Wondering if this could be an interesting thread…show a picture and see how y’all would build/replicate it. It’s likely that people with different backgrounds and from different regions would have different methods and materials. In the picture–a rendering of a new design I just started on–I have three ideas on how I might build the band onto the dome shells. But I also wouldn’t be surprised if there was a better idea than my three. I’ll share my ideas after I hear yours so I don’t bias anyone.
So I’ll ask: what materials and methods would you use to build the band that encircles the shells?
Background, the shell in the foreground is 31’D and half that in height. Hemisphere. Band is 36″ tall. Shell construction is, from the exterior in, 3″ of 2.7# spray polyurethane foam and 3″ of 4,000+ psi shotcrete reinforced with #4’s about every 14″ each way. Finish coat is acrylic stucco (synthetic stucco). Albuquerque, NM.
Replies
i'd out you in charge of it!!!!
Is the band strictly decorative, or does it have some function, like cabinets accessible from the inside, or flower beds?
Maybe its a big, pre-cast concrete lid that is craned into position.jt8
That's one I didn't think of. Thanks.
Kinda looks like a big cookie jar with a window. Weight of the precast lid would probably keep it in place.
hmm, wonder if you could find out what battleships use to rotate turrets? Install that and mount the lid on that. Then you'd have a rotating lid. Not sure what that would do for you, but it would be unusual. Maybe put windows in the lid, and have the lid rotate to track the sun to improve day-lighting?
Its a good thing I'm not filthy rich, cuz I'd probably do some strange things with the money.
jt8
Strictly decorative, though your question raises a fun idea. I like it from a design perspective. From a cost perspective, openings such as that are typically time consuming.
Soooo, treat it whichever way suits you.
cloud...eps foam full size with rebar tie-ins to your shell grid... same stucco finishMike Smith Rhode Island : Design / Build / Repair / Restore
This shows what I expected to see....there are so many ways to skin the cat, so to speak. One of the more challenging aspects of my work is selecting among the choices, because usually the builder has a specific preference based on his background, and also usually, the builder's not selected till the plans are done.
Based on what we see here, I could draw this up in 5 different ways. What are the chances the way I draw up will match the way the builder prefers?
cloud...eps foam full size with rebar tie-ins to your shell grid... same stucco finish
Using Mike's suggestion, how about geofoam EPS? It can be purchased in large blocks and formed into any shape desired. If your builder has any experience with SIP's, he/she would probably already have many of the shaping tools.
One company that sells the geofoam:
http://www.r-control.com/products/geo/main.asp
I've attached one of their pics. In this case the geofoam was used for a highway overpass. Apparently geofoam overcomes regular EPS's problem of breaking down below grade.
Only limited by your imagination.jt8
Great link, thanks! It'd seem that only a bit of thought is needed to create a jig for cutting the big blocks to the right shape.
This method does require the gunnite crew twice.
View Image
SamT
This is in line with one of my methods. Upsides are the use of consistent materials and ability to achieve any shape. Downside is it's a lot of labor. Shaping all of that would take a LOT of time. Would also have to address the rebar passing through foam between its two attachment points. If you leave the foam, the rebar will have diminished benefit, and if you cut the foam away, you allow thermal bridging in a significant way. Both can be overcome. Biggest concern is the amt of manual labor required. Having done rims before, boy oh boy they get tedious.
Once the foam is blown, I would poke anchors through the foam with the tail end sticking out on the inside far enought to be trapped in the shotcrete. Shoot the crete then build the soffit and tie it to the anchors - Depending on load - 24 to 18 gauge steel framing with a CDX ply cap set to a 1/4" per foot slope. Finally, I'd wrap the whole frame in foam and coat it with EIFS when you finish the shell.
Kevin Halliburton
And with that, the great emporer Oz gently floated away on a curtain of hot air, laughing at the unfortunate ignorance of little people beneath him. But under his breath he cursed that stupid little dog...
That's another of my thoughts. I was wondering if the curved metal frame could be more easily prebuilt in sections in a shop rather than site built. For stuff like this, I've seen the builders hesitant to shop out any portion be/c they're afraid of giving away profits. But the site-built methods usually have a high labor component...aren't usually efficiently done.
If it were me, I'd sub the eifs component to a crew that does that daily, rather than have a generic crew pick up that skill, but again, the contractors I know are concerned about subbing out their profits along with the work.
I was thinking of wedge anchors to attach, rather than setting j-bolts or similar into the shotcrete. Good shear resistance, and you can put them where you they match the attachment points in the framing, rather than getting the framing to match the bolts. Just personal pref.
