Slide 20 of 48
Notes:
- Hold downs
- Hold down assemblies are strongest when:
- the stud bolt holds in the end stud or added post are not oversized
- the stud bolts are not counter sunk into the end stud or post
- the stud bolts are fitted with washers and tightened
- Do not substitute lag screws for through bolts
- A contractor that engages in improper hold down assembly is exposed to liable should the structure fail
- Beware of nonstandard framing
- Always identify non-standard framing assembly in the existing structure, since standard details may not work in such a structure
- Identify in the pre-job walkthrough
- Identify as soon as detected in execution of the contract
- Contact an engineer before undertaking a seismic retrofit
- "Balloon framing" is one type of non-standard framing
- Common in the eastern United States between about 1850 until 1970
- Some older buildings on the West Coast may have such balloon framing
- Many buildings with balloon framing are still in service
- The intermediate floor framing joists are face-nailed to the studs
- When retrofitting balloon framed houses the same principles for creating load paths apply
- Blocking and connectors will be required at the roof and intermediate floor lines to connect the floor sheathing to the shear walls
- Additional blocking must usually be added between the floor joists to provide shear transfer nailing at the top and bottom of the sheathing
- The contractor will be held to this heightened standard of framing care in such circumstances.
- Proper anchor bolt assembly
- Washers and nuts are required on all anchors bolts
- Some building departments and engineers require square cut plate washers instead of round malleable plate washers
- Know the type of washer required
- Do not oversize the hole in the foundation sill
- It will allow the sill to slide during an earthquake before pushing against the bolt
- This unwanted movement during an earthquake can cause damage
- This will expose the contractor to liability
- A contractor should never counter sink the washer and nut if the bolt is too short
- The anchor bolt will not be effective
- The contractor will be liable for installing it incorrectly
- The contractor should not drive lag screws into the framing with a hammer
- Always screw them into place
- Before installing, check with the building department and available project engineer to verify that the hardware used has been approved
- Protection from fumes
- Always protect yourself and workers from fumes when using chemical epoxy anchors
- Check with the manufacturer, MSDSs and the building department to determine appropriateness and precautions
- Provide and use respirator filters, protective clothing and ventilation as needed
- Check the manufacturer's literature for information on the flammability of the epoxy
