HomeMy WebLinkAboutMINUTES - 05102005 - C63 s - Contra
,•���
Costa
TO: BOARD OF SUPERVISORS
County
FROM: CARLOS BALTODANO, DIRECTOR
BUILDING INSPECTION DEPARTMENT
DATE: MAY 10, 2005
SUBJECT: Consider Report on Corrosion of Metal Fasteners and Framing
Connectors
SPECIFIC REQUEST(S)OR RECOMMENDATION(S)&BACKGROUND AND JUSTIFICATION
RECOMMENDATIONS
ACCEPT the Building Inspection Department's December 30, 2004
memorandum to the Transportation, Water & Infrastructure Committee.
DIRECT the Building Inspection Director to contact the cities within Contra
Costa County advising them of the corrosion problem when using metal
fasteners and framing members with the new treated wood
11111,111111111111000 oe
CONTINUED ON ATTACHMENT: YES SIGNATURE1 00
ECOMMENDATION OF COUNTY ADMINISTRATOR RECOMMENDATION OF BOARD COMMITTEE
,,JAPPROVE OTHER
SIGNATURES
ACTION OF BO R ON ZP av APPROVED AS RECOMMENDED O R
un? -�F SUPERVISORS
UNANIMOUS(ABSENT I HEREBY CERTIFY THAT THIS IS A
AYES NOES: - TRUE AND CORRECT COPY OF AN
ABSENT:- ABSTAI'" ACTION TAKEN AND ENTERED ON THE
MINUTES OF THE BOARD OF
Contact: Carlos Baltodano(925/335-1108) SUPERVISORS ON THE DATE SHOWN.
ATTESTED: 1&4
4_9-60v
cc: Building Inspection John Sweeten, Clerk of the Board of
Steve Goetz,Deputy Director Transportation Supervis nd Co or
BY
DEP
CB:Ig
\bdord
FISCAL IMPACT
None
BACKGROUND/REASONS FOR RECOMMENDATIONS
On March 14, 2005 the Transportation, Water and Infrastructure Committee (TWI
Committee) of the Board of Supervisors considered a report on the corrosion of metal
fasteners and metal framing connectors. At the November 8, 2004 meeting and under
public comments, Mr. Joe Partansky, reported on a news article warning that the new
pressure treated wood quickly corrodes metal hardware. The Board committee
requested staff to look into the matter. At the March 14, 2005 meeting, Mr. Carlos
Baltodano, Director Building Inspection Department, made a presentation addressing
these issues. Attached is the report from the Building Inspection Department.
After hearing the report, the TWI Committee concurred with the
recommendations and requested that the attached report be forwarded
to the Board of Supervisors.
In summary the Building Inspection Department is to continue to follow
the research on the effect of the new pressure treated woods on the
metal fasteners and framing connectors and report back to the TWI
Committee as new research develops.
The Building Inspection Department recommendations are as follows as
outlined in the report:
- Stainless steel connectors and fasteners offer the maximum
protection against corrosion. These are recommended in severe
environments such as salt-water exposure..
- Hot dip galvanized fasteners and connectors with heavier zinc
coating (G185) are acceptable for general exterior use.
- Non-galvanized fasteners are adequate in dry applications such as
the nailing of wall plywood to house sill plates.
- Aluminum should never be in contact with pressure treated wood.
- Metals should not be mixed in the same connections, i.e. no
stainless nails in galvanized joist hangers or vice versa.
The TWI Committee also requested the Building Inspection Department
to contact Mr. Partansky who had initially brought the issue to the TWI
File Name glass/w:\Personal\Board Order Info\Metal Fasteners.dot
Board Date May 3.2005
Page 2 of 3
Committee. The department has contacted Mr. Partansky and
discussed the report and the finding.
Mr. Partansky also recommended that the Building Inspection
Department contact the cities within Contra Costa County advising them
of the potential corrosion of metal fasteners and framing connectors
when used with the new pressure treated woods.
Attachments.
File Name glassMAPersonal\Board Order lnfo\Metal Fasteners.dot
Board Date May 3.2005
Page 3 of 3
Building InspectionContra Carlos Baltodano
Department Costa Director of Building Inspection
County Administration Building
651 Pine Street,3rd Floor, North Wing County
Martinez, California 94553-1295
(925)646-4108
FAX (925)646-1219
N
.1.
