Finishing Stair Treads At Home
When it comes time to finish treads it is best to spread out the plastic drop cloth and set up your saw horses on top of the drop cloth, this is best to do in an outside setting. You will also want to set up a flat surface on top of the saw horses to place the treads on. Keep in mind this surface will most likely get covered in polyurethane. It would be best to use an air gun to apply polyurethane but a 2" foam brush will work as well.
The first coat of polyurethane should be laid on thick. Again working with the grain of the tread, apply a generous amount of polyurethane to the surface of the tread, make sure to coat the top and bottom of the bullnose. Once the entire tread has been coated in polyurethane you will have to leave the tread to dry overnight. Once the polyurethane has dried take a hand sander and using 220 grit sandpaper smooth out the surface of the tread. Make sure during this process you smooth out all the crevices left behind by the polyurethane. Once tread has been completely smoothed out it is time to apply another coat of polyurethane. Using the foam brush apply a thinner layer of polyurethane, still making sure to cover the top and bottom of the nosing and the entire surface of the tread.
Leave tread to dry overnight. Repeat sanding with 220 grit sandpaper once the tread has dried. Once the tread is again smoothed out apply the last coat of polyurethane. This is to be the thinnest coat and it is important to make the last coat as smooth as possible. Once tread has been completely finished store in a dry place from 24 hours with nothing touching the surface of the tread, before installation.