Radius wall hits cathedral ceiling
AndyEngel
| Posted in Construction Techniques on
Any help on this one? I’ve got a radius wall whose next stage is to intersect the slope of a 12 pitch cathedral ceiling. How do you guys handle it? Any fancy technique for making a plate? Or do you just bring the studs up plumb?
Thanks,
Andy
Arguing with a Breaktimer is like mud-wrestling a pig — Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. –Robert M. Pirsig
Replies
I would just plumb up to the rafters. A top plate would be rather challenging and probably not worth the time. Not only would you have to cut the radius but the edges would be a changing bevel. If you need the nailing, I would place blocking between the studs, cut on the radius and set level. You can step up the blocking as the roof rises. Of course, depending on the radius, 16" OC may be too much. The blocks can serve as top plates for intermediate studs. The blocks will be the same as your bottom plate.
Beat it to fit / Paint it to match
Andy,
There are a number of ways to do this, since I haven't every done it before (yet), I couldn't tell you all of the ways :-) The shape of the plate would be elliptical I believe and that isn't too hard to lay out.
Another way to do it is to tack a scrap piece of plywood to the underside of the rafters and use a laser like the PLS to shoot a dot straight up and then if they are close enough, just connect the dots. I think that would be a fairly quick and accurate way to do it. As far as the compound miter on the studs, I'm not sure. If you figured out the first and last stud, you could then divide the difference in angles by the spacing and then you would know how much to adjust the angles by as you went.
You know what I would do? Now that I think about it, I would email Ken Drake or post this question over at JLC or Joe Fusco's forum. I know Ken still haunts JLC. He would be able to pretty quickly answer your question. I doubt my response here has made any sense :-)
There is an article from JLC in June about groin vaulted ceilings that has some tips that might help you. I would love to see some pics when you are done :-)
http://www.jlconline.com/cgi-bin/jlconline.storefront/41647e53001afc5027177f0000010595/Product/View/0406fram
Thanks guys. I'd thought of Joe Fusco, which, if you know my history with Joe, might have you laughing. We haven't always been friends, but I don't know anyone better with construction math than Joe. I'll probably end up roughly locating the studs, and nailing blocking between the rafters. Then, I'll plumb up and lay out on the blocking, skipping the top plate entirely. A laser plumb bob sure would be handy. If there was an easy way to lay out the curve though... I'm pretty sure it's a parabola, btw. I'm less sure if an elipse is a type of parabola. Arguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Andy , I have an 11' r. stair wall that met an 8/12 roof. What I did was cut a 2x6 into strips . I tacked short blocks ,plumbed, on the rafters where the inside radius of the wall frame would meet the roof. Then I used the brad nailer to nail the first strip to each rafter. then I glued the rest of the strips onto the first strip and shot brads into the rafters. After the glue dried I roughly planed it to a semi smooth surface . Just enough so I didn't have any sharp edges,Still had some valleys . The strips of 2x6 made a nice laminated curved 2x4.
Andy,
I'm going to do some research. I was under the impression that the roof (in your case a 12-12) is a plane that passes through a cylinder (your radius wall if it was a full cylinder) and the resulting curve is an ellipse. But . . . .
For instance, when you run a round vent up through the roof, the shape of the hole in the sheathing is an ellipse. In a groin vault, the "hips" are elliptical, but I'm sure I'm missing something.
Briefly, here is what I found at Mathworld http://mathworld.wolfram.com/CylindricSection.html
This was the drawing I did for the stove pipe.
I don't know what I did but look at the Elliptical Vent Pipe Drawing.
Joe Carola
Edited 10/6/2004 11:37 pm ET by Framer
Hey Andy, our history with Joe sounds eerily similar.
Anyways, I've boogered quite a few of these beasts. Your idea to layout and skip the plates is probably the fastest.
Most of the ones I do are quarter segments that border a circulat stair. They terminate into trussed roofs, usually.
On of our requirments is to stop the dead air drafting from the trusses into the dead space behind the studded walls. As such, it's usually easier to sue an idea already mentioned....nail up a sheet of plywood first, then use that at the top plate.
Either way, it's probably faster to just plumb them up like you mentioned. I eyebally all the bevels because each stud will have it's own peculiar angle. I usually put the studs on 6 to 8"oc....but I do this by eye. Usually, I don't make bottom plates either...I usually just nail to the arc I strike onthe floor. If I'm in a good mood, I cut individual "bottom plate blocks" first and simply alternatly nail a stud, then a block. My criteria for putting blocks is usually decided by the oc spacing...more space means more need for those blocks.
I'm on a job now with a 21' tall radius wall ( about 10 diameter) and a cone roof (18/12). Luckily someone else already volunteered to do it...I won't have to mess with it.....whew!
If theres something interesting, I'll post a pic.
blueIf you want to read a fancy personal signature... go read someone else's post.
Interestingly ... before I read this post of yours i was about to suggest the same process to you. It sounds like a good plan to me. I agree that you need one of those little laser plumbs to shoot the spots up to your blocking (from your bottom plate layout). mytoolstore.com has the CST/Berger Lasermark bobs from $59 to $72 or their MP5 for $220. It seems like this one application could justify the cost of any of those. There is also a Dewalt model available for about $135.
