Surface Preparation

A.  Wood, wallboard, paneling, and plywood

      On the exterior surface, a weather resistant barrier of 15lb. felt or better must be applied before installing metal lath. The barrier should be applied horizontally with the top layer overlapping the lower layer, not less than 4 inches. If vertical joints occur, the barrier should be lapped a minimum of 6 inches.  Cover the entire surface area with 2.5 lb. diamond wire mesh.  Exterior applications require a galvanized metal lath.  Metal lath should be attached using galvanized nails or staples overlapping sides by not less than 1/2 inch on sides and no less than 1 inch on the ends.  Nails or staples should be 6 inches on center vertically and 16 inches on center horizontally into studs a minimum of 1 inch.  Metal lath should be kept flat against the surface and the pockets of the mesh pointing upwards.

B. Masonry

     No surface preparation is necessary if the masonry surface, (brick, block, or concrete) is clean.  Painted, sealed, or treated surfaces that are permanently bonded can be coated with a bonding agent or covered with metal lath using corrosion resistant concrete nails.

C. Metal

     Surface preparations are the same as for wood related preparation, with the exception that the use of self-tapping screws is required on the metal lath that will penetrate a minimum of 3/8 inch beyond the inside surface.

Scratch Coat

     Use Type S mortar mix for installation.  Follow mixing instructions on the bag to blend to a creamy paste.  For small projects, a polymer tile mortar may be used.  Apply a thin coat of mortar to completely cover the metal lath or masonry surface.  Scratch the surface with a rake or masonry tool to prevent having a smooth surface.  A helpful tip: mark level lines 5 inches to 12 inches apart in the mortar, using a level and trowel, a string and/or a chalk line to ensure the stone will be straight and level.  The coating will provide a firm bonding surface for the stone veneer.  Some local codes require scratch coat to dry for 48 hours before applying the stone.  Check with your local building codes prior to installation.

Installation

     Depending on the project and type of stone, installation may begin at the top or bottom of the wall.  Starting at the top will aid in keeping the stone clean.  Lay out stones randomly near the work area.  If applicable, corners should be installed first, alternating short and long legs.  The back of the stone should be brushed to remove dust prior to applying mortar.  Apply a 1/2-inch-thick layer of mortar on the back of the stone and press the stone firmly against the substrate using a wiggling action to ensure a good bond.  The mortar should squeeze out around the edges of the stone.  Remove any excess mortar with a trowel and fill in any voids on the stone's exposed edges.  Stagger the joint lines both horizontally and vertically for a finished appearance.  If needed, stones may be cut or shaped with a diamond or carbide blade, mason's trowel, hatchet, or nippers.  If mortar should get on the stone face, wait until it dries and clean with a stiff brush.  NEVER USE A WIRE BRUSH OR ACID TO CLEAN STONE.  Do not use a sponge to wipe or remove the mortar, as it may stain the surface of the stone.  If a grout line is employed in the laying of the stone, typically 1/2 inch spacing between the stones, a grout bag is used to fill in the joints.  Fill the grout bag with mortar mixture, creamy paste desired and squeeze the small end into the joint area to be filled.  Try to avoid getting grout on the face of the stone.  If this occurs, allow it to dry and brush off with a stiff brush. NEVER USE A WIRE BRUSH OR ACID TO CLEAN STONE.

Finish Joints

     Allow the mortar to start becoming firm and using a striking tool, scrape away excess grout in the joint and force the mortar into any voids.  After working the joints, use a hand broom to clean loose mortar from the joints and the stone face.  NEVER USE A WIRE BRUSH OR ACID TO CLEAN THE STONE.

Clean and Seal the Stone

     Use a non-etching concrete cleaner to remove clay, dirt, mortar residue, or other stains on the stone.  A pressure washer may be used to clean stone if it does not exceed 2000 psi, and a minimum distance of 18 inches is kept back from the stone.  We recommend that after a mortar is fully cured, has been cleaned and is dry, a water based concrete sealer is applied to help repel the elements and keep the stone clean.  NEVER USE A WIRE BRUSH OR ACID TO CLEAN STONE.

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