Vapor Retarder and Grade Beams
Vapor Retarder and Grade Beams
(OP)
I have a structural slab-on-grade system with grade beams and girders. I am trying to determine how to run the vapor retarder below the slab. Is it typical to run the vapor retarder continuous below the grade beams or can the vapor barrier be turned down at the face of the grade beam? I have always considered a retarder system (or even a barrier system) to be continuous below the slab and providing a joint or seam at each grade beam is inviting vapor/moisture propogation at these locations.
Additionally, the grade beams are supported by pile caps located below. If the vapor retarder is to be continuous, how do you handle the pile cap locations?
Additionally, the grade beams are supported by pile caps located below. If the vapor retarder is to be continuous, how do you handle the pile cap locations?






RE: Vapor Retarder and Grade Beams
RE: Vapor Retarder and Grade Beams
RE: Vapor Retarder and Grade Beams
RE: Vapor Retarder and Grade Beams
I would run the barrier under the beams as well, presumably you can cast the beams and slab together.
The risk of problems due to the break in the barrier at the pile caps is small, due to the depth of concrete between cap and top of slab.
RE: Vapor Retarder and Grade Beams
If the grade beams & girders are cast monolithically with the slab, then the vapor barrier should run below the beams & girders. BUT - be realistic about the cross-sectional shape of those beams & girders - depending upon what you've specified for base material under the barrier, it will be impossible to achieve vertical sides on the beams & girders. Further, you will create compaction difficulties for that base material near the beams & girders.
Ralph
Structures Consulting
Northeast USA
RE: Vapor Retarder and Grade Beams
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