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Concrete block foundation.

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Concrete block foundation.  (post #214952)

I've come across a deal on 1500 10" concrete blocks that have the webs pre scored at a very cheap price. I am thinking of using these blocks to build a basement on a summer home. I would be doing things different tho, I was going to knock out the pre cut webs and dry stack them and surface bond them and fill all the cores with concrete just like insulated forms. I would rebar ever course of block as well as rebar each core and use a 4000 psi concrete. What's your thoughts and concerns on this. 

About 25 years ago I worked (post #214952, reply #1 of 11)

About 25 years ago I worked on a Habitat project in Colorado where they used dry-layed concrete block and then "grouted" it (their term) after installation using a pumper setup.  This scheme worked well, using unskilled labor to set the blocks. 

But the blocks were not normal ones but had a sort of tongue-and-groove arrangement for stacking.  Don't know how this would work with normal blocks.  At the very least some temporary bracing would be required.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

I even thought of using a few (post #214952, reply #2 of 11)

I even thought of using a few dabs of construction adhesive to lock it together while building it up. 

I see no reason that it (post #214952, reply #3 of 11)

I see no reason that it wouldn't work but I'm laways wary of "good deals" like this that may end up being terrible deals. For instance, will they deliver that 24 tons of blocks because if you have to move them yourself the 'good deal" becomes a terrible deal. Do you have experience laying blocks because if not this job could beat you. 10" blocks weigh 32 pounds each and are usually laid using 2 masons to lift them. When you get to the top they aren't going to be nice and level like blocks set in mortor but will rise and fall and need a tie beam of some sort to make them flat.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

At .25 cents a block and 250 (post #214952, reply #5 of 11)

At .25 cents a block and 250 for delivery it's a steal, I myself am always  skeptical of ideas outside the box, but I'm always open minded to ideas that come with this kind of bargain. As for the weight they are heavy blocks at 48 pounds. I also forgot to mention when I pour these with concrete I was going to form it for a 4" cap / bond beam. I was also able to buy a hundred 20' 1/2" rebar for 2 bucks a pop, so it's not a big expense to load it up with rebar. 

what withstands the hydraulic pressure of the grout? (post #214952, reply #4 of 11)

When I've grouted block columns, there's an enormous amount of pressure from the concrete filling the cavity. Not to mention, all the gaps will leak like severed arteries. Mortar that has set up for a bit can withstand all those pressures. I can't imagine drystacking being able to, unless you used a really stiff mix (which will leave lots of voids). Curious if anyone has done this successfully before.

When you are grouting a high (post #214952, reply #11 of 11)

When you are grouting a high wall the grouting can be done in lifts and not all in one pour. Grout is not the same as concrete or mortar it is far more viscous and will pour in easily and not leave any voids. You still need to set the blocks in mortar and you may still need hoizontal joint reinforcement.

right, with mortar (post #214952, reply #10 of 11)

exactly. you mortar the blocks and then fill the cavities. But without the mortar, the grout's going everywhere, it seems to me

I plan on surface bonding (post #214952, reply #6 of 11)

I plan on surface bonding both sides of the wall, as for filling the blocks, I'm not going to use grout, I'm going to use a pea gravel mix used for ICF forms. 

Speak to an engineer. Grout (post #214952, reply #7 of 11)

Speak to an engineer. Grout is the normal product not peagravel

You misunderstood what I was (post #214952, reply #8 of 11)

You misunderstood what I was trying to say, I would be using a pea gravel concrete mix. 

Grouting block (post #214952, reply #9 of 11)

We grout block here as a standard practice and they use regular pump mix concrete. Our code does require #5 rebar tho. You dowel the grouted cells with one continuous (lapped and tied for 48x the diameter)  #5 from the hook at the top to the hook at the bottom, tied to the horizontal #5s. The horizontals in the foundation and bond beam are #5s too.

It will ooze a bit on a dry stack but the concrete is not gushing out. I just did it a few weeks ago with a dry stack of 16" column block. The grout was 3000 gravel mix at around a 5 slump

Greg