Introducing: Fort Denali

[Mcfish]

Just an additional thought; as I understand it, it is weight and reinforcement that are your issue. Can you drill holes, as if in a slab, in the existing concrete walls. Place basalt rebar in the holes, form a reinforced skeleton shell. Check out the samples at http://www.mortarsprayer.com/ and form the airform out of billboard vinyl. Shotcrete 1 side, remove form and shotcrete the other. Thinner shell, less weight, same strength. Is the existing tower strong enough to support the thinner, lighter dome? is there enough concrete to act as a new foundation? Will epoxy hold the basalt bar in?

[GreginAlaska]

Hi McFish, yes I can drill holes in the existing concrete and use rebar. The engineer said to drill holes 4 inches deep every 12 inches and epoxy the rebar in. He said to use #3 rebar instead of #4 and use 3" of shotcrete instead of 4". I did buy a couple of big rolls of 10mm basalt rebar and enough basalt mesh to cover the roof. I was thinking of using the rebar in one coat and the mesh in another...that should make it pretty strong I would bet. I also managed to put myself in a bit of a jamb, we did most of the interior framing and now it is going to be a challenge to pressure up the tower. So some other supporting structure would probably be a good idea now.

Thanks

[GreginAlaska]

Close up of the decorative concrete Leila did on the walls. The rim is done in rock now too, I guess I should get some new pics. Also we ended up staining the trim darker...I still need to do something with the aluminum frames and steel doors, they just don't look right.

[GreginAlaska]

zzzzzzzzzzzzzzzzzzzzz

[timbau]

Hi McFish, yes I can drill holes in the existing concrete and use rebar. The engineer said to drill holes 4 inches deep every 12 inches and epoxy the rebar in. He said to use #3 rebar instead of #4 and use 3" of shotcrete instead of 4". I did buy a couple of big rolls of 10mm basalt rebar and enough basalt mesh to cover the roof. I was thinking of using the rebar in one coat and the mesh in another...that should make it pretty strong I would bet. I also managed to put myself in a bit of a jamb, we did most of the interior framing and now it is going to be a challenge to pressure up the tower. So some other supporting structure would probably be a good idea now.

Thanks

Greg

Looking good.

You could build a free standing mesh from rebar. Then cover the rebar with your chicken wire mesh. Then try that soaking rags with a cementitious mixture. That would give yo a layer strong enough to embed the basalt mesh for the finish layers. They would be very strong.

Just a thought. That site I sent you shows the process in a much easier way.

Wishing you the best.

[mkrepel]

Greg,

I am guessing that, since we live in Alaska, you are more concerned with keeping the cold out than you are with disaster resistance for this particular roof. You have already addressed most of the natural disasters by building a concrete home. Have you given any thought to finishing this roof using a timber frame structure and SIP's? I have seen some very nice structures done this way and beams radiating out from the center of a round room can be very visually appealing.

I can certainly understand why you might like to maintain your building style throughout though.

I also had some thoughts around installing your fan in a window and adding an airlock at the bottom of the stairs. Of course, I don't know what your interior framing looks like and this approach would undoubtedly require some temporary framing to make it work. It might be worth the extra time and $ to maintain the ability to keep your roof insulation inside an air form, though. The other approaches as discussed with Tim, above, would certainly work, but may lead to some difficulties when it comes to insulating and protecting that insulation long-term.

BTW, where did you end up on the wood stove issue?

Mike

[timbau]

Greg,

I am guessing that, since we live in Alaska, you are more concerned with keeping the cold out than you are with disaster resistance for this particular roof. You have already addressed most of the natural disasters by building a concrete home. Have you given any thought to finishing this roof using a timber frame structure and SIP's? I have seen some very nice structures done this way and beams radiating out from the center of a round room can be very visually appealing.

I can certainly understand why you might like to maintain your building style throughout though.

I also had some thoughts around installing your fan in a window and adding an airlock at the bottom of the stairs. Of course, I don't know what your interior framing looks like and this approach would undoubtedly require some temporary framing to make it work. It might be worth the extra time and $ to maintain the ability to keep your roof insulation inside an air form, though. The other approaches as discussed with Tim, above, would certainly work, but may lead to some difficulties when it comes to insulating and protecting that insulation long-term.

BTW, where did you end up on the wood stove issue?

Mike

Mike Greg could have the dome sprayed with foam & then a layer of stucco put over it for insulation. It could be done like the Orion models of the domes where they spray a wall with concrete then foam then concrete again. I guess it all depends on what final look Greg want for his tower.

Just my 2 cents....

