Foundation Question

[njforno]

after many false hopes of starting, looks like we are going to get going! i have a foundation question. i live on northern nj, and i want to do a floating slab for my corner install. it will include a gas bbq and a counter as well. i am going to build this in the corner of my patio. my main question is do i need to install sonotubes for the foundation b/c it is adjacent to my paver patio? or can i be safe with the floating slab on top of 6 inches of qp, and 2 inches of sand on top of that? thanks. here are a couple of photos of the area:

[irelande5]

Re: Foundation Question

This is a question that has a lot of differant opinions here......I live in Ohio and went with sonotubes, better than nothing, not as sure as footer, good luck.

PS mine survived a nasty winter here, no movement whatsoever

[njforno]

Re: Foundation Question

thank you. i have researched it on the forum. i think that where i live, a floating slab will be fine. but uncertain if i need to use the sonotubes or not, because it will be located next to my paver patio. i have to make a decision

[stonecutter]

Re: Foundation Question

Question...what is qp?

I'm assuming it's aggregate with fines or something like it. Your slab and base prep will vary depending on your subsoil. Generally, you can get away with 6"-8" of compacted base and a 6" reinforced slab in freeze/thaw areas. I went deep with all the ovens I built in CT except one, because it was on top of ledge.

My current build here in SC has no footing other than 8" of compacted granite dust.

[stonecutter]

Re: Foundation Question

Forgot to mention, the most stable base is washed, crushed stone. Use 1/2"-1"


Oh and don't put any sand under a concrete slab..reserve that for pavers.

[Faith In Virginia]

Re: Foundation Question

One thing to keep in mind with a slab is the larger the area and differential of load the slab has a potential to crack. So, you may want to put some stress cuts in the slab. Separate the heaver load of the oven from the lighter counter and BBQ. This way if there is any movement it will crack along the cut lines.

[brickie in oz]

Re: Foundation Question

One thing to keep in mind with a slab is the larger the area and differential of load the slab has a potential to crack. So, you may want to put some stress cuts in the slab. Separate the heaver load of the oven from the lighter counter and BBQ. This way if there is any movement it will crack along the cut lines.

They put expansion joints in slabs over here to allow for the heat, I suspect your/our joints in slabs are very similar?

[Faith In Virginia]

Re: Foundation Question

Sure do Al, was thinking with a slab that size 50/50 with one side with oven load and one side counter on the other the possibility for a crack is great. As you well know if you "weaken" the slab with a cut or score a line if a crack wants to develop it will usually crack along that line. Don't see much reason for an expansion joint here on this slab.

[njforno]

Re: Foundation Question

thanks for the replies! stonecutter, "qp" is exactly as you say. it stands for "quarry processed" stone around here. i have 4 inches of compacted 3/4' to 1" qp mixed with fines compacted under my patio. i plan to do 6-8" under the oven. thanks for the tip about the sand.

faith, thanks for the tip about the stress cuts. would this be better than expansion joints? and how exactly do i do either of those? a thin piece of wood between the oven and bbq/counter area of the slab? thanks again

[stonecutter]

Re: Foundation Question

Those kinds of joints are called Control Joints. Here is a link with concise information about them.

Control joint info

[stonecutter]

Re: Foundation Question

Here is something on Expansion Joints.


Tech Questions

The difference between the two is controlling forces that are applied to the slab. Expansion Joints for movement (also for extreme temps that effect the slab...ie: what brickie mentioned)

Control Joints for static pressure and possible cracking during the cure phase.

[njforno]

Re: Foundation Question

Here is something on Expansion Joints.


Tech Questions

The difference between the two is controlling forces that are applied to the slab. Expansion Joints for movement (also for extreme temps that effect the slab...ie: what brickie mentioned)

Control Joints for static pressure and possible cracking during the cure phase.

thank you. this has been extremely helpful!