Exterior installation of PermaBASE® Cement Board
General: All framing should comply with local building code requirements and be designed to provide support with a maximum allowable deflection of L/360 under all intended live (including wind) and dead loads.
Note: Cut or score PermaBASE® Cement Board on rough side of panel.
Control Joints: For exterior installations, consult the finish manufacturer for spacing requirements. For exterior tile applications, control joints should be spaced a maximum of every 12'. If no recommendation is available, allow a maximum of 16 linear feet between control joints. A control joint must be installed but not limited to the following locations: where expansion joints occur in the framing or building (discontinue all cross furring members located behind joint); when boards abut dissimilar materials; where framing material changes; at changes of building shape or structural system; at each story separation. Place control joints at corners of window and door openings or follow specifications of the architect. Control joint cavity shall not be filled with coating or other materials.
WALLS AND CEILINGS
Wall Framing: Studs should be spaced a maximum of 16" o.c. Edges/ends of PermaBASE® Cement Board parallel to framing should be continuously supported. Provide additional blocking when necessary to permit proper attachment. Do not install PermaBase® Cement Board directly over protrusions from stud plane such as heavy brackets or fastener heads.
Ceiling Framing: The deflection of the complete ceiling assembly due to dead load (including insulation, PermaBASE® Cement Board, bonding material, and facing material) should not exceed L/360. The dead load applied to the ceiling frame should not exceed 10 psf. The ceiling joist or furring channel should not exceed 16" o.c. (Edges of PermaBASE® Cement Board parallel to framing should be continuously supported.) Provide additional blocking when necessary to permit proper attachment.
Water Barrier: While PermaBASE® Cement Board is unaffected by moisture, a water/air resistive barrier (WRB) must be installed to protect the cavity. The type and specific placement or location of the water barrier will vary based on local building codes and/or manufacturers' warranties. Consult the WRB manufacturer’s recommendations for specific installation guidelines.
PermaBASE Cement Board: Apply PermaBASE® Cement Board with ends and edges closely butted but not forced together. Stagger end joints in successive courses. Drive fasteners into the field of cement board first, working toward ends and edges. Space fasteners maximum 8" o.c. for walls, 6" o.c. for ceilings with perimeter fasteners at least 3/8" and less than 5/8" from ends and edges.
Joint Reinforcement: Trowel bonding material to completely fill the tapered recessed board joints and gaps between each panel. On non-tapered joints, apply a 6" wide, approximately 1/16" thick coat of bonding material over the entire joint. For all joints, immediately embed 4" alkali-resistant fiberglass mesh tape fully into applied bonding material and allow to cure. The same bonding material should be applied to corners, control joints, trims, or other accessories. Feather bonding material over fasteners to fully conceal.
Subfloor: Plywood should be securely glued and fastened to floor joists spaced a maximum of 16"o.c. Subfloor should be sloped at a minimum pitch of 1/4" per foot. The floor surface should be true to plane within 1/8" in 10'.
Underlayment: Using a 1/4" square-notched trowel, apply a setting bed of latex-portland cement mortar to the subfloor. Immediately laminate UltraBacker® to subfloor, leaving a 1/8" space between boards at all joints and corners. Leave a 1/4" gap along walls. Stagger joints so they do not line up with underlying substrate joints. Fasten UltraBacker® every 8" o.c. throughout board field and around all edges while setting bed mortar is still workable. Around the perimeter of each board, locate fasteners 2" from the corners and not less than 3/8" from the edges. Fill all joints solid with bonding material. On non-tapered joints such as butt ends, apply a 6" wide, 1/16" thick coat over the entire joint. For all joints, embed alkali-resistant fiberglass mesh tape fully into applied bonding material; ensure that tape is centered over the joint. Apply bonding material over fasteners to fully conceal. Remove all excess bonding material and allow it to cure.
Waterproof Membrane: Trowel apply waterproof membrane to the entire surface of the cement board, following membrane manufacturer’s installation instructions in detail.