Is the diameter of the inflated form consistent enough to allow shop fabrication to a given radius? Wedgies would work but it seems to me like they would be more work. Poking a J-anchor through the foam and wiring it to the rebar seems easier, and more affordable in both time and materials than drilling wedgies into the concrete later.
I do understand how the precision would be better with post-drill and anchor but, if it's site built, the framing on the dome side can be positioned over the anchors with little regard for the center to center framing dimensions. In fact, if you put the anchors at the elevation of the top and bottom plates, center to center is pretty much irrelevant.
Center to center dims would be more important on the outside where the foam sheathing is to be attached to the frame. The front framing members and the back framing members don't even have to be in line with each other. IMHO, light gauge steel, with its high strength to weight ratio, is the only way to frame "floating" soffits like this one. Combined with how easy it is to bend and conform steel to irregular shapes (vs. wood) it seems to me like a given in just about any dome construction but then, I really don't know my domes quite like you do either. ;-)Kevin Halliburton And with that, the great emporer Oz gently floated away on a curtain of hot air, laughing at the unfortunate ignorance of little people beneath him. But under his breath he cursed that stupid little dog...
Certainly for this, steel would beat wood. Inside....depends. I think one's comfort level with the material would trump any inherent advantages of one over the other. Possibly the same with j-bolts and wedge anchors.
The shape should be consistent enough to pre-build, as long as there's a little flex to site-adjust. If I were building again and using metal, I'd probably look into that tool that crimps the metal track, as opposed to flex-c-track. I like the customization it affords.
The flex-c-trac hasn't caught on around here yet, mostly because of availablility and expense I believe. We do at least one curved wall on just about everything we design here. Crimped track or CMU is what we specify for the curves.
I don't know why but for some reason, foreign to my current insight, I did the plates on the curved wall in my house out of wood - man, what a waste of time! I would absolutely use crimped steel track with wood studs on a re-do. One of the countless lessons I'll never forget but hope to never need again. :-)>Kevin Halliburton And with that, the great emporer Oz gently floated away on a curtain of hot air, laughing at the unfortunate ignorance of little people beneath him. But under his breath he cursed that stupid little dog...
>I did the plates on the curved wall in my house out of wood
Me, too. Drew the same conclusion, too.
LOL! Live and learn. How many plates did you turn into arched firewood before you finally got it right? Thank the lord for belt sanders hu?Kevin Halliburton And with that, the great emporer Oz gently floated away on a curtain of hot air, laughing at the unfortunate ignorance of little people beneath him. But under his breath he cursed that stupid little dog...
Actually, we did good on the plates. Can't think of one that was off. Don't even own a belt sander. One thing I learned through forced practice was scribing and cutting curves in wood.
My fatal flaw was probably the lack of a scroll saw. I even had the advantage of a full sized template plotted on the large format plotter but cutting 3' radiused curves with a skill saw is just tricky. I actually only tossed one short section but I spent some time with the belt sander before it was all said and done.Kevin Halliburton And with that, the great emporer Oz gently floated away on a curtain of hot air, laughing at the unfortunate ignorance of little people beneath him. But under his breath he cursed that stupid little dog...
I went to the local home show at the convention center here about a nmonth ago. One vendor does foam & eifs decorative elements, like medallions. They also do structural stuff like columns. I was surprised at how real the columns looked. The kid that does the foam part happened to be working the booth at the time. He said they can either work off a sketch/drawing, or a cad drawing.
So ... what about having foam ring segments made with the correct radius, then fasten them to the shell and cover all with eifs.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
And that was my third option!
I was thinking about a concrete ring. WIth some rebar wrapping around it to hold the tension.
But that would be a lot of weight if it was solid concrete. And might be expensive.
Marriage doesn't depend on finding the right spouse but on being the right one.
Background, the shell in the foreground is 31'D and half that in height. Hemisphere. Band is 36" tall. Shell construction is, from the exterior in, 3" of 2.7# spray polyurethane foam and 3" of 4,000+ psi shotcrete reinforced with #4's about every 14" each way. Finish coat is acrylic stucco (synthetic stucco). Albuquerque, NM.
Your inflated forms have to be an easier way to make that than having custom Al forms made.
For some reason that process makes me think of a cooking show I saw years ago. The chef was dipping inflated balloons into melted chocolate. When the chocolate cooled (hardened) he'd deflate the balloon and wind up with a chocolate cup...which he then put something into (don't remember). But I seem to remember that on some of them he dipped into one pot of melted chocolate...let it harden a bit..and then dipped into a second pot (maybe mixing white and regular chocolate). Made a 2-layer chocolate cup.
Now I realize I'm taking the long way 'round the barn here, but couldn't you do a variation on that? Inflate and shotcrete/foam a dome. Then come back and form up the overhang and then apply concrete to overhang and top of the dome???? And then maybe eifs the whole thing. Hmm, dont' know.
