# How to seal off opening in 3 layers of 1/2" drywall



## djgrant (May 12, 2011)

There is 3 layers of drywall on one of our ceiling areas and there is an opening for a heating register. How can I seal off that drywall so that there is no chance of loose drywall or dust falling down. The area right beneath there is where kids play and there is the heating air that will blow past it. Will spackle stick to the drywall there? Thanks.


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## joecaption (Nov 30, 2011)

And what happened to the boot where the vent was?
Why not just put back where it belongs.


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## djgrant (May 12, 2011)

What are you talking about?


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## beenthere (Oct 11, 2008)

The supply appears to still be above that hole, and not sealed.


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## DangerMouse (Jul 17, 2008)

I would be far more concerned about *THREE layers of drywall* falling on the kids than a little dust! I would take the drywall down, ALL OF IT, and put in ONE layer of 5/8" Fire-X. Then replace the register. Leave it closed if you do not need the heat there at that point in time, but leave it there. It was likely designed that way on purpose.

DM


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## Maintenance 6 (Feb 26, 2008)

You don't need drywall work. You need sheet metal. Looks to me like somebody just rough cut a hole in the duct to supply conditioned air to the room and never finished. I'd line the hole with sheet metal up to the duct, secure it and put a proper diffuser in place. I have to guess that there may be a fire code requirement for 3 layers of drywall. If it's all secure, I would leave it.


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## mikegp (Jul 17, 2011)

What are the chances of all three layers being properly secured? That would require some long screws. Is it possible they just screwed the bottom layer to the next? Glue maybe? Seems odd.


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## AtlanticWBConst. (May 12, 2006)

Maintenance 6 said:


> You don't need drywall work. You need sheet metal. Looks to me like somebody just rough cut a hole in the duct to supply conditioned air to the room and never finished. I'd line the hole with sheet metal up to the duct, secure it and put a proper diffuser in place. I have to guess that there may be a fire code requirement for 3 layers of drywall. If it's all secure, I would leave it.


^^ This would be my thought on it as well ^^

Aside from the sheet metal related work, I'd also suggest to leave the drywall where it is. One possible scenerio:

Layer # 1: Looks like older plaster board (original ceiling).

Layer # 2: Could be a lay-over repair of the old ceiling.

Layer # 3: Could be an addition of Fire-rated sheetrock to accommodate current code requirements.


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## AtlanticWBConst. (May 12, 2006)

mikegp said:


> What are the chances of all three layers being properly secured? That would require some long screws. Is it possible they just screwed the bottom layer to the next? Glue maybe? Seems odd.


Yes, they likely would have used longer screws + potentially glue - if it was professionally installed.

Example: If all 3 layers are 5/8" = 1-7/8" + 3/4" = So 2-1/2" screws would work/hold.

(When we had a dedicated drywall work-van, we always kept all kinds of lengths & types of drywall screws from 1" to 4" to accommodate any remodeling project).


FWIW: The average weight of 1/2" GWB in interior residential construction generally weighs about 1.6 pounds per square foot, so you are looking at about 5 pounds SF or less for the ceiling weight.


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## joecaption (Nov 30, 2011)

You missing your ceiling register box and defuser.
http://www.indoorcomfortsupply.com/cgi-bin/commerce.exe?search=action&searchstart=40&category=MRBX


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## DangerMouse (Jul 17, 2008)

AtlanticWBConst. said:


> Layer # 1: Looks like older plaster board (original ceiling).
> 
> Layer # 2: Could be a lay-over repair of the old ceiling.
> 
> Layer # 3: Could be an addition of Fire-rated sheetrock to accommodate current code requirements.


If so, that sure is an awful lot of sheetrock to hang on a ceiling to meet fire requirements!  scary stuff.... 

DM


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## AtlanticWBConst. (May 12, 2006)

DangerMouse said:


> If so, that sure is an awful lot of sheetrock to hang on a ceiling to meet fire requirements!  scary stuff....
> 
> DM


Not that scary.

