Barn boards are an attractive way to build furniture, cabinets or cover floors. Unfortunately, because they are old, dry and weathered, they can give off splinters if not finished. When looking for barn boards, remember that roof boards will have more nail holes than floor boards, for example. Barn boards will be weathered and have cracks, holes and variations in the grain. The same characteristics that make them interesting to use can also make them splinter more easily.
Sand the wood with a palm sander and 80-grit sandpaper to smooth out the wood overall. This will have an effect on the weathered look and will smooth out the more raised grain, but it will help eliminate the splinters.
Change the sandpaper to a finer grit, such as 120, to further smooth the wood. Take this step if you will be using your barn boards for a floor or table. Boards used for a cabinet may not need to be sanded this much.
Use a putty knife to fill any nail holes or cracks you don't want showing with wood filler. Let it dry and then sand off the excess. You can buy a wood filler to match the color of the boards if they are not completely gray. However, if the boards are very gray, you may need to consider staining the boards for a more consistent look, although this is not necessary.
Select a finish that you prefer for your barn boards. Polyurethane is popular, especially if the boards will be used as a table or floor, but tung or boiled linseed oil are also popular options. Lacquer and shellacs can also be used.
Follow the finish manufacturer's instructions to finish your barn boards. A very heavy finish, like polyurethane, should only be used when the boards are going to undergo heavy use and need to be absolutely splinter free.