Hi all, long time reader – first time poster. TIA for those fellow nerds who read the whole thing and follow along, y’all are the real MVP’s.

I’m looking to evaluate and improve our pre-slab specs. I’m based out of Central FL where we use stem-wall foundations (typically 18″+ above grade) and build CMU block homes. The market standard for pre slab vapor management is 6-mil poly stretched across the fill dirt, from inside edge of block to inside edge of block, with overlaps and penetrations taped in the field, but nothing sealing the edge to the block.

My understanding is we install vapor barriers for a few reasons: 1) so our poured concrete doesn’t absorb the moisture from the ground during the pour/cure; 2) to prevent a cured slab from accumulating moisture and becoming damp through capillary action; and 3) to help prevent termites and insects from entering the home through small holes around the penetrations in the slab.

My question/issue is – I’ve never seen anyone COMPLETELY seal their vapor barrier. I’ve seen some decent ‘college tries’ over and over, but no one really ensuring all of the penetrations are sealed/tapped up well. But isn’t this more of a pass/fail situation? Either it’s completely sealed off from the ground/fill dirt or it isn’t? if it isn’t, aren’t we’re failing on all 3 accounts above? So then what’s the point?

I’ve been thinking about upgrading to the Stego vapor barrier system and using their fluid applied product along with tape. We’ve also been considering attaching the vapor barrier starting at the inside corner of the footing/stem-wall connection prior to the fill dirt being brought in/compacted, then taking it up the exterior wall over the dirt and connecting it to the other side, so that all of the stem-wall also has a constant vapor barrier (which makes sense me because block has capillary action as well, right?).

Because this is not a commonly practiced detail in my market I’m getting quite a bit of pushback and I find myself wondering ‘is the juice worth the squeeze?’. I’ve looked for research papers discussing the issue to see just how much of an ‘issue’ it really is and have come up empty. Does anyone have decent independent studies that show the importance of having a solid continuously installed vapor barrier with measurable results that we can reference, or at least to show our trade partners and clients why this is important (if it actually indeed is) or am I wasting my time and need to go find something else to be picky about?

I’ve also heard without the vapor barrier properly installed it could contribute to excessive humidity inside the home, which because we are in a zone 2 hot/humid climate humidity is always a concern. But I have failed to find any studies that validate this concern. Real or myth?

Thanks again for all those who read and contribute, I really appreciate your time.