Concrete block shed foundation

[dta1984]

I'm building a 12'x16' shed and the area I'm putting it has a slight slope. I am using 4" thick " 16" L solid concrete blocks to help level. At the lowest point, I need to stack 2 of these blocks on top of each other. This method seems to be pretty common when I look around. I'm digging a few inches of the soil out, tamping, adding gravel and tamping again before sitting the block on top.

What I'm not sure of is if I need to put some kind of adhesive between the 2 blocks or not? Seems like they would be prone to sliding, but maybe not once everything is built in top?

 

[NUTTSGT]

Once it's built and has weight on it, it shouldn't move. However, adding some adhesive should keep it in place while you are building it. A few bucks in adhesive might prevent some frustration while you're in the construction phase.

 

[CJ7VFR]

...A few bucks in adhesive might prevent some frustration while you're in the construction phase.

Oh yeah!

There is nothing like setting the blocks up nice and even with each other, and then come to find that when you put the shed on the blocks one of the blocks moved a bit when you were not paying attention.

The blocks might not move much, but once the shed is in place it ***** to have to try to align the blocks back up.

Jim

 

[strutaeng]

I'm building a 12'x16' shed and the area I'm putting it has a slight slope. I am using 4" thick " 16" L solid concrete blocks to help level. At the lowest point, I need to stack 2 of these blocks on top of each other. This method seems to be pretty common when I look around. I'm digging a few inches of the soil out, tamping, adding gravel and tamping again before sitting the block on top.

What I'm not sure of is if I need to put some kind of adhesive between the 2 blocks or not? Seems like they would be prone to sliding, but maybe not once everything is built in top?

Are you thinking laying them dry? I would not use adhesive!

Are the blocks going to be your foundation? If so, there should be a continuous concrete footing or "footer." Do you have to be below the frostline?

The 4" CMU are typically used for non-load bearing wall and veneer. They are actually 3 5/8" wide. 8" CMU is usually used for this application, but I suppose for only 2 courses 4" is okay, but you need to use mortar. Fill the cavities with mortar and set sill anchor bolts in place.

https://www.archtoolbox.com/materials-systems/masonry/masonry-mortar-types.html

Home centers usually sell "mortar mix" that has everything already blended together, just add water.

https://www.homedepot.com/b/Buildin...Concrete-Mix-Masonry--Mortar-Mix/N-5yc1vZcdq4

Watch a Mike Haduck video on YT:

Good luck

 

[Kaizen]

As is the gj way I’ll suggest something else - use single 8x8 or 8x16 blocks. The ones with holes in them. Use every four feet esp in the middle. Get it up off the ground by several inches. This will allow air under it and keep it dry. These blocks are plenty strong. Did it this way and stacked four tons of pellets with no issues. Start with the downhill blocks and dig in as needed as you go into the hill. Roundup the grass and just need to dig around the block. Not the whole thing unless it buries itself into the hill. Lay galvanized small mesh between the blocks so animals won’t burrow in there. Frame and build floor on blocks and they won’t move. Have the corner blocks out an inch or so Incase ground heaves the shed could move a little and you don’t want it to fall off block


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[dta1984]

Once it's built and has weight on it, it shouldn't move. However, adding some adhesive should keep it in place while you are building it. A few bucks in adhesive might prevent some frustration while you're in the construction phase.

Thanks! That's what I was thinking, the adhesive will just help hold things in place while building and framing.

 

[theoldwizard1]

I'm digging a few inches of the soil out, tamping, adding gravel and tamping again before sitting the block on top.

The deeper you make this layer the less likely it will rise/fall during the annual freeze thaw cycle.

What I'm not sure of is if I need to put some kind of adhesive between the 2 blocks or not? Seems like they would be prone to sliding, but maybe not once everything is built in top?

I agree with the others. One or two beads of construction adhesive is a good idea.

Depending on where you live and what "varmints" are in your area, a dark air space under a shed is an excellent home. You have 2 choices, add more blocks so that there is air and light under the floor or before you lay down the gravel, place about a 3' wide piece of galvanized chicken wire. The varmints can not dig through it.

 

[BD1]

I leveled where the concrete blocks were going as my foundation . Only a single layer that was done 35 years ago for my 10'x16' she'd. Only 7' walls and it's still sitting perfectly level. I built it "temporary". [emoji23]



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[dta1984]

Those that have done concrete blocks, any issues with freeze/thaw?

 

[RSr]

I'm building a 12'x16' shed and the area I'm putting it has a slight slope. I am using 4" thick " 16" L solid concrete blocks to help level. At the lowest point, I need to stack 2 of these blocks on top of each other. This method seems to be pretty common when I look around. I'm digging a few inches of the soil out, tamping, adding gravel and tamping again before sitting the block on top.

What I'm not sure of is if I need to put some kind of adhesive between the 2 blocks or not? Seems like they would be prone to sliding, but maybe not once everything is built in top?

This is EXACTLY how I installed my shed foundation. When you get to the section where two rows are needed for height just stagger the bottom row by half a block so each top block rests on two halves of lower blocks. I didn't install any construction adhesive and didn't have any problems with movement during construction. Sheds been up on it for 4 winters and it's holding up well. That being said, a flexible adhesive couldn't really hurt.

 

[BD1]

Those that have done concrete blocks, any issues with freeze/thaw?

None what so ever. I'm in Northern Illinois and it's the same as when I built it.


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[Kaizen]

Those that have done concrete blocks, any issues with freeze/thaw?

As I described it I never have an issue


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[dta1984]

Thanks everyone for the responses!

 

[u2slow]

Mine was a little different. My shed/carport (20x20') is wholly supported on 9 posts. The walls aren't load-bearing. I used dry stacked concrete blocks (6" thick) for two rows before building my 2x4 & plywood 'filler walls' on 3 sides.

We'll see how it performs over the winter.

 

[dta1984]

Rather than start a new thread, I figured I'd ask a slightly different question here. Should I be concerned at all parking my garden tractor in here during the winter after plowing snow? The floor is all pressure treated, but melting snow will surely be sitting on it. Maybe I should add a sacrificial floor on top where it will park?