Common Mistakes To Avoid When Installing Joist Hangers

  • Wrong size hangers are used (either undersized or oversized),
  • The bearing surfaces are not to specifications,
  • The amount of hangers are not enough,
  • Wrong nailing,
  • Wrong type of nails
The hangers used in decking, stairs and trusses are often installed wrong, and this compromises their ability to ensure the integrity of the structure. Most often, this practice doesn't comply with the building code. It may appear to save time and money, if we take shortcuts, but in the long run, it would be costly - the unwanted repairs.

  • Use correct nails.  This line must be repeated like a mantra. Use correct nails. If not sure, ask an expert. Nails do matter. The length and size of nail is usually specified by the joist hanger manufacturer. 
  • Avoid the temptation to leave some nail holes in each hanger unfilled, however much you are tired. Its best to rest a bit, than leaving few nail holes free. 
  • Never nail straight into the end grain, which would result in splitting the wood. Nailing into the end grain would eventually lessen the nail's holding power, even if the wood didn't split, even if you can't see the split. Nail at 45 degrees.
  • For outdoors use hot-dipped galvanised nails.
  • Never use deck screws or drywall screws to install joist hangers.
  • Dont reuse joist hangers. 
  • Dont modify them by cutting them shorter. 
  • A joist or a truss must lie fully on the bearing. Don't leave gaps between the end of the joist and the beam, the truss and the wall plate.
  • To install a sloped joist, such as a staircase beam, use a sloped base hanger. Don't use a standard hanger in this case, the timber beam's bearing in only on the edge of the hanger.
  • Hanger height must equal at least 60% of joist height to achieve enough load bearing capacity and lateral stability of the connection. 
  • Remember to use the exact amount of joist hangers as specified. 
  • Never use undersized or oversized hangers. 

Correct - Joist hanger is > 60% of joist height       Incorrect - a gap is left          Incorrect - undersized hanger

There is no bearing. The sloped joist has contact with the joist hanger only at the edge. A hanger with a sloped seat must be used in this kind of situations.