If you're building a home, the pre-formed arch comes in many sizes and can fit most standard openings. It attaches to the stud, and the lip on the bottom of the arch accepts 1 ½" drywall to give you a nice rounded opening. If you're putting the arch in an existing home, you can leave the lip on for relief or you can cut it down to smooth it into the surrounding walls. If you want to cut off the lip, eyeball the estimated curve you want for a smooth finish into the wall. Then take a square and draw a line to mark where you want to cut the lip off.
Once you've done that, take the square and draw another line along the back of the arch straight down from the end of your previous mark. This will give you the line to follow so you get a nice straight cut. You can then cut the urethane arch with a hacksaw or hand saw. It's very easy.
Once the cut is finished, check to make sure that the arch is flush with the wall where you will install it. To put it in, you need a couple of drywall screws. We used three-inch drywall screws to attach it to the surrounding framing of the entryway. Make sure it is flush with the ceiling and surrounding walls and screw it into place.
When installing your arch, you'll notice it comes from the factory with a gray primer coating on it. If you've cut the arch to make it fit, you'll need to sand down the area very well where the primer has been cut off. Not only will the sanding help blend it into the wall but it's also closing the pores on the material. Urethane is a very porous material and if you didn't sand it and put a skim coat or a new primer on it before you paint it, the paint would soak right into the arch and leave you with a blotchy color that you don't want.
Once you've painted the arch and it's dry, you need to caulk around the edges so you get a nice seal that will blend in with the surrounding wall. After the caulking is dry, you can texture the surface. You can buy a spray can of texture to accomplish this. Be sure and put down a drop cloth so you don't mess up your floor, and use a piece of cardboard or other material to protect the surrounding areas from overspray from the can of texture. Let the texture dry about 5 minutes and use a wide putty knife to "knock it down".
What that means is that you need to use the putty knife to spread the texture over the arch's surface area to give it a uniform look and texture. These arches range in price from $17 to $75 and even with the purchase of the tools you'll need for this job, total price for a dramatic new look for your home is less than $100.