No fines in base for conc slab on grade
I just perused the recommendations for Building Science Corp Insight #118 for insulating concrete slabs on grade and noticed the gravel base is always labeled with “no fines”. Having recently tried to educate myself on the various types of gravel bases for permeable paving, I had found a 2012 position paper by the American Society of Concrete Contractors, ASCC Position Statement #37, that states open-graded bases (no fines) don’t meet ACI requirements for base material because they are relatively incompactible, difficult to trim, and unstable. Based on their recommendations, it seems the better choice is to add a min 10 mil vapor barrier over the gravel and terminate at the stem wall.
I’d be interested to hear anyone’s experience with no fines base under slabs on grade.
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