Supporting Floor Joists

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Supporting floor joists with joist hangers:

This house was built in 1863. Back then there was a lot less furniture and heavy appliances to add to the dead load on floor joists.

Many times floor joists were nailed to balloon framing and if you were lucky the carpenters would also add a 1×2 ribbons or ledger under the joists. In this application the 2” x 6” floor joists were “let in” or mortised into a 6” x 6” beam. To do this the 1863 carpenters cut a 3” high x 3” deep notch into the end of the joist. In the beam they cut a 3” x 3” deep mortise or pocket to receive the floor joist.

The reason for doing this was to get the floor joist and the beam flush at the top. – A very common building approach. The problem with this approach is that the 6” joist is now 3” at the beam, which becomes a weak spot.

As you can see from the pictures many of these circa 1863 joists has split and cracked at the 3” notch point. This floor has sagged a bit over time and I was concerned that the joists were being stressed too much.

Many years ago another carpenter installed a 6×6 beam and two columns at the mid span of these joists, my guess is, to reduce the bounce in the floor above and strengthen the floor system. It worked and also took a ton of weight of these stressed out joist ends.


My first course of action was to support the joist to beam structural connection with metal hangers. Because the 2×6 joists are so old they actually measure 2” x 6” and not 1 ½” x 5 ½”. Standard 2×6 joist hangers will not fit these old joists. I had to get “old work” or “rough joist” hangers to fit.

Today we still install floor joists and beams flush at the top but we use metal connectors to accomplish it instead.

Installing these hangers is straightforward. The most important thing to remember is to keep the bottom of the joists hanger tight against the joist bottom.

The joist hanger has pre-determined holes most of the holes are for nailing into the beam and there are also two holes on each side for securing to the floor joist.

It’s important to note that you cannot use any nails. Building codes require the use of joist hanger nails. These nails are hardened and stronger than normal nails to resist the shearing weight that a floor system has.

When nailing the joist hanger in make sure you push the sides tight to the sides of the joist for a nice tight fit.

Supporting Floor Joists:  To install the joist hangers I used a special nailer made by Paslode.

It’s called the  Paslode Positive Placement Metal Connector Nailer.

This mailer drives 1 ½” code approved paper collated metal connector nails in seconds. It does this with the help of a positive placement probe at t he tip of the nailer. This tip allows the user to find and align the probe into the joist hanger nail hole allowing perfect nail insertion. It is by far the easiest and fasted way to install metal connectors available.

NOTE – when nailing into the beam follow code recommendations and install 3-1/2″ long [16 penny] framing nails.

In tight quarters I needed to use a palm nailer. The palm nailer is the size and shape of appear. A single hand nail is inserted into the palm nailer’s tube; the pneumatic action of the nailer hammers the nail in.

Now the joist hangers provide supporting to the notched floor joists by giving it additional structural support to resist the downward pressure of the floor system and anything placed on top of it.

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About Who is Concord Carpenter?

~ Robert Robillard is editor of A Concord Carpenter and principal of a full service carpentry and remodeling business located in Concord, Massachusetts.

Rob is a recognized leader in tool and how-to information for building professionals.

He enjoys using his knowledge and experience to help and educate on best practices in the remodeling industry. The Concord Carpenter's motto: "Well done is better than well said!"