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geodesic dome roof

17K views 14 replies 8 participants last post by  the roofing god 
#1 · (Edited)
Good morning all,

I've been in on a few roofs, and for the most part they're not too troubling to me. My neighbor wants to hire me to reroof her dome. Were talking sixty triangular facets and five canopies. Not only do the seams run in all directions, the multiple pitches will be treacherous.

The original job is maybe 12 years old, and there is some pretty bad water damage to the drywall. That much is because the valleys around the canopies were of hemi-donkey nature and the canopies have a cricket built into them instead of draining into a gutter, so there are ten points on the roof that have 106 square feet focused into a channel 3 inches wide running parallel to a seam.

She called a few contractors, and the responses ranged from too busy to help to refusal to touch it. She asked me about roofing methods that I am not familiar with, and I recommended getting a professional opinion on them- but they all sound viable. I did indicate that if she chose any method besides composition, that my lack of familiarity with them would mean that someone else would have to take the job but I'd still like to be on the crew if possible.

The region is mountainous (central Washington) with moderate wind in spring and fall. The top five facets are 3:12, and the rest are steeper- going to near vertical at the edges. The skylights have a prefabricated flashing, which I intend to treat as base and put step on top of. I also intend to remove the crickets on the canopies and increase the canopies' pitch.

Most of the damage is due to bad valley and integrated cricket, both of which will be addressed. I am uncertain if this warrants I&W shield- 98% of the damage is under 24:12 or greater roof pitch.

I view every change in pitch, be it ridge or valley, as a liability. This roof has 1000'+/- of those and is only 16 square (!!). Is this cowardice or healthy paranoia?

(!!) Sorry, it's 32 square.
 
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#2 ·
Healthy paranoia.

Sounds like this would be a good job to work on as general labor under an experienced contractor. This gives you the opportunity to learn something new from another professional. Good luck!
 
#3 · (Edited)
I guess, without seeing it, I would suggest 100 % Ice and Water Shield where ever downward water could find its way into the structure.

Regarding the shingling; I would only "Suggest" that each lower portion triangle or pentagon be completely shingled with a very Heavy-Weight, yet flexible shingle material. I think one which lays flatter would make more sense, by not having the additional laminate to telegraph through the portions which may require getting overlayed onto.

I say overlayed, because at every angular "Hip?", rather than cutting the field shingles flush to the hip/ridge protrusion, I would prefer to allow the shingle to flow past the bump and then be overlayed with the field shingles from the next adjoining higher triangular or pentagonal section and then cut that field shingle to the angle of the hip/ridge bump out line.

I don't know the proper terminology, so I hope you get my meaning.

I would not use any hip or ridge cap shingles but use the overlay method with the angular cutting of the top overlaying shingles instead. Possibly I might make an exception to any true ridge lines which occur on the actual top portion of the dome structure.

I have read about, but have not seen the new "Duration" shingle line from Owens Corning, which sounds like it is an architectural style shingle with a solid line aggressive sealant tab, which may be a better choice for this project.

Hand sealing of "flapping or loose" tabs may also be required.

I would loive to tackle such a unique and diverse project myself.

Ed
 
#4 ·
I agree Dan101, and if one such were available I wouldn't have the job. As it is, the "contractor" who built it committed sins worthy of lashing at the pole. The only local one who claims to specialize in weird roofs is unavailable until October.


Ed the Roofer, all that you say makes sense to me. I hope standard arch. shingles will be flexible enough on a hot day. I intend to wrap the shingles over all the hips that are radial. As for all other angles, what I had in mind involves a strip of roll roofing (with fairly good color match to the shingles) to take care of the overlap across the pitch change- the original does not have this overlap, only shingles cut flush to the hip and glued down with JH.

I also follow the logic of using I&W where it will give significant benefit- at the valleys.

It appears that I will be doing the canopies and any facets with skylights for the moment. It will certainly take more time to interface with preexisting roof than start fresh, but the neighbor's resources are finite. Thanks all for the input, and more is welcome.
 