December 30, 2004
Transportation, Water&Infrastructure Committee
Attn: Steve Goetz, Deputy Director Transportation
651 Pine Street,4 h Floor North Wing
Martinez, CA 94553
RE: Corrosion of metal fasteners and framing connectors
Committee Members:
Introduction
The issue of potential of corrosion of metal fasteners and framing connectors was raised several
months ago at the Board's Transportation Water and Infrastructure Committee meeting.
Subsequent to this meeting, Building Inspection staff met with Supervisor Gayle B. Uilkema and
her staff, along with Ted Todd of the District Attorney's office to discuss the potential corrosion
of fasteners and framing connectors in association with the current pressure preservative treated
woods. After several subsequent discussions with Mr. Todd and numerous calls to testing
laboratories and wood manufacturers, we are writing to summarize our recommendations at this
time.
Issues
There are two issues that have been raised. First, is there a corrosion problem in using metal
fasteners and framing connectors with the new chemical Alkaline Copper Quaternary (ACQ) on
treated woods? Second, is there a corrosion problem in using fasteners with fire retardant treated
roofing materials?
Background
Effective January 1, 2004, the time tested method for preserving wood to be used in exterior
applications was phased out. Copper Chromated Arsenic (CCA) treated lumber has been used
effectively for over 70 years in North America. Bowing to perceived environmental concerns,
CCA was voluntarily pulled from the residential use market. CCA lumber is still widely used in
other than residential applications.
Pressure Treated Woods — Two alternative methods have emerged as the predominate
replacements for pressure treated woods. Alkaline Copper Quaternary(ACQ) and Copper Azole
(CA-A or B) treated woods are the primary replacements for CCA in the residential market.
Both have higher quantities of copper than CCA had, and seem to be somewhat more corrosive
to metal than the traditionally used formulation. Corrosion is highly dependant on moisture and
temperature. There are a variety of testing programs currently underway to attempt to quantify
the effects of this potential corrosion and what, if any, bearing it has on the average service life
of an exposed, exterior structure such as a residential deck. It is important to note that it is
common to see some corrosion on connectors, especially in outdoor use. This corrosion does not
mean that failure is imminent.
Simpson Strong Tie, a construction products company based in Dublin, California is a leader in
researching this issue. We have met with the head of Simpson's research team and had
numerous conversations with individuals and companies who are involved in this business.
Simpson's recommendations are mirrored in the recommendations of the major treated wood
manufacturers. According to Simpson the below listed recommendations may change, however
they are based on the best information they have at this time.
• Stainless steel connectors and fasteners offer the maximum protection against corrosion.
These are recommended in severe environments such as salt-water exposure.
• Hot dip galvanized fasteners and connectors with heavier zinc coating (G 18 5) are
acceptable for general exterior use.
• Non-galvanized fasteners are adequate in dry applications such as the nailing of wall
plywood to house sill plates.
• Aluminum should never be in contact with pressure treated wood.
• Metals should not be mixed in the same connections, i.e. no stainless nails in galvanized
joist hangers or vice versa.
Treated Wood Roofs — The other question had to do with the potential for corrosion of fire
retardant treated wood roof shingle and shake fasteners. Fire retardant chemicals are
impregnated into the wood fiber to impede the spread of fire. Our local codes require that this
material be used in certain hill areas, where the potential of fire is greatest.
In our department's research, we reviewed published research reports, manufacturer's literature
and code documents. We also spoke at length with major manufacturer's technical departments.
Chemco, a leading company supplying fire retardant treated wood building components, is based
in Washington. In our discussions with Chemco, they explained that the chemicals used to treat
wood shakes and shingles to be fire retardant are inert. In other words, these chemicals do not
exacerbate the corrosion of metal fasteners when used with fire retardant wood roofing. Even
though fire retardant treated woods do not add to the corrosion of fasteners, the natural wood
itself may add to the corrosion. For instance, Western Red Cedar may add to the corrosion of
fasteners due to the natural tannic acid within the wood. This is not a new situation, cedar shakes
and shingles have been successfully used for at least 100 years in California. The only reported
failures of fasteners to date have occurred in seaside communities such as Santa Cruz. The
airborne salts due to breaking ocean waves have accelerated fastener corrosion in some of these
cases. Santa Cruz and other coastal jurisdictions have enacted ordinances requiring stainless
steel fasteners in conjunction with wood roofing.
