1325 SE EVERETT MALL WAY FLYING SQUIRREL 2021-12-22

$ • • vrww dykemen.net I 1716 West Marine View Drive 426.E 59.3161 (T) 2nd Floor/Everett,WA 98201 10 December 10th,2020 Tony Lee, Code Official, City of Everett. RE: Code Alternate Proposal-Flying Squirrel Sports. Dear Tony, As allowed in IBC section 104.11,the Flying Squirrel Sports project is proposing an alternate method and material for the construction of platforms located at the building's interior. In lieu of wood or metal-framed platforms,we are proposing to use polystyrene geofoam as a structural fill material below platform decks. Polystyrene foam has been used for many years as an insulation material in exterior walls, and its use for these purposes is well documented. It has also been used for many years below concrete slabs as an exterior infill material. The product has been approved for Type V construction, as described on the enclosed ICC-IER report. (Please note that the IER report focuses on polystyrene insulation, and not on polystyrene used as infill or load bearing substrate,as it would be in this facility.) The Flying Squirrel facility is a Type III building, which is essentially the same as a Type V building, except for the non-combustible nature of Type III exterior walls. We are proposing to use the product on the interior of the building, consistent with its approved use at Type V construction. The perimeter of the platforms will be enclosed with metal stud walls faced with plywood sheathing for shear, and the interior of platforms will consist of full height geofoam, with plywood decking on top. Concealed space below the platforms will be filled with foam, and stud cavities will be filled with 3 1/2" of mineral wool, leaving no space for oxygen. The foam material has a flame spread index of less than 25, and a smoke developed index of less than 450, per ASTM E-84, in accordance with the requirements of IBC 2603. To comply with thermal barrier requirements of IBC chapter 26, metal framed walls at the perimeter will be covered with 5/8" gypsum wallboard. and the deck will be covered with 3 " nominal plywood, complying with 2604.14. Structurally, geofoam has a compressive strength capable of withstanding 7.3 lbs/sq. in,which corresponds to 1,051 psf. We believe the proposed construction to be as least as safe as that which would be provided with a wood- framed platform which is typically allowed by code, and ask that you approve this alternate method for . Sincerely W. Douglas Hofius,AIA Project Manager CC: \,. ARCHITECTURE + DESIGN ‘0H Aai aea