Can the oven be built on top of pavers or do you need a concrete base slab?

[mandyk]

Hello,
We’re going to build the Mattone Barile pizza oven on a new paver patio that we’re getting installed within a few weeks. I’m a DIY rookie and need some advice. What is the best foundation option for the base in this situation? I’m very concerned with the aesthetics of the finished product and I want the base to tie into the paver patio cleanly, but ultimately I want it constructed properly so we don’t have problems in the future.

My paver patio contractor suggested that a slab wasn’t necessary, that we could place the base directly on the pavers and that he could beef up the gravel underneath of that area for additional support. We’re also planning to build a 36"W x 30"D counter and then we’ll veneer the whole thing so it appears to be one seamless unit so needless to say it will all be very heavy. We’re in central Florida so we don’t have the freeze-thaw concerns but the soil is very sandy. I am short in stature so we’ll be going with the 4 rows of cinder block rather than 5. Is the additional crushed stone under the patio that the contractor suggested acceptable?

I also looked at the option for installing the cinder blocks two rows below grade. I thought that might be easier for us to do ahead of time. Then we could have the paver contractor come in and paver around it so the pavers are flush against the base and there wouldn’t be unsightly concrete showing. I suppose we could also just pour the slab so the finished height is 2 5/8" below the finished height of the pavers and they could bring the pavers right up to the side of the base.

Lastly, if a concrete slab is necessary, does it really need to be 5-6" larger than the oven base on all sides?

I appreciate any help or advice you can offer. Thank you!

Mandy

[Gdogg]

I wouldn’t recommend installing on just pavers. They are not strong enough to support the weight of the block, the hearth and the oven itself. I poured a slab with a 2x6 frame and went an extra 2 in deep around the perimeter. I put a gravel base and then tamped it down really well. It also has rebar in the slab as well as extending up into the first course of block. This weighs about 10,000 lbs give or take when it’s done. pavers wouldn’t last long under that weight.

Good luck.

[bikerbudmatt]

Hi Mandy and welcome to the Brickwood Forums!

You are right to be concerned first about proper construction. It is possible that your contractor is well-meaning but does not understand how much of a load is being built up from the base. And, because your soil is sandy, you will want to have a very stable foundation sunk into that soil.

Think of it the way you would a small building. It needs to be anchored (by mass and depth) and it needs to be able to spread a U-shaped load over its entire surface. Your contractor does not have pavers that will do that for you; they will crack or shift , possibly before you are finished constructing the oven.

Of the options you mention, I would recommend building the slab to dimension as shown in the plans, and as you suggest below grade to let the pavers come up to the base. For that option you do want to allow the “margin” all around, so that your pavers are not affected by shifting gravel at the edge of the base.

I’d recommend you tell the contractor this, and that he should give you the exact depth the base should be so that your finished patio is at the correct elevation. (2 ⅝ may be it, but make sure that’s what he specified and that it is writing so there are no misunderstandings later.)

In the “for what it’s worth” department, I’m building a patio around my oven this season and because of the grade in that area we will actually be raising the grade around the oven to reach the slab, then laying finish materials over the slab. In effect it will be the same thing you’re doing, though I expect the work will be harder because of the amount of fill we will need.

Keep us posted on your project, Mandy! Sounds like it will be beautiful when it is done.

[kgondoly]

Hi,
Seventeen years ago I put in an 8’ x 8’ concrete slab for a hot tub (approx 5000 lbs of water and fiberglass) and butted a paver brick patio up to the edge of the concrete slab with about 4" of the slab showing around the hot tub. The hot tube store was clear that I should not put the hot tub on a paver base. I thought it looked OK and I found the concrete easier to sweep than the pavers.

Fast forward to today. The hot tub is gone, I’ve extended the concrete pad to include the oven and a bar and the paver brick patio is still there. The slab is still perfectly flat (one minor crack that appears very stable). The paver brick patio is no longer flat. It still looks really good but the line where the bricks are next to the concrete pad have sunk maybe 1/2 -3/4".

With that background I would favor sinking the base, using the specified size and then overlapping the paver on top of the slab. I agree with Matt about talking to the contractor about your plans. He may want you to sink it a little further so that he can add some slag sand to aid leveling the paver bricks.

Good Luck.

[mandyk]

Thank you all for your responses and expertise! Matt, I think you are right that the contractor probably just doesn’t understand the amount of weight we’re talking about and he’s used to people throwing small grill islands on top of their patios. We will go with the slab for sure. I’ll talk with the contractor to see what the finished height of the slab should be to allow for sand and pavers on top so he can paver over the slab right up to the edge of the base.

@kgondoly Thanks for your additional insight about the pavers sinking compared to the slab over the years. We have a small concrete paver patio now that we’re expanding and the contractor was going to go over that concrete with the pavers but now I’m going to opt to have that ripped out so we don’t end up with a ledge of pavers sticking up some day down the road.

Thanks again for all of the help! I have so many more questions so I’ll definitely be posting looking for more wisdom from the community!

[bikerbudmatt]

@kgondoly

Seventeen years ago I put in an 8’ x 8’ concrete slab for a hot tub (approx 5000 lbs of water and fiberglass) and butted a paver brick patio up to the edge of the concrete slab with about 4" of the slab showing around the hot tub. The hot tube store was clear that I should not put the hot tub on a paver base. I thought it looked OK and I found the concrete easier to sweep than the pavers.

Thanks for that story, Ken. We just removed a hot tub that was on a composite plank patio supported by 6x6 timbers (railroad ties). Very little shift, but it did have an effect.

It also reminded me that there is one other point: a hot tub spreads its load evenly over the entire surface where it rests. If the footprint is 8x8, the load is spread so that no one area is taking, say, 5,000 pounds of mass.

The oven is built on a U-shaped concrete block wall. The load is focused on relatively narrow points.

Pavers would understandably be crushed under that. The base slab (made of 4,000 pound per square inch rated concrete) can absorb that load and spread out the forces involved. In that way it acts more like the hot tub. The rebar matrix inside the base slab also helps even out the stress, and prevents it from cracking.

I appreciate the story, Ken, because the additional information might help in the discussion with the contractor. I’d be really happy if he learns something from Mandy, because it will give him an edge to offer his customers as well!

[jamanh]

You definitely do not want to place the oven on top of patio blocks. The blocks will sink and settle with the weight of the oven which will lead to cracking of the oven and base.
In the Mattone Barile gallery, page 4 I think it is, look at the Anhorn oven, that is mine.
I poured a 6" thick slab below the depth of my patio and once the concrete blocks were set for the base I leveled above the slab with gravel and sand and ran patio blocks up to the oven base to extend my existing patio around the oven. Cutting patio blocks is good practice for when you have to cut the oven brick.