How to Replace Floor Joists

While replacing floor joists is a complex process, it is well within the capabilities of a dedicated homeowner. What follows should give you all of the information you need to accomplish this task.

Step 1 - Remove the Floorboards

Whether you are working on joists under the floorboards in your home, or joists outdoors such as a deck, you will not be able to access them normally, as they are under the floorboards. To replace floor joists, you must first remove the floorboards that cover them.

Get out your crowbar and your hammer. Put the tip of the crowbar between the floorboards and push it in. Next, use the hammer to tap it. This should lever the boards apart. Push the crowbar in further and repeat.

You should expect to damage some of your floorboards, as this method is hard to use without doing so. Because of this, you should target your efforts carefully. If you are replacing joists in your floor, chances are they are visibly damaged. Remove the floorboard closest to the damage, and then use the hole you make to view the joists to see which ones need replacing. Do not remove any floorboards that are not absolutely required, and always start with the most obvious choice.

Step 2 - Marking the Old Locations

Now that the joists you want to replace are visible, it is time to remove them. However, before you do this, it is important that you take note of  their location. Mark the location of the joists you want to replace. They will usually be 16 inches apart, but they will be 24 inches apart in some cases as well.

Step 3 - Remove the Old Joists

Select a joist, and select an end. Make a cut all the way through the joist using your saw, staying as close to the end you have selected as possible without hitting any nails or the joist hanger if it is present. Make another cut at the other end using the same strategy.

Repeat the process for all of the joist hangers you wish to replace. Once you have done this, you can remove the old joists by tapping on them with your hammer until they come out. Whether joist hangers are present or not, remove the old nails with your hammer, and then remove the ends of the old joists.

Step 4 - Replace the Old Joists

Using joist hangers with your joists is a good idea, as they increase their reliability greatly.

Begin by placing your new joist hanger at the location you have marked. Line up the top of the joist hanger with the ledger board. Hammer the speed prongs in to temporarily secure the joist hanger in place while you work, then use nails to attach it to the ledger board. The nails should be 16d galvanized for outdoors, and common for indoors. Now you can insert your new joist into the hanger and nail it in securely.

If you are lucky, you will be able to use your old floorboards again. If not, you will have to purchase and install replacements.