Drain channels on structural slab

[vlupi01]

I have read to put broken or mosaic tiles on the slab below the pelrcrete insulation with a hole drilled through the slab to create a path for moisture to escape. Can fine gravel, sand, broken glass or other be used instead?

[SableSprings]

The purpose of the tiles is two-fold. One: to provide clear pathways to the weep holes (usually 3-4 holes approx. 1/2" diameter) as an exit path for moisture and Two: to provide a moisture barrier between the hearth slab and the insulation (be it insulating concrete or a ceramic board). Fine gravel & sand will still provide a capillary path between the slab and insulation layer. Fine glass is no better and has some safety & installation issues (depending on shape of glass, piece sizes and spacing). The use of squares of small tiles (installed mesh side up) provides a safer, inexpensive, and effective moisture barrier and the channels created by the unfilled spaces between tiles (intended for grouting) allows a clear path to the drilled/formed weep holes. I additionally like the 1 foot square sections/sheets of mosaic tiles because most big box stores and tile supply businesses have discontinued styles & colors at almost give-away prices. Yard sales and friends also tend to have some surplus sheets at "bargain" prices.

I hope that helps answer your question.

[vlupi01]

Thanks, I have drilled five 1/2" holes and will go with the tile as suggested. I was trying to save a trip and a few dollars but will follow suggested method.