Here are a few books that you might want to look at if you are planning on building your own darkroom. You will have to buy a used copy of some of them, but if you click the banner below, you can search BetterWorldBooks.com and your purchases help fund literacy around the world.

1. The New Darkroom Handbook - this book is a step-by-step guide that will help anyone plan and build a darkroom. The Second Edition is revised and updated version that shows you the best design, construction and equipment to use when you set up your darkroom. The book features money saving tips that will help you put up a darkroom just about anywhere. It also contains DIY plans to build essential darkroom components and includes cutouts and design grids that help you plan the best darkroom. In addition, it contains sections on building a color darkroom and a digital darkroom.  
2. Build Your Own Home Darkroom -  this is a step by step guide to designing and building an inexpensive, yet professional quality, home darkroom for both black and white and color prints. Covering every aspect from design to full operation, this clear and detailed book is perfect for photographers at all levels. It includes information on darkroom design, woodworking for the novice, lightproofing, ventilation, worktables, building enlarger baseboards, light boxes, water supply panels, print drying racks, darkroom sinks, and much more. If you aren't into building things or don't have the proper tools, this might not be the best book for you. Keep in mind though that it could help you during the actual planning processes.
3. Building a Home Darkroom (the KODAK workshop series) - this book is the least helpful in design and layout, but it is helpful in teaching you how to do the actual construction.