While pressure preservative treatment methods have changed, the fire retardant treatments have
not. The chemicals themselves have been tested to military test specifications and shown not to
cause corrosion. The time-tested methods for installation of wood roofs have performed well in
Pressure Treated Wood 2
inland areas such as Contra Costa County. We conclude that there is not a corrosion problem
caused by the presence of the chemicals in fire retardant treated wood roofing products.
Recommendations
We will continue to follow the research as it occurs. Our understanding is that both ACQ and
CA treated wood has been marketed for over 10 years in North America. Neither of these
became dominant players until this year, but both have a several year history in the field already.
For your interest, we are including Simpson Strong Tie's most current corrosion information
recommendations (see Attachment A). Please understand these are the most conservative
interpretations of the available knowledge to date. Contra Costa County, by our Department's
estimation, is not an overly harsh environment in either humidity or air borne chemicals where it
would warrant stricter requirements. The Department has already instituted a flyer that is passed
out to the public at the Application and Permit Center that addresses this issue (see Attachment
B). Also enclosed is the handout for pressure-treated wood information that is available at Home
Depot. This handout (Attachment C) addresses the hardware recommended with treated wood.
Tags are stapled at the end of each piece of pressure-treated lumber that addresses the potential
corrosion and recommends hot-dipped galvanized or stainless steel connectors and fasteners.
Our Department will continue to monitor this issue and continue to expand its educational
program to owners and contractors both in the office and in the field.
In regards to wood shingles and shakes, like many other manufactured building components,
they are subject to the approval of a national evaluation agency. That agency is currently the
International Code Council (I.C.C.). The ICC comprises the former International Council of
Building Officials (I.C.B.O.) and two other regional agencies. We reviewed the three current
evaluations of fire retardant treated wood shakes and shingles. All three reports reference the
1997 Uniform Building Code Table 15-B-2 for the application and fastening of roofing (see
Attachment D). The Code requires that corrosion resistant nails or staples be used. This is in
keeping with what our department has long been inspecting and seeing in the field. Our
understanding is that approximately 80% of the shake roofs installed in Northern California use
electro plated galvanized staples; there currently are no hot dipped galvanized staples
manufactured. These do meet the code-approved definition of"corrosion resistant fasteners".
We conclude that there is insufficient climactic reason to justify requiring stainless steel
fasteners for wood roofing.
If you have any additional questions, or need any additional information, please do not hesitate
to give me a call at(925) 335-1108.
Sincerely,
Carlos Baltodano
Director
CB:BW:nr
Enclosures(4)
cc: Members—Board of Supervisors
John Sweeten,County Administrator
Jane Pennington,Chief Clerk of the Board
Steve Dexter,District II
Pressure Treated Wood 3
ATTACHMENT
low
UNDERSTANDING THE ISSUES www'sironri V c!"a iTt.hn?fv hn I &:?Jrjri-� .74 a-, Cr,.1. in,i ha."! rn,a fiort.
Metal connectors,anchors,and fasteners will corrode and may lose load- SBX-DOT(Sodium Borate)treated woods were shown to be less corrosive than
carrying capacity when installed in corrosive environments or exposed to CGA-C.(See Technical Bulletin T-PTWOOD04-R for details). .
corrosive materials.There are many environments and materials which may Due to the many different pressure treatment formulations,fluctuating retention
cause corrosion including ocean salt air,fire-retardants,fumes,fertilizers, levels,and because the formulations may vary regionally,or change without
preservative-treated wood,dissimilar metals,and other corrosive elements. warning,understanding which connectors and fasteners to use with these
The many variables present in a single building environment make it impossible materials has become a complex task.We have attempted to provide basic
to accurately predict it,or when,significant corrosion will begin or reach a knowledge on the subject here,but it is important to fully educate yourself by
critical level.This relative uncertainty makes it crucial that specifiers and users reviewing our technical bulletins on the topic,and also by viewing information
be knowledgeable of the potential risks and select a product coating or metal and literature provided by others.Additionally,because the issue is evolving,
suitable for the intended use.It is also important that regular maintenance and it is important to get the very latest connector information on the topic by
periodic inspections are performed,especially for outdoor applications. visiting our website at www.stmngf ie.corn/info.
