i am going to install a brick (4x8x2 size brick) patio over an existing cement patio. the cement patio is small, approx 8x8 and it bordered on all sides by wood timbers supporting a fence. the 2" thick bricks are just slightly higher than the wood timbers and dont present a problem with the door opening. my question is, can i simply lay the bricks on the concrete and fill the spaces with masons sand? or do i need a base of sand under them? i think the patio has some drainage holes built into it.