Author Topic: Pier question  (Read 7066 times)

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Offline TisaWee Farm

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Pier question
« on: August 03, 2007, 08:39:03 AM »
If I put in 8" sonotube piers, at least 4 foot deep, do they need to sit on a pad?  I'm a bit confused about that yet.

Do they need rebar in them?

Thanks again.  
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Offline glenn kangiser

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Re: Pier question
« Reply #1 on: August 03, 2007, 08:56:58 AM »
I'd keep the tubes up off the bottom a few inches - 4 to 6 so the base could spread to around 16" dia depending on loading and soil conditions (provides better support with lower pounds per square inch due to bigger area = less chance of settling). .  

Pour a bit first and let it get firm to seal the bottom of the tube - then pour the rest with a couple 1/2 inch rebars to hold things together - or as suggested by an engineer or architect if necessary.  Put your chosen anchors or bolts in the top at required level.
« Last Edit: August 03, 2007, 08:57:46 AM by glenn-k »
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Offline TisaWee Farm

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Re: Pier question
« Reply #2 on: August 03, 2007, 09:09:51 AM »
Quote
I'd keep the tubes up off the bottom a few inches - 4 to 6 so the base could spread to around 16" dia depending on loading and soil conditions (provides better support with lower pounds per square inch due to bigger area = less chance of settling). .  

Pour a bit first and let it get firm to seal the bottom of the tube - then pour the rest with a couple 1/2 inch rebars to hold things together - or as suggested by an engineer or architect if necessary.  Put your chosen anchors or bolts in the top at required level.

How would the concrete spread out?  I was thinking I'd drill an 8" hole 4 foot deep, sink the sonotube about 2 foot deep and extend it about 1-1/2 foot above ground, and pour.   Maybe I'm being too simplistic?    I had thought the cement would just go down the 4 foot, but it can't spread out if the hole is only 8", can it??

Should I be digging a bigger hole, centering the sonotube and filling, and then backfilling with stone??

Thanks for your quick responses!!!! :)


Offline John Raabe

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Re: Pier question
« Reply #3 on: August 03, 2007, 12:23:10 PM »
If you have high density soil (gravel, rock, hard clay, etc) the plan you suggest could work. You could use a #5 rebar to get the air out of the pour and settle the concrete. Leave it in the center for reinforcement.

If you have soft soil (sand and loam) then you should probably use a bigfoot type footing to spread out the concrete at the base.
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Offline glenn kangiser

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Re: Pier question
« Reply #4 on: August 03, 2007, 05:08:13 PM »
John is the guy who knows.  I was suggesting an oversize hole with only the sonotube being 8 inches, considering that it may be softer soil- - hole around 16 or so, concrete flowed out at base under sonotube, then sonotube filled,  then backfilled after the sonotube is cut off.  That would be very similar to the Bigfoot that John suggested.  So it depends on your soil.
« Last Edit: August 03, 2007, 05:08:46 PM by glenn-k »
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Offline TisaWee Farm

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Re: Pier question
« Reply #5 on: August 04, 2007, 09:46:04 AM »
My soil is EXTREMELY hard.  Clay, that seems to be pottery when you get past the nearly non-existant top soil.   I tried digging with a shovel and post hole digger, and couldn't get past about 9".  I'm going to have to rent an auger to drill the holes.    I'm assuming, then, that I can just use the sonotube and no "bigfoot"?

On another topic....
I was in Menards the other day and saw that they had some sort of "composite" beam that is about the size and shape of a railroad tie.  It is extremely heavy, but says you can nail and cut it.   I need to do some more checking to see how weather resistant it is, but could that replace the cement tube??  Maybe with a cement footer to level it?   (I figured it out.... it's over 130 bags of concrete mix if I do it by hand!)   I don't mind buying the bags....just don't wanna mix that much!    I'm not sure a cement hauler would have the patience to fill 24 sonotubes for me, would he??


Offline glenn kangiser

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Re: Pier question
« Reply #6 on: August 04, 2007, 10:39:42 AM »
I doubt the composite beam is made to do the job, but there are pressure treated foundation grade posts you could set on a gravel footing that would do the job without concrete.  John shows a soil cement backfill around them in this posting at the bottom.  That could work.

http://countryplans.com/foundation/index.html

John's plans have a sheet showing the optional footings also.
« Last Edit: August 04, 2007, 10:41:36 AM by glenn-k »
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Offline MarkAndDebbie

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Re: Pier question
« Reply #7 on: August 04, 2007, 03:31:59 PM »
Quote
On another topic....
I was in Menards the other day and saw that they had some sort of "composite" beam that is about the size and shape of a railroad tie.  It is extremely heavy, but says you can nail and cut it.   I need to do some more checking to see how weather resistant it is, but could that replace the cement tube??  Maybe with a cement footer to level it?  
I am not sure what type of beam it is - they "compose" beams from wood products and plastic, but I would not think either would typically give you the compression strength of concrete.

