Attaching concrete block to slab

[toyotadriver]

I have a question about attaching concrete blocks to a slab.

I am going to be building a wood stove base for a small wood stove in the basement of my new house. I'm planning on putting down 18 8x8x16 concrete blocks (48x48) and then covering that with a layer of durock and then putting down slate tile.

It will not be structural..just needs to not move.

Do I need to use cement or will concrete adhesive work for this purpose?

 

[rburke65]

Well....no mason here but I'm thinking in your situation the old both function well. I'm sure you will get more professional replies. Good luck. Ya might consider putting your location in your profile.

 

[macdabs]

Just make sure the surface is clean, may even rough up the concrete with a grinder where the block is going and use regular mortar mix and it will stick..

They do sell bonding agents to go in the mix, but you would be wasting your money for such a small job. Also apply a coat of tile cement (Thin set) four your durock board and let it sit overnight before you tile. Make sure you wet the block with a sponge cause the pores in the block will soak the water quickly and the tile cement needs to bond at a slower pace.

 

[dutchgray]

Mortar and gravity is all you need to hold the blocks in place.

 

[GTO]

Mortar and gravity is all you need to hold the blocks in place.

This^^^^^^^^^^^^

 

[acer66]

Mortar and gravity is all you need to hold the blocks in place.

This and if the floor needs be worked on I would just use a hammer and a chisel or a hammer drill,
to keep the dust in check.
Regular drill with a masonry bit might do the job also.

 

[Dagny]

what if you put mortar or thinset between cement board and blocks and none on the bottom. the whole thing would be to heavy to go anywhere and if you ever want to remove it a lot less work.

 

[KELLHAMMER]

For light loads , drilling 1/2" dia holes in the slab and placing rebar in them
Place the block with the cell around the rebar. Fill the cell with concrete. Space the bars every couple of feet. Typically we refer to these bars as dowels. Which may only go a couple of inches into the slab and protrude up into the first coarse of block. This is basic installation to help lock the block to the slab and keep it shifting. A higher lateral load or uplift would be a more involved detail.

 

[NUTTSGT]

For light loads , drilling 1/2" dia holes in the slab and placing rebar in them
Place the block with the cell around the rebar. Fill the cell with concrete. Space the bars every couple of feet. Typically we refer to these bars as dowels. Which may only go a couple of inches into the slab and protrude up into the first coarse of block. This is basic installation to help lock the block to the slab and keep it shifting. A higher lateral load or uplift would be a more involved detail.

This is what I would be doing.

Overkill, maybe, but I like overkill.

 

[PeterT]

If the concrete is really smooth either rough it up or maybe easier(as mentioned above) a few spaced out 1/2 pieces of rebar drilled into the existing concrete, then filling those bottom few cavities with some block core mortar. Maybe put one in each corner and in the middle of the long side. Other than that, just mortar the bottom layer with the existing concrete.

 

[LightningBG]

I'd probably skip the concrete all together.

I'd build a box out of 2x4s or 2x6, attach it to the floor with tapcons, or a .22 concrete nailer, or adhesive. Sheath it with a layer of 3/4 ply on the sides and 1 or two layers of 3/4 ply on the top. Attach your durock to that and tile normally.

If you were to build this box out of concrete blocks, how are you planning on attaching the cement board to it?

 

[toyotadriver]

I'd probably skip the concrete all together.

I'd build a box out of 2x4s or 2x6, attach it to the floor with tapcons, or a .22 concrete nailer, or adhesive. Sheath it with a layer of 3/4 ply on the sides and 1 or two layers of 3/4 ply on the top. Attach your durock to that and tile normally.

If you were to build this box out of concrete blocks, how are you planning on attaching the cement board to it?

Either adhesive or mortar to attach the cement board to the blocks.

I've thought about the wood base as well. Guess I just like the idea of concrete under a fire source....even though I know the wood base would work too.

 

[matt_i]

Id try to group the blocks. Either drill them and bolt the hollow sections thru, or you could chip out parts of the webs and pour some quick crete in the centers.

 

[theoldwizard1]

Clean, damp (so the mortar does not dry too quick).