stringent framing requirements in areas where concentrated dead loads are expected, with kitchen islands a particular focus because of their widespread use. It’s not practical, though, to expect a customized calculation and specification for every kitchen island. A more practical approach would be to follow general guide- lines that are widely effective and easily incorporated into documents and processes. Since large kitchen islands are fre- quently paired with ceramic or stone flooring, it makes sense to have the following structural design param- eters specifically attached to them: • For solid-sawn and I-joists: joist spacing beneath kitchen islands shall be reduced by one-half and indicated on the joist framing plan. • For floor trusses: floor trusses beneath kitchen islands shall be doubled. Designing for hard surfaces checklist These suggestions are in addition to the following recommendations, some of which were provided ear- lier in the article but are restated here in the interest of supplying a complete “designing for hard sur- faces checklist”: • Prepare construction documents that contain: º the TCNA Handbook installa- tion method º the weight of the installation method (from TCNA Handbook Appendix B) º the footprint of the kitchen island (and other heavy equip- ment) º a specification that joists shall be doubled, or spacing reduced by half, beneath an island • Require floor system designs based on a “total load” that includes the actual weight of the installation method • Upgrade subfloor thickness (above what is given in the TCNA Handbook method being used) • Require strongback bracing for floor trusses to minimize differ- ential deflection of joists • Offer customers (homebuyers, owners) floor framing and sub- floor “upgrades” for added pro- tection against the likelihood of tile and grout cracks and annoy- ing floor vibrations The generalized “overbuilding” that some of these recommenda- tions suggest may not seem an easy ask in an industry that prizes value engineering. But they do have enormous value – not in material cost savings – but from having effective boilerplate solu- tions to a common design chal- lenge that are also practical with respect to implementation. Tile and stone professionals would be well served if these guidelines were better known and understood by building designers. TileLetter read- ers are encouraged to help make that happen by circulating and posting the information freely. TECH TALK –––––––––––––––––––––––––––––––––––––––––––––––––––––––––– 68 TileLetter | February 2019