A fresh coat of stain can transform any wooden surface from ordinary into something beautiful. This is true even of rough-cut lumber. However, because rough lumber often contains areas with jagged or splintering areas, the application process can be a bit frustrating for do-it-yourselfers who don't know the proper technique. Fortunately, a little preparation can go a long way toward making the process easier and contribute to an attractive finish that will remain durable over time.
Work outdoors if possible. Open windows to provide adequate ventilation if you are working indoors.
Wash the rough-cut lumber thoroughly by spraying it with the pressure washer. Use a bucket of water and a coarse brush if you are working indoors. Allow the lumber to dry completely before proceeding.
Smooth any rough or splintering portions of the lumber using 80 to 120 grit sandpaper. Sand with the grain, never against it, to avoid damaging the lumber.
Place the lumber on heavy-duty drop cloths. Overlap two drop cloths to ensure that no spilled stain bleeds through.
Pour the stain into the 5-gallon bucket, about one-third full.
Apply the stain to the rough-cut lumber using the 3- to 4-inch paintbrush and working from left to right. Be especially careful to smooth any runs or drips. Use a latex paintbrush if you are applying latex stain. Use an oil-based paintbrush if you are applying oil-based stain.
Continue applying stain with the paintbrush until the exposed surface of the lumber is completely covered. Allow the stain to soak in for about 10 minutes.
Flip the lumber to the other side and repeat steps six and seven on the fresh, unstained portion of the lumber.
Allow the stain to dry for two hours. Apply another coat if you desire a darker appearance.