Durham’s may be used out doors, but it is not a waterproof material and will absorb moisture even after it is dried completely. It must be kept painted and sealed from moisture, but we do NOT recommend it for repairs on decks or porch floors. These areas are just too susceptible to moisture to be adequately protected from moisture by panting. Water will be absorbed into the boards from between the boards or from underneath the deck. The water putty will absorb moisture and if the painted putty patches get damp, it will cause the paint to peel from the putty. For this reason we don’t recommend it for repairs to decks or porch floors.
Please keep Durham’s in mind for some of your other repairs.