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double drywall - seams and hat channelling on the ceiling

post #1 of 17
4/6/08 at 8:30pm
Thread Starter 
Hey.

Working on my ceiling on my HT/Media room.

I've got Kinetic Isomax clips, Hat Channelling spaced at the max of 24", and 2 layers of 5/8ths drywall and greenglue.

I've got an area that is about 11" wide. Because I was a dunce, I spaced the hatchannelling at inconvenient spacings... They run across the ceiling at 6" /30"/54"/78"/102"/12X"

As u can see, a full 8' sheet (96") won't fit. I've got a bunch of drywall up, but am wondering if I have to have my butt seams land on a hat channeling? Right now, I am using about 6.5' sheet + 4.5' sheet to go across the ceiling. I am ending up with a bunch of near useless 45" x 48" drywall sheets left over.

Someone (fellow from DC?) mentioned that u don't have to have the 2nd layer joints line up on the hatchanneling.... Is that true? Does that apply to the ceiling?
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post #2 of 17
4/6/08 at 8:45pm
That would be me. just secure the edges to the first layer of drywall and you will be fine, TRUST ME.

But really, you should be using 12 ft sheets (cut down to your 11 ft) and you wouldn't have any butt seams.

You will need a 2nd set of hands and a drywall lift to work with tight fitting sheets.

If that is impossible, use those odd sheets just stagger them side to side and cut some 87 inch pieces to span the remainder. Alternate the butt seams from side to side so they don't line up and they will be much less noticeable.
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post #3 of 17
4/6/08 at 8:58pm
Thread Starter 
Quote:
Originally Posted by BIGmouthinDC View Post

That would be me. just secure the edges to the first layer of drywall and you will be fine, TRUST ME.

My screws don't have enough bite to actually secure the 2nd layer of DW to the 1st layer, unless there is something behind it.... My butt joints would not be secured along that span.... (ideally, between the 78" and the 102" hat channels.)

Yah, currently, I am staggering the butt joints in the ceiling.... I don't think I could have gotten 12' 5/8th's sheets into my basement....
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post #4 of 17
4/7/08 at 6:20am
Remember that the second layer needs to be secured to the hatchannel as well. You don't just secure the second layer by screwing it into the first.
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post #5 of 17
4/7/08 at 8:36am
Quote:
Originally Posted by petee_c View Post

My screws don't have enough bite to actually secure the 2nd layer of DW to the 1st layer, unless there is something behind it.... My butt joints would not be secured along that span.... (ideally, between the 78" and the 102" hat channels.)


None of my butt joints fell on the channels. You must be using the wrong screws. You need to press the drywall tight before screwing and not rely on the screw to pull the ceiling tight. You also use A LOT of screws.



See if you can find some Grabber brand drywall screws for metal channel. They have a medium thread and seem to work the best for this application. Also try the drywall laminating screws.
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post #6 of 17
4/7/08 at 8:44am
Thread Starter 
Quote:
Originally Posted by Cathan View Post

Remember that the second layer needs to be secured to the hatchannel as well. You don't just secure the second layer by screwing it into the first.

yep. Done.

I'm using 2" fine thread drywall screws to secure the 2nd layer to the HC. About a screw every 6" along the HC which is spaced about 24" OC.

P
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post #7 of 17
1/16/09 at 10:16am
Since I dont like starting brand new threads for my dumb questions...I reserruct another old one. I understand you dont have to butt seems to meet on the HC for the second layer, but I am struggling with the first layer. I installed the HC, but because we are a third floor attic, we can only do the 8x4 sheets. Do you have to cut the sheets so that two layers but and meet on the channel? I didnt even think about how the sheets would install and simply mounted the clips and HC according the instructions from Ted and John. Did I screw up already and should have mounted the channel so the seems butted evenly so I dont have to cut the 8x4 sheets on the first layer?
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post #8 of 17
1/16/09 at 10:49am
Neither the first nor second layers have to have the seams falling on a channel. Trust me. This is one of the true beauties and time savers of going with a two layer system.

