36" in Seattle Brick Oven Photos Discuss 36" in Seattle in the Good Background Information forums; Yes, we want the pad to extend far enough in front of the oven to stand on while working. That's ...

[kebwi]

Yes, we want the pad to extend far enough in front of the oven to stand on while working. That's what you mean by apron? I'm not sure I fully understand the joint you are describing. Sometimes I see construction joints described merely as a shallow gap of about a quarter inch width that extends about a quarter of the depth into the concrete, not all the way to the bottom, as in two separate pours. Are you suggesting two separate pours with a gap that extends all the way down to the gravel?

Some detail would help. I readily admit I don't know much about proper concrete foundations.

Thanks.

[Neil2]

A construction joint can be one cut into the concrete or it can be simply the joint between two pours. Your slab will have two different loadings, one where you stand and the rest supporting the weight of the oven. This will cause stress which will almost certainly crack the concrete. The construction joint ensures it will crack at a particular line instead of irregularly.

If your slab is 5 1/2 inches, you can build the entire form, place the rebar, and use a 2 x4 as a "bulkhead" to contain the first pour. The re bar can run under the bulkhead or you can notch the bottom part of the bulkhead to accommodate the rebar. The next day, remove the bulkhead and pour the other half.

Get a concrete edger (see picture) and use it on the edge of your slab and each side of the joint

[kebwi]

It sounds from your description like you don't think I need an actual gap along the joint, since I think you suggested pouring the second slab right up against the first slab. Is that correct?

I certainly want to do this right, but the frustrating thing about breaking the pour into separate jobs is that I intended to do the foundation with ready-mix. There's no point in having then come out a second time for the smaller slab since that's smaller than the hearth which I'll be doing on my own anyway.

The question then becomes, is there any point in using a ready-mix truck for the slab under the foundation or is it now small enough (with the separation you suggested) that I should just go ahead and do it myself. I just don't have many friends I can lean on for this type of work, and I only have one wife.

That'll take some thought. I'll have to determine the best way to proceed.

Thanks for the input. I'll take it under heavy consideration.

[Neil2]

"I think you suggested pouring the second slab right up against the first slab. Is that correct?"

Correct.

This is the simplest way to ensure a construction joint. If you are going to do it in one pour, you can also use the edging tool and a 2x4 to tool in a double sided joint. This will create a stress line and should control the crack to that location. (Take a look at the sidewalk in front of your house - if you look closely you will see the crack in the tooled joint),

It is just an aesthetic issue and will not affect the structural strength of your slab.

[kebwi]

Cut the straight boards for the foundation form today from 2x6s. There are two places where I will curve the form with masonite. Grinding rebar is ridiculous loads of fun btw. After all my worries about rebar, everything worked out. I pipe-bend the 1/2" 20' rebar (barely with my 160lbs) in the Home Depot parking lot to get it on my roof rack. Then at home I cut it up with the grinder, which is a cinch.

On a side-note, do most people put the handle of an angle-grinder on their "handed" side or the other side? I've tried it both ways for this project (and also used angle grinders at a rock-climbing gym a few years ago), and still haven't decided on my preference. Thoughts?

[kebwi]

@Neil2: I warming up to the idea of doing the foundation myself over two days, using your suggestion of pouring the main foundation one day, framed off tightly around the building's footprint, then following up the second day with the extended chef's slab (in the diagram, both red and green are concrete). My calculations put the main foundation at 37 60lb bags if poured 5" and the extended slab at 16-22 60lb bags if poured somewhere between 3.5" and 5", which leads to this post's question...

Do you think it would be okay to pour the main slab to 5" but raise the gravel in the "extra" slab an inch and only pour it to 3.5" to 4"? The rebar and mesh (mesh not shown) will actually connect the two slabs into a single piece even though the concrete won't be bonded along the seam.

What do you think?

[papavino]

I would think it would be okay to raise the gravel and only pour a 3.5 or 4 inch slab for the chef's slab. It's not going to be supporting the weight of the oven, so unless you weigh 6000 lbs, I think you'll be alright. Why not buy 80 lb bags of concrete and save some dough? With the amount in a slab, that money adds up.

[kebwi]

Home Depot and Lowes both currently sell 60 lb bags for $1.98 ($.033/lb) and 80 lb bags $3.48 ($.0435/lb). I think the 60 lb bags were just recently marked down from $2.98 ($.0497/lb), so the discrepancy is recent and perhaps temporary.

Therefore, I gotta stock-pile like mad!!!

[papavino]

That's a good deal, then. I wish they had been running the sale when I built mine. Buy! Buy! Buy! Buy more than you need. Because even though your calculations tell you you need X, you'll really need X+Y bags. And you can return any unopened bags.

[Neil2]

Yes, the apron can be thinner.

Looking at your plan, I would also put a tooled construction joint between the two sections of apron. Maybe at a 45 degree angle through the "thin" section of apron.