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Equipment Discussions >> Observatories

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TeslaTrek
member


Reged: 08/24/13

Rebar in pier and pier footing new
      #6322946 - 01/19/14 08:18 PM Attachment (43 downloads)

I am now digging a hole for the footing that the pier (12" diameter sonotube) will sit upon. I live in San Diego where we maybe get 1 or 2 days a year where it freezes.

1. Do I assume 1 layer of rebar is sufficient.
2. How do you bend the rebar or can i just use the wire mesh home depot sells?

thanks
Jim


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Footbag
Postmaster
*****

Reged: 04/13/09

Loc: Scranton, PA
Re: Rebar in pier and pier footing new [Re: TeslaTrek]
      #6322967 - 01/19/14 08:30 PM

You can bend rebar using a pipe although they sell rebar benders. Just slide it over one side, prop the other side on something and bend.

I think one layer will be fine. You may want to isolate the concrete from your floor using foam around the sides. Then you can dissolve it after. This way, footsteps are completely isolated.


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TeslaTrek
member


Reged: 08/24/13

Re: Rebar in pier and pier footing new [Re: Footbag]
      #6322988 - 01/19/14 08:46 PM

Thanks. Do you mean foam as in the rigid insulation foam boards or something else? I was just going to put the dirt back your the footer and pier. And how do you disolve it?

I have another question if you know. My observatory is 3' off the ground. What is the best flooring material to use?
I was going to use OSB but I realized that it is not rated for outdoors.


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roscoe
curmudgeon
*****

Reged: 02/04/09

Loc: NW Mass, inches from VT
Re: Rebar in pier and pier footing new [Re: TeslaTrek]
      #6323089 - 01/19/14 09:56 PM

Rigid foam works, you can dissolve it with paint thinner, gasoline, lacquer thinner, and probably 17 other chemicals..... of those, lacquer thinner will most completely evaporate, and thus smell the least for the next month..... you can also dig it out with a prybar or shred it with a big drill bit and vacuum up the crumbs.

Regular construction-grade plywood will hold up quite a while if 3' up, but you can also get pressure-treated ply, and there is a next-level OSB called advan-tek which is made with waterproof resins and is rated exterior. PT ply can be found at big-boxes, the advantek will likely have to come from a lumberyard.
R


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Footbag
Postmaster
*****

Reged: 04/13/09

Loc: Scranton, PA
Re: Rebar in pier and pier footing new [Re: roscoe]
      #6323297 - 01/19/14 11:35 PM

I used PT ply. I built it myself so it took a good month before the roof went up. I was glad I didn't have to worry about the floor.

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jazle
super member


Reged: 05/20/10

Loc: California, USA
Re: Rebar in pier and pier footing new [Re: Footbag]
      #6323340 - 01/20/14 12:11 AM

If you have a Class III trailer hitch with pull-out ball, use the holding pin hole in the hitch. Put on some gloves and use leverage to make some nice bends.

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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Rebar in pier and pier footing new [Re: TeslaTrek]
      #6324891 - 01/20/14 08:05 PM

You did not say how deep the footing would be. If it is a couple of feet or more thick I would place a mat of #4 perhaps 12" on center both directions near the top and bottom of the footing. You can use small concrete spacers some people call dobbies to keep the rebar off the dirt. Tie the rebar mat together with tie wire. The top mat can be placed on the concrete when you have the footing nearly full or you can use rebar to hold it in place. I would use 3 or four vertical rebar in your pier. Put a 90 degree bend in the verticals and tie them to your bottom mat. For extra strength wrap the veticals with #3 rebar. It is best not to embed the rebar in the dirt. Use spacers or suspend the rebar with tie wire.

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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Rebar in pier and pier footing new [Re: TeslaTrek]
      #6324896 - 01/20/14 08:07 PM

You can get OSB that is rated for exposure but I would recommend ply wood such as CDX. If it is exposed to the weather use marine grade.

