Manufactured Domes and Arches

[worthy]

I've put in handframed vaulted hallways. But I now I see there are pre-made domes and arches. How do these compare and hold up over the long run?

Especially for a large central dome over a centre hall staircase (See pic). Last time I checked on one of these, the drywallers could only point me to pre-cast one or two piece acrylic domes.

My eight-sided vaults look so cheap compared to the one below. I must upgrade.

[Dick Seibert]

Worthy:

For large domes I think you are better off going with a metal framed system rather than prefabricated domes, USG makes an entire system, their website has grown so that I couldn't find it, but here is some information, I had an architect design one once, but the owner fired the architect and told me to take the ceiling out. It might be simpler to contact USG and they could point you to the best information. Some very elaborate things can be done, those rockers who specialize in metal framing are pretty amazing, I used to go to the carpentry apprenticeship competitions looking for good young men, but always stood fascinated by the guys doing the metal framing.

[rogerg]

If you read the April issue of JLC you will find an article that I wrote about the dome we did. Some things I would do differently but the rotating screed concept worked pretty good.

roger

[calvert]

If you read the April issue of JLC you will find an article that I wrote about the dome we did. Some things I would do differently but the rotating screed concept worked pretty good.

roger

Roger, I read your article and congratulate you for a nice job on the dome. Your approach is similar to standard plastering techniques used for.... well who knows how long, but probably centuries.

About 15 years ago I did a few large niches (6' diameter with 7' high front opening) in a custom home where we were responsible for the insulation and plaster work.

I made a jig similar to yours with a plywood template. The difference between my template and yours was that I attached an 1/8" aluminum edge cut to an exact radius with the help of a router jig. I also cut a second edge to the radius of the surface plaster which I attached for the final finish work.

I set the jig in place and then had the framing contractor use it to act a guide for their framing. I instructed them to keep the frame 1" away from the finish radius. I applied diamond mesh and sanded basecoat plaster and screeded with the template swinging through the opening.

I changed the template edge to the finish screed and applied approx. 3/8" of moulding plaster and ran the screed through this material to produce the finish surface.

After approx. a week of drying time I was able to touch up the finish with spackling paste where there were any imperfections. A final sanding with some 220 paper produced a very nice surface. The niches were then painted by a muralist.

The front edge of the work where they came out to the finish wall plane were trimmed with a 6" cherry custom radius moulding, overlaying the plaster work to create a 1/2" reveal on the back side of the casing.

[worthy]

Thanks for the info! I also found an article on framing domes in JLC in 2009. I've seen this type built before. Apologies to the craftsmen here, but I'm a builder and would be thrilled to find a faster, cheaper way to get the same bang for the buck.

[calvert]

Worthy, the dome you pictured is probably done in GFRG (glass fiber reinforced gypsum) and done as a sectional mould or a complete unit cast, including all the details. This material utilizes a special casting plaster that is capable of fine detail while providing greater strength than a typical moulding plaster.

There are of course manufacturers that make such forms in other mouldable or castable materials, but nothing beats the look of true plaster.

[Golden]

Manufactured domes are the best way to achieve a smooth finish IMO. I have done domes both ways. The savings in labor will usually out way the cost of the Dome. Just keep in mind not to use molding plaster on joints as they tend to blead thru the paint unless you have the 28 days that it takes to cure.