| Author |
Message |
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Thu Jul 30, 2009 9:05 pm Post subject: Unistrut mounting question |
|
|
|
For those that mount with unistrut to a finished, drywalled ceiling: Do you leave the drywall in place and effectively sandwich it between the joist and unistrut, or do you cut out the section where the unistrut fits to the joist?
|
|
| Back to top |
|
 |
zaphod
Joined: 16 Jun 2006
Posts: 2002
Location: Cloverdale
|
| Posted: Thu Jul 30, 2009 9:15 pm Post subject: |
|
|
i cut out the drywall. let me get dead center of the floor joists.
when i sold my house the new owners put "repair damage from hometheater" into the sale contract 
it was fixable, but more timeconsuming that 6 holes would have been
_________________
walk gently. leave a good impression.
|
|
| Back to top |
|
|
ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
|
| Posted: Thu Jul 30, 2009 9:30 pm Post subject: |
|
|
Ben,
You talking about a ceiling that's a below a finished space, or below an attic? The attic is easy, because you can just go up in the attic and use some sleeper pieces of 2x6 or whatever you have around, and drop the unistrut through holes in the ceiling, suspended from the new framing.
If you're dropping from a ceiling below finished space, then I'd want to be damn sure I was lagging into the center of a joist. I'd probably either cut a slot for the unistrut to sink into, or if not that, then at least a decent-sized hole around the desired lag locations to be sure you're into the center of the joist.
SC
|
|
| Back to top |
|
|
garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
|
| Posted: Thu Jul 30, 2009 10:21 pm Post subject: |
|
|
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.
|
|
| Back to top |
|
|
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 12:29 am Post subject: |
|
|
| ecrabb wrote: | Ben,
You talking about a ceiling that's a below a finished space, or below an attic? The attic is easy, because you can just go up in the attic and use some sleeper pieces of 2x6 or whatever you have around, and drop the unistrut through holes in the ceiling, suspended from the new framing.
If you're dropping from a ceiling below finished space, then I'd want to be damn sure I was lagging into the center of a joist. I'd probably either cut a slot for the unistrut to sink into, or if not that, then at least a decent-sized hole around the desired lag locations to be sure you're into the center of the joist.
SC |
I'll have to check with my friend, but I believe that it is below finished space. I agree; centering or getting it close is important.
| 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. |
Last install I did was 12 lags, three pieces of strut with four bolts in each Granted I wanted a ton of maneuverability so the strut ran 48 inches along the joist.
I think I will do as Gary suggests and find the edges of the joist with a small pin or nail. Worst case, I'll cut a small slot, maybe 1/2" by 3" to show me the whole joist.
Last ceiling install I did I used 4" lags. I guess to compensate for the drywall I'll step up to 4.5".
Hopefully, ceiling mounting will not be necessary. This will be going in my friend's "man-cave" and I'm hoping we can build a platform for it to hold it over some existing equipment. He's going to send me some pictures and dimensions so I can figure something out. Thanks for the input!
|
|
| Back to top |
|
|
Belcherwm
Joined: 19 Aug 2006
Posts: 112
Location: Haymarket, Northern Va.
|
| Posted: Fri Jul 31, 2009 1:52 am Post subject: |
|
|
Five years and no problems. Lagged into three joists.
_________________
Bill
|
|
| Back to top |
|
|
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 3:10 am Post subject: |
|
|
| Belcherwm wrote: | | Five years and no problems. Lagged into three joists. |
Thanks for the feedback. Did you torque the lags at all? I'm worried about the drywall crushing, but I wouldn't want to leave the lags loose...
|
|
| Back to top |
|
|
akajester
Joined: 09 Jul 2008
Posts: 934
Location: Wisconsin
|
| Posted: Fri Jul 31, 2009 3:59 am Post subject: |
|
|
I used 3 pieces of unistrut on 3 different joists, each had 3 lag bolts. So, 9 lag bolts in total and I sandwiched the drywall between the unistrut and joists. It wasn't a problem. I took a lot of care to find the center of the joists. Even so, if one or two are off it won't make a difference with that many bolts. Total rating was around 18,000lbs of torque! I played gymnast from the finished mount for quite some time to ensure it was solid. I weigh 185lbs which is about 20lbs more than my barco.
here's a link to some pictures;
http://picasaweb.google.com/dthibode/ProjectorMount2?feat=directlink
|
|
| Back to top |
|
|
dturco
Joined: 06 Feb 2009
Posts: 3778
Location: Eastern Shore Maryland
TV/Projector: Runco DLP VX-3000i Marquee 9500 parts doner
|
| Posted: Fri Jul 31, 2009 1:12 pm Post subject: Re: Unistrut mounting question |
|
|
| CRT_Ben wrote: | | For those that mount with unistrut to a finished, drywalled ceiling: Do you leave the drywall in place and effectively sandwich it between the joist and unistrut, or do you cut out the section where the unistrut fits to the joist? |
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.
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.
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.
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.
