Moisture Control and Surface Prep
Listed below are general procedures used to waterproof areas before the installation of Natural Thin Stone Veneer. Waterproofing is an extremely important process which must meet or exceed all local building codes and BSI recommends that a highly qualified waterproofing company/contractor handle this portion of the installation or knowledgeable masonry subcontractor adhering to industry standard.
If additional moisture control is desired, a moisture-resistant barrier can be applied to all vertical wood or moisture-sensitive backup walls. Overlap adjoining sheets of moisture barrier a minimum of 2” on horizontal joints and minimum 6” on vertical joints. It is recommended by BSI to include a weep system behind an exterior installation of Natural Full Veneer and Natural Thin Stone Veneer. Contact the BSI office or visit the Web site www.buildingstoneinstitute.org for further weep system information.
It is important to provide a weather shield, fiashing, or caulk at all material transition points and at all areas that could lead to possible moisture penetration, including but not limited to all window and door openings, electrical outlets, electrical fixtures and plumbing fixtures. It is important to follow manufacturers specifications for correct installations. Flashing needs to be applied under water tables and sills, and the base of walls where this veneer meets a brick or other ledge.
Cut paper-backed lath as close as possible around electrical outlets, and then caulk between the outlet and the lath. Apply silicone caulk to the sides of all windows and doorways. Caulk all joints which occur between thin stone veneer and dissimilar materials like wood, glass, vinyl, and also at all control and movement joints which occur in the structure. Use backer rods in caulked control joints to allow for proper joint movement during expansion and contraction.
General Surface Preparation
If there is a chemical film on the wall it needs to be removed. In many instances the film may be removed with sandblasting or etching with masonry detergents. The use of acid to remove the film is also a consideration however, in all cases you should check with the manufacturer of the product(s) to make sure it will not damage the underlying surface. The removal process will also make the wall surface less smooth which will aid in the installation process.
Concrete Block or Brick
Natural Thin Stone veneer can be applied directly to any new or existing concrete block or brick surface. (Fig. 1) It is important to make sure that the existing surface and wall is sound and without defects, and that the surface has not been painted or sealed. In the case of a poured concrete wall, all form release chemicals should be either sandblasted or removed with a masonry detergent before the application of the natural thin stone veneer.
Framed Exterior Walls
For exterior walls a non-corrosive paper-backed lath is applied (see waterproofing instructions). All wood surfaces require the application of non-corrosive wire lath and a setting mix (between 1/2” – 1” thick) before applying natural thin stone veneer (Fig 2). Studs in walls are covered with exterior grade wood sheathing or cement mesh mortar units as chosen by builder. Minimum thickness of 1/2” is recommended.
For applications that involve installing paper-backed corrosion resistant wire lath: After the first piece of lath is correctly placed at the bottom of the wall, continue up the wall overlapping a minimum of 3” for each piece of lath from the bottom to the top. Wrap metal lath around and overlap at corners a minimum of 16”. Use self-furring, non-corrosive, expanded metal lath, 3.4 lbs per yard weight. Use Galvanized, barbed nails (or another quality anchor system such as galvanized screws and washers) at 6” vertical centers, in line with wall stud horizontal spacing. Place nails in furring groove or dimples to preserve 1/4” furring away from wall of metal lath. Overlap horizontal joints of lath a minimum of 1” and vertical joints a minimum of 1”. A paper-backed metal lath can be utilized to avoid the need for a separate moisture control barrier being applied prior to the metal lath.