Extra Cost: <$100 Healthier concrete is almost the same cost as less healthy concrete, and it finishes better!
What: Don’t use any fly ash or any other admix in your concrete. Just use water, sand, and Portland cement.
Why: Lots of nasty stuff gets added to concrete. Fly ash in particular is bad for your health.1 Admixtures evaporate from the concrete over time and eventually waft up into your house. These chemicals pass right through cracks in your floor that you cannot see with your naked eye.2
Concrete is like a sponge – it readily sucks up water and spreads it around. Water in concrete evaporates into your floors and walls and creates mold.3 So proper waterproofing is also very important to building a healthy home. The key elements are: have at least 6 inches of good drain rock below and on the sides of your foundation, have a good, thick (>10mil) vapor barrier taped thoroughly at every seam, and waterproof the sides of the concrete all the way up above the ground. Finally, make sure that when your landscape irrigation system is put in, none of the sprinklers are hitting the concrete.