HomeMy WebLinkAboutEngineer's Report 10.24.2016Berson
Structural
4 Engineering
October 24, 2016
Mr. Tim Lewis
9406 C.R. 325
Rifle, CO 81650
RE: Retaining Wall Inspection — 9406 C.R. 325 — Rifle, Colorado
Dear Mr. Lewis:
Per your request, Anderson Structural Engineering, inc. visited the subject residence to inspect
the existing retaining wall construction and deck bearing conditions. We understand that the
retaining wall was built approximately three years ago and the deck construction is new. No
design drawings were available for review.
The retaining wall is a dry stacked boulder wall of varying heights. A maximum height of
approximately 8'-6" was noted and the backfill was noted to be sloping up behind the wall.
Boulder sizes varied from approximately 36" width at the bottom to 12" width at the top. We
understand that no drain was installed behind the wall. A portion of the wall extending from
the new deck stair to the existing residence is mortared at the bottom. We understand the wall
has been performing its intended function and no distress was noted. The new deck structure is
built on the west side of the residence and extends from the existing house structure over the
retaining wall where it is supported by new foundations. A stairway is connected to the
extension down to grade. The deck extension is 5'-0" wide and is supported at the house and at
mid span by (2) timber columns. The end of the extension is supported by (2) new foundations
located behind the retaining wall. The span from the mid span supports to the supports behind
the retaining wall is approximately 11'-0". We understand the deck foundations were built
using 12" diameter sonotubes reinforced with (6) #4 bars. Depth of the foundations is reported
to be 48" below final grade.
The new deck supports at the retaining wall were measured to be 6'-0" behind the lower face
of the wall. Based on this location and a bearing depth of 48" below the top of the wall we do
not believe the new deck loading is applying any lateral surcharge to the wall. It was noted that
some deck joists were notched to clear the top of the wall and others were in closer contact
with the stone. The deck joists should be bear directly to the end foundation system and should
not bear directly on the boulder wall. Small rocks in contact with the joists should be removed
to provide a minimum of 1" clearance. This will provide some tolerance for settlement and will
avoid imparting any vertical deck Toad to the boulder wall.
823 Grand Avenue, Suite 340 • Glenwood Springs, CO 81601
(970) 984-0320 • email: Iandon@anderson-structural.com
Berson
Structural
Engineering
In conclusion, this inspection was limited to visible structure only. No attempt has been made
to verify the adequacy of the existing retaining wall design or the new deck construction.
Opinions presented herein, have been based on our analysis of the existing conditions, and
generally accepted engineering practice.
Please do not hesitate to contact our office for any questions.
Sincerely,
Landon Anderson, P.E.
Anderson Structural Engineering, Inc.
823 Grand Avenue, Suite 340 • Glenwood Springs, CO 81601
(970) 984-0320 • email: Iandon@anderson-structural.com