Some concrete overlay installers gave me estimates for it without saying that it shouldn’t be done, but one installer said that it can’t be done over brick because the concrete will crack because the bricks are not flat. He recommended demolition and stamped concrete instead. I don’t know who to believe now.
it’s not advisable to pour concrete over brick because brick holds moisture and will move.even if it IS 4" thick or even 6" thick for that matter…..it is not advisable to pour a new garage floor over an old one either because it will move ( crack ) so in spite of the theory that hard fill is hard fill…..all fills are not created equal……number two stone is best…….sand is second best,,,,,,,gravel is third……any other way is unacceptable…..you get one chance to do this right and have it last forever……why compromise and take a chance on anything other than the sure thing……check me out ….you’ll see….remove the brick and start over..4" thick is adequate…….
if it was a 4 in. pour you were going to do , i would pour it . no different than hard packed ground or compacted stone…2 in. or less and i wouldnt do it…