The following information was developed to provide basic guidelines for architects, engineers, and contractors regarding the installation of natural thin stone veneer. This general information brochure gives suggested guidelines; however, it does not override any local building codes.
Stone has been used for thousands of years. Since ancient times, natural stone has been an enduring symbol of wealth, beauty, and sheer magnificence. Natural Thin Stone Veneer has been fabricated for many years. Recently, machinery (by a variety of manufacturers) has evolved to cut natural full dimensional stone to natural thin stone veneer (nominal 1-1/4 inch thickness). The machinery can also cut 90 degree corners which are used for corner applications, concealing the true thickness of the stone. The results?
Natural Thin Stone Veneer weighs less than full thickness veneer thanks to the thin cut. The lightweight pieces help reduce production, shipping, and construction costs. In addition, Natural Thin Stone Veneer can be installed without footings or ledges and adheres to concrete, plywood, paneling, drywall, and even metal.
Most consumers prefer natural stone over “man-made cast concrete” materials, which is why Natural Thin Stone Veneer is becoming so popular in the marketplace.
Explanation of Natural Thin Stone Veneer
Full Dimensional Stone = 3 - 5 inches depth & 40 - 73 lbs./sq ft
Natural Thin Veneer = 1-1/4 nominal inch (generally), 15 lbs./sq ft or less
- In order to be considered a Natural Thin Veneer, the weight of the stone needs to be less than 15 lbs/sq foot as described in the 1997 Uniform Building Code.
- In order for this to be accomplished, the stone (pictured above) needs to be a nominal 1-1/4 inches thick.
- The thicknesses of other types of stone may vary depending on the density of the stone.
- Natural Thin Veneer is typically less than 1/2 (or more) the thickness of Full Thickness Veneer.
- In addition, the weight of Natural Thin Veneer can be just a fraction of Full Thickness Veneer, sometimes 75% less.
Product Specification Description
Natural Thin Stone Veneer is to be 100% natural quarried stone. No concrete composite stone is to be accepted. Stone is to be sound type and is recommended to be tested to ATSM specifications. It is also recommended that this material be packaged carefully in boxes or on pallets, stored off the ground and protected from the elements.
Consider that packaging by different fabricators varies from waxed cardboard containers, wooden pallets with wire wrapping, to wooden crates. The thin stone product is to be packaged in a durable non-staining, protective packaging designed to minimize damage to products during shipping and outdoor storage. The name of the product should be identified on each package of product.
Natural Thin Stone Veneer should meet minimum quality standards as follows:
- Thickness range: 3/4” minimum to 1-1/2” maximum
- Weight per square foot: Stone should weigh no more than 15 lbs per square foot for the thickest stone.
- Natural Formation: No open seams or starts or cracks. No high percentages of rusting or oxidizing minerals which may cause excess staining and bleeding after installation.
- Face area: Minimum 1/8 sq. ft. per face with minimum dimension of 2” in any direction.
- Corner stones: Minimum of 3” length on return on any exposed side of corner stones.
- Tests: Meets or exceeds required ASTM testing levels for absorption, compressive strength, and flexural strength for the appropriate geological stone type.
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 mason 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, flashing, 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. 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. 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.
Type N or S mortar is used for installing Natural Thin Stone Veneer depending upon the type of stone being installed. Check with producer for a recommendation.
The use of a bonding admixture with the mortar may be recommended to add bonding strength (check with your stone dealer for recommendation). Please refer to the selected bonding agent instructions for recommended mixture quantities. Extra care should be taken when using bonding agents since dropping can be difficult to remove once they cure. The use of an epoxy, thin set and/or construction adhesives should only be used in interior applications. Admixtures are necessary for all soffit or overhead conditions.
Setting Natural Thin Stone Veneer
Now that the metal lath and the scratch coat have been applied, installation of the natural thin stone can proceed.
- If corner pieces are required for the application it will be best to start with the corners first. This will provide a better guide for your pattern to continue around the corner.
- Most corner pieces will have a long end and a short end. These pieces should alternate in opposite directions, asthey are stacked, one upon the other.
- The back of each stone should be covered 100% with a thickness of at least 1/2” of mortar. A bit more mortar can be added towards the center of the back of each stone.
- The stone should be pressed firmly against the scratch coat wall to ensure a sound bond.
- Extra mortar will ooze out around the edges as each stone is set in place. This extra mortar will fill in around the stone creating your grout joints.
- If you choose not to use this method to fill the joints, then the joints can be filled with grout using a grout bag and/or a tuck pointing tool.
- Make sure to create control and movement joints in the veneer in the same places that they exist in the structure. These control and movement joints serve to allow for the movement of the structure as it settles and moves from environmental changes. Consult a local contractor, your builder, or structural engineering professional to determine the need for these special joints.
Article by: BSI Building Stone institute