HomeMy WebLinkAboutENGINEERING AND CALCULATIONS - 08-00066 - 408 Violet St - Carport408 Motet--i_'m-port
Engineering and Calculations
For
Millhollow Community
408 Violet
Idaho Falls, Idaho
November 4, 2008
Prepared by:
Ray McDougal, P.E.
Rexburg, ID
852-6236
Section A
Project Description
This report is an analysis of an existing car port that has been constructed in Rexburg,
Idaho. The structure was constructed without a permit and without building inspector
oversight. The Rexburg building department has now inspected the structure and
determined that it was not built in accordance with the International Residential Code
(IRC). The purpose of this analysis is to design a modified structure that will be safe and
appropriate for the building location
Calculations and required member sizes for post, beams, footers and shearwalls are
provided. Wood member sizing calculations were performed using the Timberdesigne
structural engineering program. Output files from the program are available upon
request.
Project Location:
Governing Regulation:
Snow Load:
Wind Speed:
Frost Depth:
Seismic Zone:
Rexburg, Idaho
2006 International Building Code
35 psf (roof)
90 mph
30 in
D1
Section B
Existing Structure Description
The carport is a typical roof covering with open columns and no walls. It is attached to
the manufactured home with the carport rafters hanging from a ledger board that is
attached to the walls of the home under the eve. The rafters extend from the house eve
continuing the house roof -line 14' out from the house wall. Rafters are 2x4 Douglas Fir
@ 24" O.C. On the lower side, the rafters bear on a single 2x6 D.F. header that spans
between support columns. The support columns are 4x4 P.T. or 4x4 D.F. at
approximately 7' O.C. A picture of the existing structure is provided as Figure 1.
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Figure 1. Photo of Existing Structure.
Section C
Analysis of Existing Structure
The existing structure has the following deficiencies:
• Ledger board may not have sufficient support. It is unknown what the house wall
stud construction is and if the ledger is adequately attached to these studs.
• Rafters are insufficient in size.
• 2x6 header is insufficient in size.
• Support columns do not have footings below.
Section D
Proposed Structure Modifications
The following upgrades are recommended to make the structure safe and appropriate:
• At each support Column, install a heavy rafter. This rafter is to be a single 2x12
D.F. Set. at each end and a double 2x12 at intermediate supports.
• At 4'8" and at 9'4" from the house, provide a double 2x6 D.F. girder that will
support the 2x4 rafters and will hang from the heavy rafters with LUS26-2
Simpson Hangers.
• Provide 4x4 supports at both ends of heavy rafters. Use 2' 2x4's on either side of
4x4 and rafter to create rafter pocket.
• Provide 15"x15"x8" Footings with (2) #4 horizontal bars and Simpson EPB 44
post bases.
(2) 2x6 Girders
Existing 2x4 Rafters
Simpson LU526-2 Hangers
Heavy Rafters
4x4 Support Columns 44 Support Columns
Simpson EPD44
38 sq. in. x8" Footings
30 sq. in. x8" Footings
Simpson EP644
Figure 2. Section View of Reinforced Carport
Heavy i.F
Figure 3. Heavy Rafter to Column Connection Detail
Section D
Conclusion
The existing carport is not structurally sufficient to support required loading for Rexburg,
Idaho. If the recommended modifications outlined in Section C are implemented, the
structure will meet required loading and provide a safe carport. It is highly recommended
that the work be performed by a licensed contractor.
This engineering analysis in only valid once the final structure passes inspection by
Southfork Design Group LLC.
Appendix A
Calculations
Section A-1 Wood Member SizinE
Given:
Snow Load = 35_psf
Dead Roof Load= l0_psf
Find:
Required Rafter and Girder Size's
Girderload = (35 _ psf + 10 _ psf X4.7 _ ft) = 212lb
- ft
From Timberdesign, Use (2) 2x6 D.F. #2
rafterload = (45 _ psf X8 _ ftX4.7 _ ft) =1440 _ lb
This point load occurs at 4.7' and 9.4'
From Timberdesign, Use (2) 2x12 D.F. Sel.
Section A-2 Footing Sizing
foundwall = 45- )(8 _ ft X7 _ ft) = 2520 _ lb
l ft lb
Area = 2520 _Ib =1.7 _ ft2 =16' x16'
1500
- ft
Use a 2_ft2 x 8" Footings..