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Geodesic Dome Roof Advice/Help

luhar's picture

Geodesic Dome Roof Advice/Help (post #210462)

 We purchased a geodesic dome with five gables. We've had several people, including roofers, tell us that the roof has 3-5 years of life left. The roof has two layers of shingles (new laid on top of old). However, the more I dig into renovations the more I find wrong with it (pictures can be seen at: www.domeroof.wordpress.com) For example:   

1. There was a fair amount of aluminum flashing used at the junction points between the dome and gables. I'm finding numerous cracks and holes in the flashing.

2. The flashing mentioned above was cut flush with the roof decking. As a result, the roof decking absorbed water and rotted, in some areas, as far back as the wall. This allowed water to run down the wall and rot the sill plates in some areas. 

3. No eave starter strip or drip edge was used along the roof decking edges. 

4. There are a few somewhat dark spots on the drywall inside, which indicates to me that there may be leaks.

5. Apparently, dry rot is a common issue in geodesic domes due to lack of ventilation in the roof. As is often the case, this roof does not have ventilation. 

It appears to me that the best way to tackle these problems is to have a new roof installed and I have a few questions for people who may have experience with these types of structures.

1. The total roof surface area is about 2000 sq. ft. Does anyone have a ballpark estimate as to how much it will cost to properly install a new roof and flashing/eave drip edge? Some rotting wood will need replacement as well. 

2. The gables have gable end vents. Is this enough? Or should ridge vents be installed?

3. Does anyone have information on new methods for ventilating this type of roof?

4. Does anyone know of a roofer in Northwest Washington State who is experienced in doing these roofs?

5. Can anyone offer recommendations on what kind of materials should be used on the roof (i.e. brand of shingles, type of underlayment (I would like something better than tar paper))

6. Do roofing companies offer a discount if the homeowners tear the old roof off?

Any other recommendations are welcome!

Thanks....

I can't offer much advice, (post #210462, reply #1 of 17)

I can't offer much advice, but I don't think the current roof has a year left as is.  Maybe some flashing repair can extend it a bit.

I would coat the dome with ice and water shield under the next new roof though.  I don't think there is any possible way to ventilate the roof, and doubt it would help even if you could. 

MarkH - Thanks for the ice (post #210462, reply #5 of 17)

MarkH - Thanks for the ice and water shield suggestion. I've been wondering about that......

Foam roof? (post #210462, reply #9 of 17)

I saw this while looking online.  Unusual, but promising. http://www.sprayfoam.com/newsarchives/ar...

This is an interesting (post #210462, reply #13 of 17)

This is an interesting solution in that you are gaining an insulating value of about R-10 with the foam following by a waterproofing layer with similar integrity to that of a paint on shower membrane.

However, I see the following issues with it:

1. It creates an amorfic looking coating vs. the crisp geometery of geodesic dome. Bottom line is that (IMO) it's ugly as hell.

2. Depending on climate, interior insulation, and conditioning requirements inside, this could create dew point issue within the framing or sheathing structure.

3. I would question the durability of the 24 wet mil coating in terms of puncture resistance (storm debris) and solar degradation.

I agree that a continuous memberane is warranted for this complex roof enclosure. The Grace ICE & WAter suggested earlier as shngle underlayment was great advice. Having said that. I'm wondering if a TPO memberane might be a better option worth investigating.

Good points.  I was wondering (post #210462, reply #14 of 17)

Good points.  I was wondering about the same things.  I think it would be an irregular surface, likely ugly.  I don't know how it would hold up to hail, possibly well, but likely not.  There could be dew point issues,  but that dome is in a fairly moderate climate, so I kind of doubt that would be a problem.  I think a lot of problems would be related to the skill of the "roofer".  I found it interesting though.

TPO would make a nice roof, as long as all the seams were done nice, which could be, but that would be a lot of labor, in my opinion.  But I'm no roofer. 


Copper would be pretty cool.  Probably it would be prohibitively expensive.

Cool - Thanks! (post #210462, reply #15 of 17)

Cool - Thanks!

30-40 years ago domes were (post #210462, reply #2 of 17)

30-40 years ago domes were all the rage and, had blogs existed, there would be several popular ones for domes.

Perhaps, if you dig around, you can find a dome roof "online community" where folks will have experience with them and can offer some advice based on real experience.

Here is an interesting article from which you might be able to glean some ideas: http://www.shelterpub.com/_shelter/domeb...


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

DanH - Thanks for the link. (post #210462, reply #6 of 17)

DanH - Thanks for the link. I'm noticing that domes are no longer a hot commodity based on the lack of online information. 

here's your ballpark... (post #210462, reply #3 of 17)

luhar wrote:

 

1. The total roof surface area is about 2000 sq. ft. Does anyone have a ballpark estimate as to how much it will cost to properly install a new roof and flashing/eave drip edge?

Here's your ball park estimate: alot.

Really, why don't you save yourself the run around and call a professional roofer in your area to get an idea what your up against form a cost perspective. It doesn't really matter what kind of ballparks you get from breaktime.