An ellipse is formed by a plane surface cutting a cylinder. A parabola by a plane cutting a cone parallel to the angle of the cone. If the plane is not parallel to the cone surface angle then a hyperbola is formed.
Andy,
A Radius wall can be viewed as if it were a Stove Pipe going through the ceiling. This was a thread a while back about a 7" stove pipe going through a 6/12 pitch roof.
You can view a Stove Pipe as if it were a Gable Stud. It's running Vertically up to the bottom of a Rafter and then through it.
Now all you need to do is find the pitch of the roof. In my attached drawing the pitch is a 6/12 or 26.57°.
If you were to cut a Gable stud, you would set your circular saw at a 26.57°.
If you want to you can just take a piece of the same exact size stove pipe and cut it on a Miter Box with it set at 26.57° then you can scribe that for your molding it will fit exact. It will have the Elliptical shape already there.
This way you don't have to draw out an Ellipse or try and figure out the Major Axis and Minor Axis like I have in my drawing.
The key thing is knowing the pitch of the roof and how you get the pitch of the roof.
For Example with a 6/12 pitch and 7" Stove Pipe:
6 [Inch] [Pitch]
7 [Inch] [Run]
[Diagonal} = 7.8262 or 7-13/16" (This is the Major Axis)
The Minor Axis would be 7" the width of the stove pipe.
Another way you can figure the Major Axis:
6/12 Pitch Unit Legth x Pipe Width(Diameter) / Unit Run = Major Axis.
13.4164 x 7 = 93.9148 / 12 = 7.8262 or 7-13/16" = (Major Axis)
http://forums.taunton.com/n/docs/docDownload.aspx?guid=3A98D629-8068-465C-879D-CD3579F56360&webtag=tp-breaktime
Joe Carola
Edited 10/6/2004 11:22 pm ET by Framer
Like the others have said, and we've all presumed this is not a bearing wall, do it without a top plate.
Roughly locate where your circular wall meets the bottom chords of your trusses or rafters of the pitched ceiling, and then fill this whole "not to be plated" area with 2x cats. This will be the surface for toenailing the tops of your bevel-cut studs.
Now is the time for some serious laser or plumbob work, to define the elliptical segment. From your stud layout on the circular bottom plate fixed to the floor below, plumb up from each stud corner mark to the cats and chords above. After you have made all your marks on top, connect the ceiling dots and eyeball the whole scheme to see how it "fairs." Its gotta look like a smooth curve. Adjust marks as required. If your curve was smooth below, any bumps on top were the result of plumbing jiggles.
Now cut and install all your studs, and here is what I would do after that. Cut beveled 2x lumber to go between studs at the top, and face nail these to the cats and chords. They don't have to be curve-cut, unless you're anal. Just make them point to point on the convex side or sides where you will finish with wall materials. Nail them in a little bit to be tangent to the curve, for an convex wall. Now you'll have continuous nailing for the wall finish at top, and your studs are braced a little better at their top connections, by these fitted "plate segments."
If you are rocking the surface, your studs need to be pretty close together. Six inch spacing is what I did last time, for a 38" radius inside-curve wall. For a convex wall, just tack a little shim to the center of each chorded "plate segment" to boost out the rock so it fairs the curve.
And post pictures when done.
Edited 10/7/2004 9:17 am ET by Bob Dylan
Thanks all for the ideas. I'm thinking of nailing 2 x cats between the rafters for nailers. Since this roof is being insulated with closed cell foam, I don't need to worry about air sealing. There will be fire cats to close off the odd spaces to the sides of the wall.
This seems as good an excuse as possible to buy a laser plumb bob.
BTW, the room is 12 ft. wide, out to out, and the radius of the wall is 7 feet and change. The effect is about 2/3 of a circle, which stops at the outside wall. The top of the wall will hit both sides of the cathedral. There are windows in the outside wall behind the curve, and we framed what I'll call tunnels between the curve and the window ro's. It's a pretty cool look.
AndyArguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Andy,
You're probably in bed by now, staring at the ceiling wondering "how the heck am I gonna do this tomorrow?".
I'm not sure that the height from the floor to the ceiling has been indicated.
I was thinking about putting up 3/4 ply on the ceiling, shooting the points up, or dropping them down to the plate. Wth reference points as to where to re-install (what you will have left of) the plywood, remove it, cut it and then double it up and re-install it, then run the studs up.
You may have to bevel (plumb)cut or just short cut the edge of the ply. If you short cut it you will need to plumb each stud, if you can bevel, then you may have an edge to work to.
My second thought was to raise the studs to one level just below the rafters, either with some type of plating or again, plywood. Now you are at least closer to where you want to be and hopefully the solution will be as well.
Sounds like you're havin a blast up there!
Good luck,
EricI Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
Andy,
Please take and post some pics. Pretty please with sugar on it :-) It sounds like it's turning out really nice and I'm not just saying that. If you get a chance, I would love to see pics.
