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HomeMy WebLinkAboutB15-0006_B15-0006 Engineers letter_1420823940.pdf the mj Mueller co., inc. 8 January 2015 Mr.Steve Loftus NAIL RACQUET.CLUB 4695 Racquet Club Drive Vail, Colorado 81657 Subject: Snow Management Plan VRC Buildings 1 and 2 Atyour request,this office has structurally determined the snow load capacity of the above mentioned roofs. The purpose of the review is to determine the capacity before and after the proposed roof replacement and determine the maximum depth of snow that can be supported according to the present building codes. Original structural plans, details and specifications as prepared by C CLAY DAVIS dated 5-30-78 were available for review: The 2012 International Building Code is the present code adopted by the Town of Vail Building Department. The current design snow load for roofs sloped at 3:12 is 100 pounds per square foot.' The following items are to be noted • a) ORIGINAL ROOF . The original roof was a 3 ply built-up roof with"Geo-Rock"slag on top of 3"of rigid insulation over 2x6 T and G decking..The total weight of theinsulation, roof and slag is 10.0 pounds per square foot (psf) b) PROPOSED ROOF The proposed roof will be Asphalt Dimensional Strip Shingles over%:' plywood on 434" Perlite Foam Insulation on a vapor retarder over the existing 2x6 T and G decking to remain. The total weight of the retarder,foam, plywood and shingles is also 10.0 psf. See"Replace Roofing" as prepared by ROOFTECH CONSULTANTS, INC.dated 8/20/14 for plans,details and specifications of proposed roofing system. c) ROOF CAPACITY In the case of VRC Buildings 1 and 2,the timber rafters with the longest spans,are the weak link of the roof structure. The 4x10 and 6x10 Doug-Fir#1 timber rafters are typically spaced 48"on center (oc). There are a few select bays that are spaced a bit further than 48"oc,but these conditions typicallyhave additional intermediate points of support The 4x10 rafters typically span 12'-11`1/2" (horizontal projection centerline to centerline of support) maximum and are capable of supporting 70 psf snow at a maximum deflection of 1/240(0.66"). The 6x10 rafters are also designed for civil architectural and structural engineering • p.o. box 2747 vail, colorado 81658 476-2627 476-2637 (FAX) Page 2 Mr. Steve Loftus 8 January 2015 typical spacing of 48"oc. The 6x10 rafters typically span 16'-0"(horizontal projection centerline to centerline of support) maximum and are capable of supporting 65 psf snow at a maximum deflection of 1/240(0.83"). d) SNOW MANAGEMENT PLAN Since the new roof on the original structure is not capable of supporting the current design snow loads,the TOV building code is requiring that the ownership create a"Snow Management Plan". A "Snow Management Plan"requires snow to be removed when a maximum depth is reached. The depth is determined by the snow load capacity and the density of the snow. The density of snow varies greatly, depending on exposure,year and time of the particular winter,snowpack,etc. 20 pounds per cubic foot(pcf) is generally assumed as the design snow density for this type of calculation in this environment. Therefore the 4x10 rafters can support 3'-6"of snow and the 6x10 rafters can support 3'-3"of snow. When the snow depths are greater than these depths at the center of the spans of the rafters,snow removal for all orparts of the roofs must be completed. Contact a structural engineer to coordinate localized snow removal when the situation exists:.Keep in mind that thecode design deflection is achieved only in the worst of cases. n conclusion,the proposed roof system for Buildings 1 and 2 weighs the same as the original roof system while increasingthe depth of,insulation 50%. According to current code,the snow load capacity of the longest spans of 4x10 rafters(12'-11 W) is 70 psf,and the snow load capacity of the longest spans of 6x10 rafters(16'-0")is 65 psfWhen the snow depthat the center of the referenced spans exceeds 3'-6"for the 4x10 rafters,and 3'-3"for the 6x10 rafters,TOV codes requires some or possibly all of the snow to be removed from the roof. This inspection and report have been prepared in accordance with generally accepted engineering practices in this area,for use by the client in determining the snow load capacity of the existing roofs. The conclusions and recommendations submitted in this report are based upon visual inspection of the completed building and review of the original structural construction documents. It is to be understood that a limited amount of structure is visible in a completed building. This inspection does not warranty the building against future repairs for hidden or inactive mechanisms,or compliance with any past, present or future building and/or zoning codes. If you have any questions regarding _x, _ e contact this office at the phone number shown on fe < the cover sheet. -*y 0 +L Sincerely.yours, ; ,.K THE M J MUELLER CO. IN jit Mark J.Mueller,PE 4 ` .,1.,,, i p't. '' President a . 1 ..