A deck treatment can restore your dry, cracked deck to a its original beauty. If the weather in your area requires that your deck be in direct sun or rain for months at a time, the cracking can be severe. If you have had your deck checked and it is sound, you can go ahead and fill the cracks that are under 4 inches long. If your deck has cracks that are longer than 4 inches, you need to remove those individual boards and replace them with new wood.
You can use wood filler or Bondo to repair your dry cracked deck. You will use wood filler if you aren’t planning on painting or staining the deck.
Wood filler can be purchased from any home improvement store. You will clean the deck, fill the cracks with the filler and allow it to dry. You can then stain the deck if you’d like. You should understand that wood filler is not permanent. With the expansion and contraction of wood, the filler will become loose and fall out over time. You can simply fill the areas again as you need to.
Bondo is a more heavy duty solution to dry, cracked wood on your deck. You will mix and apply the Bondo to the cracks. You will let it dry completely and then sand the deck with a belt sander. Because Bondo will not be the same color as your deck, it is best to apply a paint or opaque stain to the deck once you have sanded. Though the Bondo will last longer than the wood filler, you will still have to check and maintain the filled cracks.