does anyone have plans on building a hearth for a pellet stove?

Answer 1

For woodstoves the hearth must meet the "R-value" requirements for the stove. This should be defined by the stove manufacturer and be part of the manual that comes with the stove. While pellet stoves may be somewhat less demanding, you should still consider R-values to be sure there is sufficient air-gap / insulation / non-flammable material between the underside of the firebox and combustible wall and floor material.

I recently installed a woodstove (not pellet) and needed to build a hearth for it on an existing plywood floor. I needed to meet a 1.2 R rating, where R-values of various material are as follows (for thickness specified):
Gypsum or plaster board1 1/2″ 0.45
Wallboard, Wonderboard, or Durock1 1/2″ 0.20
Ceramic board (Fiberfrax or Micor)1 1/2″ 1.10
Nominal solid clay brick1 1″ 0.20
Ceramic wall or floor tile1 1/4″ 0.01
Mineral wool insulation2 1″ 3.12
Cement mortar 1″ 0.20
Horizontal still air 1/8″ 0.92

I therefore used cement board (48" x 30" sheets) suspended over a 1" air gap created by using 2x1/2" cement board strips 2-3" wide spaced about 1 ft apart, making sure there were supports under the expected leg locations for the stove (450lbs / 4 legs). The outside dimensions were large enough to meet the requirements specified by the manufactuer. I then framed the outside with wood and tiled the upper surface with ceramic tile over a thinset mortar. The edges and wood frame were then finished in oak mouldings stained to match the hardwood in the room.

I could specify sizes, but you can size according to your requirements/taste. The only important dimensions are the overall thickness (at least 1.5" (1/2" air spacing (1" in my case), 1/2" cement board, plus 1/2" for tile and adhesive)) and the need to ensure the spacers under the cement board are located under the legs of the stove (although this may be less critical if the pellet stove has a pedestal base).

Walls can be treated similalry if required, although instead of tile one may prefer 1/2" thick brick or stone slices to give a more rustic appearance.

Answer 2

I had a pellet stove in Washington state, and it came with a fireproof base, much like concrete backer board used in wall construction.

I made a frame the same size as the base board, addded regular red brick, cemented in the brick as though I was building a wall section, reset the pellet stove when the base had cured, and refitted the chimney.

It wasn't fancy but looked good, and served a purpose.

Steven Wolf