Slab Recommendation

[azpizzanut]

Hello All,

My build is a self designed 38" oven of brick. I'm ready to stack blocks for the top slab and need a recommendation for rebar reinforcement, or none at all. The inside, unsupported dimension, is 36 inches by 48 inches. The outside is 52" x 72". The slab will float without tie-in. The ground is stable, no frost heave and no geological faults.

The front opening will be supported by one row of block on top of two iron angles. I'll be using high strength 5000 psi concrete mix in bags from the local materials store. The form will be made of 2" x 6" wood but the slab will be 3 1/2" thick and poured over 1/2" cement backer board. There will be a temporary wood board placed in the center to hold up the backer board as shown in some fb forum photos. Am I doing this right or do I need rebar reinforcement? There seems to be controversy about this.

Second question: The materials store offered a variety of sand in grade sizes from 40 to 120 for the fire clay mortar. Is there a preferred grade for oven mortar?

I appreciate your guidance in advance.

Cheers

[azpizzanut]

Correction, the outside dimension is 52" x 64"

Cheers,

[Nic The Landscaper]

Your slab does need rebar, You should be making a grid, 12 to 18" on center with minimum 1/2" bar. The backer board is a waste of time and money, just pour the slab 3.5" thick with 5000 psi and your good to go.

[dmun]

The materials store offered a variety of sand in grade sizes from 40 to 120 for the fire clay mortar. Is there a preferred grade for oven mortar?

The mesh sizes for sand is the coarseness of the sieve: bigger numbers mean finer sand. I'd go for the fine stuff.

do I need rebar reinforcement? There seems to be controversy about this.

No controversy: only a few people wanting to put rebar in the insulation layer where it does no good. You need to reinforce your support slab.

[azpizzanut]

Thank you NicTL and dmun.

I found a site that shows how to tie rebar. I just happen to have the proper tie wire. I'd been using it for other projects. The top slab will have reinforcement.

Cheers,