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stardust1968
newbie
Reged: 08/19/07
Posts: 4
Loc: Illinois
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Does anyone have a good source for purchasing a sonotube to pour a concrete footing for a pier?
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Celestron Nexstar 8iSE/SkyShed Pier
SkyShed POD
Celestron NexImager
Orion Starshoot DSCI
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Mirzam
super member
Reged: 04/01/08
Posts: 118
Loc: Lovettsville, VA
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Home depot.
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polaristom
super member
Reged: 12/17/07
Posts: 157
Loc: Alaska
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The Home Depot near me only has a 10" or maybe a 12" diameter tube. I'd call the local concrete redi-mix company. If they don't have them they would certainly know where to get one. Unfortunately the larger sized tubes only come in 12' lengths. So you'll get enough to build three piers. Ask if they have one with a damaged end, maybe they'll give it to you for a good deal.
This is what I plan to do, next spring. I'll probably use a 24" to 30" tube between 3' and 4' long. This would still be less than one cubic yard of concrete. This will just be the base, I'll install a steel pier on top of this from below the floor up to the heigth of my mount.
Edited by polaristom (10/25/09 07:44 PM)
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Restricted
journeyman
Reged: 08/21/09
Posts: 9
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Try a building supply company. Preferrably one that specializes in commercial work (at times I use 10 to 24 inch Sonotube), rebar, rebar ties, etc.. Use the Sonotube above ground as a concrete form. You can do it many ways, but two stakes,opposite each other on the outside, screwed in with ONE screw from the inside on each will allow you to "level" the tube above the bored hole. I don't know how deep you plan on making the pour, but below frost depth in your area, plus the needed stability of the weight atop will determine it. Pour the concrete so it comes in direct contact with the earth, you don't need Sonotube to the bottom of the bore. insert rebars, screed off, insert any j anchors (use a bolt pattern template), and let set up at least overnight. Cut the tube off the next day.
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Gargoyle
super member
Reged: 03/13/08
Posts: 135
Loc: Long Island, New York
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I had difficulty locating a tube with my required diameter (14"). I tried Home Depot, local building supply houses, etc., to no avail.
I ended up digging the hole with a 14" diameter-4.5' depth and poured directly in the hole. I supported the pier with wired rebar, and within 15" from the top of the hole inserted a 14" diameter ring made of aluminum flashing (18" strip width). This allowed the cement portion of the pier to project 3" above ground level, provided a measureable diameter target to place the steel pier bolts into and also provided for a rounded finished look.
My neighbor works professinally with cement and advised against using a sonotube for the entire length, stating that there would be far less movement of the pier with direct pour vs. a sonotube which would need to be backfilled with sand, soil, etc..
Including the dig, mix and pour we were done in under three hours...... The next day I removed the aluminum flashing ring and it looks perfect.
Jerry
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Meade 8" f/10 LX90 GPS
Meade 10" LX200-R on permanent pier
MoonLite CS 2" Focuser
ETX-125 PE
StellarVue SV80ED(Blue)and F50M2 Finder Scope
DSI ProII
DSI III
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polaristom
super member
Reged: 12/17/07
Posts: 157
Loc: Alaska
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It depends where you live. Placing concrete in direct contact with the side of the excavated hole will work fine if you live in an area that doesn't experience frost or frozen ground. If the ground does freeze the Sono-Tube allows the ground to "slip" as it freezes and will reduce the tendency to "jack" the pier base out of the ground. If you dig your base below the local frost depth and then mushroom out the bottom of the hole, this will also help anchor the base and reduce jacking. Always install a Sono-Tube in the frozen active layer portion of the base.
Remember this is free advice and may be worth twice that much!
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Restricted
journeyman
Reged: 08/21/09
Posts: 9
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I guess I have to disagree with you a bit here. Frost heave forces push upward on anything in the ground to move it, such as a stone or concrete footing.That's why farmers find new stones in fields on the surface in the spring of the year in frozen climates. The lateral force produced from the freezing of moisture laden soil is negligable, meaning that it's equal on all sides so it won't move. Footing don't get pushed sideways, only up. I do a lot of construction in my area where frost depth is 48 to 60 inches. The idea of pouring that deep is that the ground will not freeze at that depth. There is no truth that a sonotube will provide "slippage". Frozen ground expands and will push any weight up. You don't want to use sonotube below ground as at the paper rots, it will create a void and allow movement. I've been pouring street light and utility pole bases for a time.
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Mirzam
super member
Reged: 04/01/08
Posts: 118
Loc: Lovettsville, VA
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Another point to consider is that the observatory structure will shelter the soil around the pier. If you arrange for drainage to run off around the sides of the observatory, the soil underneath will remain relatively dry--reducing the potential for frost heave.
Jim
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Gargoyle
super member
Reged: 03/13/08
Posts: 135
Loc: Long Island, New York
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I never thought-considered about the paper rot on the sonotube, it makes sense though. Nevertheless my neighbor was pretty adamant about not using a tube, so perhaps he know about this too. I agree with you about frost heave and frost line depth. I checked that prior to the hole dig for that reason and the frost line here is 36", so I'm good to go.
Jerry
--------------------
Meade 8" f/10 LX90 GPS
Meade 10" LX200-R on permanent pier
MoonLite CS 2" Focuser
ETX-125 PE
StellarVue SV80ED(Blue)and F50M2 Finder Scope
DSI ProII
DSI III
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