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xinull
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# Posted: 17 Feb 2021 10:11pm
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Does it matter structuraly which direction my top cinder blocks will be when i build my piers?
I know they aren't lined up right in the picture, one is the top cinder blocks parallel to the beam and the other is the top cinder blocks perpendicular to the beam
..and maybe i'm over-thinking it ;)
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xinull
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# Posted: 17 Feb 2021 10:12pm
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btw, i didn't mention, but i'll have a piece of PT sitting between the beam and the blocks. That's why there's a space in the picture!
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ICC
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# Posted: 17 Feb 2021 10:47pm - Edited by: ICC
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Depends on what is under the pictured top layer of blocks and how everything is connected.
A column constructed of two or more block layers should have the voids filled with concrete and perhaps a length of rebar passing from one layer to the next. That column should be sitting on a proper concrete footing also with rebar that connects the footing to the blocks stacked above. Do that and then it doesn't really matter.
How will the wood be connected to the concrete column?
If using PT any metal, including fasteners, must be of a type suitable for contact with PT.
If the bottom face of the eams is less than 12" above the ground surface the beams should be all PT. Similarly if the lower edge of the floor joists are less than 18" above the ground the joists should be PT.
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xinull
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# Posted: 17 Feb 2021 11:04pm
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I wasn't going fancy
starting from the bottom, i have an ABS pad used for mini-homes similar to what's found on this link
https://mobilehomedepotmi.com/transport/set-up.html
then i would have 2 rows of 16x8 cinder blocks
then a piece of PT 2x12x16"
then my girder which is composed of 4 ply of 2x10 (not PT)
the height of the 2 layers of cinder blocks will be 16" + 2" for the ABS pad...that's 18". That's why my 2x12x16" between my blocks and girder will be PT and my girder will not. I feel i have enough height off the ground to not require my girders to be PT.
The girder and the PT spacer will be tied together with either a bracket or probably just toe-nailed together. But i had no plan on tying the PT spacer to the blocks
I didn't have plans on filling the blocks with concrete either.
I was however pondering if i should be putting mortar on my columns between the blocks or not. A lot of people in the area here are telling me not to, they say it's easier to adjust the piers if needed be. or to replace an older individual block when they get older or damaged. I was told by a brick layer that i wont gain any strength in adding mortar between the blocks, but i'll loose a bit in stability. I guess i dont know how much stability would i be loosing from having loose blocks
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Brettny
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# Posted: 18 Feb 2021 05:54am
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In a concrete block wall the mortar just holds things together until they fill the center of the blocks. In this situation I wouldnt use mortar. With a good gravel bed I would fill them with concrete. Usualy your height adjustment is done at the top of the colum.
Have you priced out solid 8x8x16 block?
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WILL1E
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# Posted: 18 Feb 2021 08:56am
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xinull Ill be doing an almost identical setup. Instead of that tiny home pad you are going to use, i am buying precast 24" round by 6" thick pads. I then plan to do a minimum of 2 layers of cinder blocks, maybe more if the topography requires it. I do plan to use rebar and concrete inside as well. For the little added cost, it should firm things up quite a bit.
I haven't decided what to put between my blocks and the non-PT beams yet...or which style of bracket to use.
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ICC
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# Posted: 18 Feb 2021 09:14am
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Quoting: xinull pondering if i should be putting mortar on my columns between the blocks or not. A lot of people in the area here are telling me not to, they say it's easier to adjust the piers if needed be. or to replace an older individual block when they get older or damaged.
By the same reasoning it would be easier to repair a floor if we just laid the boards out on top of the joists and didn't nail them down.
Filling the voids with concrete makes the whole column act as one piece, not four individual pieces. DRy stack the blocks, use short pieces of rebar and fill with concrete or mortar/grout mix.
I would not use solid concrete blocks as then you do need to mortar them together.
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ICC
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# Posted: 18 Feb 2021 09:16am
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Quoting: xinull But i had no plan on tying the PT spacer to the blocks
No concerns about uplifting from high winds? That is why houses are secured to the foundation. Even mobile homes use tie downs of some kind.
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rpe
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# Posted: 18 Feb 2021 09:19am
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My local supplier sells 'bull-nose pier blocks' that are 16" square, with two rectangular cavities for filling.
These are what the locals use in my area for pier work. For taller piers, I drilled into the bedrock, installed rebar, poured a pad, and threaded the blocks down over the rebar filling the voids as I went.
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xinull
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# Posted: 18 Feb 2021 07:56pm
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Quoting: Brettny Have you priced out solid 8x8x16 block?
No, i didn't even know they existed. I guess i'm a little wet around the ear for these types of things.
