3530 COLBY AVE COCOON HOUSE 2020-01-13

Tony Lee From: Scott Schreffler <SSchreffler@GGLO.com> Sent: Tuesday, December 12, 2017 11:44 AM To: Tony Lee Subject: FW:Acoustic report Attachments: IBC Noise.pdf Tony, In designing the corridor walls,we are confronted with a situation that is common in wood-framed buildings requiring STC 50 corridor walls. In effect,these walls are rarely built to STC 50 because of the structural requirements and the entry doors. See below judgement by the acoustical consultant which describes this condition. Fortunately we do not have any bedrooms adjacent to the corridors. We request approval of hits condition and please let me know how you would like us to reference this in the drawings. Thanks, Scott Schreffler AIA,LEED AP®BD+C Associate D+1 206.902.5560 C+1 425.870.2656 GGLO SEATTLE/LOS ANGELES WWM.GGLO.COM From:Jerry Lilly [mailto:jerry@jglacoustics.com] Sent:Wednesday, November 8, 2017 8:24 PM To:Scott Schreffler<SSchreffler@GGLO.com> Subject: RE:Acoustic report Scott: During our discussion this afternoon I pointed out that the International Building Code (see attached excerpt) requires all walls between living space and an interior corridor to have a minimum STC rating of 50,which is the same requirement as walls separating adjacent living units. In this project all of the walls between the corridor and the living units include an entry door. Although the entry door itself does not have to have an STC rating of 50,the corridor wall is not exempt from this requirement. A typical solid wood door without acoustic seals will have an STC rating of about 25, so when this door is placed into an STC 50 wall,the net result is a composite STC rating of about 30(taking into account the 25 rating for the door and the 50 rating for the wall). Your current drawings show a corridor wall assembly with an STC rating of 40,which when combined with an STC 25 door will yield a composite STC rating of 30. This is the same composite STC rating as with the STC 50 wall. In this case,there is no benefit in the sound isolation by improving the corridor wall STC rating from 40 to the Code minimum 50. However,there is a substantial cost increase in upgrading the STC 40 corridor wall to an STC 50 corridor wall. It would be good if the code official would permit minimum STC 40 corridor walls where there are unit entry doors into the living units. I'm sure that the owner could find better e for these otherwise wasted dollars. Jerry G. Lilly, P.E. 175