2024-25_NTCA_Reference_Manual_dig_dwnld

Ceramic and Stone Tile Installations Over Engineered Wood Structural Floor Assemblies For Informational Purposes Only Design professional must engineer system to accept tile installation

SUMMARY OF I-JOISTS DESIGN AND CONSTRUCTION GUIDELINES FOR TILE INSTALLATION

• Engineered wood (EW) products must be properly stored (covered, off the ground) in accordance with manufacturer’s instruc tions to prevent excessive moisture absorption. Avoid excessive concentrated loading of EW and all other wood framing after installation, especially if exposed to prolonged periods of rain.

• I-Joist design and selection must be based on realistic uniform dead loads (weight of materials) for a tile installation (especially if a thick mortar bed installation is proposed), as well as anticipated concentrated loads whenever possible.

• The maximum deflection of an I-Joist under ceramic tile floor finishes should be no greater than L/480 under live loads, and not the code required minimum of L/360. The Natural Stone Institute (NSI) recommends maximum deflection of L/720 under live loads for natural stone tile installations. • If tile is to be installed in limited areas only (kitchen, bath, foyer), an increase in stiffness for the entire residence may not be nec essary or economically feasible. It is more practical to decrease I-Joist spacing to 16 in. (406 mm) or 12 in. (305 mm) on center under those areas if possible. Offset the joints of the underlayment layer from the joints of the subfloor, utilize solid blocking between joists to both support subfloor panel edges and stiffen the subfloor panel (plywood or OSB) either as a preventative or corrective measure. Gluing the subfloor panels to the joists will increase the stiffness of the floor-panel system. Gluing the T&G of subfloor panel joints will increase floor stiffness even more. • Follow manufacturer’s required construction details for all floor-framing conditions to ensure specified performance of EW prod ucts (examples: solid blocking over support beams, load bearing web stiffeners where required, blocking near perimeter support walls, or use of “wet” design values to provide added safety factor. • Provide bracing for the bottom flange of exposed I-Joists in unfinished basements with lateral wood bracing or metal bridging even if not required by the I-Joist manufacturer (required only for certain I-Joist depths/sizes) to protect from increased torsion and vibration common to I-Joists.

Photo courtesy of the National Tile Contractors Association

NTCA Reference Manual | 2024 / 2025

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Chapter 2 | Substrates