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PWiIson
<br /> SURVEY / ENGINEERING
<br /> October 2,2015
<br /> Ken Van Winkle
<br /> Everett Housing Authority
<br /> 2715 151"Street
<br /> Everett,WA 98201
<br /> Re: Professional Structural Engineering Assessment 2015-098
<br /> Meadows 1 —3, 1115—1123— 1131 Rainier Avenue, Everett,WA
<br /> Dear Mr.Van Winkle:
<br /> Wilson Engineering, LLC is pleased to submit to you our report on conditions and potential repair
<br /> methods to the buildings (Meadows 1 —2—3) at 1115— 1123— 1131 Rainier Avenue. You called us to
<br /> look into buckling of siding that has been observed, assess the probable cause, and make
<br /> recommendations.
<br /> SUMMARY OF OBSERVATIONS AND DOCUMENTARY EVIDENCE
<br /> Please refer to the photos on pages 3 - 5. Along with the drawings, and an illustrative sketch, they
<br /> illustrate better than words much of what will be described herein.
<br /> I was on site on Tuesday, August 25, 2015. I was shown a number of locations on the buildings, most
<br /> notably on Meadows 3, where the cedar siding had buckled, in some cases more than an inch. Please
<br /> refer to photos 1 and 3 for two particular cases that stand out. By the time our second close observation,
<br /> I had already formulated the beginnings of a theory of as to the nature of the buckles, so other
<br /> observations were made with that in mind.
<br /> One other location with a very small bulge was drilled on Meadows 2. No strap was found. Subsequent
<br /> analysis of the drawings(obtained from RMC Architects) made it clear that none should have been there.
<br /> ANALYSIS
<br /> It was believed before my site visit that the bulges were caused by deformations in the rim board.
<br /> However, this is not consistent with the pattern that has been observed. First, none of the buckles occur
<br /> at the first floor level, only on upper levels. Also,they have been mainly observed in locations adjacent to
<br /> double studs alongside windows,where hold down straps are attached.
<br /> Hold down straps tie the walls on floors above and below together to resist earthquake and wind forces.
<br /> This explains why buckles are in line with the jambs of window openings, and are at floor-to-floor levels.
<br /> These are exactly the places that hold downs are called for. Please refer to the attached design drawings
<br /> S2 and S10,along with an annotated excerpt from S10.
<br /> At the location of photo 1, as shown in closeup by photo 2, a hold down strap was found. It was out of
<br /> plumb approximately 1 1/4 inch. In the case shown, it is likely that the strap was poorly installed--there is
<br /> a nail seen in the photo where none is supposed to be. However, such out of plumb installations can
<br /> also be the result of wood shrinkage due to drying of the top and sill plates, as explained below.
<br /> Depending on the orientation of the growth rings to the cut of the lumber, and the moisture level at which
<br /> it was installed, wood can shrink up to 6% in the across grain direction. Shrinkage parallel to the grain is
<br /> generally much less. Assuming shrinkage of 4%, with no shrinkage in the engineered lumber rim joist,
<br /> this amounts to 0.04 x 4.5"=0.18." For a strap spanning a 19"distance across the 18" rim,this can result
<br /> in a large buckle, as shown on the diagram which was worked out on a computer aided drafting program
<br /> and checked mathematically.
<br /> This is a recognized issue with the use of hold down straps, versus other types of hold down systems.
<br /> The attached article discusses this topic. Nevertheless, whether or not the straps were buckled or if they
<br /> were poorly installed, it is quite important to get them properly installed, i.e. flat to the studs and
<br /> sheathing.
<br /> Since the orientation of grain cuts is random, and not all lumber is likely to have been exposed to wet
<br /> conditions before or during construction, the resulting buckles will also be likely to be relatively few and
<br /> randomly distributed. This appears to be the case at Meadows.
<br /> Since the wood siding has random grain orientation, it will at some locations have buckled of its own
<br /> accord. These cases should not usually approach the 1" and larger displacements underlain by hold
<br /> down straps, however. They would be more likely to appear like that seen in photo 4, in which the cross
<br /> section of the siding is warped.
<br /> WILSON ENGINEERING,LLC 805 Dupont St,Suite 7,Bellingham,WA 98225 (360)733-6100 www.wilsonengineering.com
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