Q:
I’d like to place a radiant slab in a house I am refinishing. But here in Maine, nobody seems to know about the lightweight concrete that is often referred to in Fine Homebuilding. Can I buy lightweight concrete in bags and mix it myself, or do I have to have a truck deliver it premixed?
Ralph Moll, Windsor, ME
A:
Rich Ziegner, former assistant editor, replies: The lightweight-concrete product that’s often used in radiant slabs over wood framing is called gypsum concrete. Maxon Corporation (920 Hamel Road, Hamel, Minn. 55340; 800-356-7887; www.maxxon.com) makes a version called Gyp-Crete Therma-floor. A similar material is available from Hacker Industries, Inc. (Box 5918, Newport Beach, Calif. 92662; 800-642-3455; www.hackerindustries.com), called Gyp-Span. You can only get gypsum concrete through licensed applicators—exclusive dealers that also pump the stuff.
If you’ve got a small pour, and you want to mix the gypsum concrete yourself, Gyp-Crete Thermafloor is available in 50-lb. bags; Gyp-Span comes in 80-lb. bags. Both are mixed with sand and water. Call Gyp-Crete or Hacker Industries to find licensed applicators in your area, or check the Yellow Pages under “Concrete Contractors.”
