How do I Build the Masonry Section of a Fireplace?

Base and Stucco Finish

• 1

  Mark out the precise measurements of your fireplace surround. Attach building paper to the wall using heavy-duty staples or roofing nails to construct a moisture barrier. Each section of building paper should be a continuous length to minimize water leaks through seams. Work upward from the bottom and overlap sheets of paper by at least four inches. Code specifications in certain areas require more than one layer of building paper.

• 2

  Install metal lath, a lightweight, flexible metal grid-work that serves as a base for the mortar, onto building paper using 1 1/2-inch roofing nails or fencing staples. Drive nails or staples into wall studs every six inches. Ensure the lath is installed rough side out, with round indents facing outward to secure mortar. If the lath feels smooth when running your hand upward over the grid and rough when running your hands downward, you've installed the lath correctly. Overlap lath sheets one inch horizontally and two inches vertically during installation.

• 3

  Attach metal edging along edges of wall with roofing nails to ensure clean corners when applying mortar or stucco. Nail on a drip screed, a metal edge used to catch dripping mortar or stucco, at the base. Use aviation snips to trim excess edging, lath and drip screed. Always wear safety goggles and heavy gloves when trimming metal to prevent eye and hand injuries.

• 4

  Mix your veneer concrete or stucco according to manufacturer's directions to achieve a creamy, peanut butter-like consistency. Slather the concrete or stucco onto the metal lath using a mortar hawk and metal trowel. Use a downward motion to fill the indents, then fan out side to side to build a 1/2-inch thick initial scratch coat. Press firmly to fill any voids and smooth over.

• 5

  If you are building a stucco finish, mix several test batches of your stucco to evaluate the right color and consistency. Apply your trial samples to a wood board and allow them to dry for an hour to assess the cured color. Pick your desired batch and record its mixing proportions. Mix your finish batch with slightly more water than the scratch coat, though it should not run on the mortar hawk. Apply your finish coat of stucco with a metal trowel. Achieve textured finishes by carpeting you trowel, flinging wet stucco on your final coat with a whisk brush for a wet-dash texture or smoothing the wet-dash finish out with a trowel for a dash-trowel finish.

Stone-veneer Finish

• 6

  Follow Steps 1 through 4 of the previous section.

• 7

  Build the foundation for your stone-veneer finish by allowing your initial 1/2 inch coat of mortar to dry for 20 minutes, then combing it with a notched tiling trowel, creating grooves in the mortar that veneer stones will grab onto. Allow this combed coat to cure at minimum overnight.

• 8

  Design the layout of your veneer stones. Use painter's tape to outline the shape of your fireplace surround on a smoothed drop cloth taped to a flat surface. Allow 1/2 inch joint space between each stone. Stagger stones of different colors, shapes and sizes, beginning with the corner pieces and moving inward, to create just the right look. Measure the top and sides of the fireplace opening and cut corner pieces that match the opening's depth, allowing room for a gate or doors to be installed in front of the fireplace opening, if this type of fire barrier is desired. Use a grinder to mark your corner piece cuts, then tap a hammer to the excess material to create a natural break.

• 9

  Wet each stone before applying the mortar, then spread the mortar 1/4 to 1/2 inch thick over the back of the stone. Create a furrow using the point of the trowel down the midpoint of the applied mortar. Adhere the stone veneer beginning with the header and sides of the fireplace opening, then outline the edges of the surround. Fill in the field of the surround last, working from the top down. Press the stones onto the surround until the mortar oozes out of the sides. Use a whisk broom and a striking tool, a simple 1-by-1-inch piece of wood that looks like a tongue depressor, to clean out the joints. Remove any errant mortar that adheres to the front of your stones with a whisk broom after it dries to avoid staining. Allow the mortar to cure overnight.

• 10

  Fill a grout bag with grout mixed to the consistency of pudding. Cut the tip of the bag, press out any air bubbles and twist the top closed. Fill the joints of your surround with grout, starting from the top and work your way down. Fill the joints until the grout is level with or protrudes slightly from the face of the stones. Allow grout to cure about 60 minutes. Using a striking tool, strike or shape the grout profile to achieve your desired effect. Create a natural looking finish by going over grout with a whisk broom. Allow grout to cure for 48 hours before lighting your fireplace.