Building a geodesic dome greenhouse

Rent a cherry-picker. ;-)

Tropicalaria,

"The trick, of course, will be accessing the top of the dome to put these in..."

Everything else you have done so far seems to be pretty well thought out in advance. Besides Stressbaby's suggested rather expensive rental of a cherry-picker, do you have some alternative plans in mind for attaching the membrane? You probably don't want to rent a cherry-picker every time a windstorm damages the membrane.

Perhaps a "tinker toy" moveable cantilever and/or bridge scaffolding could save the day. Or devise a "poor man's" cherry-picker rig.

I notice you joined Dave's in 2003 and, apparently by coincidence, all development at the TekStar website stopped in 2003. Is TekStar dead? Has TekCad2 been extincted by some superior competitive software?

MM

Gotta be something here that you could send up to do repairs after a storm. =)
http://www.androidworld.com/

Tropicalaria,

Since the cherry-picker may not be a feasible approach (although who wouldn't want their very own cherry-picker?), I think you need to devise a way to mount the covering from the inside. If you do mount the cover on the inside, the framework "skeleton" will be exposed to the weather. That might look kind of cool, but the skeleton should be painted to increase its weather resistance. After painting the framework, you could pick from a couple of inside-mount alternatives:

(1) Simply use your stapled plastic lathing method to mount the woven plastic material to the inside side of the 2x4s, only use a lot more staples and use the longest ones your stapler can shoot.

(2) Beef up that idea with rigid lathing with screw-on attachment and incorporate a rubber strip for added water proofing to deal with the pooling that will occur in the outside "cells" after rains.

There are advantages to having the cover on the outside. The outside cover doesn't leave an exposed skeleton that will retain water after a rain and retard snow slide-off in the winter. Also, with an outside cover in place, you have the option of adding inside insulation in the form of bubble wrap and/or an inside-mounted second plastic membrane. So in order to get those benefits, devise a way of mounting the outside cover from the inside. A couple of approaches to achieve that come to mind.

(1) Take advantage of the holes in your hubs, and bring your lathing through those and secure the end-pairs on the inside to tensioning hardware that will let you conveniently increase the tension on the lathing by turning a screw thread. That can put a lot of tension on your lathing, so you might want to choose a stronger material for it.

(2) Secure the outside lathing with "special fasteners" that will pass through small holes drilled in the 2x4s. These "special fasteners" could be simple braided wire loops or strong nylon or dacron cords. The technique for mounting these from the inside will involve pushing long "feeder wires" through the holes from the inside, and then attaching the special fasteners to the feeder wires on the outside within reach of ground level. Then pull the feeder wires from the inside to bring the lathing membrane assembly up into place and pull the "special fasteners" in through the holes in the 2x4s for tensioning and securing inside. That will, in effect, "sew" your outside cover onto the framework, while working from the inside and within reach of ground level outside.

MM

I built a shed, and had to paint it so built a "scaffold" it was ricckitty and scary to use but got the job done.

Dyson,

I have considered purchasing some commercial scaffolding for some maintenance projects around here. It's expensive stuff made of demountable steel framework, and mostly suitable for conventional type structures. But steel scaffolding can be used in situations where ladders simply aren't up to the job, even the fancy multi-configuration ladders.

However, Tropicalaria's dome is about 20 feet in diameter and about 13 feet high, so a custom-built scaffold, even a movable one, that would give him outside access to all of that framework, in my opinion would be a structure comparable in design difficulty, construction difficulty, and materials requirements to the dome itself.

I plan to build a small lean-to greenhouse from a kit or from scratch (none of the attached/lean-to kits that I have seen have 10-mil triple wall polycarbonate, and it gets cold here in Maine). A dome greenhouse wouldn't look architecturally correct attached to this conventional two-story house and, for that reason alone, I doubt seriously that our town government would grant a building permit for such a structure.

But if I were to design a dome-type standalone greenhouse, based on the "experience" of this message thread, I would seriously consider a double-dome design whose exterior open dome structure would serve as a permanently attached dome-shaped scaffolding that would give the user easy access to maintain the outside cover of the inner dome greenhouse structure.

MM

Sorry if the information was ill founded .... but I did build a rather rickety scaffold (scared the devil out of me) to paint the shed. Got the job done.

