Using 8″ sonotubes to pour short piers under a porch- Do I let the footings dry, set the tubes on top and fill them, or set them down a little in the wet footings? Thanks- Dave
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im no pro... but i have seen the footings and tubes filled at the same time.
such as in this picture... the 1x's keep the sonotubes plumb/level/square wherever you want the top of them to be
View Image
Thank you- Seemed like a good idea at first, but wouldn't the weight of the concrete in the tube push it out at the bottom?
If you're not very careful about placement, you could move the bottom of the tube over. If you're worried about deformation of the tube, I've got 11- 7' tall columns cast here holding up my rather heavy roof. Worked fine but I set the tubes on existing concrete with a plywood form to keep the bottom in place.PAHS Designer/Builder- Bury it!
My footing and tube was poured at the same time.
By the way, to make sure there wasn't any loose fill left in the hole before pouring, I used a [Home Depot] Ridgid wet/dry heavy duty vac to suck it up. It worked great getting my cell phone out of the 5' hole too. 8:)
VaTom- Thank you- Then there's a good joint made between the dried and wet concrete? Thanks again- Dave
good joint made between the dried and wet concrete
No. Only the steel makes it structural. Otherwise you simply have concrete sitting on concrete.
Sounds like you have it under control. Cold joints are fine, not water-tight, but structurally OK as long as there's steel across the joint. How much and what size are another topic.
My columns were engineered to include 4- #4 vertically with #3, 8" oc, ties. All in an 8" column. Vibrating was interesting.
Earthquake resistance is considerably more complicated.
PAHS Designer/Builder- Bury it!
Edited 6/23/2005 8:36 pm ET by VaTom
In my area, Reading PA, I'm lucky if I can get below frost line before hitting bedrock. Often the hole for a 12" concrete column end up being 36" because of boulders and what not. Therefore I've used a sonotube for only the top eight inches or so to form up a nice pier on top of a huge blob of concrete that'd make Jaba look skinny...
".....Vibrating was interesting........" The tubes I bought advise against vibrating- Thanks for the the info on the rebar- Dave
wouldn't the weight of the concrete in the tube push it out at the bottom
Well, the "book" answer is that you only put a foot or so deep in the tube, and only after the footing starts to "set." Then, you keep adding in lifts up the tube.
The reality of it, is that it "depends." If you start the footer and first batch up the tube a bit stiffer, then "ooze out" is minimized. The amount of rodding/vibrating is very dependant on how much bar is in the form and tube, too.
I don't, personally, like setting the tube into the wet footer. But, that's just me, too.Occupational hazard of my occupation not being around (sorry Bubba)
Mac-
"....I don't, personally, like setting the tube into the wet footer. But, that's just me, too...."
How do you prefer? I've never done it, don't need speed or convenience, just a way to get it plumb in the right spot at the right height- Do you allow a square footing to dry with rebar protruding and then set the tube on it? Do you backfill around the bottom to avoid flooding out? Is the joint good between the footing and the pillar good if done like that?
Thanks for your help- Dave
I have only used sonotubes on two residential jobs for decks many years ago, so my experience is limited.
However, I have set colse to 150 on commercial work. I all cases of commercial aplications we poured the footings first and the tubes later. All of the steel in the footing was tied and set on chiars, and the vertical steel for the piers tied and stubed up before the footing pour. After the footing was poured and finished level we tied the remianing steel for the piers, and set the tubes over it. The bottom of the tubes were held in position by nailing 2x material to the footing around the tube. It was then plumbed and braced at the top with stakes and 2x lumber.
On large exposed sono tube columns that were stripped and exposed later, one of the companies I worked for had the specialty steel bracing collars and turnbuckle hardware to set and brace the tubes. Others either rented the bracing hardware, or we braced with lumber (a lot of it) for colums up to 14' high. Consolidating the concrete on tall columns with a vibrator was common, but care and experience are needed to keep from seperating the the denser aggragate into a layer at the bottom of the columns. For small piers we just touched the vibrator to the ouside of the tube, dipped in and out quickly, or just rodded the pier by hand. Through all those pours I don't ever remember having a honeycomb or any other problems.
You said you have the time, so why not do them in two pours? Footers first, then the tubes.
Dave
Dave- There's always time when you're mixing concrete in a wheelbarrow- Thanks for the education- I am much obliged- Dave
How do you prefer?
Usually to build a 2x4 collar top & bottom for the tube, the bottom rests on the footing or it form work, and the top sets to pre-registered plumb/tru/square forms. If the pier is substantial enough for a full cage of rebar, that's set first and tied into the bar from the footing. Then place a stiff set of concrete at the base, and fill from there.
Mojp, BB, & VaTom all expressed similar thoughts to mine as to practice and technique.Occupational hazard of my occupation not being around (sorry Bubba)
Thanks Mac, and I'll get out of your hair- Much obliged- Dave
and I'll get out of your hair
Don't mind my hair, needs cutting anyway <g> . . . Occupational hazard of my occupation not being around (sorry Bubba)
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I usually mix my concrete in small batches in a rented electric mixer, so things happen rather slowly. I pour the footings first, and by the time I go back to the first holes to set the tubes, the footings are firm enough to support the weight. I sometimes 'screw' the tubes into the soft footings a bit to hold them in place and then backfill just enough to keep the forms in place. Then, I fill the tubes, and backfill as I double-check to be sure the tubes are still where I want them to be.
Al Mollitor, Sharon MA
we have poured the footer, let dry, then set sonotube, backfill aroundto top then pour with concrete, after concrete set, pull the paper off top foot and leave rest. let the termites eat it. would not do if you have wood close but most of our sono tubes are just lightpole base.
We haven't any termites in N Idaho- Just yet, anyway- Thank you- Dave
Mojoman- There you have it- Many thanks- Dave