# How do I attach first course of cinder blocks to a concrete slab?



## HotRodx10 (Aug 24, 2017)

The typical way I've seen that accomplished for a building that's already built would be to cast rebar into the slab that extends up out of the slab about 7" above the slab, aligned with the center of where the openings (cells) of the blocks will be. Then, when you set the blocks, you fill the cells that have rebar with cement grout. This allows you to set the garage on the blocks and then drill holes through the sill plate and into the grouted cells to install wedge, sleeve or epoxy anchors after it's set in place and aligned.

The threaded rods seem like they would work also, but it may take some jockeying around to get the holes in the sill plate aligned with the threaded rods. With this approach, it's best to grout around the threaded rods, so you're not relying on tension in the threaded rod to keep things from shifting.


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## Distriived (Dec 4, 2020)

Thanks for the reply that sounds like it would work best for the company moving the garage since there are already existing holes in the garage sill. Then they'd just have to redrill the holes and anchor them. Do I use the same grout that I fill the blocks with to set the blocks in then?


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> The typical way I've seen that accomplished for a building that's already built would be to cast rebar into the slab that extends up out of the slab about 7" above the slab, aligned with the center of where the openings (cells) of the blocks will be. Then, when you set the blocks, you fill the cells that have rebar with cement grout. This allows you to set the garage on the blocks and then drill holes through the sill plate and into the grouted cells to install wedge, sleeve or epoxy anchors after it's set in place and aligned.
> 
> The threaded rods seem like they would work also, but it may take some jockeying around to get the holes in the sill plate aligned with the threaded rods. With this approach, it's best to grout around the threaded rods, so you're not relying on tension in the threaded rod to keep things from shifting.


Good plan here.


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## Nealtw (Jun 22, 2017)

Distriived said:


> Thanks for the reply that sounds like it would work best for the company moving the garage since there are already existing holes in the garage sill. Then they'd just have to redrill the holes and anchor them. Do I use the same grout that I fill the blocks with to set the blocks in then?


Way not have him pour a concrete curb at the same time.


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## Distriived (Dec 4, 2020)

Nealtw said:


> Way not have him pour a concrete curb at the same time.


He said he doesn't do that. Maybe I'll call other contractors.


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## Nealtw (Jun 22, 2017)

Distriived said:


> He said he doesn't do that. Maybe I'll call other contractors.


Who is building the forms?


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## Distriived (Dec 4, 2020)

Nealtw said:


> Who is building the forms?


The same construction company who's pouring the slab.


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## b.rooster4321 (Apr 22, 2020)

If the existing garage has 8 foot walls already without the course of block you don’t need the course of block unless you just want a taller in the studs are now


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## XSleeper (Sep 23, 2007)

A course of block gets the siding up above grade so that it doesn't rot. Most siding should be a minimum of 6" above grade.


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## HotRodx10 (Aug 24, 2017)

Distriived said:


> Do I use the same grout that I fill the blocks with to set the blocks in then?


I think you _can_; I don't know if you'd _want_ to. I just know the grout for the cells should be a cement _grout_, rather than a _mortar, _which is a lower-strength product that's usually used for setting blocks. I haven't really worked with either one personally, so I'm not sure if the grout is significantly more difficult to work with than mortar. Hopefully, someone more familiar with masonry construction can enlighten us both.


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## Boogity (Nov 30, 2020)

Don't forget the doors. You don't want to step or drive over an 8" block under the doors. Your new foundation layer needs to match the existing layer height. Think it through and plan ahead carefully. 

I have done something similar and I poured a flat slab. About 4"higher than grade. Using an electric hammer I roughed the concrete surface around the perimeter. Cleaned that surface really good. Then layed my course of concrete blocks, not cinder blocks, with mortar. I left openings at the doors. I filled all of the block openings with concrete and fastened the 2"x6" base plate of the wood framing with 1/2" diameter concrete expansion anchors about 48"apart. That was 20 years ago and it still looks like a new installation.
I didn't mean to get so wordy, sorry.


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## 3onthetree (Dec 7, 2018)

You need to consider how you are moving the garage first. You obviously aren't dragging it with 3 stall openings on one wall. What I am picturing without any info:

So if it is raised onto beams, and the dollies for those outrigger beams will roll clear outside of your new foundation, then you can rebar the CMU course into the slab first, and the garage will just move over top of it and then set it down.

If you are using another method, where the moving dollies/implement will need to roll on top the slab to place the garage, then you cannot have any stem wall pre-built. You will have to place it, build temp shoring to keep it raised, then drill the rebar/anchors into the slab and place the CMU afterwards.


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