0102-146 (RR) Structural CalcsE
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February 14, 2000
STRUCTURAL ENGINEERING CONSULNT
54-625 AVENIDA BERMUDAS. LA 46TA CALIFORNIA 92253
760.564.0884 PHONE • 208.361.5447 EFAX • t ,
SECONSULTANT@EARTH LINK. N�'i
Mr. Mark Harold
City of La Quinta
Department of Building and Safety
.78-495 Calle Tampico `
' La Quinta, California 92253 t
f
Regarding: Roof Report for Mr. & Mrs. Pete Anderson=717-:21 La-Quinta
Dear Mark: ,
On February 12, 2000, 1 performed a structural inspection of the existing Composition and white rock roof.oi'th locateWdt
77-284 Portrero. The owner wants to remove the existing roof and replace it with a new Mission style Clay tile..,.T fe '""'?t�►e weights
approximately 12 pounds per square foot. ^
+ History
ii" The home was constructed within the last Twenty Five years. The roof is constructed of 2x8 DF#1 o4tter rafte[A,spaced 4, on
r center. The rafters are covered with plywood (unable to verify thickness) and a composition built-ups'oftatboite rock. The
Living room and Kitchen areas represent the most critical portion of the residence that needs to be veri' edr, thy' ate sed fiig.
+ The attached analysis addresses these areas. The new tile will be restricted to the gabled roof sectionkZvith�sl { ;t 1 9`m I�
" pitch. All flat or shed sections of the roof will, be hot -mopped to match existing with the exception oftf�olo tlltr. a3lied.
Construction k r.
The home appears to be consistent with the quality of home typically associated with Conventional Ppscript Co*� ekho.4
Little if any consideration is made for lateral load resistance. Inasmuch as homes of this size are ,generallX governdd n + Orces gfi
is my opinion that the additional lateral load from the tile roof will not sufficiently alter the abili, o'ghe_stedetge"to reojs > q
forces as derived by prescriptive methodology. C r x lir
LL
The attached analysis represents a conservative dead load and appropriate live load for the e ;
�c-
converts the applied loads for the slope of the member. The structural members verified am,
S1 considering bending stress in accordance with the 1997 Uniform Building Code for Douglas-��
t version of the code has reduced allowable stresses due to a ten-year study performed American
. , quality of wood available for new construction. The stress used is considered to be more conse
original date of construction. The deflection due to bending (is or is not] within code allowaft,
`opinion that the roof framing can support approximately 12 pounds per square foot of C
not exceeding 2 pounds per square foot.
�k It it- thPrPfnrP my nrnfnccinnal anininn that thn'nwnnr may inetall a %'lav Miceinn Tiln ni
foot above the weight of the existing sheathing.
Construction Limitations:
1
2.
3.
4.
I
The contractor shall not load or stack roof tiles adjacent to or above any long span
limited to garage header, beams above sliding glass patio doors, intermediatq.tbaitt
opening exceeding 4'-0" in width. All materials should be located above soli&bean
Weight to a known foundation.
The contractor shall not place loads or stack materials on cantilevered roogel 't
The contractor shall be aware of all changes to structural members includiK atrli
doors and windows shall be reported to ttie engineer of record for possible r$
The contractor shall look for damaged joists or rafters prior to loading theNp1��'o
middle half of the beam on or near the bottom edge may fail during loading.!Ji,! s
to the existing to compensatet5 the imperfection
STRUCTURAL ENGINEERIpIG FOR CUSTOM HOMES • REAWDEI,• COMM€RCU,L • LIGHT INDUSTRIAL • SEISMIC RETROFIT &F3TAi%`l)'
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?f Timl5ii f of %icr the
tj mauls use at
therefor �f8;ss'{ 1
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Page 2
5. EMPORTANT: The increased weight of tile applied to the roof may have an effect upon the deflection of the roof eave.
Where excessive or noticeable deflectionsl occur at extended eave, the engineer shall be notified to determine the cause and
to provide remedial measures.
6. The roofer shall provide all ICBO reports required by the building official prior to obtaining permits and commencing work.
7. The eaves at the West and East end of the home are long cantilevers. The contractor shall pay particular attention to the amount of
deflection occurring at these locations and shall notify the engineer of any changes that may occur for possible mitigation design.
Conclusions: i
and shall not to exceed 14 pounds per square foot including any new underlayment. Additional deflection is expected at the roof
rafters due to the additional weight. The additional deflection for the condition calculated is within Uniform Building Code allowable
limits.
Changes in the lateral load resisting system may occur due the additional weight of the tiles. The owner has been made aware of this
possibility prior to issuance of this report. The owner has chosen to add the new tiles and not upgrade the lateral system of the
structure.
Size and depth of existing headers has been assumed and can not be field verified without removal of exterior finish and interior
gypsum board. Therefore, the contractor will notify the engineer of any conditions causing excessive deflection (bending) should
occur.
Please contact my office at your convenience with any questions you may have related to this report. If this report is issued to the
homeowner or roofing contractor, please submitithe original with your initials at the bottom to the building official prior to obtaining
permits. This is to acknowledge your review and! understanding of the information, special instructions and potential risks associated
with this work.
