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xinull
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# Posted: 22 Jun 2021 21:00
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I was at the home hardware today and was explaining how i was building my piers and they told me that the solid 3" concrete blocks would not hold the weight of the cabin and would just disintegrate into pieces from the shear weight. Now i find this a little hard to believe, but here I am asking the real experts with experience 
So, Plan "A" was to build 1 layer of 2 8x8x16 concrete blocks on top of a 2" ABS mini-home pad. Then place 2 solid concreate block of 3x8x16 sitting on top. Then i would have a Pressure Treated spacer on top (not shown in picture) and then the skids/girders on top of that. The guy at home hardware said the solid blocks were not made for compression and would break apart.
If the first plan goes to shit, Plan "B" is to use the same ABS mini-home pad, then 2 layers of 8x8x16 concreate blocks and a layer of PT spacer, then the skids/girders
so my question, structurally, do any of these 2 design have capacity to fail under load?
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Brettny
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# Posted: 23 Jun 2021 05:42
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They make 8x8x16 blocks with no holes.
How big is the building and what's the frost dept?
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WILL1E
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# Posted: 23 Jun 2021 08:04
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xinull I was planning on a similar setup as you so i'm curious what others have to say. I'm not familiar with that ABS pad you referenced...do you have a link?
My plan was to put down a 24"x6" pre-cast concrete pad, then stack 2 layers of 8x8x16" hollow blocks. I would then put rebar into the hollow sections and fill them with concrete to basically bond everything together. I would use thinner block or 2x PT lumber to get the beams of my build level.
I look at my local hardware store website (Menards) and they just spec all of their concrete block as "standard" and/or "construction", with no callouts that one vs. the other is made of a different grade of concrete. Even the block manufactures flyer doesn't spec the concrete being used.
So i think as long as you use construction type blocks vs. landscaping ones, you should be fine. My hardware stores call them out different, but not to say they are actually different in terms of strength.
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Brettny
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# Posted: 23 Jun 2021 08:26
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https://www.lowes.com/pd/Headwaters-Construction-Materials-Standard-Concrete-Block-Co mmon-8-in-x-8-in-x-16-in-Actual-7-625-in-x-7-625-in-x-15-625-in/3471601
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ICC
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# Posted: 23 Jun 2021 09:39
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There are cinder blocks and there are concrete blocks.
Cinder blocks use portland cement and fly ash (cinders) from burning coal. They are lighter but not as strong as concrete blocks.
Concrete blocks are made from portland cement, sand and aggregate. Heavier and stronger than cinder blocks. Concrete blocks often use a small amount of fly ash in the mix. Concrete blocks can also come in different grades, made with different density concrete.
Cinder blocks cannot support the same loads as concrete blocks. Cinder blocks are prone to moisture damage. They lack the tensile and shear strength of concrete blocks.
Sometimes cinder blocks and concrete blocks are used in an engineered pattern to reduce the weight of a wall and retain the strength of the concrete blocks.
Masonry piers for a cabin should be all concrete, no cinder. The hollow cores are used to reduce weight as well as to provide a void that can have rebar inserted and then filled with concrete mix. Solid blocks are stronger and sometimes specified for walls that bear heavy loads. One advantage of using hollow-core blocks for piers is that rebar can be inserted and the voids filled with high-strength concrete mix. That can be stronger than a solid block column.
Most of the people at a home center or hardware store will not be aware of the differences. The most knowledgeable people will be at a company that makes and sells blocks.
Link to everything to did not know about masonry blocks.
Another
There are numerous other cinder vs concrete pages. Google is your helper.
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WILL1E
Moderator
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# Posted: 23 Jun 2021 09:44
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ICC to the rescue again!
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ICC
Member
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# Posted: 23 Jun 2021 09:45
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The block brochure linked to in an above post states they are construction-grade. That probably means they are concrete, not cinder. They have a website and a telephone; you could ask the manufacturer.
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paulz
Member
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# Posted: 23 Jun 2021 10:00
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Quoting: WILL1E ICC to the rescue again!
Can you picture him on Jeopardy, construction category?
There was a thread awhile back on some kind of lightweight (aircrete?) filler. Maybe it was more for fence posts but I think I saw it used in building blocks. Has it come into common use and sold at the big box stores?
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xinull
Member
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# Posted: 23 Jun 2021 12:44 - Edited by: xinull
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Quoting: Brettny How big is the building and what's the frost dept?
building will be ~20'x28' on 3 rows/skids of 5 pads
i'm building piers on the surface, we've had this discussions on my other threads already. i dont really feel like re-hashing it. But for the record, frost is at 4-5 feet, i think.
Quoting: ICC There are cinder blocks and there are concrete blocks
i'm pretty sure my 8x8x16 are concrete. I bought them at home depot already, and one of the question on the product page was "is it made out of fly ash" and the answer from the manufacturer was no.
But i'm not sure about the 3" block, i haven 't purchased them all yet, i just bought 4 for testing the height. But i can certainly find out since i'll be buying them directly from the manufacturer anways (Shaw Brick), so they should be able to tell me.
If all blocks are concrete, are any of the configuration I showed above in any risk of failure though? Specifically my plan "A", which has a solid 3" on top of a hollow 8" block. I've seen it on the internet, so it must be correct, right lol :p
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ICC
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# Posted: 23 Jun 2021 16:33
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If you stand the blocks with voids so the void is open to the top that is correct and as strong as that block can be. If the block is laid on its side so the voids are going side to side horizontally, the block can easily collapse depending on the load. So both of your pictures look okay for concrete blocks used to support a small cabin.
