Telescoping Jack Posts

Telescoping jack posts are often used as a quick, economical way to reinforce a structural member that needs additional support. There have been some mixed messages on when you can use them and when you should not. Telescoping jack posts are capable of carrying a 4000 to 6000 lb. allowable load depending on the extension length and manufacturer, which is a pretty good capacity for most retrofit and reinforcement situations. Most jack posts we see in the field are installed upside down. The screw thread should be on the bottom. There is also nothing that really holds the post assembly together other than the initial force created when tightening the post against the framing.

For that reason, we have seen many jack post failures when they lose their initial tightening force. Jacking against a new footing, creates an extra load on the footing that would normally not be seen by a standard masonry pier installation. Sometimes that additional load can cause the footing to settle which relaxes the tightening force enough in some cases to where the post can collapse if there is no more load being transferred to it. It is also possible to have some initial settlement with a regular masonry pier but a masonry pier will not collapse in such cases and usually, most people do not catch the fact that there is a slight gap between the pier and the supporting member when it does settle. Here are our suggestions of when you can use telescoping jack posts in lieu of masonry piers.

  • When adding additional reinforcement to a floor system to take “bounce out of a floor” when the floor already meets Code without the posts.
  • When jacking against an existing masonry foundation wall such as a basement half wall.
  • For the DIY homeowner that will occasionally tighten the screws every so often should the jacks loosen.
  • When jacking against an existing large pier footing to replace a damaged pier.
  • When using for temporary shoring during renovations.

Although the telescoping posts do have the added benefit of providing some actual jacking force to lift sagging floors, most manufacturers will indicate they are not to be used for such purposes. One other thing to note, the cap plates for the telescoping posts provide four holes to connect the plates to the framing and footing. Those connections are really unnecessary due to the nature of the post assembly and how it works.

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