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THE BOEING comes <br />000R1)INAII0N 5111-FT <br />From: Leonard Astemborski No.: 209 <br />M/S OH-13 Job No.: <br />266-3563 Date: Oct. 10, 1996 <br />FAX 342-8167 <br />To: Steve Miller <br />Tim Tyler <br />City of Everett Building Department <br />CC: <br />Subject: High Bay Factory Office Build Out <br />Stair towers will be two hour fire rating for their full height. The new stair tower <br />walls are designed using a two hour rated shaft wall system. Where required, <br />existing stair tower walls will be upgraded to meet a two hour fire rating. All stair <br />tower doors, both new and existing, are 90 minute rated. Existing stair tower <br />walls are constructed of 3/4" cold rolled channels at 16" o.c. with metal lath and <br />314" plaster cover on both sides for a total plaster thickness of 2-1/4". The <br />closest two hour U.L. rated system that resembles this composition is U.L. <br />Design No. U413. This design system uses the same framing as existing walls, <br />but has 2-1/2" total plaster thickness. <br />A variance is required t-) allow the 2-1/4" system in stead of the 2-1/2" system. <br />This situation occurs at approximately twelve existing stair towers of the current <br />high bay factory off icu build out project. <br />O Box 3707, Mail Stop OH-13 <br />Seattle, WA 98124-2207 <br />