It is common to See Some corrosion on connectors especially in outdoor Stainless Steel is always the most effective solution to corrosion risk.However,
applications.Even Stainless Steel can corrode.The presence of some corrosion it is also more expensive and sometimes more difficult to obtain.To best serve
does not mean that load capacity has necessarily been affected or that a failure our customers,Simpson is evaluating the options to identify the safest and
will occur.If significant corrosion is apparent or suspected,then the wood, most cost-effective solutions.Based on our testing and experience there are
fasteners and connectors should be inspected by a professional engineer or some specific applications that are appropriate for ZMAXIHDG or G90
general contractor and may need to be replaced. connectors(see chart below.)
In the last several years,pressure treated wood formulations have changed Because increased corrosion from some newer pressure-treated wood is a new
significantly.Many of thQ new formulations are more corrosive to steel con- issue with little historical data,we have to base our recommendations on the
nectors and fasteners than the traditionally used formulation of CCA-C. testing and experience we have to date.It is possible that as we learn more,
Simpson testing has shown that ACD-C,ACQ-D(Carbonate),CBA-A and CA-B our recommendations may change,but these recommendations are based on
treated woods are approximately 2 times more corrosive than CCA-C,while the best information we have at this time.
GENERAL SIMPSON RECOMMENDATIONS
•Outdoor environments are generally more corrosive to steel.If you choose •Testing indicates wood installed dry reduces potential corrosion.If dry wood'
to use ZMAX or HDG*on an outdoor project.(i.e.deck,patio cover),you is used,see our website for additional information.
should periodically inspect your connectors and fasteners or have a profes- •Using a barrier membrane can provide additional corrosion protection,see
sional inspection performed.Regular maintenance including water-proofing Technical Bulletin T-PTBARRIER04.
of the wood used in your outdoor project is also a good practice.
•For WDDd with actual retention levels greater than 0.40 pcf for ACQ,0.41 Due to the many variables involved,Simpson cannot provide estimates on service
pcf for CBA-A,or 0.21 pcf for CA-B(Ground Contact),Stainless Steel life of connectors,anchors or fasteners.We suggest that all users and specifiers
connectors and fasteners are recommended.Verity actual retention level also obtain recommendations for HDG,ZMW IG1 85),,mechanically galvanized,or
with the wood treater other coatings from the treated wood supplier for the type of wood used.However,
e When using Stainless Steel connectors,use Stainless Steel fasteners. as long as Simpson's recommendations are followed,Simpson stands behind its
When using ZMAX/HDG galvanized connectors,use fasteners galvanized product performance and our standard warranty(page 4)applies.
per ASTM A153.
GUIDELINES FOR SELECTING THE PROPER CONNECTOR
0 Evaluate the Application. Low Use Simpson standard painted and G90 galvanized connectors
Consider the type of structure and how it will be used.These recommendations as a minimum.
may not apply to non-structural applications such as fences. Mad=Use 2MAX/HDG galvanized connectors as a minimum. Use
Evaluate the Environment fasteners galvanized per ASTM A153. -
High Use Type 304 or 316 Stainless Steel connectors and tasteners.
Testing and experience indicate that indoor dry environments are less corrosive
thin outdoor environments.Determining the type of environment where a Connector Coating Recommendation-Structural Applications
connector or fastener will be used is an important factor in selecting the most
appropriate material and finish for use on the connectors and fasteners.To help
in your decision making,consider the following general exposure information:
li�(ddis-*iall an teifido'cavities,and raised� 6
fl,
Interioi Dry'Uge: d". o r applications
6
C.A of enclosed buildings that have been designed to ensure that condensation and.
W
07 other sources of moisture do not develop.
Exterior-Dr1r.Includes outdoor installations in low rainfall environments r Dry LOW LOW Med Mod High High High
and no regular oWsuri to moisture.
co
Exterior-Dry LOW WA2 Med High High High High
o Exterior-Wet Includes outdoor installations in higher moisture and rainfall
environments. Exterior-Wet Med WAI Med3.4 'High High High High
Higher Exposure Use:Includes exposure to ocean salt air,large bodies of water,
Higher Exposure High WA2 High High High High High
fumes,fertilizers,soil,some preservative treated woods,industrial zones,acid
on,and other corrosive elements. Uncertain High WAI High High High High High
Evaluate and select a suitable 0 pressure-treated wood for the intended 1. Woods with actual retention levels greater than 0.40 pcf for ACQ,0.41 pcf for
application and environment CBA-A,or 0.21 pcf for CA-B(Ground Contact level).
