foundation slab

[Clive Hughes]

Im confused by the instruction for 5.5" base. If I add 3.5" pea gravel it only leaves " for concrete and rebar. Am I missing something? Clive

[splatgirl]

Hi and welcome!
Set your formwork so that you have 5.5" of board above the level of the gravel. Assuming you use 2 x 6's for the form, they should be more or less just touching the gravel bed for a 5.5" thick slab.
Does that answer your question?

[Clive Hughes]

Thx yes makes sense. Although 30 bags of mix at 0.5 cu.ft.per bag, over the base area of 42 sq.ft only has a depth of 4.25". Thx again. Clive

[splatgirl]

IIRC, mine took 38 bags. Your problem was that you bothered to do the math
Good luck!