Overlapping valances are an ideal solution for any window because of their flexibility. They are an excellent solution for a small window and for very large window such as slider and French Doors.
When you have multiple overlapping valances, you will need a double curtain rod. You will alternate the valance on the front and back rods to achieve the overlap. Double rod pockets are necessary on the valance to ensure the valances have the same drop on the front. Valances on the front rod will use pocket one and valances on the back rod will use pocket two.
We recommend that you allow for a 25% overlap in your calculations. This will give you a beautiful full look. So for example lets say your slider is 84″ wide. Adding the 25% will give you 105″ of valance required (84″ x 1.25 = 105″). We recommend that you use an odd number when overlapping for symmetry. Take the 105″/3 = 35″. So you would order three valances at 35″ to give you a beautiful finished window treatment.