Hi, I’m beginning the journey of building the grande, and once I saw the list of 64 count concrete 80-60 lb bags, I would rather have a truck come in and pour the base and the 3-piece slab all with 4000 or 5000 PSI concrete. Then I could build the block walls with rebar and when ready have a truck come back out and pour to fill the core. Anyone ever done this method? I would think it would save a lot of time, maybe more expensive but worth it I think. I am an amateur so please correct me if I’m missing something here. We have a cement manufacturer business a mile down the road and have used them before to pour shed slabs and a patio. Eh? Thanks for any advice.
We did have someone come and pour the slab for us, we did the rest. In hindsight we would have also had them come back and fill the core. It turned out alright, though had to do a little patch work.
We built a mattone barile next to an outdoor fireplace. Both were built atop a contractor-poured concrete patio base. We’re glad we didn’t do that ourselves. The core of the 3 piece slab needs to contain an insulating material so having a contractor pour that with concrete would be problematic. The three piece slab (took four 80 lb bags of cement)wasn’t difficult to pour into the molds but what WAS difficult was lifting those 3 pieces onto the block walls. There are a lot of comments about this which you can review. Some folks used a rented hoist. Others used some really beefy guys. We (my wife, teenage daughter and I) used a combination of our compact tractor with forklift attachment and the winch on our ATV. Be sure to note the difference between using perlite vs. vermiculite (retains moisture longer than perlite) if you use the mixture instead of using castable refractory.
Hi @DocM. I think you’re right on both counts: you certainly can have a load of concrete brought by a truck, and it will without doubt be more expensive. Some of it depends on how close your build is to a concrete plant—and you’re very fortunate to have one so close by. I’ve heard there is the possibility of getting a “short load,” but you’re paying for the delivery crew and the mileage more than you are for the material.
In my own case, I poured the base using a rental mixer from the orange store. Of course that’s only about a third of the concrete needed. My solution was to purchase a mixer from Harbor Freight, on the “Soup Nazi” theory (“I don’t need your soup. I can make my own soup!”). I do not recommend this for anyone lacking mechanical ability. I am very average in that regard (although I’m one of those weirdos who absolutely enjoys assembling Ikea furniture), and it was a challenge to decipher the (incomplete) directions and match them up with the ill-fitting parts in the box.
But hey! it’s supposed to be an adventure, right?
If you use the truck, you’re going to double your already-expensive cost for concrete by having them come back just to fill the block cores. I’d suggest that you purchase 10 60-pound bags of concrete, and mix just those in the wheelbarrow. It’s not as hard as it might sound, and it will allow you to use the recommended method of filling all the cores on the first row of blocks, then proceeding to the second level.
You could fill everything at once, as you’re proposing, but that means standing with a sounding rod and making sure all the air voids have been worked out of the bottom row—from four feet up. The delivery drivers will NOT do that for you; that’s your job. They will be under pressure to get your VERY short load out of their truck and back to the plant, because they have about a 1 hour window from the time the truck is filled. So they will not want to hang around and watch someone working with concrete for the very first time (right?) trying to poke their stiff product into tricky holes.
On the bright side: you are already mixing mortar and have tools at that step, so you will gain a lot of satisfaction (and admiring looks from family and friends) if you also mix and pour this small amount of concrete.
I wish you the best with your project, and hope to see pictures when you’re ready!
@Peter — the slab lifting is definitely the weak point in this process; although it has to be said that the alternatives are worse. We used a combo of rented hoist (which got each slab to the right height) and beefy guys (which got it into position). In hindsight, one more beefy guy could have saved us $80 for the hoist. We used an appliance dolly to move the slabs from where they were poured to the staging area.
And thanks for mentioning the perlite! I remember you had regrets about the Vermiculite and wished you had known before you used it.
@Patricia, did you deal directly with a “ready-mix” plant, or with a contractor? It sounds like you weren’t completely happy with the job that was done. (I’m not completely happy with the base slab I mixed and poured myself, either. I have some patchwork to do on the top, and we’re planning to face it with some hard flat material.)
@bikerbudmatt - thank you for all the great information. Makes a lot of sense. Its really nice to be able to chat with people who have done this before. Do you think it would be ok to use 5000 PSI for the base slab along with the hearth slab? I would have to if I have the mixed concrete delivered. How much does each section of the hearth slab weigh? I would be laying the hearth slab frames on a back patio that’s partially covered from a deck above. If its covered appropriately some rain washing down on them would be ok right?
The instructions says 20 60-pound bags. Is this if you want to fill all the holes?
So you used 4 80-pound bags for all 3 hearth slabs? Yeah I will do the perlite mix myself. How much do you think each hearth slab weighs? This is all great information. Thank You.
Yes. You’re just making a much stronger slab than absolutely needed.
I estimated that each slab weighed about 420 pounds.
As for rain, I did my forms on a level patio that was not covered, and instead covered the slabs with polyethylene (painter’s plastic). It’s helpful to the curing process to cover them the first couple of days anyway, because you don’t want them drying too quickly. (You also have to water them occasionally…I got them mixed up with my spouse’s garden at one point! ) I’d recommend placing the forms on spare 2x6s to give you a little “purchase” space underneath. They’ll be easier to move than if they are flat on your patio.
Once they are cured rain is not going to hurt them. It will eventually take a toll on the base of the form, if (like mine) it’s going to be a while before you can remove them from the forms and set them into position. If that’s the case just be cautious when you first start moving them.
I found that just over 2 bags was enough to fill all the voids on a course, and I did five courses. (Six seemed to place the oven too high for our use.) My manifest for concrete was 70 60lb bags, for frost-proofing sills, base, slabs, and block fill. I ended up with about 16 bags left over when everything was done, but should point out there is an allowance of 8 percent built into the materials lists.
We were very happy with the slab, poured by the contractor. We were not as happy with the filling of the core. Our first layer must not have been mixed quite right…we pounded it down however there were a couple small pockets on the corners. We were able to fix. Neither of us had concrete mixing experience. Either way we will have great pizza! Had to cover it up for the Winter as we didn’t quite get it finished, so excited for the spring thaw.
We are in the same boat as you. These cold months are making me hungry for spring—in more ways than one.
Thanks for clarifying the dissatisfaction. It confirms my thought about what it would be like to try to get concrete into those cores after all the blocks were laid. I confess I cheated and did concrete after laying two courses. It was worth it mixing mortar for two, then changing over to concrete and filling voids. It was also easier because I could see directly down into the core of the lower course each time.
Hope things warm up soon and best wishes for your bulld.
Sorry, each slab took almost 4 x 80lb bags, which is why they were so heavy and challenging to lift.