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Old 10-21-2007, 08:32 AM   #1
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5- #5 rebars E/W


I am attempting to install a lally column in my basement. My architectural plans show that I need a 2.5" x 2.5" x 1.5" footing to support the column.

The footing needs to be reinforced with "5- #5 rebars E/W"
Because the hole is 2.5" x 2.5" do I need (5) 2 foot bars evenly spaced parallel to each other? or do the bars need to be positioned in a particular fashion? What does "E/W" mean?

regards

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Old 10-21-2007, 11:57 AM   #2
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5- #5 rebars E/W


It sounds like a substantial footing.

The note means 2 layers of 5 - #5 bars laid parallel each way (E/W at 90 degres to each other) for a total of 10 bars. Keep the bars at least 2" away from the forms to give you adeqauate concrete covereage.

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Old 10-21-2007, 12:36 PM   #3
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5- #5 rebars E/W


Thanks for the reply ccmason

I cannot just dig a 2.5 x 2.5 hole and not use a form right? I must dig a 3x3 approx. hole and place a 2.5x2.5 form in the hole.

Thanks again
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Old 10-21-2007, 02:29 PM   #4
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5- #5 rebars E/W


You can usually place concrete in a bank pour situation (no forms) as long as local code does not prohibit and the soil is cohesive (clay) and will retain the excavation walls. Most likely if you bank pour it is better to slightly increase the size of the footing to ensure that it is larger that the detailed dimensions.

Also as a note make sure that the soil below is adequate for support of your lally column (most likely 3,000 psf in residential situations).

Good Luck
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Old 10-21-2007, 04:17 PM   #5
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5- #5 rebars E/W


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Originally Posted by Material Tester View Post
make sure that the soil below is adequate for support of your lally column (most likely 3,000 psf in residential situations).
How do I determine if the soil its adequate? And if it's not?

Can I use make shift supports to keep the rebar of the bottom? I don't feel like running out just for them. How far should the bars be off the bottom?

Do I have to compact the bottom of the pit?

Thanks for the input MT

Last edited by jelly; 10-21-2007 at 04:20 PM.
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Old 10-22-2007, 12:28 AM   #6
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5- #5 rebars E/W


How do I determine if the soil its adequate? And if it's not?

Depending upon the type of soil will depend upon how to determine if it is adequate. Clay can be tested with a small hand held device called a penetrometer. It uses a spring to determine the unconfined compressive strength or bearing strength of the clay. For sand or granular material it is necessary to utilize some type of cone penetrometer to determine the blow count of the material and then calculate the strength form this number. This test can be performed in the excavation for the Lally column. Consult with your design professional regarding what you need to do and if they would want a materials laboratory to perform the testing (if necessary). Also somewhere in the plans you have (most likely a note in the footing detail or in the general notes) will have the required bearing capacity listed as X,XXX pounds per square foot. What type of soil do you have in your area?

Can I use make shift supports to keep the rebar of the bottom? I don't feel like running out just for them. How far should the bars be off the bottom?

You can use small masonry/concrete blocks or small metal chairs designed for this purpose. Do not use wood!!!! The bars should have 3" of cover in accordance with the American Concrete Institute, since the bottom of your footing is an unformed piece (in direct contact with the earth at the time of placement). Depending upon whether you bank pour (no Forms) or use forms will also affect the rebar coverage. If you dont use forms keep 3", if you do keep 2". A review of your drawings may indicate the desire for the rebar to be placed in the center of the footing. If this is the case you can suspend the bar from boards across the excavation. Make sure that they are securely fastend so thay don't shift greatly during placement. Also the rebar should be tied together using wire for that purpose. The reason for tying is to secure the bar and to ensure that they don't move during placement.

Do I have to compact the bottom of the pit?

If the material a natural clay then no. Clay does not usually get sufficiently disturbed during the digging process to necessitate recompaction. If your sub-grade is sand then you will need to recompact. The reason is that sand gets readily disturbed during excavation and will need to get redensified prior to concrete placement. If you are using a crushed stone to grade the excavation then you will need to compact that as it will settle if you don't. Regardless of what you hear there is no stone that does not require some level of compaction. The compaction limits the materials ability to settle as time goes on.

I am assuming that you are hand digging the hole so have fun and take care of your back!!
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Old 10-22-2007, 07:24 PM   #7
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5- #5 rebars E/W


Thank you so much for all the information MT.

The inspector came by and had me remove the form. He was here for 2 minutes and left. I now have a 32" x 32" footing hole. I poured four 80lb bags in the hole and it hardly made a dent.

I hope it's okay to finish in a couple days when I get more concrete. I made some holes in what I already poured to help the bond when I add to it.

Thanks again for everyones response.
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Old 10-22-2007, 10:12 PM   #8
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5- #5 rebars E/W


jelly -

Your first post gave the footing size as 2.5" x 2.5" x 1.5". I assume you meant 2.5' x 2.5' x 1.5'.

If your footing is really that thick, you probably can survive the error of a cold joint. Just make sure you have the first pour clean.

In reality, with a footing that thick, you could even get away without ant reininforcement under some code.

You are concerned about the soil capacity. - The architect knew that the configuration of the house was and what loads were expected. If there were no soil borings or probing done, he probably went on the conservative side to make sure it worked for any forseeable conditions. It is not unusual to do this for a single footing within existing structure, since it is cheaper to over-do the footing than to spend the money on a soil investigation - especially if your labor is "free". If you have questions about the design or construction, ask the designer since he signed off on the design and is responsible.
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Old 10-23-2007, 09:11 AM   #9
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5- #5 rebars E/W


Quote:
Originally Posted by concretemasonry View Post
If your footing is really that thick, you probably can survive the error of a cold joint. Just make sure you have the first pour clean.
"cold joint" is adding fresh mix to mix that has already cured and hardened?

What do you mean by a "clean pour?"

And yes, my back does hurt today!...

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