I'd reckon to say that Horsehair plaster & wood lathing weighs more per SF than 3 layers of conventional 1/2" GWB per SF.

I could be wrong, but that stuff is dang heavy, if not heavier.


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## djgrant (May 12, 2011)

The extra layers of drywall were simply added to make the ceiling flush with another spot that was 1 inches lower.

"Maintenance 6" is correct, someone rough cut a hole in the duct and put a hole in the drywall but didn't put any other sheet metal like they probably should have. During our renovations, the 2 extra layers or drywall were added.

I don't think I have the skills necessary to do the sheet metal work. Is it really important to do the sheet metal? It seems to provide lots of air as is. Is there any other concern?


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## joecaption (Nov 30, 2011)

There is no skill involved in this one, if you can turn a screw driver and close up a wire tie you can do it.
All your going to need is the size of the hole to go buy the ceiling adapter.


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## djgrant (May 12, 2011)

So it sounds like you're saying I just get an adapter and the adapter is screwed to the duct?


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## djgrant (May 12, 2011)

I don't think there is enough room for something like this: http://i21.geccdn.net/site/images/n-picgroup/HTC_57231281.jpg

Are there pre-made pieces of rectangular sheet metal (the size of the register) with a flange area on the inside to fasten to the duct?


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## joecaption (Nov 30, 2011)

Since there is no picture of the duct we will just make a guess. 
The adaper gets sliding into the whole and the pipe or hose just slip right on. Is it metal pipe or flex duct?
Flex would use a radiator type clamp or a wire tie and duct tape over the joint, (foil duct tape, not cloth type)
A metal one would use short duct screws with a hex head on them.
Once in place you go inside and attach the defuser to cover up the hole where the air come out with the two screws that come with it.


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## djgrant (May 12, 2011)

It's a large rectangular duct with a rough-cut hole in the side. Nothing is going to just clamp or fit on. Something will have to be fastened on.


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## Maintenance 6 (Feb 26, 2008)

Measure the rough opening size and the distance from the ceiling to the duct. Get a sheet metal shop to make a boot to fill the space in a size closest to a standard diffuser. Then attach it to the duct. The problem with not having the sheet metal is that your conditioned air is leaking into the ceiling cavity where it is not only costing you money, but stirring up dust. Also a diffuser will allow you to regulate the airflow into the room.


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## Willie T (Jan 29, 2009)

Unless all you are asking is how to seal the edges of a register install...... Shame on us for not telling him the easy and obvious way to do this.

Assuming everything is solid and sound up there.......

Simply cut the ceiling side piece of drywall 2" bigger, all the way around......

Then cut the center (sandwiched) piece 1" bigger all the way around......

Now, fasten in wide pieces of backer wood to the top sides of the upper piece of drywall, leaving it hanging over the edges of the opening of the hole about an inch. 

Ready to install three rectangles of drywall. Use type "X" or type "C" drywall.

One to match each of the holes in each layer. Screw and glue each layer, and seal the edges with d/w mud as you build downward.

If you need a picture, let me know, and I'll draw a quick one..... but I think you can understand this.

Normal heating or cooling won't affect the bare drywall, but if you're nervous about temps getting too high, screw in a sheet of metal above everything before you begin installing the layers of drywall.


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## beenthere (Oct 11, 2008)

Drywall as a supply chase is prohibited by code, if the air temp can exceed 120°F.


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## djgrant (May 12, 2011)

Willie T said:


> Unless all you are asking is how to seal the edges of a register install...... Shame on us for not telling him the easy and obvious way to do this.
> 
> Assuming everything is solid and sound up there.......
> 
> ...


I sort of understand what you're describing, but it sounds like you're closing off the hole entirely when you say "Ready to install three rectangles of drywall . . . One to match each of the holes in each layer."


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## Willie T (Jan 29, 2009)

djgrant said:


> I sort of understand what you're describing, but it sounds like you're closing off the hole entirely when you say "Ready to install three rectangles of drywall . . . One to match each of the holes in each layer."