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TeslaTrek
member


Reged: 08/24/13

Re: Rebar in pier and pier footing new [Re: jazle]
      #6324962 - 01/20/14 08:29 PM Attachment (23 downloads)

Your tip on using the trailer hitch gave me an idea. I don't have the trailer hitch described but I had two old bolts sticking out of the patio pad where a post had been. Perfect to bend the rebar. So bending rebar was easy!! thanks all.

jim


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stmguy
sage


Reged: 10/11/12

Loc: Western NH
Re: Rebar in pier and pier footing new [Re: TeslaTrek]
      #6325569 - 01/21/14 06:15 AM

I used a couple of trees that were close together
Norm


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Footbag
Postmaster
*****

Reged: 04/13/09

Loc: Scranton, PA
Re: Rebar in pier and pier footing new [Re: stmguy]
      #6326833 - 01/21/14 07:26 PM

I'm just glad nobody was looking when I bent mine. It would have made a funny video.

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n1wvet
super member
*****

Reged: 04/22/11

Loc: Northern Virginia, USA, Earth
Re: Rebar in pier and pier footing new [Re: Footbag]
      #6327452 - 01/22/14 12:31 AM

An acetylene torch can also be used to bend and cut rebar. Heating it up to a nice red makes it easy to bend - even right angles. A cutting torch can be used to cut it.

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Skunky
sage


Reged: 09/16/13

Re: Rebar in pier and pier footing new [Re: n1wvet]
      #6327476 - 01/22/14 12:48 AM

Here in so cal, use poly wood... If not, you'll be hating in a few years when you have to rip up your deck and replace it.. Subterranean Termites love our observatory wood decks

Your 1-2 days of freezing is nothing to worry about.. The ground doesn't freeze. i'd be more worried about our ground shifting (all the ground near the coast is pretty much sand.. they built the houses on sand dunes and wetlands..) and earthquakes.. Not going to do much about earthquakes but 1.5 tons of concrete in a pyramid shape in the ground sure does prevent any shifting.. a 3.6 quake (small of course) and my pier footer laughed out loud.. lol!


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Rebar in pier and pier footing new [Re: n1wvet]
      #6328593 - 01/22/14 02:58 PM

Quote:

An acetylene torch can also be used to bend and cut rebar. Heating it up to a nice red makes it easy to bend - even right angles. A cutting torch can be used to cut it.




Heating rebar is not a good practice.


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mattw
sage


Reged: 07/19/06

Loc: Arkansas
Re: Rebar in pier and pier footing [Re: TCW]
      #6328649 - 01/22/14 03:18 PM

Quote:

Quote:

An acetylene torch can also be used to bend and cut rebar. Heating it up to a nice red makes it easy to bend - even right angles. A cutting torch can be used to cut it.




Heating rebar is not a good practice.




Yea, probably better to use a grinder (with a metal-cutting blade) or a skilsaw (with a metal-cutting blade). Only takes a few seconds, and is quite safe, with reasonable precautions.


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Rebar in pier and pier footing new [Re: mattw]
      #6328717 - 01/22/14 03:49 PM

For the small number of cuts needed for a pier a reciprocating saw with a metal cutting blade works fine. You only have to cut half way through and then bend it and the remainder will break.

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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: Rebar in pier and pier footing new [Re: TCW]
      #6332789 - 01/24/14 02:23 PM

TCW, etal,
And the reason for not heating rebar is..... the coating contains zinc, either zinc chromate (Lime green color), or galvanized (battleship grey). Very bad for your lungs when inhaled.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: Rebar in pier and pier footing new [Re: Startraffic]
      #6333783 - 01/24/14 10:52 PM

Not heating rebar is a structural issue. Changes the temper. On construction jobs with structural inspectors that practice is strictly verboten. There also is a minimum radius for bending rebar(I would have to up look what that is). Heating will tend to give you a sharp 90. I have never seen galvanized rebar but you can get epoxy coated for wet environments.

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Bill Lee
member
*****

Reged: 04/03/07

Loc: Massacusetts
Re: Rebar in pier and pier footing new [Re: TCW]
      #6341245 - 01/28/14 03:06 PM

Does a pier need rebar? I ask because, I always hear people putting rebar into their piers, but it seems to me that the concrete is always under compression, not tension (except for any bending loads).

I poured a 12 inch diameter pier, 4 feet above ground and 4 feet below ground (frost line), 10 years ago with no rebar and it's going fine.

My wife is a construction manager (custom homes) and she doesn't put rebar into foundations. I asked her this very same question, and she told me I didn't need it.


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Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Rebar in pier and pier footing new [Re: Bill Lee]
      #6342078 - 01/28/14 11:08 PM

The reason for rebar is to resist cracking due to lateral loads. The ground can shift and place loads on the side of the pier, especially during heavy rains or frost heaving.

-Dan


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