Slab Help! Need advice before I start

[okn]

Hi everybody. So I finally decide to start the process of planning my oven. Got wife buy in , went and got city buy in , and then I started to lay this thing out. Wow... just a little bit bigger than I thought. The issue is, as you can see from the photos, my slab will be half on an existing slab. At first I said great, less concrete to pour, then I thought I should check how level it is. Well, it slopes about a 1/4 inch for the entire run. Not crazy out of level, but definitely not spot on either. I already knew I was pulling that palm and some roses, but what about the slab, is this something I can work with. I have know idea how the patio was poured or made. So please give me some advice! BTW I'm planning a 42"... maybe I should go smaller? I would love to hear the thoughts of the experienced out there.

PS I will be buying the HF 10" tile wet saw (their best one) tomorrow at their parking lot sale for 189.99. Stop me know if. it's a bad idea

[aceves]

Re: Slab Help! Need advice before I start

Hi okn,

You have a couple of options:

1) Rent a jackhammer and break up part of the existing slab that you have marked off as part of the oven slab outline, this way you can pour a level slab for the entire oven. This is more time, money and labor. This would also give you 2 different level slabs.

2) Pour a half slab just as you marked it with the same slope/decline as the existing slab. You will not have to break up the existing slab at all, just pour a new one that will "extend" the current slab and slope. This would be my personal preference and my advice to you.

The reason for the existing slab's slope is for water run-off when it rains. You only need a very slight slope. Once your half slab is poured, you will set your concrete blocks over both slabs and they will also have the same slope as the entire slab. Once all this is done, you will then pour a LEVEL hearth that will even everything out. Meaning that although your slab and stand have a slight slope for water run-off, your hearth and oven will not have a slope if you pour a very level hearth.

This is what I did on my build. I poured a complete slab with a slight slope to the back. The blocks were set up and completed with the same slope, and then I leveled my wood forms in all directions and poured a level hearth. You will be the only one that knows that there is a slight slope on your foundation slab, and to the naked eye, everything looks level.

Please note, this is a very important step: You will have to cut a groove/channel on one of the rear blocks for the water to "escape" from inside your stand, otherwise you will have water pooling inside your wood storage area. What I did was cut a groove in one of the first blocks (touching the slab), stuck a piece of 1" metal pipe in the groove (same length as the block), and voila, an access for the water to run through the stand if it rains.

Hope this helps.

About the HF saw, I cannot comment on that, as I am using a borrowed saw and have no idea if the one you're getting is a good deal. Any other members care to comment on this issue?

aceves

[Neil2]

Re: Slab Help! Need advice before I start

"I have know idea how the patio was poured or made."

I would assume that the existing slab was made/designed for its current purpose as a patio slab. Therefore it would not likely have been reinforced much if at all (unless it was built by some nut like me).

This will probably crack if partially loaded with the proposed oven.

My advice would be, for the footprint of the proposed slab, to cut the portion of the existing slab out. You can do this with an angle grinder and straightedge or rent a concrete cutter to make the clean cuts then jack hammer/impact hammer out the concrete.

Then pour a monolithic reinforced slab for rectangular area outlined.

As for grade, this is not critical at this point. Any leveling as required can be made up in the block wall as you go. Note that it is advisable to have your final suspended hearth slab surface sloped to drain. A slope of somewhere in the order of 0.5% will do the job and will be unnoticeable.

[PizzaIdiot]

Re: Slab Help! Need advice before I start

There might be another option.
Its hard to tell from the picture the actual dimensions of the pad, but if it's a 42" oven it is probably 73"x86".
Since the oven is round and there is a lot of empty space in the back corners, you might be able to 'trim' the back corners and move the oven further back towards the corner. It would over where the tree is now and you'll wind up with a 5 or 6 walls rather than 4.