Footing for cement block fence post?

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Old 03-09-15, 03:22 PM
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Footing for cement block fence post?

Hi,

I am checking in the make sure that I am not missing anything before pouring my footing for 6 of my concrete posts in the front yard.

The block is 12" x 12" x 8" tall,
The footing is 20" x 20" x 2' deep,
Rebar is 1/2" thick x 2 pieces
Column will be 6' tall with cap
Located in Sacramento, CA no frost issue.
Already checked with the utilities companies and marked the underground pipes.

There will be 2 sliding gate however, those won't be attached to the concrete columns at all. Where there are no gates, there will be wrought iron fencing attached between the 2 columns similar to the picture #1 below, picture #2 & 3 are my mock up of the footing.

A few questions I have are:

1) Is my footing dimensions large and deep enough to support the column?
2) Do I need to add any crushed rock to the bottom of the footing first?
3) Do I have to raised the rebar up a few inches above the bottom of the footing?
4) If I placed some concrete blocks in the footing then pour concrete mix to fill it would the integrity of the footing compromised? I have a bunch of extra blocks that I like to used up that's all.

Thanks
Anthony
 
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Old 03-09-15, 07:34 PM
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antnida -

For the following points:

1). Probably wide enough, but possibly thick enough.
2). You need concrete (2"+) under the reinforcement to get a good bond between the steel and concrete.
3). See # 2 above. Usually, the concrete masonry units sit on top of the poured footings.
4). You will need vertical steel in the columns/pilasters.

It is especially important if they are on the property line between neighbors or the public.

Most cities in CA have standard details available to make construction easier, eliminate confusion and being "red-tagged" after completion. I have seen slightly different standards between privacy walls whether the are party walls between lots or walls facing public property surrounding a development

Dick
 
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Old 03-09-15, 07:54 PM
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Dick,

Thanks you for the inputs. I'll start on it tomorrow. I checked with a building inspector before regarding the fence project and he gave me some spacing guidelines around fire hydrant and lights pole and such, height is fine without a permit so I am good to start my first footing tomorrow.

Thanks again.
Anthony
 
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Old 03-09-15, 08:39 PM
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I know my vision is rapidly deteriorating, but your footing (form) depth doesn't look anywhere close to 2' thick. If the block you're showing inside the form is 12" x 12", I'd guess your footing to be just under 8" thick.
 
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Old 03-10-15, 07:31 AM
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Bridgeman45 -

I thick he needs at least 8" thick. I am not fond of thick footings unless they are large, either for overturning or poor soil conditions. I don"t see a lot of wind loading on those columns (even if the Santa Anna or similar winds come up). I just like to keep the stresses withing the "magic" 45 degree area from the exterior of the pier or wall, so there is no flexure and reliance on the rebar placement that can be a little "iffy".

If the gates were attached to the columns, it would be a different story just as the possibility of protection from the road traffic.

Dick
 
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Old 03-10-15, 09:32 AM
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Dick, I'm in total agreement on 8" being thick enough for block pilaster footings. Just questioning his dimensional accuracy, since he initially stated that the intended footings would be 20" x 20" x 2' thick.
 
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Old 03-10-15, 03:00 PM
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Hi, BridgeMan45

I had 24" deep because I didn't know how deep was sufficient for this column so I thought of 24" deep from placing one of the steel fence post.

I reduced the deep to about 13" with the bottom 3-4" will be crushed rock, leaving me about 9-o9 - of deep for cement. Thanks you for the inputs, help save some digging and cement as well.

Thanks
Anthony
 
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