That's why I wrote the first sentence. Your post sounded like you wanted to seal up the hole.

This is the title to your post : *How to seal off opening in 3 layers of 1/2" drywall *


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## djgrant (May 12, 2011)

I guess my post could be interpreted that way. I said "How can I seal off that drywall" meaning seal off the sides of the drywall just to reduce potential for dust or chunks to fall down or whatever. "Seal off that drywall could also mean seal off the "hole in the drywall".  Sorry for the confusion.


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## mae-ling (Dec 9, 2011)

Is that a oval hole just cut into the bottom of you main trunk? 

Buy a flat strip of Ductwork metal. Bend it into a rectangle that fits inside your hole and sized for a register. Bend tabs inwards on it to screw into the existing hole. (bend tabs first then make into rectangle).
DO a google search on sheet metal bending.

You basically need a rectangle extension extension to get down to the surface of the drywall.


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## djgrant (May 12, 2011)

Yeah that looks like exactly what I need (well I'm still not sure about the "need" part. FWIW, it has been in it's current state for the past 8 years since the previous owners did these renovations). I don't have a sheet metal bender though. I've used one a long time ago so I know what they are. The one I used was a huge one.


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## Gary in WA (Mar 11, 2009)

"I'd reckon to say that Horsehair plaster & wood lathing weighs more per SF than 3 layers of conventional 1/2" GWB per SF.
"------ you reckon right.

5th down the list: http://www2.iccsafe.org/states/Florida2001/FL_Building1/PDFs/Appendix%20A_Weights%20of%20Building%20Material.pdf

djgrnt, any sheet-metal shops or trade vocational schools in the area?

Gary


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## mae-ling (Dec 9, 2011)

djgrant said:


> Yeah that looks like exactly what I need (well I'm still not sure about the "need" part. FWIW, it has been in it's current state for the past 8 years since the previous owners did these renovations). I don't have a sheet metal bender though. I've used one a long time ago so I know what they are. The one I used was a huge one.


Can bend it with a couple of pieces of angle iron or even 2x4 or 1x4


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## djgrant (May 12, 2011)

I found a metal shop and I will send them a spec for something that looks like what mae-ling drew.


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## djgrant (May 12, 2011)

Just a few things:

-I found a sheet metal shop, I'm going to send them a spec and see how much it costs
-What is a diffuser? Is that the same as a register? Or is it something else?
[email protected]: can you send me that drawing or file? I may just use that and put dimensions on it. I'm also just curious what program you used to draw that.
-Any advice on drilling holes in the duct? I've screwed holes in a hollow metal door just recently and just used a drill at lowest speed and took my time (so the drill bit wouldn't heat up)
-Should I just screw it to the duct? Or should is there something else I can do to seal the joint?


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## coupe (Nov 25, 2011)

djgrant said:


> There is 3 layers of drywall on one of our ceiling areas and there is an opening for a heating register. How can I seal off that drywall so that there is no chance of loose drywall or dust falling down. The area right beneath there is where kids play and there is the heating air that will blow past it. Will Spackle stick to the drywall there? Thanks.


 assuming the drywall is properly fastened? the simplest fix, is to buy a heat register, they usually have a flange around them about 1 1/2 inch. which would stop ant large pieces of drywall from falling through. typical size about 4x12 inches, and just fasten with screws at each end. as far as dust falling through, simply apply two coats of good quality gloss paint on the exposed drywall, let dry completely between coats to seal it good.

I've done jobs for DuPont that required 3 coats of epoxy on all exposed gypsum, each coat to dry 24 hours between coats. meaning, we'd cut a sheet on Monday, cut all boxes or protrusions for pipes and such, epoxy coat each one, epoxy coat again on Tuesday and Wednesday then could finally hang the sheet on Thursday.

the hole in the duct work look irregular, but air will pass through it. I think you can screw register through drywall right into the sheet metal duct with 2" or 2 1/2" screws. just try to keep screws as straight as possible! if needed? pre drill the holes the same size as the shank of the screw


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