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Stephen, Cut two pieces of plywood to match the exact radius you need. Spread them apart about 3 feet and nail a couple of 2×4’s between them to form a sort of cradle. Place a sheet of 1/2″ rock on it face up and wet it (out in the sun preferrably). Let it dry and it will begin to sag and conform to the radius of the plywood. Repeat this process several times and you will achieve the perfect arch you need using 1/2″ rock! I have used this method several times and it works beautifully.
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Stephen;
A combination of bending forms, water and gravity were used to hang the 1/4 inch flex on this ceiling, the radius was 16 feet wide and the board bent real easy to fit it, the eliptical archs had a 70 inch minor and about a 90 inch major and had to be wet to conform. We wet and moulded the drywall and then set it in corners to dry before hanging and it worked real well. I have been tempted to tent over the bending forms and use a little bit of steam for the real radical bends on the thick rock. I think you should let your board dry before installation to keep the screws from pulling through.
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Anyone have any experience bending half-inch drywall? i need to make a 42" radius on about 6 feet of stud wall 16oc. I was going to wet the back side and try to apply it horizontally. Am i nuts to try? Thing is, 1/4" bendable is hard to come by...
*Steve, There are several options to try. Time and finish are your primary concerns as I see them. First and my prefered is two layers of 1/4" but since you said that is rare in your area my next choice is a layer of 1/4" luan covered by 3/8" rock. I have used this on many arched openings and barreled commecial ceilings in malls. The luan provides excelent backing if you use 1" coarse drywall screws and a light thin speading of adhesive. Now since you said the length was 6' I would railroad this rock. Comming off the radiused sheet to the flat walls allows an easy verticle joint to tape and the 1/8" difference in the thickness is not difficult to feather in. Additonally you only have a single horizontal joint on an 8' ceiling. The second method is to score the back of 1/2" rock and bend/break the back. I do not like tis methodbecause of the skim coating process to feater out the "facetts" of the surface. For me to labor intensive and the finnisher needs a real good hand. The final method I know of is to make a jig on the horizontal. Kind of like a cut open barrel. The set your rock on top and slightly weight the middle. After a few hours to a ay gravity will take its coarse. This only works on very shallow curves. As well if you use too much weight- snap. I strongly disagree with wetting any drywall, ever. Good luck, hope this helps.
*Dave;What do you mean when you say railroad the rock?We are in the process of doing an arch ceiling now. However, the sides taper to zero and the height drops to meet an existing ceiling. We will be using 3/8 drywall. We thought of wetting it to get the shape. What is your reasoning for not. Right now I do not have any sizes but I will in a day or two. Neil Rubinson
*Stephen:To get 1/4" rock go to a "real" drywall supplier, not a home center. Sure it's going to be a little pricey, but you only need a few sheets, right?My dry wall guy uses 2 layers of 1/4" rock, bends it i withthe grain, and wets it. There was some discussion (and disagreement) here about the gran in drywall about 2 months ago, I just relaying what the 55 year old - "did drywall all his life" guy told me.One arch he reciently did can be seen in my coffered ceiling thread I posted about 2 or 3 weeks ago. He actually dipped the rock in a 55 gal barrel of water.
*I'll have to back Stephen on the 1/4" drywall not being available thing. I'm not sure where he is but I can't get it here.I used to live 100 miles north and it was hard to find. Where I am now, no body has it. I'd have to drive the 100 miles to pick up a sheet.
*NEIL,Railroading is laying rock on its side. This gives you horizontal joints. Here in Baltimore this is most commonly done in residential work.My reasons for not wetting drywall are that in two experiences the paper wrinkled on the face. Perhaps just a bad batch, who knows. Since then I have found that I do not need to. If I take my tie I find most 3/8" and nearly all 1/4" will bend. The absolute last thing I personally would do is score the back. I do not like the segmented pieces, To me I see weakened Drywall. Additionaly I know my weaknesses and finishing is one. The les I do the happier I am. Others thogh are very successful with this method.The tightest bend I have made is a 28" radius.It was a narrow row home downtown and had a 10' ceiling. As part of a kitchen remodel the owner wanted to take out a constricting door at the end of a 6' hall leading into the kitchen but still wanted the separation. In the hall were two doors (one closet and one basement). I barreled the ceiling putting recessed spot lights into it for artwork opposite the doors. The arch went from a smooth transition on both walls and formed a half barrel. I made 3/4" plywood ends and filled it with 2x4 studs 10" O.C. Experiment for your radius. A larger radius doesn't need as tight spacing. Next I used 1/4'" bendable ply. Then 2 layers of 1/4" rock. When cutting the rock I left the second layer short by an inch to allow easier finishing. When I have the ends meeting an existing ceiling I use a Flex bead that is Paper with 2 metal strips in it.
*Stephen, Cut two pieces of plywood to match the exact radius you need. Spread them apart about 3 feet and nail a couple of 2x4's between them to form a sort of cradle. Place a sheet of 1/2" rock on it face up and wet it (out in the sun preferrably). Let it dry and it will begin to sag and conform to the radius of the plywood. Repeat this process several times and you will achieve the perfect arch you need using 1/2" rock! I have used this method several times and it works beautifully.
*Two experiences. In humid South Carolina, 15 years ago, I wanted to drywall around about 4' radius. Best advice seemed to be: set (5/8", commercial code) sheet rock on 2 widely spaced sawhorses, face up or down as needed, spray liberally with water both sides, wait for approximate right sag, screw in place while wet. Didn't take long for sag, worked great, no paper separation, etc.Coupla years ago, central valley CA, dry as bone, I tried same technique, for 6' radius. I soaked and soaked that (1/2") drywall, and couldn't get it to even THINK about bending. Was sprayed-on water just evaporating before it could be absorbed? Go figu
*.........make your mold board from plywood... cut and nail up expanded metal lath and finish with brown coat or Durabond....easier than screwin around with the drywall..
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Well. Thanks for all the great comments and suggestions. Found some rare 1/4", wet it, let it sag over some buckets and it went up nice. Going with the 1/2" was tempting dc, but as I'm now living in Colorado (moved here from Michigan a few months ago, where I would have went for it) I heeded Jim Lewis' message anddidn't even try, since it's dryer than a bone here in Boulder (at least according to my sinuses). So, thanks again, all.
*Well. Thanks for all the great comments and suggestions. Found some rare 1/4", wet it, let it sag over some buckets and it went up nice. Going with the 1/2" was tempting dc, but as I'm now living in Colorado (moved here from Michigan a few months ago, where I would have went for it) I heeded Jim Lewis' message anddidn't even try, since it's dryer than a bone here in Boulder (at least according to my sinuses). So, thanks again, all.