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GreatForge t1_je3jjx5 wrote

Just to be technical, what you are asking about is an isolation joint, not an expansion joint. It never hurts to add one in this scenario, the main reason being differential settlement of the two slabs causing cracking if they can’t slide past each other. You can use impregnated asphalt isolation joint or a couple layers of 30 lb felt paper. Make sure you compact the soil and put a base of gravel under the slab prior to pouring. This helps prevent settlement cracking.

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blackhatrob OP t1_je4dl1n wrote

Thanks for this

Was planning to contact the soil, add 2-3” of gravel, then compact again before pouring. I’m thinking the felt paper may be the best material for me as the hose slab has some decent chunks of concrete that came through the underside of their forms that I’ll be pouring over. The paper would let me wrap around that as opposed to a fiber board.

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