Code Case Study 1

Deck &  Roof  Problems

The photos that follow are an actual example of the problems that can be encountered when a building is built without a proper building permit or plans review by a Code Official.  A contractor built this deck and roof to connect a mobile home with a carport.  Since the deck and roof were attached to the primary dwelling, a building permit was required, and the deck and roof should have been placed on a foundation or piers extending below the frost line.  Many of the problems which must now be corrected could have been caught in the plan review stage, saving both the homeowner and contractor considerable time and expense.

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1.  2x6 posts from deck roof improperly supported on carport roof transferring load to plywood sheathing –  (Photo 1)

Ref. IRC Sec. 801.2 requiring all roof loads to be transferred to structural elements

2.  2x6 posts from deck roof  improperly supported on main building roof transferring load to plywood sheathing - (Photo 2)

  Ref. IRC Sec. 801.2 requiring all roof loads to be transferred to structural elements

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3. Corners of roof unsupported at main building except for 3 nails in the rafter into building fascia (Photos 3, 4, 5)

Ref. IRC Sec. 801.2 requiring all and ceiling construction to be capable of accommodating all loads imposed (including 40 psf snow load specified for local area)

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4.  No joists restraining rafters; no plate or header to support rafters (photos 6  and  7)   Ref: IRC Section 802.3.1 requiring ceiling joists and rafters to be nailed to each other … and the assembly to be nailed to top wall plate.

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5.    The fourteen foot rafters supporting the roof  exceed the maximum allowable rafter span;  The allowable span for #2SPF-2x6 rafters with 40 psi ground snow load is 10’-8”. (Photo )

 Ref IRC Tables 802.5.1(3) and 802.5.1(4)



6.  No flashing between shingles and carport   (Photo 7)

IRC 905.2.8.5 requires other flashings (against vertical surfaces) to be in accordance with shingle manufacturers instructions


7.  Roof is supported by face nailing rafters into 4x4 posts.  (Photo 7)




8. 4x4 roof supports posts use “Post-Ups” – which are desined for mailboxes and signs – not 40 psf roof loads (Photos  8, 9, and 10) 

Ref.  IRC Section 403.1.4 All exterior footings and foundations shall extend below the frost line specified in Table 301.2 (40 inches)

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8.  Simpson rafter hangers are nailed in with roofing nails not the appropriate nail as specified in the installation instructions (Photo 11) Ref IRC Definitions for  Manufacturers Installation Instructions and Listing

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9.  Sheathing has gap with rafter at building roof  (photo 12)   IRC 905.2.1 Asphalt shingles shall be fastened to solidly sheathed decks
10.      Ledger is nailed to main structure; Deck is supported using floating supports (photo 13)  Since the deck is connected to the main structure it requires a foundation Ref.  IRC Section 403.1.4 All exterior footings and foundations shall extend below the frost line specified in Table 301.2 (40 inches)

Photo 13 - click to enlarge

11.  No underlayment or flashing has been provided in valley (photos 14,15)

 IRC 905.2.8.2 requires closed valleys (valleys covered with shingles) to be lined with 36” wide roll roofing, specialty underlayment, 24” wide metal, or two layers of 18” and 36” wide mineral surface roofing.

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12.  Only a single nailed layer of underlayment has been provided along the outside edge of the roof  (Photo 15)  

IRC 905.2.7.1 Ice protection is required extending from the eave line 24” inside the exterior wall line

13.  No drip edge over carport eave (photo 16)  

IRC 905.2.8 requires an .019” corrosion-proofcap flashing

14.   Roof slope is less than 2:12 (photo 16) IRC 905.2.2

Asphalt shingles shall only be used on roof slopes greater than two units vertical in 12 units horizontal

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15.  Deck nails are standard steel - not corrosion resistant (photo 17)

Ref: IRC 319.3 Fasteners for pressure preservative and fire-retardant-treated wood shall be of hot-dipped galvanized steel, stainless steel, silicon bronze or copper.

16.  Ύ” tripping hazard needs threshold transition (photo 17)

Ultimately, the homeowner hired another contractor to remove and replace the deck and roof.  This contractor submitted plans for review, and called for the required inspections as the work progressed.  The work passed all of the inspections and the homeowner is very pleased with the completed project.  Photos 18-20 show the completed project..


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