Deadnuts - we're in the (post #210462, reply #7 of 17)

Deadnuts - we're in the process of lining up roofing bids. But I've received some good advice from this forum in the past and I value information from people that have "been there."  When the roofers show up, I'm hoping to be able to ask informed questions since I'm finding that there are few contractors who have experience with these roofs. The ones who sound competent will get the most consideration......not that I'm competent enough to judge but at least I'll gather a few suggestions here. 

you're mixing apples and oranges (post #210462, reply #11 of 17)

luhar,

My comment was specific to your solicitation for cost estimates here on breaktime; not construction advice. IMO, the former is inappropriate (or at least a waste of time) while the latter is the whole point of this forum page.

other recommendations The (post #210462, reply #4 of 17)

other recommendations

The purists will croak and be all over me for this, but:

a. the main part of the roof itself does not look that bad, unless it is very brittle.

b. question: did the original valleys somehow have galv. nail use right in the aluminum valley for there to be holes???   I'm SE of Seattle and have a lot of aluminum on roofs which have lasted 40 years with no problem, but did use aluminum nails!

c. here is the croak part:  Buy a 5 gallon bucket of fibered roof cement.  Next warm day lift the edges of the shingle near the gutters and coat every thing up under the shingles and the valley with roofing cement.  Pull any galv nails you see going thru the aluminum and fill/cover the holes with roofing cement..

 good for another 10-15 years.   Inspect the roof every few years, and add roofing cement as needed.  

Junkhound - you're just a (post #210462, reply #8 of 17)

Junkhound - you're just a couple of hours southeast of us. The first thing I did after we purchased the house was buy some Henery Wet Patch (based on recommendations from several others) and started filling holes/ patching shingles. I agree with you - the purists will hate that I said that - but something had to be done with the potential major leakers right away (roofers around here are booked out a month or more just to look at the house). I completely understand that it's a bandaid fix that will be painfully ripped off in the future, but at least it stopped some of the water for the time being.

A - You're correct, the shingles themselves really are not that bad considering their age. They're not brittle and we've had several roof educated people tell us they have a few years of life left.

B - We've only had the house for a couple of months so I don't have the whole story on the roof or the valleys. What I do know is that the previous owner did not maintain the house. There are not visible aluminum nails in the flashing. I assume that, in the process of cleaning the valleys of pine needles at some point, someone must have used a heavy hand and gouged and punctured the flashing. Or, during the last re-roof, tools or shingles must have been slammed into the flashing?

C. I can certainly patch the visible flashing cracks and holes and seal the edges, but when I look at the rotting roof decking edges (where flashing was not installed and/or not extended out far enough from the house) I think to myself "what's the point? I'll patch everything up there, but down here I'm still going to have rotten wood." I also look at it and question what else they did incorrectly. 

Worst case scenario - I've got plenty of wet patch left over!

I kept our old roof (actually (post #210462, reply #10 of 17)

I kept our old roof (actually 2 generations back) going for 3-4 years by applying (to maybe 30 square feet) some sort of gray latex glop (a thick paint -- not like roof cement) and a fabric mat.  Not pretty, but it was easy to install and totally waterproof.  Main problem with it (besides the ugly) is the roofers were cursing when they had to tear it off.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

I don't see anything there (post #210462, reply #12 of 17)

I don't see anything there that's too scary  as far as re- roofing. Most domes were homebuikt so I expect your roof was a DIY job as well. 

I see lots of existing problems and if it was my roof I'd be out there tearing it off tomorrow. You need Weatgerguard or some other type self sealing underpayment before you start shingling again. I'd weave the valleys instead of leaving them open to catch leaves and debris. You've got plenty of pitch to carry water off.  Drip edge is a must and I'd want big gutters as well. I'd be amazed if you didn't have rot at the bottoms of your walls already. 

You can strip it yourself but that's going to leave the roof exposed for longer than if you pay a roofer to do it. I expect you'll find a lot of rotten plywood and maybe even some framing that will need to be replaced. I would not let the roofers handle any wood repairs. The roofer won't like that but too bad, they aren't carpenters. 

No matter how you do this it's going to be a big job and not cheap. 

Florida Licensed Building Contractor, 45 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Thanks Florida - this is (post #210462, reply #16 of 17)

Thanks Florida - this is helpful. I know you're right about the rotting walls - I've already found some. 

DID YOU FIX THE LEAKS IN YOUR ROOF? (post #210462, reply #17 of 17)

Hello,  I found your forum pretty interesting, I myself am interested in buying a geodome type home  however there have been a few previous owners who has gave the house up because of a leaky roof issue.. Now I have been doing a lot of research from back to the 60's till today and From what I read is that yes the roof on a Geodesic type house is tricky.. in my opinion it must be done right the first time and so on.. and with a lot of weateherguard etc.  Another thing a lot of people have been saying is that apperently people think their roof is leaking when really it is a moisture issue with poor ventilation inside..  My biggest concern obviously being a first time home buyer is not to get screwed over.. now I know a few people ( with more money than I have )  have tried and given up.. However I don't think they realise it could all be because of a ventilation issue..  So.. the question I  am wondering is.. What if Geodesic type houses had an air exchanger system installed in them.. allowing the house to be fresh and less moist.    you have to consider all the extra room for air at the top.. it has to move and be vented out.. So I think the main thin with a geodesic home would be a good solid proffesional roof with weatherguard and drains to capture rain .. and a proper ventialion system .. What do you think?  How was your experience after you put on a new roof?  Hopefully it all went well and didn't cost too much.. What did you use for a roof? and did you end up putting in vents in the roof?