Laminated drywall ceilings

[mgbinspect]

For a period of time here in Richmond, it was considered the ultimate to use two layers of 3/8" dryall for ceilings (around the late 40's to early 50's I think), which I'm interested to hear from someone who know why it was supposed to be so nice.

At any rate, I was inspecting a home with this system and the ceiling was about to fail completely. It was sagged in the center several inches and obviously being held up by the perimeter.

I cautioned the 80+ year old lady that she needed to address this condition immediately. She went on about how she had lived there for 40 years and I didn't know what I was talking about.

As soon as the inspection was over, she went to the grocery store. When she returned she opened the front door to discover the living room ceiling had indeed come crashing down while she was gone. Had she been in the room it probably would have killed her.

I've heard of this double layer of drywall when a mat for radiant heat is between the layers, but does anyone know why the two layer ceiling was supposed to be so Cadillac even if radiant heat was present?

[Bain]

So the drywall's fine for forty years, but inspector-dude spends a few hours in the house and the ceiling caves in the very same day.

Too coincidental, I say. Clearly you did something to cause the ceiling to fall.

(Or so someone will likely try to say . . . )

[mgbinspect]

Nope, this happened about 8 year ago. I was afraid to so much as touch it. But once I pointed it out, the agent and buyer could see how unbelievably sagged it was. I have no idea what had kept it from falling sooner. I can't imagine any fasteners more than 3 feet in from the perimeter were even touching the ceiling joists. It was shocking and I didn't hang around in that room long. Nonetheless, I don't think anyone accepted the urgency of the condition and thought I was overstating the case until the selling agent called later that same evening to inform me that it did fall down. I spent 6 years cleaning up those messes and making it look like it never happened. It was pretty obvious to me that angels alone were holding that ceiling up. I'm no fortune teller and certainly did not expect it to fail that very day. I just knew it was a ticking time bomb that could kill someone.

She lived alone. Now maybe she messed with it with a broom stick or something after we left. Who knows..

At any rate, is anyone familiar with laminated drywall ceilings?

[Jim Katen]

I've never heard of using two layers of 3/8" GWB like that. It seems like it would offer little or no advantage over a single layer of 5/8" material. Seems silly.

However, I have heard of using two layers of 5/8" GWB for sound attenuation. It works remarkably well.

- Jim Katen, Oregon

[Rocon]

Two Questions:

1. Were the boards actually laminated with an adhesive between the layers or was the base layer fastened to the framing and the face layer attached to the base layer with laminator screws?

2. Were the Gypsum Wall Board (GWB) panels at ninety degree angles to the other layer?

The typical reasons for applying two layers of 3/8 GWB instead of one layer of 5/8 are:

1. Applying two layers gives you a smother finish than one layer of 5/8 when applied to uneven framing.

2. Two layers of 3/8 GWB applied to arched ceiling makes it less likely that you will have flat spots in the board and also less likely to crack a sheet compared to 5/8 when bending the rock. The face sheet has less friction when it moves against the face of the base sheet instead of against framing. The two layers of 3/8 GWB can be adhesively laminated or not in this assembly. The face layer must be fastened off maximum 8 in. on center to support loose fill insulation in the ceiling.

3. Adhesively laminating the GWB together or turning the face and base sheets at ninety degrees is typically used when trying to achieve a higher Sound Transmission Class (STC) rating on an assembly (as fire wall assembles have become more common this type of STC rated assembly is less common since it is not a fire rated assembly).

[mgbinspect]

I honestly don't know about the adhesive, as I've never seen it pulled apart, but I do seem to recall that the sheets were indeed installed at 90 degrees. It was always mentioned as that "extra mile" practice of upscale builders. Of course, it isn't practiced any longer, so I suppose it didn't prove to be worth the effort.

Thanks for the input.

[prhales]

I have lived in my home for the past 30 years. My contractor recommended laminating the drywall on my living room ceiling. There was a new 3M glue that could be used to attach the 2nd layer that would form a permanent bond and nails or screws would not be necessary. The reasoning behind this: We have a 2 story dwelling and the living room is 17X24. Due to activity above the likelyhood of nail pops was certain. We had to use southern yellow pine 12" oc to pass code. The 2nd layer just caved in two days ago and came crashing down. We did not have any water leaks or roof damage. It is easy to see the glue just gave out and there was nothing else to hold up the 2nd layer. The first layer seems to be in good condition but I haven't checked it with a level or straight edge to see if there are additonal issues. Due to storms locally we had lost power on two occassions in the past few days and the humidity level was approaching 90%. Additional moisture may be the straw that broke the camel's back. BTW, the 2nd layer was applied 90 degrees to the first layer. My insurance agent said they would probably not cover the damage. According to them this is not uncommon. No inspector available until next week. I am keeping my fingers crossed.

[Ben H]

I have lived in my home for the past 30 years. My contractor recommended laminating the drywall on my living room ceiling.

Did this happen 30 years ago?

Due to activity above the likelyhood of nail pops was certain.

Why not use screws?

[Jim Katen]

I have lived in my home for the past 30 years. My contractor recommended laminating the drywall on my living room ceiling. There was a new 3M glue that could be used to attach the 2nd layer that would form a permanent bond and nails or screws would not be necessary.

"New Product" are two words to run away from.

The reasoning behind this: We have a 2 story dwelling and the living room is 17X24. Due to activity above the likelyhood of nail pops was certain.

Total BS. Properly installed drywall does not experience nail pops.

We had to use southern yellow pine 12" oc to pass code. The 2nd layer just caved in two days ago and came crashing down. We did not have any water leaks or roof damage. It is easy to see the glue just gave out and there was nothing else to hold up the 2nd layer. The first layer seems to be in good condition but I haven't checked it with a level or straight edge to see if there are additonal issues. Due to storms locally we had lost power on two occassions in the past few days and the humidity level was approaching 90%. Additional moisture may be the straw that broke the camel's back. BTW, the 2nd layer was applied 90 degrees to the first layer. My insurance agent said they would probably not cover the damage. According to them this is not uncommon. No inspector available until next week. I am keeping my fingers crossed.

I'm not sure that the codes 30-years ago allowed the ceiling board to be installed without any fasteners. I'm away from my code library now, but my recollection is that nails were required regardless of any fancy dandy adhesive.

You might push back at your insurance company. I've heard of them relenting to particulalry squeaky wheels.

[gpdewitt]

The townhouse I live in, built 1965, has 2 layers of 1/2" GWB on the firewalls between units. It's just nails, no glue, standard pattern. Framed with staggered 2x4 studs 16"O.C. each side. Bat insulation woven through the studs. Because of the way all the electrical boxes are set for one layer of drywall, I speculate that either the builder was unsatisfied with sound transmission, or the AHJ required more drywall for fire resistance. I hear very little of my neighbors, mostly transmitted through floor framing.