How To Fix Damaged Floor Joists | Repair or Replace?

The list of jobs and projects that need completing in our homes can often feel endless – but damaged floor joists should be a top priority for all. Once a joist has lost it’s structural integrity, it’s at risk of being unable to support the floor which can then lead to further structural issues and damage. 

How To Know Whether Or Not Your Floor Joists Are Damaged 

One of the easiest ways to detect whether or not your floor joists are in a poor condition is by walking across the floor. A sagging or bowing in the floor, or the feeling that it is bending, will be sure ways to tell if the joists may need fixing or replacing. Another way to inspect the floor is by doing a marble test – place a marble in a corner of the room on the floor, and see if it rolls to a dipped area. 

You can test this out in different areas of a room, placing the marble on spaces you believe to be higher, to see if the marble rolls away. The marble test will work better on hard floor surfaces such as wood, as opposed to thick carpeted rooms. 

If you’re concerned your floor joists may be damaged as a result of flooding, fires or severe pest problems, then the joists should be thoroughly inspected, even if the floor above seems stable. This is due to water damage, and damage from other causes, potentially causing rot, twisting or splintering in the joists.  

How To Know Whether To Repair Or Replace 

You’ll need to fully examine the floor joists in order to determine whether or not they can be repaired or replaced. Minor damages to the wood of the joists will probably result in a quick repair job to ensure the floor is fully and properly supported, however, if the joist is damaged than the structural support to the floor is compromised, and a replacement will need to be made. 

If you’re unsure of what you’re looking for or are uncomfortable in being able to determine the severity of the issue, it’s always best to get a structural engineer or professional to take a look at the joists for you. While such appointments can vary in price, the cause of further damage will cost far most in the future if joists are left unattended. 

How To Replace A Floor Joist 

So long as you have access to the joists in order to remove and replace them, replacing a floor joist can be done in fewer steps than you may think.

It’s important that before you begin the job, you wear appropriate personal protective equipment (PPE) so that you’re kept as safe as possible throughout the task. The amount of PPE required will be dependent on the location of the joists and the conditions you’ll be working in, though protective eyewear is essential for all. Before starting the replacement, ensure you also have a good amount of lighting. 

Equipment Needed:

• PPE 

• Work light

• New floor joist 

• Pry or wrecking bar 

• Reciprocating saw

• Construction adhesive 

• Bottle jack 

• Spare blades for your reciprocating saw 
  

Step One:

First, you’ll need to measure your damaged joist end to end, to ensure the new one is the same size – make sure you measure it before removing it. As a general rule, the joist should be approximately 12 inches longer than the room it spans, though your original may be less. Cut your new joist the same size as the original, so that it fits in the exact same way. 

Step Two:

Using a pry or wrecking bar, carefully pry the damaged joist from the subfloor, hammering wedges of wood between the joist and the subfloor as you go along to make this easier. 

Step Three:

Once you’ve been able to loosen part of the joist, use your reciprocating saw to cut it vertically in order to weaken it. Working across the span of the joist, pry it from the subfloor, cutting through nails is necessary – this is where you may find you’ll need additional blades, as they may break when cutting through the nails. Keep going until you have removed all of the old joist from the area. 

Step Four:

Next, apply a bead of construction adhesive to the top side of your new joist, and slide the new joist roughly into place – you’ll need an extra pair of helpful hands here. 

Step Five:

Get your bottle jack and place it alongside one end of the joist. Then, position a block of wood between the jack and the subfloor. 

Step Six:

Carefully raise the jack and subfloor enough for you to adjust the joist into its position. 

Step Seven:

Once you’ve tapped the joist in place, fasten it to the beam or supporting wall at each of its ends. 

Step Eight:

Finally, you can lower the jack and remove it, along with the blocks of wood. 

Fixing floor joists may seem daunting but with these tips, you’ll find it’s easier than it first appears.