28.06.030 Conventional Construction Methods and Materials for Floating Structures and Walkways Using Log Support Systems.

City Code Section

(Amended by Ordinances 181437 and 191154, effective March 1, 2023.)

  1. A.  Floating structures.  The following methods and materials are approved without engineering provided the highest point of the roof structure measured from the top of the float does not exceed 75 percent of the minimum width of the float.
    1. 1.  The logs and stringers forming the floats under floating structure must conform to these provisions:
      1. a.  The structure on the float cannot be larger than the float.
      2. EXCEPTION: Decks raised above the level of the float deck and balconies will be permitted to project a maximum of 3 feet 0 inches beyond the edge of the float provided such projections do not affect the stability of the float as detailed in Section 28.06.040, the projections do not extend beyond the legally established boundaries of the slip in which the floating structure is located and provided the required separations between structures is not reduced by the projection.  Engineering calculations must be provided to verify that any projections beyond the edge of the float will not affect the stability of the float and structure.
      3. b.  Floats supporting combo-structures and which have a boatwell that interrupts the continuity of the float must be an engineered design or comply with prescriptive alternate methods of construction as adopted by the Director under Section 28.03.010.
      4. c.   Raft logs are to be 16-inch minimum diameter at the tip and must be spaced no greater than 18" between tangent points.
      5. d.  Bearing walls should align over stringers or center line of logs.  When such alignment is not feasible, adequate support for bearing walls must be provided.
      6. e.  If the Certified Structural Inspector or Certified Floating Structure Inspector or an architect or engineer responsible for the design of the floating structure finds the completed log raft insufficiently stable for the intended structure, they may then require the stringer layout to compose a rigid frame by the addition of side chords and fixed joints or cross bracing or by an alternate engineered design.
      7. f.  Logs must be Douglas Fir, Sugar Pine, Lodge Pole Pine, Western (Idaho) White Pine, Alaska Yellow Cedar or Sitka Spruce, sound and free of all bark above the water line.
      8. g.   In a floating structure foundation float at least 50 percent of all logs must be full length.  Segmented logs must be alternated between full-length logs.   Joints in segmented logs must be staggered a minimum of 3 stringer spaces apart laterally on alternate segmented logs.  Not more than one joint may be used per segmented log assembly. All outboard logs must be full length.
      9. h.  Logs must be notched so as to provide sufficient bearing for the stringers.  The seat of the notch must be a minimum of 4-1/2 inches above the water level when the float is fully loaded.
      10. i.  Wood stringers must be nominally a minimum of 6 inches by 10 inches for one and two story structures and be preservative treated in compliance with Subsection 28.06.020 B.  Steel stringers must be of a size to provide equivalent bearing surface and load capacity as a wood stringer used for a similar conditions and must have a minimum web thickness of 0.250 inches.
      11. j.   Stringers inside of perimeter bearing walls must be placed on the logs not more than 4 feet on center and fixed to the logs with headed steel rods a minimum of 5/8 inches in diameter and a minimum of 20 inches long.  These pins are to penetrate the log at least 10 inches.  All log to stringer contact points must have two pins.
      12. k.  The wood construction below the joists is to be inspected for proper construction and soundness of logs, including dapped bearing connections, prior to installation of joists.  Inspections must be performed by a Certified Structural Inspector, a Certified Floating Structure Inspector, a licensed architect or a licensed engineer.  The person performing the inspection must prepare a report of the inspection.  The inspection report must be submitted to the Director for review and approval prior to continuing the construction of the float.
  2. B.  Walkways leading to floating structures.  Floating walkway supports may consist of preservative treated 6 inch x 6 inch wood stringers not more than 6 feet-0 inches on center or preservative treated 4 inch x 6 inch wood stringers not more than 5 feet-0 inches on center.  Steel stringers of a size to provide equivalent bearing surface and load capacity as a wood stringer may be used for similar conditions.  Stringers must be anchored to the logs with headed steel rods (pins) as described above.  Single headed steel rods (pins) may be used at interior logs.  Maximum joist spacing is 2 feet-0 inches on center.
  3. C.  Floatation.  Floating structures must have adequate floatation to maintain a clearance above the water of 1 foot 0 inches minimum from water line to the top of the walking surface for walkways and walks and 1 foot 8 inches minimum from the water line to the finished floor level for the lowest occupied floor of all other floating structures, under all applicable load conditions.
  4. D.  Mooring connections.  Mooring connections must be adequate to keep the moorage in place under all reasonable load conditions. The following minimum connection standards are deemed to provide adequate connection to resist average load conditions.  Where a local condition imposes greater than average load conditions on a moorage, the builder must provide adequate connection to resist such loads. Such connection must be designed by an Oregon registered engineer to resist the actual loads expected.
    1. 1.  Floating structures must be anchored to the moorage structure with connections to the floatation system of the structures.  Connectors must be provided as indicated below.  These points must be a minimum of one foot from each end of the float.
      1. a.  For floats where floatation logs are parallel to the current flow connectors must be provided at each outside log and at not more than 15 feet apart at interior logs.
      2. b.  For floats where floatation logs are not parallel to the current flow connectors must be provided at each outside log and at not more than 15 feet apart at interior logs with one additional connector provided at the upstream outside log approximately midway along the length of the log.
    2. 2.  The connections must consist of a steel bracket or other approved connection.  The bracket is to be 3/8 inch thick and adequate in size to support the pins.  Pins are to be a minimum of 4 inches apart.  This bracket must be fixed with a minimum of three, headed steel rods (pins) a minimum of 5/8 inch in diameter that penetrate the floatation log at least 10 inches.  The connections from the bracket to the walkway or piling must consist of chain with a minimum link wire diameter of 1/2 inch or other approved connection device.  If attached to walkway logs, the boom chain must be looped around the second log or most secure log of the walkway.  Walkways must be adequately secured to pilings. 

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