The Purpose of Putty
Wood putty, sometimes called wood filler, is a smooth, pliable substance that dries to a durable, hard finish. It is used in a manner that is similar to Spackle. While Spackle fills, repairs and disguises holes in walls, wood putty does the same for wooden furniture, fences, window frames, porch posts -- just about anything made of wood. Once dried, it can be sanded smooth and painted so that patches are virtually undetectable. There are numerous brands and several types of wood putty. For filling cracks and holes in an exterior wooden fence, use exterior wood putty, as it is designed to withstand the elements.
Preparing for Putty
Prepare your fence properly for the best, longest-lasting results. Putty adheres best to clean wood, so it's important to give your fence a thorough power washing to remove any dirt, dust, grease, spider webs or bird droppings. After washing, allow your fence to dry completely. If your fence has any areas of soft, rotten wood, break off the loose or crumbling pieces, and apply a wood hardener to any remaining soft spots. Follow the manufacturer's directions, and allow the hardener time to dry completely, which may be anywhere from two to 24 hours.
You can easily and quickly fill small nail holes, screw holes or worm holes with wood putty. Simply scoop out a bit of putty with a putty knife, then spread it onto, into and over the hole, filling the hole and scraping off any excess in one quick swipe. For larger holes, such as knot holes, place a piece of masking tape across the back of the hole, then fill with putty, using the masking tape as a temporary support. When the putty is completely dry, remove the tape, sand the area smooth to match the surface of the wood, and you're ready to paint.
Filling cracks is similar to filling holes. Use a putty knife to spread wood putty across the cracks while at the same time pushing putty down into the cracks to completely fill them. Masking tape works well as a temporary backing for larger cracks. Use the knife to remove excess putty. Sand and paint once the putty has completely dried.
Not Just for Old Fences
It makes sense to apply exterior wood putty to a weathered and worn wooden fence. Although it might not occur to you to apply it to a new one, most new fences actually benefit from a good going-over with wood putty. There are usually plenty of knot holes, nail holes and dents left from sunken screws and maybe even a few cracks in a new wooden fence, especially if it is made from a lower-grade wood. Once the putty has dried and been sanded smooth, the fence is ready for painting.