Joist hangers are simple to install, but ignoring details can cause issues with inspectors and lead to project delays. At our office, we often see the same mistakes repeated—simple errors that are easy to avoid with proper care and following best practices. Here are the five most common joist hanger mistakes we see, and how to avoid them.
1. Using the Wrong Nails (or Screws)
Joist hangers are designed and tested with specific nails. Always consult published content for fastener tables and installation guides listing required fasteners. MiTek’s phone app provides a simple way to find this information in the field. At the bottom of each chart is a description of the nail diameter and length. When selecting nails at the vendor, focus on the specified diameter and length, not the descriptions or penny weight callouts, especially with pneumatic nails.
Only use screws specifically designed for connectors, such as MiTek LumberLOK connector screws or WS Screws. Avoid using construction, deck, or similar screws. These screws need an independent evaluation, may require replacement, and could cause delays.
Notes:
- Alternative fastener charts are published and available for approved alternate fasteners. Allowable load value adjustment factors are also provided.
- Double shear or slant nails require full-length nails to penetrate through the carried joist into the supporting member.
2. Improperly Sized Hangers
For various reasons, incorrectly sized hangers are installed at the jobsite. The best solution is to plan ahead during framing and install the correct hanger from the start. Repairs can be costly and might require an engineer to design a proper fix by adding shims or blocks. If necessary, refer to Design of Filler Blocking with MiTek Hangers.
3. Missing Nails
Every hole in a hanger serves a purpose. Missing nails—especially in double-shear configurations—can drastically reduce load capacity. Inspectors often flag incomplete fastening for remediation.
Notes:
- Some hangers have MIN/MAX nailing options: MIN requires filling all round holes, while MAX requires filling diamond and round holes.
- Strap-style hangers don’t require filling all round holes. For the required fastening, refer to MiTek’s published content.
- We often get questions about the larger holes in our nailed hangers. These holes are for manufacturing purposes and do not require fasteners.
4. Improper Member Alignment
Carried joist members must be installed flush with the supporting member, with a maximum gap of 1/8”. Larger gaps will need to be evaluated or corrected. MiTek publishes load reductions for gaps larger than 1/8” and up to 3/8”. For gaps exceeding 3/8”, the installation of an independently attached shim or blocking will likely be necessary.
5. Installation Sequencing of Inverted Flange, Skewed, or Sloped Hangers
If the supported beam is skewed or slopes more than 5 degrees, a specialty hanger is necessary. Off-the-shelf or special-made hangers are available, but planning for installation is often required.
Inverted flange hangers need careful planning since they must be installed prior to framing members or trusses.
Do It Right the First Time
Delays and callbacks waste time and money. By following MiTek’s installation guidelines and choosing the right hanger and fasteners for the job, builders can prevent rework, pass inspections on the first try, and ensure long-term serviceability. Proper preparation results in a faster, more dependable installation
For additional information, or if you have questions, please contact the MiTek Engineering department.