Quoting: ICC Filling the voids with concrete makes the whole column act as one piece, not four individual pieces. DRy stack the blocks, use short pieces of rebar and fill with concrete or mortar/grout mix.
sounds good, so a piece of rebar in each hole? so 4 piece per pier? How does the rebar actually strengthen the piers, i guess it's the same reason as to why you put rebar in concrete foundations, but i dont know the explanation 
Quoting: ICC No concerns about uplifting from high winds? That is why houses are secured to the foundation. Even mobile homes use tie downs of some kind.
In the last 4 years, i haven't seen excessive winds that would concern me. But i'm open to suggestions. With a pier foundation, what would you recommend? attaching an anchor type to the girders and into the ground?
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ICC
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# Posted: 18 Feb 2021 09:29pm - Edited by: ICC
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Quoting: xinull How does the rebar actually strengthen the piers, i guess it's the same reason as to why you put rebar in concrete foundations,
Concrete by itself is very strong in compression and very weak in tension. Concrete does not stretch, it breaks. Tension strength of concrete alone is maybe 1/10 that of the compressive strength.
Compression is the load that the weight of the cabin applies to the column; vertical load, straight down.
Tension involves all the other loads, laterally and uplift. Most of those loads come from wind, except for things like the lateral impulse load when someone backs their truck into the cabin corner. 
Leaning a ladder against a concrete block wall creates a tension load on the side closest to the ladder and compressive load on the side away from the ladder. Wind blowing against the side of a building on concrete block piers also creates tension and compressive loads on the column.
Steel reinforcing rods and steel wire will stretch if a high enough tension load is applied to it. But under normal design loads the steel will not begin to stretch. The steel will prevent the concrete from pulling part or failing under a bending load. Rebar has the bumps to allow the concrete to fully encase and grip the steel and not slip under load.
Quoting: xinull In the last 4 years, i haven't seen excessive winds that would concern me.
A similar type of thinking preceded this last week's record-breaking prolonged cold in Texas that resulted in frozen water pipes, low functioning natural gas electricity generation, nonfunctional wind turbines, etc. Meanwhile, the properly prepared power systems in MN and other states functioned fine. Need I say any more?
Lack of uplift prevention is one of the reasons foundations like this are not approved for habitable buildings codes. Do a search for mobile home anchors. Those would be better than nothing with a block column as you wish to build upon. Mobile homes are usually the first casualty in a high wind event.
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xinull
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# Posted: 19 Feb 2021 12:35pm
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Thanks for the explanation on the rebar strengthening the piers, that was pretty awesome and easy to understand.
Quoting: ICC Need I say any more?
No you dont I have no issues doing things "the right way". I'll definitely do some more research on various anchor solutions to tie everything down
thanks
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Brettny
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# Posted: 20 Feb 2021 05:50am
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How deep is your frost line?
If your going to do blocks and feel the need to attach them to the building why not just use bigfoot forums with a sono tube? You can cast in an adjustable anchor this way.
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xinull
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# Posted: 22 Feb 2021 10:29am
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any type of in-ground foundation is highly not recommended in my area. Even if they go past the frost line, there's too much movement. I've seen sonotubes at 45 degree angle that were about 6-7 feet deep, and that only took less than 10 years.
Everyone in my area is either converted or converting to on-ground foundation, piers using cinder blocks or railroad ties. The ones who have already had them have not seen any major movement.
It's also a little easier. The area is pretty remote. The road used to be more accesible in the past, as it was maintained. So back then, you could get heavy equipment on those roads. But not anymore. the roads are ravaged by years of neglect.
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Brettny
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# Posted: 22 Feb 2021 10:46am
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I would do the big foot footing ontop of the ground with an adjustment rod. It's just one solid block with a cast in anchor/adjuster.
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xinull
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# Posted: 23 Feb 2021 07:23pm
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not sure i understand the "adjustment rod", do you have an example?
as for the Big Foot Footing, you think that would be stable and durable enough above ground? I never thought or seen anyone using one in that manner
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Brettny
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# Posted: 23 Feb 2021 07:49pm
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https://www.homedepot.com/p/Simpson-Strong-Tie-EPB-Hot-Dip-Galvanized-Pier-Block-Elev ated-Post-Base-for-4x4-Nominal-Lumber-EPB44PHDG/100506799
As for the big foot footings there I think 24in at the base. Way wider than the 16x16 concrete blocks. No I haven't seen them used in this manner before either but it's a building on blocks. There just needs to be a way to spread the load transferred to the ground and a way to keep the load stable.
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WILL1E
Moderator
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# Posted: 24 Feb 2021 08:10am
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Do they make adjustable rods like the one you linked for built up beams, such as 3 2x's layered together?
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Brettny
Member
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# Posted: 24 Feb 2021 08:15am
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I'm not really sure on that Will.
Acme threaded rod is prety cheap and if you have a welder you could make your own adjustment rod. Or you could just use shims. It really depends on how fancy you want to get and how much you expect to have to adjust the level.
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