I am putting up 2 layers of 5/8 sheetrock perpendicular to channel/joist. With just one layer, we land the edges of all sheet rocks to the channel/joist. What I am hearing is with 2 layers I don't have to do that. So there will be edges hang between channel/joist which will sag/drop a little. I heard this will resolve itself when the second layer is put up and it will pull everything nice and straight.

questions:

1) is this correct?
2) Wouldn't the second layer have edges hang between channel/joist which will sag/drop a little?
3) for question 2, they said they pop in a few screws on a second layer end where it hangs between channel that I want to snug the two layers together, is this correct?
4) is this a good method? or just land all edges to the channel? BTW, the channel is only 1" wide so space is limited. Landing two edges to 1" of space is mind blowing.

What I am actually doing is joist->furring channel(hat channel) -> sheetrock(5/8) -> green glue -> sheetrock(5/8)

thanks!

 

Wait for others to respond but no way would I not have the edges on structure if I was doing this.

 

Well, with glue near the seams, I doubt it's as much of an issue, but then you are still depending on the first layer to support the second near the seams. You'd have to increase the number of screws in the first layer. Screwing sheetrock to sheetrock is a waste of screws IMO. No way you can tighten them together.

I'd just cut them all so it lands where it should. Or add something to give more to screw to.

 

If you don't hit ceiling joist on the edges with your screws, your ceiling will most surely sag and fail. As Vic mentioned, screws into sheetrock are useless, there is no holding power. If the ceiling is already sagging, then the new layer will not correct that. Proper repair would be to remove the sagging ceiling and install new.

 

It seems you are doing this to help prevent sound transfer. If so, I would land all butt ends on framing for the two layers of drywall. I would also probably tape the first layer before attaching the second layer. I would also stagger the butt joints and tapered joints so that all joint are offset from the layer below.

If you are having a tough time landing two butt ends on your channel face you can always install a second short piece of hat next to the one the joint is landing on and screw one of the drywall ends to that channel.

 

Yes, I am doing this for sound control. I have done two small rooms with the standard method, edges on channel. If I don't have to land two edges on a 1" wide channel that would save a lot of time for the bigger room. I got this advice from a guy who have done it many many times.

 

He may do it that way all the time but what do his ceilings look like 5-10 yrs down the road?
I'd rather play it safe

 

Really depending on the PAPER of the first layer to hold the second layer if using glue. Land on structure. Are you turning your sheets or running them the same direction with stagger?

 

For the second layer, I am running them the same direction, stagger and offset seams. I feel this method is safe, structure wise. But for the edges that are not landing on the channel that drop/sag a little.... I too do not think screwing drywall to drywall would pull it straight.

 

BTW, Green Glue is glue like substance but not glue/adhesive. So, it is not holding the second layer.