REINFORCEMENT OF ROOF TRUSSES

Specifications

 

General

Contractor shall provide all necessary labor, materials, and equipment to perform the work as indicated herein and on Drawings 1 – 4. Materials and installation shall conform to the North Carolina Building Code, 1996 Edition. All work shall be in compliance with good construction practices. Contractor shall secure all necessary permits and licenses.

Modification of Trusses Over the Dining Area

  1. The intent of the repair design is to strengthen the existing trusses without removing or modifying any of the existing chords, webs and bracing. Cutting or removing any of these members could seriously weaken the trusses.

  2. Any loose, inadequately nailed, or rotted existing truss webs and chords shall be repaired or replaced.

  3. Install new web members in accordance with drawings Nos. 3 and/or 3A. Wood shall be Southern Pine, kiln-dried, Structural Grade 2 or better.

  4. Plywood gussets shall be 3/4" APA Structural 1 Rated Sheathing, Exposure 1. The gussets shall be installed on each side of the joints per drawings Nos. 3 and 3A. Alternate 1: Use two rows of 10d nails, 2" on center, staggered. Alternate 2: Use two rows of 8d ringed shank nails, 1" on center. Glue gusset plates to truss members with casein glue per manufacturer’s instructions. See drawings for sizes of gussets and number of nails per member.

  5. On the sides of the truss where a single gusset place cannot be used because existing web members are in the way, two gusset plates shall be used. The gusset plates shall be sized so that the joint strength in the same as though a single piece of plywood were used. Contractor shall consult the Engineer if conditions are encountered where equivalent strength gusset plates cannot be installed.

  6. A continuous 2 x 4 ledger strip shall be installed under the truss supports as shown on drawing 1 & 3, detail A. Attach the ledger strip to the brick wall with Simpson 5/8" x 4-1/4" Hex Head Sleeve-All expansion anchors, #SL62414H. Install the anchors at 8" on center.

Modifications of Beam over Kitchen

  1. Install a new wall support under the beam according to drawing S1 & S2. Wood shall be Southern Pine, kiln-dried, Structural Grade 2 or better. Prior to installation of the support, verify that the existing concrete slab is at least 4" thick by drilling a hole in the slab near the post location. If the thickness is less than 4" thick, install a 24" x 24" x 10" footing under each post.

  2. Fabricate and pre-drill the steel flitch plates according to Drawing 1. Verify existing conditions and fit before fabrication. Use 1/4" steel plates. The steel shall conform to ASTM A36. Pre-drill the plates for 5/8" diameter bolts.

  3. Jack up the existing beam so that there is no sag in the beam between supports. Remove and/or install wedges between the trusses and beam as necessary to fully support the trusses. DO NOT OVER JACK. Consult Engineer if there is the possibility of damaging the roof structure. Repair of damages to the roof due to excessive jacking shall be at the Contractor’s expense.

  4. Use 5/8" diameter ASTM 307 bolts. The bolt holes in the steel and wood shall be a minimum of 1/32" to a maximum of 1/16" larger that the bolt diameter. Tight fit requiring forcible driving of bolts is not permitted. Tighten the bolts with enough force to create friction between the steel plates and the wood beam.

  5. Install a new 6 x 6 wood post under the end of the beam per detail B on drawing #4. Attach the beam to the wood post using two Simpson # 1212HL T & L Strap ties. Prior to installation of post, verify that the existing concrete slab is at least 4" thick by drilling a hole in the slab near the post location. If the thickness is less than 4" thick, install a 30" x 30" x 10" footing under the post,

  6. Toe spike each truss to the beam with four 16d nails for lateral support.

  7. Once the flitch plates have been securely fastened to the wood beams and the supports have been installed as detailed, carefully remove the temporary supports under the beam. Stop work if any signs of structural distress appear and notify the Engineer.

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