Building with CMU blocks ?

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Old 02-12-17, 04:36 PM
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Building with CMU blocks ?

I am building an a-frame home myself, need a few questions answered. First and foremost is foundation. Plan on digging 40" below grade, leveling, then digging a 16" trench around perimeter and a straight line through the center of the square. Going to fill that with an inch or two of inch minus and pouring a footing. I plan to use CMU's for foundation wall as code allows. However, my local building code does not state how many courses of block I need to use.
Any ideas? Suggestions? Can I get away with one course and still have integrity?
 
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Old 02-13-17, 03:15 AM
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Welcome to the forums! Your profile is incomplete so we don't know where you are located. It helps us to know that. Any block foundation will need to be above grade before you lay in wood, so you will need to determine that ahead of time. I am not sure what digging a 16" trench is going to accomplish. Your footing will probably need to be at least 12" wide and deep, depending on your local codes.
 
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Old 02-13-17, 03:25 AM
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The width/thickness of the footer depends on local codes so check to make sure it will fall within their guide lines. It must also be at or below the frost line.

It's best to have the foundation high enough where the wood is protected from ground moisture whether it be from vegetation or snow.
 
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Old 02-13-17, 05:19 AM
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Also check with your inspectors if they will allow the crushed stone to be installed prior to their inspection. Mine want the trenches bare so they can check the soil for firmness/compaction.
 
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Old 02-13-17, 01:09 PM
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Awesome stuff guys, thank ya's for the input so far. Sorry I neglected location, not used to talking on forums yet.
I'm in franklin county, missouri. Local codes state that footing must be twice as wide as the wall being built on it,so if I use 8" wide blocks the footing has to be 16" wide. No less than 30" below grade for frostline. At least 2 continuous run no 4 rebar for reinforcement.
As far as the blocks and building codes go, minimum of one course to a maximum of 5.
 
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Old 02-13-17, 02:41 PM
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If your footing is 16" wide, you will need a much larger trench then 16" in order to frame up the footing with lumber. You will also need room to work the concrete during the pour. I can't say how wide is common but I would think double (32") or so would be a good.
 
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Old 02-13-17, 02:57 PM
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Generally I do not set forms for footers. I use the trench and just fill it with concrete. Only if the footing goes above ground or if there was a digging error will I set forms.
 
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Old 02-13-17, 03:02 PM
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I found it's easier for me to get a level footer if I set a form board on one side, never saw a need to form up both sides. I don't generally see forms used for footers in new residential construction.
 
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Old 02-13-17, 04:35 PM
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Well that just goes to show you what I know about pouring footers. I seem to recall seeing them framed up, but then I may just be thinking what I see on plans. They are always square on the prints.
 
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Old 02-13-17, 04:49 PM
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I was gonna pour it right in the trench. Easy peasy.
 
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Old 02-14-17, 05:13 AM
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Yea, I pour right into the footer. I drive rebar stakes throughout the area and hammer them down so the top of the stake is the pour depth. I also use the stakes to hold the rebar up and in place that reinforces the footer.
 
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Old 02-18-17, 07:51 AM
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Pilot Dane has all the information you will need to pour a footer. Working as a construction inspector, I reviewed the all documents and plans for the footers before I gave the OK to pour. Most of the projects I was involved in, I was onsite to inspect and OK the subgrade. If the subgrade was not sufficient to support the footer, I would have the contractor over excavated and replace the material with approved backfill material and compacted to 95% of the proctor. In a trench pour I have seen contractors use laser levels to place 16 Pd nails into the side of the excavation and use them for leveling the top of the footer. If rebar is need in the footer, the contactor was allowed to use chairs or concrete bricks to support the horizontal rebar. Vertical reabr was placed in the trench and tied to the horizontal.
 
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