Quote
(I figured it out.... it's over 130 bags of concrete mix if I do it by hand!)   I don't mind buying the bags....just don't wanna mix that much!    I'm not sure a cement hauler would have the patience to fill 24 sonotubes for me, would he??

Here's what I learned when I had my foundation done...

The guy hauling the cement is paid to do just that - drive the truck. He did not help us and I was told that was typical (I also gathered this from looking at his clothes compared to mine after the pour. He moved the shoot with some sort of hydrolic and added water to the mix when asked.

I was worried about the two of us working quickly enough for the truck driver. The guy I worked with said the driver wouldn't care how long it took us (as long as we weren't the last pour of the day) when he went back he would just be given another assignment. Concrete is fussy about time - the driver wasn't.

Get help - concrete is heavy. I paid a guy $500 to dig the footer, rebar, grade stake, and pour (labor only). It was well worth it.

BTW - I don't know what you drive, but 130 bags (even the small 60lb bags) would be too heavy for most trucks.

A "short" load was one that was less than 6 yards for me. I figured 5 yards and ordered 6 because it was about the same price for 5 with a short load delivery charge or 6 without.

Offline John Raabe

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Re: Pier question
« Reply #8 on: August 04, 2007, 04:09:23 PM »
If you do use posts instead of concrete piers make sure you get "foundation grade" pressure treated material. You don't want landscape timbers. I don't think any of the plastic wood composite materials have been rated structurally. These are for decorative light duty things like decks and steps.

You can also increase the life of a bearing post by wrapping it 12" (6" ea side) at the grade line. A butyl rubber tape like I use in the Sunroom and Greenhouse details would be the longest lasting but asphalt flashing tape would work too.

This will protect the post at its most vulnerable place - where moisture and air are both available. Link to a product I have not used but might be of interest:


http://www.mfmbp.com/post.htm
(Seems a bit light duty to me, but it's on the right track.)

Here's another material designed for use in pole barns. I think it is interesting how they cove out the post to provide greater uplift resistance.

http://www.postsaverusa.com/smartpost.html
« Last Edit: August 04, 2007, 04:25:46 PM by jraabe »
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Offline TisaWee Farm

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Re: Pier question
« Reply #9 on: August 10, 2007, 11:15:10 AM »
I called the cement contractor today and told him I was doing piers.  He said he'd use "6 bag and air" mix cement.  Any clue what that means??!??!?!?   Will it work?

Offline glenn kangiser

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Re: Pier question
« Reply #10 on: August 10, 2007, 01:38:15 PM »
6 bag is a strong mix - six sacks per cubic yard.  Air entrainment should help with freeziing if I remember right.  
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Offline TisaWee Farm

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Re: Pier question
« Reply #11 on: August 11, 2007, 04:11:00 AM »
Quote
6 bag is a strong mix - six sacks per cubic yard.  Air entrainment should help with freeziing if I remember right.  

So that's a good thing?   "Strong" won't make it brittle, will it?    When I originally told him sonotubes, he said "5-bag", then he asked if I was taking the tube off.  I told him "yes" so he said "we'll make it 6 bag and air, then".


Offline glenn kangiser

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Re: Pier question
« Reply #12 on: August 11, 2007, 06:02:14 AM »
I don't see why he differentiated unless it is common to leave the tube on for a bit of insulation there.  It is usually normal to take the tube off but that is in exposed cases where the concrete would be visible.  YMMV
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Offline PEG688

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Re: Pier question
« Reply #13 on: August 11, 2007, 06:55:56 AM »
The" six sack mix" finish's better,  the "air" makes it flow better , you'll get a better looking pier with less work . If your pier will not be seen the 5 sack mix will be fine . If he's pouring it and he's given you a price thats fixed let him do what he wants , it sounds to me like he's knows what he's doing.

    Addin "air" sound like B/S but it's not , there are a few other things that can be added to concrete , calcium in various amount depending on how cold it is speeds curing . You don't want a 2% mix on a hot summer day :o :o


   Lamp black for color various shades .

   Pea stone for exposed "look" , pea stone is nice if your pouring a finish stair as well , the small agragate "works " nicer , doesn't make the job harder than it needs to be.  

    Fiber crete is well fibers in the mud strands of fiberglass strenghtens the mix , used a lot for garage  floors , the fibers can be burned off with a  weed burner /torch  IF they bother some one . The fibers help prevent cracking , some what.

 There , more than you wanted to know about concrete  ;D

      
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