How to Replace Deck Joists

Decks are exposed to the environment all year long, so it's no surprise that they can become damaged after battles with rain, snow, ice and drought. Occasionally, you'll have to replace one or more of your deck joists. It may sound like a big job, but there are ways to replace your deck joists that won't give you too many headaches and will extend the life of your deck another few years.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Hammer or screwdriver
• Tape measure
• Screws or nails
• Joist hangers
• Lumber
• Circular saw

1. Identify the joists that need to be replaced. If there are a substantial number to replace, consider rebuilding from scratch since replacing the joists would not only be time-consuming, but the wear and damage might indicate that the problems are throughout the structure, not just in the joists. However, if only a few are bad, it may be more economical to replace them.

2. Purchase new joists that are made of the same kind of wood as the damaged joists. This will ensure that the new wood expands at the same rate as the old wood.

3. Pull up any boards that are attached to the damaged joists. If they are secured with nails, you can strike them from underneath to loosen them from the joists, and then pry them up from the top. If they are secured with screws, you'll need to unscrew them all from the top.

4. Mark each board with a number and orientation code so they may be replaced in the proper order once the repair to the joists is complete.

5. Unscrew the damaged joists from the joist hangers. Lift the joists out of the joist hangers and remove them from the deck.

6. Trace the old joists onto the new joist material very carefully. Check that the replacement joists match the dimensions of the old joists exactly to prevent warping or sagging.

7. Treat the new joists with weatherproofing.

8. Inspect the old joist hangers to assess whether they are damaged as well. If they are cracked, broken or excessively rusted, go ahead and replace the hangers.

9. Slip the new joist into the joist hangers. Screw the new joists into place.

10. Replace the deck flooring boards according to the number and placement code you developed as you pulled them up in the beginning.

Tips & Warnings

• It is possible to replace only a small section of a joist if you notice a problem in only one confined area. Cut the section out of the joist, and then patch in a piece that matches the removed section exactly. Be aware that this may cause unusual warping if not secured properly.
• Inspect all of the boards you pull away from the damaged joists for the same problems, since rot is extremely contagious and spreads rapidly.