Paul, thank you for your inquiry. Where to terminate the vapor barrier should be determined by the Design Professional. Most design professionals will specify ASTM E1643 which addresses installation practices for below-slab vapor barriers. In that standard the perimeter termination is prescribed in paragraph 6.5 as: “Extend vapor retarder over footings and seal to foundation wall, grade beam, or slab at an elevation consistent with the top of the slab or terminate at impediments such as water stops or dowels.” Thus, you have three locations the vapor barrier can be sealed to: foundation wall, grade beam, or the slab itself. So, if impediments don’t prevent you from doing so, yes, you should, in following the guiding standard, wrap up the outside edge of the [cured] concrete slab. If, however, bringing the vapor barrier to the height of the slab exposes it to the elements (sunlight particularly), you may want to consider terminating and sealing at grade as UV is a major pro-degradant of plastics. This would NOT meet the standard, but it is often a deviation project teams approve for reasons cited. Once you’ve determined where the vapor barrier is terminated, you then need to decide if you will be sealing the vapor barrier to the concrete slab, the foundation wall, or the grade beam. Having said all that, again, first and foremost, be sure to defer to the Design Professional’s specification or installation instructions before proceeding.

Gravel provides a solid foundation for your concrete as it can be compacted. It also improves drainage, preventing water from pooling beneath the concrete.

@@PushaDee thanks, yeah I can see how the gravel could also work as a barrier to reverse water vapor coming up from the soil under it also.