Remember most bay windows are custom - it is the combination that you create that creates the design expense of the new header which I am told runs approximately $300-$500 depending upon your contractor and your location. The seating options range from full chairs in the bay window to a complete cushioned area to built in storage roof, you will want to factor this into your remodeling budget. I will respond with detailed information on the materials, tools, and improvement successful and I hope they'll prove helpful to you too. It is a trio of the best of the best - the bay window for adding