MM, I was joking about the cherry-picker. I like your suggestions, very creative. With the film on the inside, he would have to drill drainage holes in the frame so that the water would run off and wouldn't pool in the cells.

If I were doing it, I would consider a series of platforms that would allow you to climb the outside of the structure. I'm thinking of a 2x12 with a short section of 2 1/2" pipe attached at an angle on the ends, sized so that the 2 1/2" pipe sections fit into the hubs on the GH. I might build 3 or 4 of them for use at different heights on the outside of the GH. For repairs, he could pop off the "hubcaps," insert the short pipe sections of the stand into the hubs on the GH, climb up onto the stand, remove more hubs, insert another section, and so forth. All of this assumes the structure is solid enough to support the weight.

My guess is that Tropicalaria has a plan and that he has been working on it again this weekend.

Edited to add that this thread wouldn't be complete without a reference to the ultimate geodesic dome GH: http://www.mobot.org/hort/gardens/CLhistarchit.shtml

This message was edited Nov 12, 2006 6:19 AM

Dyson,

Don't be sorry for your post. The idea of a scaffold was relevant. A scaffold is much more convenient than a ladder for painting.

MM

Stressbaby,

Before we moved to Maine, we lived in the St. Louis area and we frequently visited the Climatron and the rest of the Missouri Botanical Gardens in Shaw park. About a year before we left, they added butterflies in the Climatron. I suspect they did that because Chesterfield (a nearby suburb where we happened to live) built a full-blown butterfly house that was loaded with a wide variety of tropical butterflies.

http://www.butterflyhouse.org/

http://www.slfp.com/ButterflyHouse.htm

It was an interesting piece of architecture, but not a dome. It was a large uniquely styled greenhouse loaded with tropical plants, a few trees, and a pool. They had a hatching room to renew the supply of butterflies. We visited the Sophia Sachs butterfly house and Faust park frequently.

Your idea to use the hubs as attachment/support points for removable movable access platforms seems like a good possibility. The structure should be strong enough to support the weight of the access platform(s) and one or more persons.

MM

Tropicalaria,

It has been a while since we heard from you. We miss your updates on your dome greenhouse project. Did you solve the problem of attaching the membrane, or is that still a pending problem?

MM

Yeah I'm looking for progress reports too. Any updates?

I've been pretty busy lately and haven't been on the site for a while. Sorry for the long hiatus. Once the really cold weather set in, the urgency to get the structure complete went away, since it was too late to use it this season.

In the end, we just used a tall ladder on the inside and leaned over to cover adjacent triangles. I modified the the above plan only that I removed the top triangle from the patch so that I could place a single pentagon in the top of the dome, overlapping each of the five patches, rather than have the five seams culminating in a point at the top.

The first step was the installation of the five patches around the top. I created a template by pinning a piece of tarp to the side and tracing out the struts. It was tricky since there is a center cut into the middle of the piece. Then I unrolled the plastic over the top of the template and cut it out along the lines, leaving plenty of overlap.

Each piece was placed on the dome with handclamps. When the positioning was right I stapled the plastic lathing onto the center seam by bending over it from above. After I had two of them in position I secured the seam between them, reaching the top half from above and the bottom half from a ladder outside the dome. On each seam I left the top and bottom edges loose to be able to slide in the adjoining top and bottom plastic.

I continued around until four out of five pieces were in place. I needed to leave one off so that I could get the pentagon at the top attached.

Next, I traced out a pentagon onto my tarp in the same way had done the previous pieces, including the center cut. In reality, no sliver is cut out of the pentagon--it is just a single cut where the plastic increasingly overlaps outward from the center, in the same way you might make a cone out of a circle with a radial cut in it.

This piece was poked up through the center and positioned around all of the edges and along the cut. Note that on all of these pieces the position of the cut on one of the struts is vital, since the overlap is very small in the middle. Also, except for this top one, all of the center cuts have to be overlapped so that they shed water downwards.

Once positioned, I started pinning down the seam of the top pentagon from the open side of the dome where I had left off the fifth side patch. Yes, I'm pretty high in the air here. Note that I'm leaning on the dome itself, and have someone below steadying my ladder.

