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Eddy G
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# Posted: 28 Jan 2016 06:39pm
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Our cabin is 22' across the back.
The whole cabin sits on cement block footings.
The ground under the cabin is less then even...
So the front of the cabin sits on one block (above ground) and by the time you get to the back of the cabin there are 4 to 6 blocks (above ground)...I say above ground because I believe the blocks go down at least 4' below the frost line.
The cabins been there since 1955 and still pretty strait and solid so they are working.
So across the back the cabin sits level on and across these blocks (single blocks by the way solid 8x8x8 blocks)
I plan on putting a 5'x14' addition off the back...5' out and 14' across...
I plan on using full size blocks...8x8x12...standard concrete/cement/cinder blocks whatever you want to call them... the blocks sold at home depot or lowes...
Why? Because I have a bunch of them for free...
Now the questions (about time right?)
Do I need to fill the holes in all the blocks with cement?
I'm thinking, I dig down 4' (below the frost line). Put the first block in the ground and fill the holes in the block with quickcrete. Then use mortar between the next 8 or more blocks.....
Do I need to fill every block as I go or once I have them all stacked up? My thought was I'd put some rebar down the holes and then fill them.
Next question.
I'm going 14' across so I'm going to piggyback off the back out 5' and use 3 footings across the back 14'.
A full block footing on each corner and then one in the middle.
Is it better to set the addition (like the entire cabin) directly on the blocks (with shims to level it)... or are there benefits or disadvantages to using wood piers (4x6's?) and setting those on top of the block... It would easier to level addition (I'm guessing)....
If I did use piers on the blocks would I need something between them?... like a bug shield or something?
Anyway, those are my questions.... Any help would be appreciated.
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bldginsp
Member
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# Posted: 28 Jan 2016 07:59pm
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You don't need to be 4 feet below the frost line, just at or slightly below. What is your frost level below grade?
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Eddy G
Member
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# Posted: 28 Jan 2016 08:27pm
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I believe its 4'.......I could be wrong but I've always believed the frost line in New England was at 4' below the surface.
Now to clarify the only things I have ever built on piers where tool sheds and decks in the Boston Suburbs and the Cabin is in south western New Hampshire but I don't know how much that matters.
I'll google it...
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Eddy G
Member
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# Posted: 28 Jan 2016 08:39pm
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Okay, I see the confusion. I typed 4' "below" the frost line.
What I meant was 4' from the surface to get below the frost line.
In Massachusetts and New Hampshire the frost line is generally 33 to 42 inches and 48" is recommended...I found Vermont literature that suggest going down as far as 60" but that's up North....
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Don_P
Member
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# Posted: 28 Jan 2016 09:26pm
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You should pour a footing first that is at least 4" wider in each direction than your 8x8x16" standard CMU's (you're in the big leagues now, concrete masonry unit  ) Footing, 2'x2'x8" thick. put 4 pcs of 18" long rebar in a # pattern 3" off the bottom. Support 3 or 4 pieces of rebar with an L bend. tie the bottom of the L to the footing rebar and align them to fit inside the cores. Pour the footing. The pier is cross stacked blocks, 16x16". Tie whatever connector you are using to attach pier to deck to the core rebar and pour the grout fill in all cores. More with houses than here but never leave an open core under a building, seal at least the tops. Termites love to run inside of blocks, force them out to where you can see them. A termite shield is never wrong. Treated lumber can sit on the block or in a saddle cast into it.
Anyway, see what we just did there, you have a snowshoe down to spread your weight out and help stabilize, the pier is locked together and unlikely to buckle. It is tied top and bottom. Standing a post on top of that pier adds another hinge to destabilize things, there is only disadvantage. Whatever you use as a pier, whether it is wood or CMU's, should run unbroken between points of support, one piece from footing to deck girder. You wouldn't cut a crutch in half and duct tape it back together, makes even less sense when there are thousands of pounds leaning on it.
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Eddy G
Member
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# Posted: 29 Jan 2016 04:58am
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Great points and information. That's just what I needed. Thank You...
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Thelar
Member
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# Posted: 29 Jan 2016 04:45pm
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Would it be easier to use sono tubes and concrete? Just spit balling a little. The holes would be smaller, so less digging. About the same amount of concrete. Can use rebar to prevent cracking from lateral movement, but depending on soil may not be needed. Add a saddle bracket to the top to secure your framing. Would the overall cost be similar? Maybe.
Good luck with your addition. Would like to see pics if you do go the block route.
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Eddy G
Member
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# Posted: 29 Jan 2016 09:19pm
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I don't think sonotubes are long enough.... First I need to dig down 48" (4') below the surface.... frame and pour a "12 pad for either the block or tube so a regular so no tube I've seen at home depot (for example) is only 4' long and would only stick 12" from the surface. I'm guess the front of the cabin/addition is off the ground more then that and the far side is close to 3' off the ground....
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Steve_S
Member
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# Posted: 30 Jan 2016 06:37am
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Sonotubes come in any length you want and are pennies compared to block which you would still have to fill with concrete along with the rebar.
For a "Tube Base" if you want to further simplify & get a better end result, I'd suggest a BigFoot Forms. I've used these with great success and I'll tell ya now, using a 2nd one as a funnel is really a big time saver. A pair of extra hands to help and you'll be done likety split.
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