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-   -   How do I frame an arch out of 2x4? (http://www.diychatroom.com/f19/how-do-i-frame-arch-out-2x4-9807/)

murray59 07-11-2007 06:00 AM

How do I frame an arch out of 2x4?
 
I'm planning a drywall arch. This in in the interior. I will have a lower 1/2 wall, 40" high and 10 or 12 inches wide (depending on the diameter of the columns I use). There will be a column at either end going up to an upper part of the wall that will have an arch. This is wood framed, covered in drywall with rounded corners. I've done lots of framing but I'm not siure how to make the arch. I hope I've explained this clear enough.
thanks, Murray

AtlanticWBConst. 07-11-2007 06:15 AM

It is done using plywood cutouts. You bascally have to create the arch using a "built-up" 3/4" plywood arch. It is cut with a jig saw. 2 sides (see illustration on link) Double each side up with 2 layers of 3/4" and you have 1-1/2" 'Framing'.

You may also do it with a single layer of 3/4" plywood and cut lengths of 2x3 to install all along the radius (in the jamb area and overhead area) - by using the 2x3 segments, you can follow the curve. You don't neccessarily have to place them side by side. YOo can space them about every 6" too. This method is also good if the wall is wider than a 2x4 interior wall.

Link example of plywood cut out:

http://home.austin.rr.com/wjayne/ArchDoor.htm

You could also look into this: "Insta-arch" (if such an application would work for your design):

http://www.instaarch.com/instaarch.asp

murray59 07-11-2007 06:19 PM

I forgot to mention that it will be about 10-12ft long.

AtlanticWBConst. 07-11-2007 06:23 PM

Quote:

Originally Posted by murray59 (Post 52585)
I forgot to mention that it will be about 10-12ft long.

You should do the plywood method...

clasact 07-11-2007 06:50 PM

wish I would have thought to ask about this subject that looks pretty simple and would have looked great in my house .I will have to look around and see if I can still use that somewhere I think I could do it

dtmbizzle 07-14-2007 03:43 PM

Quote:

Originally Posted by AtlanticWBConst. (Post 52501)
It is done using plywood cutouts. You bascally have to create the arch using a "built-up" 3/4" plywood arch. It is cut with a jig saw.

Original poster- Hope you don't mind my stepping in, but im doing something similar!

My questions is, how do you get the curve on that plywood so perfectly round, or smoothly from one side to the other? If you were cutting with a Jigsaw, i'd imagine you'd have to trace/draw the curve on there with a sharpie, or something??

zel 07-14-2007 08:07 PM

I think once you nail them together, you sand them all at once to get them all the same.

AtlanticWBConst. 07-14-2007 09:03 PM

Quote:

Originally Posted by dtmbizzle (Post 52903)
Original poster- Hope you don't mind my stepping in, but im doing something similar!

My questions is, how do you get the curve on that plywood so perfectly round, or smoothly from one side to the other? If you were cutting with a Jigsaw, i'd imagine you'd have to trace/draw the curve on there with a sharpie, or something??

You decide the ''curvature'' that you want.

Do a layout of one side based on 1/2 the overall width measurent.

Use that to create a template. Then simply reverse it (the template) onto the other side. You will have a perfect match 100% of the time.

Cut out with a jig saw or scroll saw & sand. Check and recheck to make sure that it has the curvature that you want...& sand.

crecore 07-15-2007 09:08 PM

A little Geometry goes a long way in construction. Measure the horizontal width of the opening (this is the chord "y"). Measure the vertical distance between this chord midpoint and the top of where you want the arch (this is called a Sagitta "x"). No one uses that word but it sounds impressive! :thumbsup:

http://upload.wikimedia.org/math/c/e...7fd6816bd9.png

Now place the plywood on the floor... if you need two pieces wide lay them end to end. Measure from each bottom corner of the plywood the calculated radius and find the common center. If you are working on a subfloor put a screw here. If not you can put a screw in a piece of plywood with a cement block on it or something. Then make a string tied to the screw the length of the radius and tie to a pencil. Trace your arc. Move to saw horses. cut with jigsaw.

murray59 07-15-2007 11:59 PM

Now I wish I'd paid attention in math class!

AtlanticWBConst. 07-16-2007 04:48 AM

Quote:

Originally Posted by crecore (Post 53037)
A little Geometry goes a long way in construction. Measure the horizontal width of the opening (this is the chord "y"). Measure the vertical distance between this chord midpoint and the top of where you want the arch (this is called a Sagitta "x"). No one uses that word but it sounds impressive! :thumbsup:

http://upload.wikimedia.org/math/c/e...7fd6816bd9.png

Now place the plywood on the floor... if you need two pieces wide lay them end to end. Measure from each bottom corner of the plywood the calculated radius and find the common center. If you are working on a subfloor put a screw here. If not you can put a screw in a piece of plywood with a cement block on it or something. Then make a string tied to the screw the length of the radius and tie to a pencil. Trace your arc. Move to saw horses. cut with jigsaw.

I was going to mention the whole string, pivot and pencil method, but door-way/entrance arches generally don't have that profound of a circular curve at their corners.

crecore 07-16-2007 06:33 AM

Quote:

Originally Posted by murray59 (Post 52500)
I'm planning a drywall arch. This in in the interior. I will have a lower 1/2 wall, 40" high and 10 or 12 inches wide (depending on the diameter of the columns I use). There will be a column at either end going up to an upper part of the wall that will have an arch. This is wood framed, covered in drywall with rounded corners. I've done lots of framing but I'm not siure how to make the arch. I hope I've explained this clear enough.
thanks, Murray


this sounded large to me... with a half wall at either end it would have to be wide... or he's very short. :laughing:

Anywho, my house, which I deemed European Adirondack :thumbup: has six structural faux marble painted fiberglass reinforced poly resin columns above a steel beam supporting a triple 2x12 lvl for the second floor. I cut the columns down to 7 feet and built down the lvl with blocking above them. I have like 12-14' arches between. These arches define the spaces (dining, living, kitchen, hall) but leave an open feeling. You can easily hit 20-30' radiuses when doing this kind of arch. I'll see if I can find a picture.


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