I'd have to steal my wife's camera, and learn how to post pics! I'll give it a whirl when the rafters are up next week.
AndyArguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Andy, If you want to try the string method of drawing an elliptical arc I will try to talk you through it.
First chalk a line which will be the center line of the long axis. Then measure out 7' and drive a nail. From there strike an arc both ways 118.79" on the CL. This is the placement of the two nails. 16.97" is the rafter length per ft. X7' =118.79.
Tie a length of the least stretchy line, like spider wire fishing line to one CL nail, and run it through a washer dropped over the first nail and tie it off tight to the other nail at the opposite end of the CL. Pull the nail in the washer, and strike the arc on your P/W plate material. Once you have your roof framed, you can take your stock up on the roof to cut the line with your reciprocating saw while holding your saw plumb will take care of the changing bevel.
Cut the one foot off the top end, and flip it over , and it should work going down the other side. Good luck, and let me know if you have any questions. Keith
Keith, where did you get the 7 ft. dimension? Was that the approximate radius that I gave you?
Thanks,
AndyArguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Yes, I thought that was what I read. Did I misunderstand what you were asking?
I don't know why the thread disappeared right after I posted it. My answer was not up as long as it took me to type it.
I have another method to draw and or cutting ellipses, which is far more accurate, but it takes longer to make the jig. The other method uses a trammel arm with two holes drilled through it ate the short radius and long radius, with slides which ride in slots at right angles to each other. I use T-slots with UHMW plastic slides, and with a router making the cut on the end of the arm. The track or slot lengths need to be as long as the difference between the long and short radii.
If I didn't understand the dimensions and or situation, clue me in and we can start over. If you would like to contact me personally go to http://www.treetales.com
Good luck, Keith
Keith
I would call you more artist than carpenter, some breath taking work(art).You should post pictures of your work in the gallery, for all to enjoy.
greg in connecticut
Thanks Greg, I need to figure out how to do that, and get someone to re-work the website so I can get more recent photos loaded. I am, shall I say keyboard challenged. I've got this great computer, but I just barely know how to use it. Cheers Keith
That was the number I'd given. Just wanted to be sure that it wasn't some mysterious mathmatical constant, like Avagadro's number. 16.97, of course, is the rafter length per foot run of a 12 pitch roof.
Awesome stuff on your site, btw.
AndyArguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
Do you understand everything OK about the methods? The most important thing about the string method is to get the least stretchy line that you can get your hands on, and keep the tension as constant as possible. Go to the walmart fishing dep. and get the highest # of the new high tech line that you can find. Not monofiliment.
And did I understand that the arc crosses the ridge, and if so that wherever that line is you can just flip that part over, and the plumb cut will work going down the other slope.
Also you may want to set up something on the ground to hold the P/W at a 45 degree slope while you saw the line plumb with the recip saw.
This may be more than you are inclined to do.
If I were going to frame a curved wall that intersects a roof plane, assuming that appearance would be important, I might:
Lay out the wall on the deck using my chalkline and pencil as a compass. Draw in the rafters and 4X4 studs and write next to them their approximate angular orientation relative to the roof. Use the red line as a reference for all angles.
Use the angled line on the right,which represents the slope of the roof, to determine the long point of each 4x4 stud (construction calculator).
Next lay down the stud on the 12" SCMS at the angle shown on the small blowup of the stud in the left side of the pic. In this case, set the saw at 45 degrees and 25 degrees, tilt and bevel. The goal here is to get the angle of the roof plane. Then cut off the unneeded corner on the side that will nail to the rafter. The rafters shown on the right side of the circle will determine the location of the studs. The small red marks in the lower right quadrant of the circle indicate the approximate position of one stud.
Note that the left side off the circle is there to show the method and the right side is to approximate the placement of the studs.Les Barrett Quality Construction
Andy, for finding the compound angle cuts, I have a little tool which is over at a job-site that will pick the angle of slope right off of the top plate. I think it is called an angle finder. It is a little square with a weighted protractor dial.
If you will lay out your studs with a line more or less perpendicular to a tangent to this elliptical top plate., then all you have to do is hold this thing up to the line while it is temporarily screwed into place, this will tell you what angle to mark with your speed-square, then swing it around square to that and it will give you the tilt angle for your saw.
I don't know where I got this thing, but it really comes in handy on jobs like this. I just Google "angle finder tool" and found it at speedway motors for about $10
Sounds like a cool tool. Thanks for all the help. And yes, I did understand your directions.
AndyArguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
How about using the flex-c track material that's on the market now? The idea from an early post about using a laser plumb bob is what I'd do.... lay out the circle on the floor, shoot the dot at the ceiling, mark, repeat, connect. Nail in enough blocking in the lid to 'catch' all the dots. Then install the flex-c track along the dots, and use that to figure your studs, which should be fairly easy because the track will demonstrate the compound angles for you. On the acute side of the wall/ceiling junction the track will impinge on the wall plane, so you may need to furr out, or backcut the rock.