Terra-Dome Earth Shelter Build

[SamWalton]

I don't really understand the need for rebar. Correct me if I am wrong, but you are pouring this floor on top of another poured floor, which I assume has rebar. Is that correct? If so then why not just use the fiber strands in the concrete. That would eliminate the possibility of someone stepping on the rebar during the pour and damaging the pex. I recently did a pour for a shed that my B26 was being stored in. I used steel and fiber strands. The concrete plant said it was overkill and wasting my money. They said the fiber strands gave it a rating very close to steel. I don't know if I believe that, but I do know that it is very strong and really helps prevent cracking in the concrete, which I would think was your main concern. Understand I am not trying to tell you how to do it, you are obviously very capable. Just wondering why.

Carl,
We are pouring a single slab. I don't like the fiber because the strands end up sticking out of the surface. Most recommend burning the surface whiskers off. I like the steel myself. I also believe these extra expenses will help extend the life of our home for many generations to come.

 

[psj12]

I had a 30 X 50 pad for my barn poured near to where your terra dome is. I asked the contractor to use steel mesh and bar in it. He assured me that the fiber was more than enough and cheaper.

4 years later there are three sizeable cracks near the front portion of the slab. I should have listened to myself and insisted on the at least the mesh with the fiber.

Since that time I have done some reading on "post tensioned" slabs where wire cable is run through the slab inside plactic sheaths, to keep it fron adhering to the concrete. The wire is then then tensioned with hydraulics and anchored when the concrete has reached about 75% of cure. This keeps the concrete under compression all the time making the slab much stronger.

 

[Carl Bert]

I had a 30 X 50 pad for my barn poured near to where your terra dome is. I asked the contractor to use steel mesh and bar in it. He assured me that the fiber was more than enough and cheaper.

4 years later there are three sizeable cracks near the front portion of the slab. I should have listened to myself and insisted on the at least the mesh with the fiber.

Since that time I have done some reading on "post tensioned" slabs where wire cable is run through the slab inside plactic sheaths, to keep it fron adhering to the concrete. The wire is then then tensioned with hydraulics and anchored when the concrete has reached about 75% of cure. This keeps the concrete under compression all the time making the slab much stronger.

To start off I am all for the use of steel in slabs subjected to heavy loads, I just didn't understand his need for it, because I thought it was a slab being poured on top of a slab. In that case rebar would have been an unnecessary expense, in my opinon.

As far as your 30x50 slab is concerned, there are many factors that will cause cracking, steel or no steel. Slab thickness, amount of gravel under slab, gravel not compacted, poor drainage around slab, use of slab prior to its full curing, the use of accelerators, to make the concrete dry quicker and the list goes on. Don't sell those fiber strands short. Its been tested and proven (so I'm told) that they add strength and minimize cracking. At $7 to $9 a yard it just doesn't make sence not to use them, and there are different types. They have some today that will not effect the finish. And then there are metal strands, best of both worlds.

I've never seen the tension cables used in anything other then precast planks. I guess its possible, but it seems that there would be a lot of variables to be considered. Such as strength of concrete (too much water), size of cable, controlled amount of tension put on cable, consistant thickness of concrete, depth of cable in concrete. Just can't see all this being controlled on the job site.

 

[HiddenHollow]

The 20 story hotel where I work was built with the cables under tention and then concrete poured. They used flying forms and went floor by floor. We have to get the floor x-rayed if we are going to drill any holes. You can't drill through the cables because you will compromise them. The whole building is under tension.

 

[KubotainNH]

Very neat build. You'll like the radiant heat, we installed it in our stick built house, warm feet is a great thing. I'm curious to see how you finish the inside.

 

[SamWalton]

Very neat build. You'll like the radiant heat, we installed it in our stick built house, warm feet is a great thing. I'm curious to see how you finish the inside.

Thanks and we are looking forward to warm feet too! Attached floor plan

 

[SamWalton]

I picked up carpolisher's shipment of water proofing material. It weighted 360 lbs so I re calculated the quote and it was $301.51. They charged me $245.12 and the cost of new from MFR was $67.50 x 9 = $607.50 + $100 (freight) total $707.50 - 245.12 = Savings $453.38

Thanks Again Bob

 

[carpolisher]

I picked up carpolisher's shipment of water proofing material. It weighted 360 lbs so I re calculated the quote and it was $301.51. They charged me $245.12 and the cost of new from MFR was $67.50 x 9 = $607.50 + $100 (freight) total $707.50 - 245.12 = Savings $453.38

Thanks Again Bob

No problem.... Glad to help.

 

[KubotainNH]

Thanks and we are looking forward to warm feet too! Attached floor plan

I like that big sun window in the ceiling. Your house should be nice and cool in the summer. I'd like to see how that concrete dome is done.

 

[SamWalton]

I like that big sun window in the ceiling. Your house should be nice and cool in the summer. I'd like to see how that concrete dome is done.

Many pictures are in earlier threads. They simply use a fiberglass dome mold with 2100 lbs of rebar laid on top and standard forms for walls followed by a single concrete pour.