[Mcfish]

Wow, lots of comment here in a few hours. Why do you have to pressure up the turret? Place skeleton frame. Drape the blue tarp or use recycled billboard tarp over the reinforcement. Pull it down moderately tight (tie it off, sand bags, even rope below the lip. shoot from inside; pull airform off when dry. Go outside and shoot from the other side; 2 layers of 3/4 inch, see the basalt videos David has here. Foam the outside as thick as you need it. Stucco over the basalt mesh in lieu of chainshell. No need to pressurize the airform, just have enough tension on it to keep the shotcrete from deforming it too much. If you already have the basalt stuff you're set. Do you have engineering issues with gov't control? There may be members from this forum who know a thing or 2 or people who could help.

[GreginAlaska]

No problem with government controls here yet McFish, my main problem is I've been a process operator all my life and this is the first thing I have built. I was just thinking of using the standard monolithic dome procedure because I already have an airform from monolithic. I do like the ideas you have shown me and I did check out the videos. So I guess there would be nothing wrong with using a steel rebar cage, covered in chicken wire and cement soaked rags, and use it like an airform, would there? Then come in and do the monolithic dome under it? And use the basalt rebar on it? That would make for a tough, effecient dome roof I would think.

I like the way you think out of the box.

[GreginAlaska]

Greg,

I am guessing that, since we live in Alaska, you are more concerned with keeping the cold out than you are with disaster resistance for this particular roof.

Well I am building it just a couple miles from where Sarah Palin lives, I think it needs to stand up to a nuke. (ha j/k not meant to start a political discussion) Ya energy is the main thing, natural disaster is the next IE fires, man made disasters after that and longevity after that. I kind of wish I had put all basalt rebar in it though, I wonder how much longer that would have made the building stand?

You have already addressed most of the natural disasters by building a concrete home. Have you given any thought to finishing this roof using a timber frame structure and SIP's?

I hadn't thought about SIPs, could you make a dome with them? But I did talk to a guy in Seward about a timerframe roof. I really like the sketchup drawing he did, I don't think I can afford it though. I'll post a pic of his drawing.

I can certainly understand why you might like to maintain your building style throughout though.

Well the garage does have a flat, conventional roof on it. Jim Kaslick had drawn it up to be attic storage space but then my wife decided she wants to buid an apartment up there. We couldn't agree on how to modify it so I just had the flat roof put on until we either:
1. Come up with something she likes and works
2. death intervenes. heh

I also had some thoughts around installing your fan in a window and adding an airlock at the bottom of the stairs. Of course, I don't know what your interior framing looks like and this approach would undoubtedly require some temporary framing to make it work. It might be worth the extra time and $ to maintain the ability to keep your roof insulation inside an air form, though. The other approaches as discussed with Tim, above, would certainly work, but may lead to some difficulties when it comes to insulating and protecting that insulation long-term.

BTW, where did you end up on the wood stove issue?

Mike

I am going to put a masonry heater in it. We plan on ordering one of the kits and get a mason to help us put it together.

[GreginAlaska]

Timberframe builder idea

[GreginAlaska]

another

[mkrepel]

Greg,

I was thinking of a simpler roof. 8 or 12 pie-shaped panels of the proper size to provide some pitch. Straight beams under the seams. A key post under the peak. Tension beams at ceiling level ( or collar ties) would be optional as your walls would provide plenty of resisting force to hold the roof up. The roof eave would still be round. This roof would not be a dome. The timber frame would be much simpler (aka - cheaper) and the whole thing would be easier to build. 10" EPS, 8" XPS, or 6" PU foam SIP's would provide the recommended R-40 for a roof in our area. The drawback is that it is a major departure from the original plan and not as long-lasting as a MD. Also, your tower would be almost devoid of thermal mass inside the insulation, which would not be as energy efficient as a MD. I think it could be done so that it would be difficult to see the change from the ground, especially since you have soffit framing on the main part of the house at the eaves, but you would always know.


Mike

[BWARDEN]

Greg,

Been a while since I checked in here, so I may not be totally up to speed, and this idea might not make any sense.

Why couldn't you get MDI to make you a small air form that just fills the inside of your tower? It would be a complete balloon, cylindrical covering the inside of the tower walls, have a circular floor to seal any openings to the rest of the house, and a domed ceiling to match your desired roof line. The domed airform ceiling would have to be slightly mushroomed, ie, a larger diameter than the tower walls, so that it could be placed over the exposed vertical rebar coming up out of the wall, with the rebar puncturing through the air form, and fit flush with the outer diameter of the tower wall. Or, have a full mushroom, and have some overhang of the roof past the wall edge, giving some protection to the outer tower wall. Some engineering would probably need to be done for an overhang, but the airform would provide natural curvature there for strength. Put an airlock to enter the tower airform on your roof, entering through the tower door. Then build the roof as a conventional monolithic process. Spray the ceiling until the thickness matches the inner tower wall. The airform will protect the walls and floor of the tower from the foam and concrete over sprays.

[GreginAlaska]

That's an interesting idea Bob, looks like I have several ideas to choose from. I ended up putting a cheap, temporary wood roof on it until next spring, so I have some more time to decide exactly what I am going to do.