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
Rebar in pier and pier footing
Started by
TeslaTrek
, Jan 19 2014 08:18 PM
44 replies to this topic
#1
TeslaTrek
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Posted 19 January 2014 - 08:18 PM
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
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
#2
Footbag
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Posted 19 January 2014 - 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.
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.
#3
TeslaTrek
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Posted 19 January 2014 - 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.
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.
#4
roscoe
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Posted 19 January 2014 - 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
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
#5
Footbag
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Posted 19 January 2014 - 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.
#6
jazle
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Posted 20 January 2014 - 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.
#7
TCW
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Posted 20 January 2014 - 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.
#8
TCW
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Posted 20 January 2014 - 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.
#9
TeslaTrek
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Posted 20 January 2014 - 08:29 PM
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
jim
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#10
stmguy
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Posted 21 January 2014 - 06:15 AM
I used a couple of trees that were close together
Norm
Norm
#11
Footbag
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Posted 21 January 2014 - 07:26 PM
I'm just glad nobody was looking when I bent mine. It would have made a funny video.
#12
n1wvet
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Posted 22 January 2014 - 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.
#13
Skunky
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Posted 22 January 2014 - 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!
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!
#14
TCW
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Posted 22 January 2014 - 02:58 PM
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.
#15
mattw
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Posted 22 January 2014 - 03:18 PM
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.
#16
TCW
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Posted 22 January 2014 - 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.
#17
Startraffic
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Posted 24 January 2014 - 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.
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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.
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#18
TCW
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Posted 24 January 2014 - 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. 
#19
Bill Lee
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Posted 28 January 2014 - 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.
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.
#20
Midnight Dan
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Posted 28 January 2014 - 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
-Dan
#21
tim57064
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Posted 29 January 2014 - 10:29 AM
+1 on Dan's comments.Frost in the ground will cause problems with a pier that has no rebar in it.
A little extra insurance at a small expense.
A little extra insurance at a small expense.
#22
Bill Lee
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Posted 29 January 2014 - 11:33 AM
Dan, Tim,
Thanks. I'd heard that rebar saves you from "bad pours".
I would question the real need due to lateral loads and frost, since rebar is not required, nor used in foundations our houses, here in the northeast. If there were ever a problem with lateral loads, and frost, it would be in the foundation of a house, and less so in a pier.
I'm not trying to be argumentative (and I'm sure this will bring nasty comments), but it seems to me that people put in rebar simply because "its always done in large buildings". Indeed, I asked one of my fellow club members why he put rebar into his pier and he said "it makes it stronger".
I'm just trying to determine if using rebar is a myth, or a real engineering requirement.
Thanks. I'd heard that rebar saves you from "bad pours".
I would question the real need due to lateral loads and frost, since rebar is not required, nor used in foundations our houses, here in the northeast. If there were ever a problem with lateral loads, and frost, it would be in the foundation of a house, and less so in a pier.
I'm not trying to be argumentative (and I'm sure this will bring nasty comments), but it seems to me that people put in rebar simply because "its always done in large buildings". Indeed, I asked one of my fellow club members why he put rebar into his pier and he said "it makes it stronger".
I'm just trying to determine if using rebar is a myth, or a real engineering requirement.
#23
Starman27
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Posted 29 January 2014 - 12:15 PM
My piers sit on square concrete bases that go down 4.5 feet. The base is wider at the bottom. The pour included rebar. They have been in place 25 years without noticeable deterioration or shifting. We have significant freeze/thaw conditions. Your pier base is relatively small compared to a house and subject to many conditions that can move it or damage it. My previous observatory had a 6 foot aluminum pier embedded into concrete below the frost line. It was not as stable as needed and suffered over the five year period I used the observatory. Learned my lesson.
#24
Midnight Dan
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Posted 29 January 2014 - 02:57 PM
Hi Bill:
I'm not sure where you're getting that information. I'd check with your local building inspector.
I'm also in the Northeast, near Rochester NY, and rebar is required in foundation pours here. You're absolutely correct that side loads in a basement are much larger than in a pier. In our climate, you simply could not pay me enough to build a house on top of poured concrete basement walls that have no rebar.
In fact, you can look up your (Massachusetts) building codes online. Your state has links to the ICC code site because that's what they use. Check out this page for foundation wall specs:
http://publicecodes....12_4_sec004.htm
Scroll down to the section for concrete foundation walls and you'll see the required spacing and size for reinforcing bar.
As Tim points out, it's cheap and easy to add rebar to your pier. Do you really want to take the chance of having to dig up a cracked pier after an observatory has been built around it?
-Dan
I would question the real need due to lateral loads and frost, since rebar is not required, nor used in foundations our houses, here in the northeast.
I'm not sure where you're getting that information. I'd check with your local building inspector.
I'm also in the Northeast, near Rochester NY, and rebar is required in foundation pours here. You're absolutely correct that side loads in a basement are much larger than in a pier. In our climate, you simply could not pay me enough to build a house on top of poured concrete basement walls that have no rebar.
In fact, you can look up your (Massachusetts) building codes online. Your state has links to the ICC code site because that's what they use. Check out this page for foundation wall specs:
http://publicecodes....12_4_sec004.htm
Scroll down to the section for concrete foundation walls and you'll see the required spacing and size for reinforcing bar.
As Tim points out, it's cheap and easy to add rebar to your pier. Do you really want to take the chance of having to dig up a cracked pier after an observatory has been built around it?
-Dan
#25
TeslaTrek
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Posted 01 February 2014 - 11:03 AM
Thanks for all the tips. Yesterday a little problem occurred. We are in the worst drought in many years, and yesterday it rained. Even though the hole was covered up, the rain runoff filled the hole with 8" of water. I pumped out the water.
How long should I wait to pour the footer?? Just wiat until it feels dried out? I'm thinking that it just needs to be dry to the touch.
How long should I wait to pour the footer?? Just wiat until it feels dried out? I'm thinking that it just needs to be dry to the touch.
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