Note there are a lot of people who don't know the difference between cinder blocks and concrete blocks, and because of that, they will use the two terms interchangeably. Unfortunately, some of those people work in stores that sell blocks.
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ICC
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# Posted: 23 Jun 2021 16:43 - Edited by: ICC
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Quoting: paulz I think I saw it used in building blocks
You can see many things used incorrectly on the internet 
It could be used for filling concrete block voids but it would not be as strong as if filled with standard concrete. I'm not sure but I think it is only maybe half as strong as standard concrete. It is good for filling space that does not need good strength.
Using concrete for most fence posts is a waste of concrete, IMO. It is a fast way to refill the hole that was dug for the post. I prefer to ram the earth that was excavated back into the hole with a digging bar that has a mushroom head. You can actually pack all the dirt that was removed back in around the post. Concrete can also be a sponge for collecting moisture which may be detrimental. I mostly only use concrete around posts that are going to have lateral loads, like gate posts.
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paulz
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# Posted: 23 Jun 2021 18:05
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Here's that aircrete thread
https://www.small-cabin.com/forum/2_9916_0.html#msg136655
Looks like it is more for walls. There was another something used for fence posts I saw, more like expanding foam.
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Steve_S
Member
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# Posted: 23 Jun 2021 19:57
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I'm presently prepping for an accessory building for lawn tractor, snow blower and small work area, 16'x8'.
area prep:
Cleared the soil of trees, roots, & rocks for a 20'x30', elevated from driveway. Put Geotext down, then 6" of A-Grade Crushed gravel and compacted it.
Setting out 15pcs of 18"x18"x3-1/2" concrete "Cottage Blocks" centered at every 4' point. (every 6x6 connection) Base is 6x6 PT @ 4' centres. 2x6 PT @16oc between beams. 3/4" Ply for floor. Overbuilt for a purpose, LOL.
I've used cottage blocks many times up here in North Eastern Ontario. Whether skid or beam they work well. The really critical part is what is under it, do not underestimate Nature coming up and wreaking havoc. A good drainable packed gravel base (4"-6" thick) with enough surrounding the structure (generally 2' min is suggested) to mitigate water & freezing issues. Even a french drain to get water away, is wise. The GeoTextile is a heavy duty landscape cloth and it really helps keep roots and such managed. Plus, it helps keep the gravel in place and makes for a good long-term solid base.
Cinderblocks are NOT suggested, especially in a region subject to freezing temps and wet periods, they will only last a couple of freeze thaw cycles before they start to crumble. You want a Solid hard concrete block, something that won't crack and split.
Please believe me when I say this is a lesson best avoided... IF it is worth doing, then it is worth doing right ! and we all know about building on the sand right...
Quoting: xinull building will be ~20'x28' on 3 rows/skids of 5 pads
I think that 4 skids rather than 3 for 20'w. may be more prudent. That will be quite heavy, therefore you will want to distribute that more widely and that further reasserts the need for a good solid base under the whole thing.
I should mention that while putting a large structure on skids can & is done, this method is usually most suitable for buildings that can be moved on a trailer, so 16x8 or 20x8 or so.
Regarding your floor, I very strongly urge you to really work out how you want to insulate and prep it. And how to seal it from 'critters'. I mention this now, because it is a boatload easier to do while putting it together than afterwards and teh results are better as well. It can really make or break the comfort level of the place on cold days.
Alternative to blocks which works quite well and folks use it for cabins & decks etc, are Bigfoot forms which can be used both underground with sonotubes or as weight distributing piers on a hard-packed surface. This provides an option of using post saddles set into the concrete in the tube
LINK: https://www.bigfootsystems.com/include/bigfoot-footing-forms.htm
Available in Canada/USA
I'll be using some of the BF20's for my front porch post bases.
Hope some of it helps, good luck
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Brettny
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# Posted: 24 Jun 2021 06:00
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20x28 I would be putting on sono tubes below the frost line. That's a prety big building to keep level...and some times more blocks just means more area for the frost to push on.
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snobdds
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# Posted: 24 Jun 2021 15:46
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Blocks have no lateral support just laying on the ground. Then only have compressive support.
Need to bed them in somehow to get that lateral support to keep the cabin from moving and side to side. This could be as simple as driving in rebar 4 feet through the blocks and mortoring them in. It's not perfect, but it would sure last a long time.
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candie_lea
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# Posted: 20 Jul 2023 19:47 - Edited by: candie_lea
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Quoting: ICC Masonry piers for a cabin should be all concrete, no cinder. The hollow cores are used to reduce weight as well as to provide a void that can have rebar inserted and then filled with concrete mix. Solid blocks are stronger and sometimes specified for walls that bear heavy loads. One advantage of using hollow-core blocks for piers is that rebar can be inserted and the voids filled with high-strength concrete mix. That can be stronger than a solid block column.
How high from the footing can you stack 12'x16'x8' blocks if you are going to fill them with rebar and concrete?
We are having issues with our build site and having to put our footings deeper in the ground. I'm trying to decide if I need some kind of fill that will bear the weight or if I can just make extra-tall piers with a deep footing.
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ICC
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# Posted: 20 Jul 2023 21:05
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S limiting factor to height will be the degree of lateral support and what the potential lateral loads at the top of the clumn will be. Engineering may be needed; often better than a guess.
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