Ln
The treated wood-supplier should provide all the information needed regarding 2.-Borate treated woods are not appropriate for outdoor use.
the wood-being used.This information should include:the specific type of wood 3.Test results indicate that ZMAXIHDG will perform adequately,subject to regular
CX
treatment used,if ammonia was used in the treatment,and the chemical retention maintenance and periodic inspection.However,the nationally-approved
level.If the needed information is not provided then Simpson would recommend test.method used,AWPA E12.94,is an accelerated test,so data over an
the use of Stainless Steel connectors and fasteners.You should also ask the extended period of time is not available.It uncertain,use Stainless Steel.
treated wood supplier for a connector coating or material recommendation. 4.Some treated wood may have excess surface chemicals making it potentially
more corrosive.if you suspect this or are uncertain,use Stainless Steel.
0 Use the chart-on the right;which was created based on Simpson's testing
'and experience to select the connector finish or material.
It a pressure treated wood Product is not identified on the chart,,Simpson has Compare the-treated wood supplier's recommendation with
not evaluated test results regarding such product and therefore cannot make
the Simpson.recommendation.
any recommendation other than the use of Stainless Steel with that product. f 1.
Manufacturers may independently provide test results or other product use If these rec6rr1mendations are different,Simpson recommends that the most
information-,Simpson expresses no opinion regarding any such information. conservative recommendation be followed.
g�
3%4
s
,r
1,
E
i
`l
f '
Y
f�.� ori-►- r r �� _4..7�..__ _
17
.. 1
------------
-- ♦.. �.a a_____.._-__ _.. _ _ 1 -
r i
_ r
Press u re-w mate ood Information
* If the wood is wet and heavy,butt deck
boards to _' ' 'f
gether as some shrinkage will
occur, if wood is dry and light separate
boards slightly(max. 1/8'1 to allow for
future swelling.
a For 2" lumber,use 12d nails or 3"
screws.For 5/4" decking,use 10d nails
or 2 1/2"screws.
a Screws take longer to drive than nails,
but hold boards securely and will allow
for easier removal if necessary.
e To protect against checking,warping,
and other effects of moisture,apply a
water-repellent coating annually.
E IN"j:tf(6jj&I&]Q 01?14 0:LAI 1j"4 b
Use hot-dipped galvanized or stainless * Do not bum pressure-treated wood.
steel fasteners. *Wear a dust mask,goggles,and gloves
Hot4pped galvanized fasteners when cutting or handling treated or
meeting ASTM A 153 and connectors untreated wood.
made of ASTM A 653 Class G185 &After working with wood,wash exposed
sheet or better,are recommended for areas thoroughly.
protection against the effects of *Wash work clothes separately from
moisture often present where treated other household clothing before reuse.
wood is used. *Pressure-treated wood should not be
For Permanent Wood Foundations,use used where it may come into direct or
304 or 316 stainless steel. indirect contact with drinking water,
•Other exterior coated fasteners may except for uses involving incidental
be suitable.See manufacturers'specs. contact such as fresh water docks and
Direct contact with aluminum is bridges.
NOT recommended G-e,aluminum e Do not use pressure-treated wood in
flashing). circumstances where the preservative
may become a component of food,
animal feed,or beehives.
* Do not use pressure-treated wood for
mulch.
This pressure-treated wood product is backed by a lifetime limited warranty.
Ask your associate for details.
020612 388520
UC=ANNE
AVWM OT
TP.
M ; AWPA
IMM C2,C9
STVL
trnueGuardjr.14.10iod CA-9 p1wd
LVEW UW"MOMOLMM 17 371.6 116921� ICWM A= OM
bwbeftdo W6 Mh
FanaNtt o.WCOMMM"by Amk 7mMW Uch.IoL Fw HwAft hftatftn me lwvu.ZWL r
020610 255376 1 Lr-39 A""""'J"o
P I CZ C9
STVS.
wmnwuuemnGwuama X"7 37164 169H21211113 1
COPMR AZOLE#61K
Cnq W 3W*=MW;M or M61 CMS
"MMM"Wrais W"Mond
3=6
TABLE 15-S-2 2001 CALIFORNATiLFAGMENT D
TABLE 15-13-2—WOOD SHINGLE OR SHAKE APPLICATION
WOOD SHINGLES WOOD SHAKES
Not Pwmlfted below 3 Unbs Vertical in 12 Unha Horizontal Not Permitted below 4 Units VwUcal In 12 UnlU Narlmntal
P514 810") (33-3%Slope)'
ROOF SLOPE See Table I&C Sao Table 15-C
1. Deck requirement Shingles and shakes shall be applied to roofs with solid or spaced sheathing.
When spaced sheathing is used,sheathing boards shall not be less than 1 inch by 4 inches(25 mm by 102 mm)nominal
dimensions and shall be spaced on centers equal to the weather= with the cc fasteners.When
posure to coincide th e pla ment of f ners.
