Hey guys…
We’ve always used forms for our footers before, however, this time we’re going to pour directly in the trench.
Any tips or suggestions?
Suggested slump?
Leveling techniques?
Much appreciated.
Also… code requires the rebar to be elevated at the time of inspection. What is typically acceptable for elevating the rebar? Rocks? I know we used wire cages back in the day, doing commercial pours. But I wouldn’t even know where to get something like that today.
Edited 5/14/2004 5:35 pm ET by petmonkey
Replies
That's the method commonly used here in FL.
But we don't have to dig for a frost line, either, so, 12" below undisturbed ground, 16" wide for frame and 20" wide for CMU.
Most of the time it's a monolithic pour so forms to the outside to whatever finished floor height unless there's a stem wall.
Care is taken to assure a level footing using grade stakes, which have to be pulled after pour.
If you haven't used soil forming before you have to take care not to try to cut to full width before you get to depth, about shovel wide down the center to start. Otherwise, your sides will cave. I always use a flat shovel. I'll usually make the final side cuts to the trench just before setting the rebar to confirm the width and cleanup any minor caves caused by loose soil or careless stepping. No such thing as backfilling against the sides of a soil trench. Don't forget to throw the spoils at least 2-3 feet away from the trench. It will be more than you expect and always fall back in plus get in the way as you try to work.
Rebar is placed on chairs. Get them at HD, Lowes or your concrete supplier. Currently 28 cents each at HD.
Lowest slump to get it to flow easily. You want to chute it with minimal hand work. Many times we have to use a pea stone pumpmix because we can't get the truck close enough. Costs more, about $30 more per yard plus the pump at about $250 and up, but those guys place much better than a chute monkey. And no wheelbarrow, which is good.
we do it everyday no big deal, who cares what it looks like, its buried.
It's best to tie the chairs to the rebar, and tie in the transverse bars so the concrete doesn't knock your rebar all over the place.
Following on the idea that slump 4 keeps you pretty much in the range of the mix design and anything past slump 6 is (in my opinion) too much water, if you want an easier day (small crew, or you are just feeling generous that day) you might consider using a super-plasticizer. A few bags of SP will bump the 4 up to a 6 or 7 for about 45 minutes, makes for a real easy day. Unless you have steps and bulkheads, then forget it.
You also might call about a boom. That way you can pump 3/4" aggregate, and you can probably do this all by yourself. A good boom operator is worth a lot. If you aren't accustomed to dragging a hose, or if your crew isn't, it can be tiring at best, dangerous at worst.
While the hard-cores will all say this is too expensive, if you are working by yourself or with one other person, it sure makes an easier day.
DRC
Dave,
I agree with everything you wrote!
We always drive some rebar grade pins in about every 6 '; then mark thier location on trench or ground with paint so u can find them once their covered with crete.
Cool -- OK enough of this construction talk on Friday night, let's get over to the Tavern for an ale, eh?
DRC
Thanks for the replies Ralph & Dave. Very helpful.
The excavator dug the trench today... we'll see what it looks like tomorrow morning.
Since we usually use forms and screed the concrete, our tolerances are usually dead on... but what is considered an acceptable deviance for the mason?
My biggest concern is getting a level surface without having forms to use as screeding guides.
anything below block elevation. Its better to be inch low than 1/4 inch high. But i would drive some rebar to grade, super plastize the concrete and use a concrete vibrator to move
another YUP!..
live longer, less chiroprater bills.
YUP
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
"live longer, less chiroprater bills."
Yes, indeed. Were it not for the chiropracter, I don't know how I'd do this stuff. <G>
DRC
formed footers would be the exception rather than the rule here in Australia.
This is a typical footer beam intersection http://quittintime.infopop.cc/attachments/6322-DSCN0018.JPG
steel is y12 deformed bar
to ensure footers are level we set up a laser during the pour and shoot level pads every couple of metres and then screed to that.
http://quittintime.infopop.cc/attachments/6324-DSCN0025.JPG
and we pump or crane and kibble all our concrete, both footer and slab
http://quittintime.infopop.cc/attachments/6373-DSCN0017.JPG
full story here
http://quittintime.infopop.cc/ubbthreads/showflat.php?Cat=&Board=Gallery&Number=6316&page=0&view=collapsed&sb=5&o=&fpart=1
regards
mark
http://www.quittintime.com
Edited 5/14/2004 10:43 pm ET by MARKCADIOLI