1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Hearth Extension Substarte

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by pine138, Dec 10, 2011.

  1. pine138

    pine138 New Member

    Dec 6, 2011
    Southwestern Maine
    I am in the process of replacing my old wood insert with a new one and let me tell you, it has been quite the learning experience! Anyway, one of the things I have learned is that I need to install a hearth extension for my fireplace. My fireplace has a 17" brick hearth that is raised 10 inches above the plywood subfloor. The user manual of the stove I intend to buy indicates a minimum thickness of 0.5 inches and a thermal conductivity K factor of 0.84. If I did my research and math correctly, that translates to a R factor of 0.05 using the formula R = (1/K x 12) x T, where T = thickness in inches. Given that Durock cement board has an R of 0.26 per half inch, I am thinking that I will be OK with a 0.5 inch Durock substrate. Is that correct? Also, is there a special kind of thinset that should be used?

    Helpful Sponsor Ads!

  2. raybonz

    raybonz Minister of Fire

    Feb 5, 2008
    Carver, MA.
    Welcome to the forum pine! Durock Nexgen has an R-value of 0.39 per 1/2" the original Durock was 0.26.. I used thinset cement between the floor and the cement board and between all other layers.. Have fun!


Share This Page