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Expert: - 6/16/2008


Question
We own a bungalow in S. Quebec, built on a concrete slab.  We will eventually have radiant hydronic in-floor heating installed via an over-pour.  Because there are several variables involved, we have no idea how much higher the finished floor will end up being.

Problem is, we will have a woodstove installed this fall and want the hearth to be raised, even after the over-pour is complete.  Previous owner left us with an ample supply of concrete blocks.  We thought we could cement these in, on their sides, at appropriate spacing to provide enough support for the total load, top with cement board installed with an appropriate adhesive, then cover with the slate tile we want to use.

Would this work, and do so safely?  Are the concrete blocks strong enough to handle this load, used on their sides?  If so, what would be the best medium in which to set the blocks, and the appropriate adhesive?  What thickness of cement board should be used?

The stove we are leaning towards is a Jotul Oslo F500, with a weight of 445 lbs.

Thank you for your time.

Answer
Martine,

Being that you have a non combustible floor to begin with, your plan with the concrete blocks sounds fine. Any thickness of cement board will be acceptable since nothing combustible is in the construction anywhere. Another option to consider is to wait on the blocks and raised hearth until you do the over pour for the heating system. You could simply put down a cement board on the floor that provides the dimensional protection required by the stove manufacture and an interior telescopic pipe that can be raised at that time. Good luck and thanks for asking.

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Randy Brooks

Expertise

Inspection of Masonry, Pre-cast Tilt-up, and Factory Built Fireplaces as well as Free Standing & Insert, Gas, and Wood Appliances. We also provide Hearth Fire Loss Investigations, Litigation Support, Consulting Services, Flue Sweeping, Installation and Repair. Additionally, I’ve been a chimney sweep for 23 years, service and install hearth appliances as well as being recognized by the Superior Court of California as an expert witness.

Experience

Brooks Chimney Sweeping Since 1989 Ojai, CA Owner / President www.brooks-hearth.com

Organizations
NCSG, MEMBER,(National Chimney Sweep Guild), Member since 1990, Board of Directors representing Region 6, (CA, NV, AZ, UT, OR, WA, ID, WY, MT, AK and HI,) 2004-2011, ethics committee chair, 2004-2005, executive committee member, Vice President, 2006-2008, President, 2008-2011. CSIA, BOD (Chimney Safety Institute of America,) Board of Directors, ethics committee chair, 2004-2005, executive committee member, Secretary, 2005-2006, Vice President, 2006-2008, President, 2008-2011. HPBA, MEMBER, (Hearth, Patio, & BBQ Association,) since 2002. NFPA Member, (National Fire Protection Association) Since 2009. Technical Committee member for the 211 Standard.

Education/Credentials
California State Licensed Contractor, C61-D34, #750710. http://www2.cslb.ca.gov C.S.I.A., (Chimney Safety Institute of America,) Certified Chimney Sweep, #2580. Held since 1990 re-certified in ‘93, ‘96, ‘99, ‘02, ‘05, '08,'11. http://www.csia.org F.I.R.E. (Fireplace Investigation, Research & Education Service,) Certified Inspector, #FP-006. Held since 2000, re-certified in ’03, ‘06. http://www.f-i-r-e-service.com Fireplace Investigation, Research & Education Service,) Advance Expert Consulting & Witness, certificate, ’05 N.F.I. (National Fireplace Institute,) Certified Gas & Wood-Burning Specialist, #133851. Held since 2002, re-certified in '05,‘08. http://nficertified.org

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