Moisture
If the surface of the wood is too wet to paint, it should be left to dry out before any paint is applied.
Movement
Any movement in the wood can cause cracking to occur. If movement is likely, a single pack floor coating is recommended.
Dirt/Contamination
Any dirt or contamination of a surface will impair the adhesion of the paint coating. The only solution to this, is to remove all the contamination prior to painting.
Flaking Paint
If the surface has been previously painted, some detaching of paint from the surface may occur. Prior to applying a further coat of paint, all loose and flaking paint must be removed.