We decided to cover the center of the pentagon, where the seam comes together in the middle of a hub on a horizontal plane (i.e. it isn't sloped to shed water) with a circular "hat". Thus, a ~14" circle was attached with small strips of lathing on each hub at the top, and the seam lathing came down over the top of that. The pentagon itself is sloped down on each face, so should shed water (though not snow!). Eventually one of more vents will be cut out from the inside around this pentagon, but that will wait for summer when we can better judge how much ventilation will be needed.

After the hat and seam were attached I went to work around the sides. Each edge was attached from the next triangle over, all around the pentagon. You can see the circular "hat" here as it appears from the inside.

Next triangle. The beginning of the seam was started from within the triangle itself, and then the ladder was moved and I came up from within the next triangle so that it could be pulled flat.

Topside. I was using extra long staples to be sure that the seams would hold. The electric staple gun allowed me to easily place all of the staples at full extension, but because of the 9/16 staples they didn't fully penetrate the wood unless I really held the gun tightly to the surface. For this reason, I had a hammer up there to pound in anything that wasn't flush. I can't imagine only doing this with the hammer, though, since I generally had to keep two plastic surfaces in tension (opposite directions) under a tensioned plastic lathing strip, and I could not have done this if I needed both hands in order to place a fastener with one and use the hammer with the other. The hand clamps were in constant use and I occasionally tacked a bit of plastic in place with a single staple to keep it there while I held an overlapping piece.

You may be able to see on this picture that the plastic lathing at the ends of each strut is attached on either edge. This is to go around the metal straps that hold the struts to the hubs. Since the edge is thin and weak here, I used more staples. In fact, I used a lot of staples throughout. We've had quite a few wind storms (this area is famous for them) and nothing has loosened in the 65mph gusts. I will also mention here that the plastic quite nice to work with--much sturdier and more resistant to creasing and kinking than any other flexible poly that I've used.

Now it was time to position the fifth side piece. Again, the clamps were used and each side checked.

When we were sure of the position, the top and middle seam were clamped and the whole side was rolled up and inserted through the middle triangle so that I could work on the top seam of the patch. Here I am temporarily tacking the top into place.

The pentagon was folded back down over the side patch and pentagon lathing on each side of the open side was finished out to the edge over the top of the plastic of the side patch. Then, the last edge of the pentagon was finally attached.

The side patch plastic was unrolled back over the side of the dome and I moved over to the next triangle to secure the center seam. At this point, the patch was not attached on either side, just at the top. After starting the seam from inside the triangle, it was finished from a ladder outside the dome.

After the seam was finished, each side of the patch was similarly completed from the inside the first and then from outside the dome for the bottom half.

Sorry to place these out of chronological order, but here is a picture of the first patch that was placed on the dome, attached only with hand clamps because all of the edges have to be overlapped with other pieces. Note that at each vertex all of the pieces have to be overlapped at once, so most seams were left unfinished at the ends until everything was in place.

Here are the pieces being cut out. The plastic is 10' wide X very long, so I unrolled it and restacked it accordion-style to be able to pull it off linearly. After the first couple of pieces I found it easier to use a previous piece as the template for each subsequent piece. The trapezoidal patches are rotated to fit with each other as they come off the roll.

Unfortunately, I ran out of plastic, due mostly to my failing to account for the large amounts of overlap that I ended up using on each patch. I will need to reorder to get a bit more plastic to finish off the external covering. The only pieces I'm missing are the triangles between each lower patch, but without them I can only attach the top halves of the patches, and I can't go clear to each corner. Because I don't want these flapping in the wind (currently gusting to 55mph tonight) I'll wait to do any more until I get the rest cut out.

For standing by me in the wind and through the single-digit (F) weather while I added all of the above pieces, I need to thank my Dear Wife who helped me plan and keep track of everything, my father-in-law who steadied the ladder and passed things up and down for me, and my mother-in-law who took care of the four curious children watching from the window.

All of the rest of the pieces should be doable from the ground, by a single person, but I'm sure my DW will come up with something I've forgotten which requires her assistance.

She still thinks I'm crazy for putting up a dome, but I'm not sure that has changed her opinion of me any. My father-in-law is trying to convince my mother-in-law that he needs to put up one of these for storage at his house. My kids just think it's cool.

I'm with your kids.

I am agog. The design calculation, fabrication and construction is thrilling. I've been fascinated by 'Bucky's babies' for years, what a cool concept. Following your progress has been a joy, thank you.