They do however need to overlap and it's a good idea if the seams from the first layer are at least 12 inches from the seams on the second layer.

You should screw both layers to the channels
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post #9 of 17
1/16/09 at 11:58am
Technically, all butt joints should land on HC, first AND second layers. However, taking the shortcut has the advantage of simplicity on its side. If you want to just throw up the sheets willy nilly the at least use laminating screws on the butt joints of the second layer.
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post #10 of 17
1/16/09 at 7:47pm
Quote:
Originally Posted by TJ7 View Post

at least use laminating screws on the butt joints of the second layer.

To complete this thought on the second layer you always use a screws on both butt joints and the other joints whether they fall on a channel or not. If they are on a channel you use regular screws, if they fall in between you use laminating to secure the edges to the first layer.
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post #11 of 17
1/17/09 at 6:48am
Quote:
Originally Posted by BIGmouthinDC View Post

To complete this thought on the second layer you always use a screws on both butt joints and the other joints whether they fall on a channel or not. If they are on a channel you use regular screws, if they fall in between you use laminating to secure the edges to the first layer.

Complete Dumb a$$ question here....I understand the screws for the first layer and lengths...are these laminating screws different than drywall screws? I am wondering if I should provide the screws to the drywall crew? I know they are going to think im crazy when they see this HC on the wall and everything I insist...I personally dont care since im paying, but want to make sure I give and/or tell them everything to get it right. Would you ming positing a pic or link to the type of screw I need for this second layer when it does not land on the HC? Much appreciated....
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post #12 of 17
1/17/09 at 8:25am
http://www.grabberman.com/Media/Tech...ittals/136.pdf

Grip-rite (HD/Lowes) also has a drywall laminating screw.

I'm going to be honest I've never understood the mechanical dynamics of what makes them different then the regular screws other than they are thicker. What is more confusing is that they are described as temporary but for our applications they need to be permanent.
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post #13 of 17
1/17/09 at 9:02am
The design of the thread allows them to obtain a measurable pull out value when screwed just into drywall; similar to how these work:


Fantastic time-saver
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post #14 of 17
1/18/09 at 3:40am
Not to try and confuse you, but I'll throw out another solution that worked for me. In the places where I knew the seams of the 2nd layer of drywall would not fall on HC, I screwed a thin strip (about 4" wide) of 1/4" luan behind the 1st layer of drywall as it was going up making certain the luan didn't touch any joists. Assuming you mark where the strips are you can then screw along the seams of the 2nd layer through into the luan and it will pull the seams tight to the 1st layer.

I didn't know about laminating drywall screws, or I would have definitely used those.

-Tom
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post #15 of 17
1/18/09 at 5:10am
One more scenario...
I don't think it really would have made a difference in the long run given the rigidity of 5/8" sheets, but there were two sheets in my second layer that had one row of screws (based on typical channel spacing) I could not adequately screw into the channel. A row of Liquid Nails Construction Adhesive did the trick. I wedged a 2X4 under that part of the row for good measure until it cured. Again, I'm only talking about a small portion of a sheet, but this was a simple solution.
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post #16 of 17
1/18/09 at 6:14am
This is all really great information and I am feeling much more comfortable on how to relate this to the drywall crew. I think I will also provide the screws and label them first layer, second layer, second layer not on HC, etc. I did meet with the drywall owner yesterday and he said on my angled celing and the celing itself he recommended some drywall glue to adhere to the HC. Now I am thinking thats not what we want to do as you want the resillency, correct? Am I thinking through that correctly? If adding glue would not affect the board and what we are trying to accomplish then I guess it would be ok. Just trying to understand if that would be bad or not so I can tell him yes or no....

Thanks guys, this input is outstanding.
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post #17 of 17
1/18/09 at 7:18am
The number one thing you can do is NOT allow the crew access to the longer screws until they finish the first layer. Too long of a screw on your first course (or even second, actually), and you'll "short out" your decoupling efforts.
You don't need to put adhesive between the channel and the drywall.
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