Properly installed platform key for free-standing fireplace

Q. I understand that marble expands and contracts and requires a different approach when applied to a vertical versus a horizontal surface. How do you make sure marble tiles will remain in place vertically on a wood stove platform wall and horizontal base? I have some experience with ceramic tile and mastic. What do I use and how do I cut marble to fit? -- Vicki Ojdrovic

A. Before addressing the question, I need to point out that this type of job requires a building permit and inspections. Also, you'll need to construct a noncombustible platform and walls for any use of a free-standing fireplace or wood stove.

Build the platform and wall surfaces using half-inch cement board, cement base bonding mortar, and a noncombustible finish surface like marble tiles (in your case).

The vertical walls must have 1 inch of airspace behind the cement board, easily accomplished by using half-inch copper couplings behind the cement board to hold it out from the combustible wall. Pass a 3- or 3.5-inch screw through both the cement board and coupling and directly into the framing member for each coupling. Space the couplings about 12 to 16 inches apart. Do not overtighten the screws or the couplings will cut into the wall surface.

Vertical walls will take time, but you can speed up the process by marking the coupling sites. Apply a small amount of construction adhesive to these areas and place the couplings into the adhesive. Let it set up overnight before applying cement board. To make it easier to hang the cement board, mark the coupling locations on the cement board and pre-drill for the fasteners.

Finally, base the overall design of the noncombustible surfaces on the overall size and placement of the unit, and follow the manufacturer's and mechanical code recommendations.

A single wall pipe has to be located a minimum of 18 inches away from any combustible wall surfaces. This measurement, however, can be reduced to 9 inches when a noncombustible surface is constructed and the surface extends a minimum of 12 inches on the other sides of the unit.

Most important, however, in the overall design is that at no point on the pipe can a measurement be taken that is less than 18 inches to the combustible wall. This means that the noncombustible wall needs to extend out far enough so the pipe's required minimum clearance measures to the noncombustible surface first before the combustible surface.

Extend the platform out 18 inches minimum in front of the loading side and 12 inches minimum on the other sides of the unit.

Mario & Sons, a local company that specializes in natural stone, said you have nothing to worry about when applying marble tiles to vertical and horizontal surfaces; only thick slabs require unique installation methods. Cut marble tiles with an electric tile saw cutter that uses a diamond blade and water. You can rent one from your local rental yard.

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What's your question?

Send your questions about home repair or remodeling to Leon Frechette at C.R.S. Inc., P.O. Box 4567, Spokane, WA 99220-0567, or by e-mail to [email protected]. No phone calls please.

You can also visit his Web site at www.asktooltalk.com for previous questions, home repair tip and general remodeling information.

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