§ 150-128  Sound Isolation Construction.
   Construction as outlined in this section that satisfies the requirements of the zoning ordinance and for purposes of this amendment is considered to meet the interior noise standard specified in § 150-125.  Each item indicated in this section shall be identified on the project drawings which are submitted with the permit application.  Certification by an acoustical engineer or registered architect shall attest that construction practices and the materials of the structure will achieve the interior noise level reduction required by the prescribed noise attenuation standard.  The engineer or architect shall submit relevant information to permit the City Building Official to verify that the proposed measures will achieve the specified interior noise level standards.
   (A)   Noise level reduction—25 decibels.  For a building located where a noise level reduction of 25 decibels is required, the building shall be constructed as follows:
      (1)   If wood frame construction is used, all exterior stud walls shall have interior and exterior surfaces of an approved material at least as massive as half-inch gypsum wallboard, and the intervening space (studs) shall contain fibrous thermal insulation having a resistance of R-11 or greater.
      (2)   Arrangements for any habitable room shall be such that any exterior door or window can be kept closed when the room is in use.
      (3)   Any air duct or connection out-of-doors must contain an interior sound-absorbing lining acoustically equivalent at least to fiberglass duct liner one inch thick and of a length greater than five times the diameter of the duct.
      (4)   The ceiling below an attic space shall include gypsum board or plaster at least one-half inch thick; fibrous thermal insulation having a resistance of R-19 or greater shall be placed above the ceiling.
      (5)   There shall be no direct openings, such as mail slots, from the interior to the exterior of the building.  All chimneys shall be provided with well-fitted dampers.
      (6)   All openable windows shall be sound rated assemblies having sound transmission class (STC) of at least 24.  Fixed windows shall be well sealed and at least three-sixteenth-inch-thick glass.
      (7)   All entry doors shall be solid-core constructed, close-fitting units with weather-stripping seals incorporated on all edges to eliminate gaps.  Air gaps and rattling shall not be permitted.
      (8)   Masonry walls, if used, shall be at least equivalent in weight to eight-inch, lightweight concrete blocks, at least one surface of which is painted or plastered.
      (9)   The roof deck shall weigh at least seven pounds per square foot with roof sheathing containing a solid core at least one-half inch thick.
      (10)   Rooms when in use are expected to contain furniture, or other materials that absorb sound equivalent to the absorption provided by wall-to-wall carpeting over a conventional pad.
   (B)   Noise level reduction—30 decibels.  For a building located where a noise level reduction of 30 decibels is required, the building shall be constructed to incorporate the features described in preceding subsections (NLR 25 dB) with the following additions:
      (1)   Windows, fixed or openable, shall be sound-rated units with a sound transmission class (STC) of at least 32 (double-glazed).
      (2)   A ceiling or exhaust duct for the forced air ventilation system shall be provided with a bend in the duct such that there is no direct line of sight through the duct from outside to inside.  The bend shall be lined with the equivalent of fiberglass duct liner one-half inch thick.
      (3)   The top floor-ceiling construction shall consist of plaster or gypsum board at least five-eighths inch thick.
      (4)   The floor of the lowest room or area shall be a concrete slab, or shall be sealed against exterior noise.
      (5)   Masonry walls, if used, shall be at least equivalent in weight to eight-inch, lightweight concrete blocks.  At least one surface shall be painted, plastered or covered with gypsum board.
      (6)   The roof deck shall weigh at least 12 pounds per square foot.  Wood roof sheathing shall be continuous (plywood) and at least five-eighths inch thick.
   (C)   Noise level reduction—35 decibels.  For a building located where a noise level reduction of 35 decibels is required, a building shall be constructed to incorporate the features described above (NLR of 25 and 30 dB) with the following additional features:
      (1)   The use of exposed wood beam ceilings is prohibited unless sound isolating treatment is provided between the ceiling and roofline.  The minimum treatment shall consist of rigid fiberglass board, nominally two inches thick placed over the interior ceiling and under at least one-half inch of plywood sheathing.  The sheathing shall be nailed only to the beam or major frame members and not to the interior exposed ceiling at points between the beams.
      (2)   For attic spaces ventilated to the outside, the attic floor shall be decked over with one-half inch plywood or equivalent and all cracks caulked.  R-11 insulation shall be placed between the floor joists.
      (3)   Roof deck shall weigh at least 20 pounds per square foot.  Roof sheathing shall be continuous, weighing a total of at least four pounds per square foot.
      (4)   Wood paneling less than one-half inch thick shall be used only over gypsum board of at least five-eighths inch thick.  Interior gypsum board walls shall consist of two layers of one-half-inch board nailed directly to the studs.
      (5)   Fixed or openable windows must be sound rated units with at least a sound transmission class (STC) of 36.
   (D)   All residential buildings shall be constructed with minimum R19 exterior walls, R30 roofs, dual-glazed windows, and solid wood, foam-filled fiberglass or metal doors to the exterior.
('80 Code, § 7-47)  (Ord. 1857, passed 7-18-79; Am. Ord. O2002-10, passed 2-20-02)  Penalty, see § 150-999