1-inch-by-4-inch(25 mm by 102 mm)spaced sheathing is installed at 10 inches(2:54 mm)on center,additional 1-inch-by-
C1 4-inch(25 mm by 102 min)boards must be installed between the sheathing boards.
A Sheathing shall conform to Sections 2317.2 and 2320.M9[for DSA/SS]23224.2 and 2326A.IZ 9 ffor OSHPD 1,2&41
C 2322B.2 and 2326B.I2.9.
2. lnterlayment No requirements. One 18-inch-wide(457 mm)interlayment of Type 30 felt
shingled between each course in such a manner that no felt is
exposed to the weather below the shake butts and in the
keyways(between the shakes).
3. Undedayment No requirements. No requirements.
Temperate climate
Severe climate: Two layers of nonperforated 7�pe 15 felt applied shingle Sheathmia shall be solid and,in addition to the interlayintnt of
In areas subject to fashion shall be installed and solid cerwntentogethler with felt"jW between each course in such a manner that no felt
wind-driven SDOW or approved cementing material between the plies extending 0 posed to the weather below the shake butts,the shakes
roof ice buildup from the cave up the roof to a line 36 inches(914 in is ex
in)inside shall be applied over a layer of nonperforated Type 15 felt
the exterior wall line of the building. applied shingle fashion.Two layers of nonperforated Type 15
felt applied shingle fashion shall be installed and solid
cemented togetherwith approved cementing material between
the plies exfromthe cave up the froe.roolto a line 36 inches
(914 nim)inside the exterior will line of the building.
4. Attachment Corrasion-resistant nails,minimumNo.142/rgage, Corrosion-resistant nails,minimum No.13-gage,7/3rinCh
Type of fasteners 7132-inch(5-6 mm)head,or corrosion-resistant staples,
(5-6 mm)head,or corrosion-resistant staples,when
when approved by the building officiaL approved by the building official.
C1A Fasteners shall comply with the requirements of Chapter 23[for DS41SS]23A[for OSHPD 1,2 41 23D,
DivisionIII, &Pan UL
Fasteners shall be long enough to penetrate into the sheathing 3/4 inch(19 mm)or through the thickness of the
sheathing,whichever is less.
No.of fasteners 2 per shingle 2 per shake
Exposure
Field of roof Weather exposures shall not exceed those,set forth in Table 15-C
Hips and ridges Hip and ridge weather exposure shall not exceed those permitted for the field of the roof.
Method Shingles shall be laid with a side lap of notess than 1112inchesShakes shall be laid with a side lap of not lea than 11/2 inches
(38 mm)between joints in adjacent courses,and not in direct (38 mm)between joints in adjacent courses.Spacing between
alignment ftm'W's.*in alternate courses.Spacing between shingles shall shakes shall not be less than-3/8 inch(9.5 mm)or more than 51p,
be approximately 1/4 inch(6.4 mm Each shingle shall be inch(15.9 mm)except for pTeservadve-treated wood shakes,
nt
only, U
fastened with two nab o Y,positioned approximately 314 which shall have a spacing not lessethan
inch(19 mm)from each edge and approximately I inch(25 114 inch(6-4 mm)or more than /s inch(9.5 mm)
mm)above the exposure line.Starter course at the eaves shall Shakes shall be.fastened to the sheathing with two nails only,
be doubledL positioned approximately 1 inch(25 mm)from each edge and
approximately 2 inches(51 mm)above the exposure line.The
starter course at the eaves shall be doubled.The bottom or fust
layer may be either shakes orshint):es.Fifteen-inch or 18-in*Ch
(381 mm or 457 mm)shakes may used for the starter course
at the,eaves and final course at the ridge.
5. Flashing
Valleys Per Section 1509S
Other flashing Per Section 1509
l
A
C When approved by the building official ffor DSAI
A OSBPD Is,2&4 enforcement agency,wood shakes ay be installed on a slope of not less than 3 units
vertical in 12 units horizontal(25%slope)when an underlayment of not less than nonptrforated 7ype Umfielt is installed.
3=7