Concrete Pad for Evaporator

[SeanD]

I'm breaking through my thin, old floating slab to make a concrete pad for my evaporator to sit on. The firebox base is a little over 2' x 2'. I'm planning a pad that is 3' x 3'.

How much stone would you recommend and how thick a slab?

Is 6" of stone with a 6" slab on top enough?

Sean

[n8hutch]

That should be sufficient. Knowing your existing slab is only 2" thick you could run some rebar under your existing slab in all directions to keep your new pad tyed into your existing slab, normally we would drill the slab and pin it that way.
Then again maybe you want it to float independently of your existing slab

[ScottyWelden]

I've done a number of slabs--usually 4" on 6-8" of compacted gravel. I always use reinforcement screen--never a crack.

[MISugarDaddy]

You may want to consider making the slab large enough to support the entire evaporator, not just the firebox base, so that your evaporator stays level.

[n8hutch]

I have had good luck keeping slabs from moving by putting 2" of rigid Styrofoam underneath.

[maple flats]

I went down below frost level, poured 2 pads, a 4x4' for the firebox end and a 4' x 2' for the back legs. Then I laid up concrete blocks and capped it all with 6" re-inforced (rebar) concrete. If you use a floating pad, it can shift and you will need to recheck the level and correct as needed and when needed.

[SeanD]

Thanks for the responses. Turns out I won't need to put in a new base after all. The whole area under the evaporator is solid ledge about 3" below the top of the slab and about the size of a Honda - so far. They poured the slab right on top of it. The voids I was hearing were areas where they left or put sand in. It drops off as I move a few feet from the evaporator, but I'm stopping there for now.

The amount of fill I'm going to need will be very little in the end. I'll have some crusher run left over from another project I'm doing. Can I use that instead of 3/4" stone? It would be nice to take care of two projects from one pile of fill.

Sean

[maple flats]

crusher run makes great fill, and it packs nicely.