No matter what type of wood was used in constructing your fence, several natural enemies can cause it to dry out and crack. Extreme weather and climate shifts are typical culprits of wood fence cracking. Despite the age of your fence, with proper care and prevention methods, you can prevent cracking in the wood and help maintain the fence for many years.
Pressure-treat your wooden fence with an oil-based preservative such as pentachlorophenol, recommends the University of Wisconsin Extension. Oil-based preservative paints only have protective qualities at a surface level, and because they do not penetrate the wood, they do not protect wood used underground such as fence posts. You will need to use a pressure treatment spray and apply it directly to the wood fence. If you haven't built the fence yet, purchase wood that has already been pressure treated at a home improvement store.
Make a wax-based water repellent to apply to the wood fence before painting or staining. For every gallon of repellent, boil 1 1/2 cups of linseed oil and add it to 3 quarts of solvent such as turpentine. Break off 28.4gr pieces of paraffin wax and mix into the linseed oil/solvent solution. Set it out in warm sun for several hours to melt the mixture together. Using a paintbrush, apply the wax solution to the fence. Allow it to dry for several days.
Stain a fence that has been treated with a wax-based water repellent. Use a semi-transparent stain, which will not cover the fence with a film that will eventually crack. If you want to paint your wood fence, use one coat of an oil-based primer followed by two coats of acrylic latex paint such as exterior house paint. Do not use a varnish because it will crack or peel in sun and rain.
Do not try to melt the wax, linseed oil and solvent mixture over an open flame, as the wax could catch on fire. Though it may take more time, allow the wax solution to slowly melt in a warm sun.