How to Build an Outdoor Fireplace

Outdoor Fireplace

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Overview
  • Working Time: 10 hrs
  • Total Time: 72 hrs
  • Skill Level: Advanced
  • Estimated Cost: $200 to $400

One of the best ways to turn your backyard from great to even greater is to build an outdoor fireplace. Creating an area where people love to gather transforms your backyard into a favored spot for family and visitors. Backyard features like barbeques, pools, hot tubs, pergolas, decks, and outdoor kitchens are important anchors for drawing people together—the same holds true for outdoor fireplaces.

Basics of Your Outdoor Fireplace

This fireplace may look like it's made of stacked ledgestone, river rock, fieldstone, or any other decorative stone of your choice. But the real secret is that its super-structure is constructed of inexpensive 16-inch and 8-inch concrete cinder blocks. So, the cinder block is the structure of the fireplace, and the veneer stone is the look of it.

A poured concrete slab provides a sturdy, level pad for the fireplace. Atop this base is an open-front box made of cinder blocks for storing firewood. On top of this box are hearth blocks. This is where a second box—the firebox—is located. Besides providing room for the wood, this arrangement elevates the fire so that it is easier to maintain. Plus, it raises the fire to a more comfortable viewing height for those sitting around it.

Quarter-inch-thick cement board faces the concrete cinder blocks. Light-weight manufactured veneer store then faces the cement board.

Codes and Restrictions

It is important to check with your local permitting office for any codes and restrictions relating to outdoor fireplaces. Your community may require a building permit. Air quality measures may prohibit wood-burning fireplaces in your area when air quality conditions are poor.

What You'll Need

Equipment / Tools

  • Protective gloves
  • Tamper
  • Tape measure
  • Masonry hammer
  • Hammer
  • Concrete trowel
  • Shovel
  • Bubble level
  • Circular saw
  • Square
  • Hacksaw
  • Hoe
  • Mortar mixing pan

Materials

  • 33 full concrete cinder blocks, 8-inch by 8-inch by 16-inch
  • 12 half concrete cinder blocks, 8-inch by 8-inch by 8-inch
  • Manufactured veneer stone
  • 6 cement backer boards
  • 2 metal flue caps, 24-inch by 24-inch
  • Mortar
  • 26 bags of 80 lb. quick-set concrete
  • 6 bags of 50 lb. gravel
  • Nails, 2-1/2-inch
  • 2 two-by-sixes
  • Rebar, 42 inches by 6 feet
  • 2 steel angle, 1-1/2-inch by 72-inch
  • 2 hearth blocks, each 42-inch by 32-inch
  • Masonry nails

Instructions

  1. Locate the Outdoor Fireplace

    Outdoor fireplaces should be close enough to the home for easy access, but not so close that it's a safety hazard or a nuisance. Depending on local codes, you may want to locate the fireplace at least 20 feet away from the house. Nearby patio covers can trap smoke. The area underneath the fireplace should be strong. Water in the area should drain away from the fireplace. If water collects around or under the fireplace, the concrete pad will eventually crack.

  2. Clear and Level the Area For the Pad

    Clear and excavate a section in the ground 70 inches long by 56 inches. Flatten the ground and level it. Tamp the soil down with the tamper. Spread about 2 inches of gravel and flatten the gravel.

  3. Build the Fireplace Pad Form

    Cut the two-by-sixes into two sections that each are 68 inches long and two sections each 40 inches long. Use the hammer and nails to construct the concrete form. Place the form on the gravel. Use the square to make sure that the form is squared off and perfectly rectangular. Cut the rebar to size.

  4. Pour the Fireplace Pad Concrete

    Mix the quick-set concrete with the hoe in the mixing pan. Pour half of the concrete in the form, place the rebar, then pour the rest of the concrete. Allow the concrete to fully cure.

  5. Lay the Fireplace's Wood Box

    Lay seven of the full-size blocks in a U-shape: three in back, two on the sides. Lay the two half-size blocks at the ends of the U-shape. Mortar the blocks onto the concrete pad. This is the bottom course of blocks in a three-block level box.

    For the second course, alternate the blocks. The seams from the bottom course should straddle the middle of the blocks on the upper course.

    The third course is a duplicate of the first, bottom course.

  6. Create the Lintel

    With the hacksaw, cut the steel angle to 68 inches. Place it across the front of the wood box as a lintel for support.

  7. Lay the Hearth Blocks

    Securely mortar down the two hearth blocks on top of the wood box. Mortar the seam between the two hearth blocks.

  8. Build the Fire Box

    The fire box will be built on top of the hearth blocks and is a smaller version of the wood box. Use two full-size blocks across the back, one full-size block on each side, and one half-size block on each side. Build three courses, duplicating the method used for the wood box.

    With the hacksaw, cut the steel angle to 48 inches. Place it across the front of the fire box as a lintel for support.

  9. Add the Chimney Caps

    Add the two chimney caps side-by-side on top of the fire box.

  10. Lay the Veneer Stone

    Cut and lay the cement board across all areas of the fireplace that will receive veneer stone. Mortar down the board and follow by nailing into place with masonry nails. Mortar and add the veneer stone to the cement board.