Keep us updated if this hypothetical turns into a real project!
Edited 11/3/2004 4:43 pm ET by JohnT8
>but couldn't you do a variation on that? Inflate and shotcrete/foam a dome.
Why didn't I think of that! :) Actually, that's what we do. No rigid formwork. Only we spray from the inside, so it's foam first and concrete later.
>Then come back and form up the overhang and then apply concrete to overhang and top of the dome????
It's the "form up the overhang" part that I'm focused on here. Looking for the most cost effective ways to do it. Also using it as an excuse to just talk about methods and materials and see how different people do things.
>Keep us updated if this hypothetical turns into a real project!
It is real. Real client. Real check that really cleared. I'm now doing the design and hoping the builder won't wanna choke me over this soffit detail.
>but couldn't you do a variation on that? Inflate and shotcrete/foam a dome.
Why didn't I think of that! :) Actually, that's what we do. No rigid formwork.
Yes I KNOW you do the inflated, I've seen some of your other posts. That's why I started off that reply with "Your inflated forms have to be an easier way to make that than having custom Al forms made."
Looking for the most cost effective ways to do it.
Oh...cost effective? Did you mention cost effective in the original post? None of my suggestions are cost effective, I specialize more in Rube Goldbergs. ;) And along that line...hmm,
1. you create the dome
2. excavate the 'lid' detail on a piece of ground (aaaah dirt forms!).
3. pour concrete into the excavation and let cure
4. Crane the piece up (did I mention putting the steel eye-hooks in?) and set it on top of the dome.
This method has government contract written all over it :)
It is real. Real client. Real check that really cleared. I'm now doing the design and hoping the builder won't wanna choke me over this soffit detail.
Awesome! Not only do we want updates, we want more pics! Before, during, during, during, during, during...after.
jt8
Edited 11/3/2004 5:44 pm ET by JohnT8
Showing pix will depend on the client taking them. I know this builder well, great guy, but he don't do pix! Hopefully the client will.
Just a thought. We used to build boats out of a high density foam products called cflex. We'd lay it out on a form, then cover it with polypropylene cloth, reinforce with carbon fibers and epoxy it. It produced remarkably stong yet light weight hulls. Sooo... You could always build a form and set the rims up as a false work. If the diameters match well you could make a cloth and epoxy seam and then stucco.
Might work. It would not be load bearing however.
This is the kind of thing I was looking for (the others, also)....something where we bring in influences from another industry to solve a new problem.
I'm wondering what other ideas are out there...what other solutions just waiting to be connected to the right problem.
And along comes the guy who kicks sand in your face at the beach.<G>
Aside from the cool look of the dome, its structural aspects are a strong draw. Didn't you say that the design should be able to withstand 300mph winds?
Not that you would get 300mph winds, but the location would determine if hurricanes, tornados or potentially wicked thunderstorms are in the forecast.
Would this attachment diminish the overall soundness of the dome if anchored via protruding rebar or even tapcons? Would the overhang tend to be ripped from the domes primary structure, not necessarily damaging the dome but carrying off a major portion of the overlying foam and applied finish? Or, are any add-ons specifically designed to be sacrificed should there be cause?
I like.........
Build the dome as usual, strip the foam covering down to the shotcrete in the band desired, power nail the metal track and build out a horizontal soffit, wrap with Dens Glass (I think you can get a bend if the radius is large enough), add foam butting to the existing, fiberglass cloth and let the EIFS guys finish the whole thing.
Don't forget to add a ring of lights to the outside of the band set to blink in a sequential pattern during which you play the mathematical theme to Encounters of the Third Kind.
I like the lights!!! Especially that close to Roswell.
It would have no effect on the stability of the underlying structure.
I've had many conversations with my engineer and some builders about the treatment of such accessories. We've, in general, decided to treat them like awnings and other artistic elements. In typical conditions, they'd work just fine. In most unusual cases, same. But in the most extreme cases--in the US that'd be a direct hit by a tornado, as far as wind speeds--then the band might be damaged/lost. As long as the structure isn't compromised, and so, the occupants are safe, that's reasonable if all parties are duly informed and agree. Certainly it's site specific.
Sorry, that old idea won't work if you spray from the inside, foam first.
How about taking two bands as shown below, carpet tape them to the balloon. Foam 'em on, then just clean the tabs before gunniting.
After stripping the balloon off you can just use piffin screws to attach wood framing to them.
View Image
My FFIL has some tool hangers that look like this, but the tabs are only 2" long.
SamT
Build a donut to drop on a baseball.
Sissy.
<G>