLP VX-3000i Marquee 9500 parts doner
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| Posted: Sat Aug 01, 2009 12:45 am Post subject: Re: Unistrut mounting question |
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| CRT_Ben wrote: | | dturco wrote: | It is not necessary to remove the drywall to install the Uni-Strut. As Gary pointed out earlier find the studs by pushing a small nail, like a 2 1/2" finishing nail up into the ceiling to find the beam. Hold the nail with pliers to make it a lot easier on your hands. Find a beam go left and right of the solid spot until you can't feel the beam any more , mark each outside edge and you will be able to find the center that way. To make for a good install make sure you have the lags no further from the front and back of your Uni-Strut than 4" from the beam.
Also you will need a piece of Uni-Strut a least 48" in length if you are to cross 3 beams and your beams are 16" on center.
That of course assumes that the first beams is exactly where your P/J needs to be for throw distance {which ain't likely] so don't be surprised if you need a 60" piece of uni-Strut. |
It sounds like you are placing the strut across the beams? The install I just did, I put the strut along (parallel to) the beam, then the strut that was bolted to the PJ went perpendicular to the beams. I'm sure both ways work but I just found this easier, at least for that particular install. Is there a particular reason or advantage to going perpendicular for the strut that's right on the joists?
| dturco wrote: | | As far as how tight to make the lags hold the ratchet you are using at the head in your palm, not the back of the handle, twist it as tight as you can this way which should max out at about 30 lbs of torque on the bolt head. You wrist can't generate much more torque in this position with out really hurting or breaking. |
Good tip, thanks!
| dturco wrote: | | Also I used drywall screws to TEMPORARILY mount the Uni-Strut. This made it easier to make sure I had found a beam each and every time. It also made for the pilot holes for the lags. |
Interesting about temporarily mounting the strut - did you do that just to line things up and get a sanity check that everything was heading in the right direction? I'd be afraid of splitting the beam with a pilot hole that small, though  I can't remember what exact size bit I used but I did the standard "drill bit same size as shank" method.
| dturco wrote: | | Your lags need to have a 1 1/2" penetration into the beam so assuming 1/2" drywall the1/8" Uni-Strut and a 1/8" washer you will need 2" lags as a minimum. Maybe 2 1/2"- 3" Anything larger and your wasting your time. |
Hm...I felt pretty safe with 4" lags with nothing in between but I dunno how I'd feel about 2" lags in the same situation. Can you explain why a deeper penetration is not useful, at least for added safety/overkill?
Thanks all for the feedback! |
Sorry I skipped the drill bit part, I had to go to work. The reason I went perpendicular to the beams was to insure weight distribution over a larger area. It also was for a trolley type set up for the future when I change screen size{s} In theory I should be able to slide the P/J closer or further away easily.
The Lag bolts after 3" usually have no threads on a portion of the shank so if there is no thread there is no more holding power in that portion of the lag.
The screws were for a sanity check as you said, and also so I just didn't have to hold them up overhead or use a dead man pole. etc.
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ronholm
Joined: 26 Jan 2007
Posts: 12111
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| Posted: Sat Aug 01, 2009 2:45 pm Post subject: |
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| CRT_Ben wrote: | | ronholm wrote: | If yall can find "ledgerloks" in the hardware store they are SO much easier than lags... and stronger too...
We use them everywhere code will allow us... they are stronger than a 1/2 lag for ledger board purposes and require no predrilling... I am certain they would be more than adequate to hold a projector up...
http://www.fastenmaster.com/productdetails.aspx?catID=8&prodID=9 |
What am I missing? It looks like a screw. |
It is hardened.... and has more holding power, and the same sheer strength of a 1/2 inch lag.... And to ice the cake... with a 1/2 inch lag... you have to predrill the hole... Then use an impact or wrench to set the lag...
Grab a ledgerlok and a cordless drill... and DONE... fast...
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