Weep hole and FB board placement

[david s]

A vermicrete slab is considerably cheaper than calcium silicate board. However it takes more labour to mix and place and the free water in the mix requires removal, preferably before laying the floor bricks over it which traps the moisture remaining in it. This problem is eliminated if a dry calcium silicate board is used, although it can suck up moisture at the same rate and quantity as a vermicrete slab will if it gets wet, so the weep holes are good insurance as underfloor moisture is the hardest to get rid of . I've had experience with the oven insulation building up moisture just from our tropical humidity even though there was no rain entry.

Any moisture left under the floor will travel in the opposite direction from the heat so the placement of the weep holes is probably not that important, but a decent pathway to them will facilitate exit. It is far easier to cast in the holes (I use some foam which is easily removed) when the supporting slab is laid than having to drill them once it's set. Dodging reo bar and the hole blowing out can therefore be easily avoided.

you might find the attached study on drying a vermicrete slab useful.

Vermicrete insulating slab PDF.pdf

[mnagy]

Here’s the planning for my next step… I’m gonna put one course of bricks around my concrete block stand flush with the poured reinforced concrete top. Then I’ll put a row of bricks on their side around the perimeter making a space for 4” of vermicrete. I’ll use some scrap tile between the concrete and vermicrete, and will make sure there are some 3/8” holes through the top slab for drainage. Anything else I should think about for this step? Thanks!