_________________
Firefly rules. Can't stop the signal.
http://www.hulu.com/firefly
|
|
| Back to top |
|
|
akajester
Joined: 09 Jul 2008
Posts: 934
Location: Wisconsin
|
| Posted: Fri Jul 31, 2009 1:44 pm Post subject: |
|
|
I believe I used 3/8" lag bolts that were 4" long. I predrilled the lag holes and used some bar soap on the bolts to get them in, otherwise they get really hot and can snap which can complicate things. I used this pdf here on Curt's site and it was very helpful;
http://www.curtpalme.com/docs/DIY_ceiling_mount.pdf
|
|
| Back to top |
|
|
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 2:17 pm Post subject: Re: Unistrut mounting question |
|
|
| 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!
|
|
| Back to top |
|
|
garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
|
| Posted: Fri Jul 31, 2009 2:40 pm Post subject: |
|
|
| CRT_Ben wrote: | | Last install I did was 12 lags, three pieces of strut with four bolts in each |
Good God, you could hang a CAR from that!!! 
4" lags are great, but 2" would probably be enough if you've got 12 of them. Do definitely drill pilot holes (I wouldn't think drywall screws would make a big enough hole!?), and do definitely soap up the lag screws first. That makes a huge difference.
|
|
| Back to top |
|
|
Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
|
| Posted: Fri Jul 31, 2009 2:52 pm Post subject: |
|
|
| Belcherwm wrote: | Five years and no problems. Lagged into three joists.
|
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.
_________________
Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
|
|
| Back to top |
|
|
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 2:57 pm Post subject: |
|
|
| Person99 wrote: | | Belcherwm wrote: | Five years and no problems. Lagged into three joists.
|
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?
|
|
| Back to top |
|
|
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 2:58 pm Post subject: |
|
|
| garyfritz wrote: | | CRT_Ben wrote: | | Last install I did was 12 lags, three pieces of strut with four bolts in each |
Good God, you could hang a CAR from that!!!
4" lags are great, but 2" would probably be enough if you've got 12 of them. Do definitely drill pilot holes (I wouldn't think drywall screws would make a big enough hole!?), and do definitely soap up the lag screws first. That makes a huge difference. |
Aware that 4" is probably overkill but it's my Pops' theater and if it fell and killed him I'd be a bit sad.
I soaped up the lags and they went in easily.
|
|
| Back to top |
|
|
akajester
Joined: 09 Jul 2008
Posts: 934
Location: Wisconsin
|
| Posted: Fri Jul 31, 2009 3:06 pm Post subject: |
|
|
|
Exactly, it's done for safety reasons. I'd rather double the install time and be safe with myself and my family sitting underneath it. I don't believe that's ignorance. I clearly looked up the specs before-hand and knew exactly what I was doing, and knew it was overkill. It's also WAY cooler to say your mount can hold 18000lbs of torque instead of 250lbs.
|
|
| Back to top |
|
|
ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
|
| Posted: Fri Jul 31, 2009 3:09 pm Post subject: |
|
|
Drywall screws definitely will not make a pilot for a lag screw. They'll make a nice pilot for you to drill the pilot hole for the lag, though.
Lag screws are designed (and will hold with maximum power) to be screwed into a drilled pilot hole. If you don't pre-drill, you'll weaken both the connection and the framing member itself. For soft wood (like fir framing), about 3/4 of the major diameter (O.D.) is adequate. So, a 1/4" lag should have a 3/16" pilot hole.
Don't forget, if you're using a longer lag with some shank, you can drill the pilot to the shank's depth at the screw's O.D., and save yourself some cranking.
Oh, and this is extra anal... But, soap will actually corrode galvanized screws over time. Not that the fastener would fail because you used a little Ivory Coast on the threads, but it's better use a little paraffin, bees wax... Even wax shoe polish or vegetable oil.
All you wanted to know about screws and drilling:
http://www.shortrunpro.com/ScrewAndHoleBoltGuide.aspx#Screw_Guide
SC
|
|
| Back to top |
|
|
ronholm
Joined: 26 Jan 2007
Posts: 12111
|
| Posted: Fri Jul 31, 2009 3:32 pm Post subject: |
|
|
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
_________________
Play stupid games, win stupid prizes
|
|
| Back to top |
|
|
CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 3:56 pm Post subject: |
|
|
| 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.
|
|
| Back to top |
|
|
tri_joel
Joined: 03 Jul 2007
Posts: 646
Location: Northern Virginia
|
| Posted: Fri Jul 31, 2009 4:15 pm Post subject: |
|
|
| Quote: | | Exactly, it's done for safety reasons. I'd rather double the install time and be safe with myself and my family sitting underneath it. I don't believe that's ignorance. I clearly looked up the specs before-hand and knew exactly what I was doing, and knew it was overkill. It's also WAY cooler to say your mount can hold 18000lbs of torque instead of 250lbs. Smile |
What's holding up the joists? Probably 1" tiki nails drove into joist hangers. So many of them the joist end probably split into pieces.
_________________
www.vawinesnob.com
|
|
| Back to top |
|
|
|
|
