I know it has probably been discussed before, but how tightly can we curve gypboard? I am looking at a spec house job with a bumpout staircase with the inside corners at the landings being 32″ radius. I am now trying to get some info on something called “1/4″ hi-flex” board, which sounds like the right direction. Maybe two layers of that on studs tightly packed at, say, 6″ centers at the curved parts. From the low landing the curved corner runs up about 17 feet, and the high one has a vertical run of about 10 feet. The 32″ radius is seen in plan view. A quarter-circle tangent to adjacent walls.
Edited 10/28/2002 8:37:20 AM ET by Gene Davis
Replies
"...but how tightly can we curve gypboard?"
It depends.
Honestly, Gene, it does.
Two layers of quarter-inch gypsum can easily handle a 32" radius. though it depends a bit upon how careful the crew is when installing, it's likely that 1/4" dry standard gypsum board will conform to the bend. You can facilitate the bending by draping the sheets over a few sawhorses...supported as neccessary...then wetting down the face of the board. Often times you can wet and install, but if this is your first time you can wet, let the board sit overnight to assume the bend and dry out a bit, then install the next day. The board will snap more readily when wet, both when moving it and when getting it to conform to the bend, so be a bit cautious for your first layer. allowing it to dry overnight will reduce the likelyhood of the board snapping during installation.
Often times, if the first layer is installed wet, the second layer can be installed dry and it will conform nicely to the bend.
It may be intuitive, but use more screws to reduce the tendency for the paper and core to let go under the stress of holding the board to an inside curve as it is installed. Also, overlap the butt seams from the first layer to the second.
The first time you bend gypsum is the hardest...and even the first time really isn't that hard. Still, have an extra sheet or two of 1/4" on hand...just in case.
If you are in a humid climate drape it over a 55 gallon drum for a few days it will curve onits own. Also you could make some wood bucks in the radius that you need , wet the backs and let bend . If you are dry bending you need more studs closer with the thinner sheets.Don
an 18 inch radius is no problem, we just did a cove ceiling on that radius and it was a snap.
bb,
"...it was a snap."
Not an encouraging choice of words considering the topic.<g>
Was the ceiling cove done with 1/4" over 1/4"? Did the curve go tangent to an adjacent flat? How smooth was the transition from curve to flat? I am thinking of doing this design, using the laminated rock method, but the original prototype was done down in that part of New England where, believe it or not, skimcoat veneer plaster rules over rock. In some little pockets of countryside approaching Providence, RI, you will actually pay more to get a sheetrock job done in residential housing than getting it plastered. Go figure. Or, go and get plastered.
Gene: Here is some drywall that was bent to an 11 inch radius on the inside of the stair stringer I built last year The guy doing it just moistened 1/4 inch drywall and slowly bent it around a form training it. It went in real nice.
Edited 11/3/2002 9:25:16 AM ET by Stan Foster