#5 ·
I did a geo roof once, and that was a 3 in 1 job...first, last, and only! The roof is still fine, but what a bear. It was interesting to start, but that wore off.....and it was a real challenge. If I get my old files retrieved from my dead computer, I will post some pics of it.
 
#8 ·
Here's some of the latest things I've heard from my neighbor (I don't have the job just yet). The owner/engineer/architect at Oregon Domes is no longer distributing some of the information (which may or may not be helpful) on preferred layout techniques because she's "Tired of hearing about people's leaky roof." I hear she's also tied up in a legal battle of some sort.

Now she sends people to her "preferred roofer". My neighbor already hired a "preferred contractor" who made a leaky roof from day one. Did I mention that he also crowned some of the floor joists down? There were a lot of other things, like I think he purchased some mis-cut lumber(1.5" by 8.875") and he put vinyl directly on subfloor with insufficient support (very bouncy).
 
#9 ·
In reading about geodesic domes and cedar shingle roofing, it sounds like I have the worst of the worst! To complicate matters, my dome has 5 A-frame extensions (16/12 pitch) going around the dome itself. There is a lower (ground) level and lots of redwood decking going around the entire dome.

I live on a mountain top in Colorado (elevation 7200 ft.) and get lots of very, very high winds. Interestingly enough, even though the house is 22 years old, the wood shingles I have are holding up better than my neighbors' asphalt roofs and their winds are much less severe.

But...yeh, it's time to replace the roof. Because the roofing of the dome itself comes down to within 4 ft. of the deck, and because the A- frames are so steep, you see a whole lot of roof. To give you a sense of what the rest of the house looks like, the 4 foot risers are also redwood but $ permitting I will be putting cultured stone (that matches the stone on the gound level) on the risers, and putting stucco on the front of the A-frames which consist mostly of large trapazoid/triangle shaped windows. This additional work is necessary since the birds have made huge holes in the A-frame soffets and above the patio doors (any place they can find something to perch on (trim, light fixtures, speaker covers, etc)). Back to the roof. As such, asphalt shingles do not appeal to me. Someone suggested spraying it with polyurethane foam and then polyrea (?) paint. Because I sit right on top of the mountain I'm afraid I would look (as the person said) like a big golf ball. I need 45 squares. Any recommendations for an alternate roofing product that would be appropriate for the dome configuration before I put wood shingles back on??

Any advantage to wood shingles over wood shakes if I stay with cedar?

Also, anyone have experience with ordering shingles from outside the U.S? Or should I stick with whatever source the roofer may already be working with.

I'm a retired sort of old lady trying to keep this place going so money is an issue; although I am prepared to spend the cost of another wood shingle roof. As the various messages by roofers have indicated, no one really wants the job so efforts to get someone to "think" about it have been unsuccessful. I'll actually worry about getting a roofer once I know what I'll be using since I'm finding out that not all roofers are created equal.

If anyone has had the patience to read this, THANKS. Hoping I get a reply... If I figure out how to add a picture, I'll do so.

This is my first time in a chatroom!!
 
#10 ·
Welcome Caseman,

I think for your question to be answere properly, we would definitely need to see some photos of your home. Put up a few general eterior shots which show the intricate shapes you described.

If I can offer andy advise, I will be glad to help.

Ed
 
#11 ·
Ed and I both have out thinking caps on for you.....but, we need the pictures. Your description sounds challenging...I can only imagine the vision of the designer/builder. With 5 A-frame projections, the form of the dome was basically lost...meaning it's actual function.

There are 3 in my area, and none since. All built in the late '70s.
 
#13 ·
I believe from discussing this roof with her, someone that wants a challenge could make a Colorado vacation out of it......If I wasn't 8 months out on work, I would actually think about it, simply because I love a challenge.
 
#14 ·
Permanent Roofing Systems out of Montreal has a fantastic roofing system for this type of building. Go to RCS and look for Pgriz, a forum poster.
 
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