Sincerely,
Dennis S. Wish PE
Structural Engineering Consultant
Notice
This review or inspection is limited in scope. We have'Imade a visual inspection of a portion of the existing building. Because marry structural
conditions which cannot be verified, certain assumptions have been made. These assumptions, which include facts relating to the original design, the
structural properties of building materials and actual construction practices, cannot easily be verified without additional destructive testing or
exposure of additional areas of the structural framing. Verification, if possible, would entail considerable effort and expense and is beyond the scope
of this project. Any conclusions or recommendations included in our report may therefore be based on professional opinion and experience rather
than brown conditions. This report is not intended to clover mechanical, electrical, architectural, geologic or other features not specifically noted.
I have read and acknowledge the information, opinions and risks as indicated in this letter:
Owner Print dame Date
Contractor Print Name �:,h ' Date
'd
IT
Dennis S. Wish, PIE !'
Title:
Job #
54-625 Avenida Bermudas
Dsgnr:
Date:
I O:OOAM, 14 FEB 00
La Quinta, California 92253
Description
(760) 564-0884 Phone
Scope
(208) 361-0447 E -Fax
•
Rev: 510301
U-: Ver 5.1.3,224un-1999,Win32
General Timber Beam
Page 1
-
(c) 1983.99 ENERCALC
c% ro rim file:leciindomor. roof rC Ott.CCW:
Description Worst Case Roof Rafter - Mission Tile Roof (DL- 15.00 psf) - 2x8 DF#1 @ 16" o.c. typical
General Information
calculations are designed to 1997 NDS and 1997 UBC Requirements
Section Name 2x8
Center Span 15.00 ft
....:Lu
0.00 It
Beam Width
1.500 in
Left Cantilever ft
.....Lu
0.00 ft
Beam Depth
7.250 in
Right Cantilever It
.....Lu
0.00 ft
Member Type f
Sawn
Douglas Fir - Larch, No.1
Fb Base Allow 1,000.0 psi
.
Load Dur. Factor
1.250
Fv Allow 95.0 psi
,Beam End Fb*
Pin -Pin i
Fc Allow 625.0 psi
Repetitive Member
f
r
E 1,700.0 ksi
Full Lengh Uniform Loads
i
Center DL
26.60 #/ft LL 26.60 #/ft
Left Cantilever, ' DL7
#Ift LL #/ft
Right Cantilever t DL
Y
#/ft LL #/ft
Fr 1;tit, GU4 '73Y1Ss14.. $N.LM1 w't ': : �
Summary
F
•
Beam Design OK
Span= 15.00ft, Beam Width
= 1.500in x Depth = 7.25in, Ends are Pin -Pin
Max Stress Ratio
0.792: 1
Maximum Moment
t
r
1.5 k -ft Maximum Shear " 1.5
0.6 k
Allowable
1.9 k -ft Allowable
"1.3 k
Max. Positive Moment
1.50 k -ft
at 7.500 ft Shear:
@ Left
0.40 k
Max. Negative Moment
0.00 k -ft
at 0.000 ft
@ Right
0.40 k
Max @ Left Support
0.00 I k -ft
Camber:
@ Left
0.000 in
Max @ Right Support
0.00: k -ft
@ Center
0.561 in
Max. M allow
1.89
Reactions...
@ Right
0.000 in
fb 1,366.37 psi
fv
55.03 psi Left DL 0.20 k
Max
0.40 k
Fb 1,725.00 psi
Fv 118.75
psi Right DL 0.20 k
Max
0.40 k
Deflections
CenterDead Load
Pa �•
Total Load Left Cantilever...
Dead Load
Total Load
pan...
- 0 in
-0.748 in Deflection
0.000 in
0.000 in
...Location
7.500 ft
7.500 ft ...Length/Defl
0.0
0.0 11
...Length/Defl
481.1
240.55 Right Cantilever...
'
Deflection
0.000 in
0.000 in
...Length/Defl
0.0
0.0
Stress Calcs
Bending Analysis
Ck 29.908 Le
0.000 ft
Sxx 13.141 in3 Area
10.875 int
Cf 1.200 Rb
0.000
CI 0.000
Max Moment
Sxx Read Allowable fb
@ Center
1.50 k -ft
10.41 in3
1,725.00 psi
"
@ Left Support
0.00 k -ft
0.00 in3
1,725.00 psi
@ Right Support
0.00 k -ft
0.00 in3
1,725.00 psi
Shear Analysis
@ Left Support
@ Right Support
1 Design Shear
0.60 k
r
0.60 k
Area Required
5.040 in2
5.040 in2
Fv: Allowable
118.75 psi
118.75 psi
Bearing @ Supports
I.
Max. Left Reaction
0.40 k
Bearing Length Req'd •
0.426 in
Max. Right Reaction.
0.40 k
Bearing Length Req'd
0.426 in
Query Values
'
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M, V, 81 D @ Specified Locations
,m,.tFlWvuw'"Enaeas5:fiararwim,.:mr,,:iNilbs'6.:Fvw'rai-.yFu4sruk'sx."YWr'r'uLii'r.J;Whicd•M4Yldii•Eh
Moment Shear
dtbFiw" a'4still:L §uN�Y .:...
Deflection
@ Center Span Location =
0.00 ft 0.00 k -ft
0.40 k
0.0000 in r
@ Right Cant. Location =
0.00 ft 0.00 k -ft
0.00 k
0.0000 in