Tropicalaria,

Back on Nov 8, 2006, at 5:21 AM I asked,

"I notice you joined Dave's in 2003 and, apparently by coincidence, all development at the TekStar website stopped in 2003. Is TekStar dead? Has TekCad2 been extincted by some superior competitive software?"

I'm sure you were quite busy and didn't notice that question. But I've answered my own question. New activity on the TekStar website, http://www.tekcad.com/home.html has brought it "up to date." I have to admit that the TekCAD2 software and TekStar's other products look rather interesting, even though they are a bit "pricey".

I congratulate you on your dome greenhouse. Very ingenious, and interesting. Domes seem to have a fascination for everyone.

MM

Your Greenhouse is really COOOOOOOOLLLLLLL!!!!!!!!!!!!
Thank you for detailing this project for the rest of us to see. I have always loved Domes and have yet to build one. But, you have inspired me. I am dusting of my old dome book from the seventies. Hmmm...

That Green house is Great one thing you might think about is changeing the top plastic for the new type Solar panels its thin supper strong and bends to shape that way you could heat it and light it for next to nothing paul

Update?

Not a lot to update at the moment. With the advent of spring all of the temporary plastic bottom panels are currently off. No leaks this winter, and the dome has proven rain, snow, and wind proof and I'm happy with the performance of the plastic. I'm again thinking about refinishing the north wall with something other than plastic for insulating and reflection/absorption benefits, but I'm not sure what to use. It will have to be waterproof from inside and out, and I'm just not very knowledgeable about this kind of exterior construction.

I'm also kicking around the idea of doing the lower sections in multi-wall polycarbonate, but again that's a lot of seams to seal. Preformed edges would cost more than the polycarbonate itself, and would still require taping and caulking.

MaineMan-
I'm sorry, I did miss your question the first time around. Looks like you found your answer.

phicks-
I would be concerned about loss of light. There's a lot of light diffusion and scattering up there, and I also need top light for the taller plants/trees.

I haven't been around DG much since my last post; my gardening mostly goes dormant with the plants now that I'm not propagating/selling very much. Maybe if I get the dome set up the way I want this year that will change again.

the light comes tho the thin type solar panels

With the colder nights it's time to close the dome. The bottom is sealed with four trapezoids (basically the tessellated patch from this post: http://davesgarden.com/community/forums/p.php?pid=2884716 minus the top triangle, turned upside down) and five triangle patches (just the top four triangles from the same patch). Then there is the door and the portions around it which will need to be closed up as well.

Here is the first of the lower trapezoids clamped into place on the frame.

As in the top patches, the center seams have to be positioned, secured and lathed before the outer seams.

At the edges, the bottom patches have to be leaved under the top patches, and the triangles have to be under the trapezoids. There are only five points around the greenhouse where the corners of the patches meet, and for each of these joins there are five corners which have to be layered in the right order. All of the edge seams around one of these vertices are under the lathing before I work on the corner. I tack down the lower layers with a single staple while I pull the upper layers into place so that they can all be pinned under the same lathing.

There is 6-12" of margin on each piece which greatly simplifies positioning (each patch is up to 12' x10' but the center point and interior cut have to be positioned to with 1/2" vertically, horizontally, and rotationally) but also allows each of the corners to be secured under all of the other seams of the vertex, giving me greater confidence in the integrity of these points.

Back in the 1980s my partner and I built a 2 frequency dome out of 2x2s and hubs made from hurricane straps. They were the kind of hubs where you cut a slot in the ends of the struts and slide the arm of the hub into the slot, then bolt on. That dome lasted about two years even though it wasn't PT. It was such a cool place to hang out in; I even installed a fluorescent light at the apex for night use. With hanging plants and a pea rock floor, it was a little piece of futuristic paradise!

Now, after reading about your dome project, I'm inspired to build another one! It's been on my mind for years, but now I think it's time.

BTW, have you ever visited this link?
http://www.gardendome.com/
I may get a hub kit from them for my new dome; they have so many different choices and designs, it almost makes me giddy!

Thanks for sharing your dome journey,
LariAnn

We'll need pictures, of course, when you start your new dome!

I ran into the Garden Dome site when I was trying to figure out how to cover this dome. My dome is similar to their Garden Dome 3 http://www.gardendome.com/GD3.htm with the base extension. By coincidence, their proposed door opening with the base extension is in the same location as mine, too.