Spiral design is a way of laying out information that makes it easier to internalize.

Cognitive scientists have shown that people learn better when they are allowed to revisit the same topic over and over, especially when they can use information from a previous exposure to help them understand the next.  This is equally true for learning which brand of product fits your needs as it is for gaining an understanding of US History.

When producing content with a spiral design you assume that you cannot share all the relevant information in just one page.  Instead you start with something critical, and discuss it in very broad strokes (for example, why someone might need the services of your industry).  As you generate additional content you produce pages that can be reached from your “ground level” page that provide slightly more in depth information on related topics (for example, descriptions of the various areas of service offered by your industry).  These pages should eventually link back to a more sophisticated discussion of the critical topic.

When writing the “next level” discussion of your critical topic you can assume that the readers have a basic understanding of the subject.  And you can afford to discuss more complex questions (like why a potential client should pick you over the competition).  You will probably want to include links back to the various pages on the “ground level” as well as new links to higher level related content (like what your offerings or expertise is in each of the listed service areas).

If there are areas of your industry that you do not serve, go ahead and use these higher-level pages to refer visitors to colleagues who do specialize in that area.  It’s not like you’re losing any business, and you will show that you can fairly appraise your limits and still serve as a resource when they have been surpassed.

As you may have realized, you can also set up smaller spirals inside the supporting content that will allow visitors to gain a greater understanding of a smaller aspect of what you do.  Depending on the nature of your site, you could produce any number of levels, each more complex and more informed than the last.  As long as you keep returning to the same critical subject (or subjects) you are employing spiral design.

The one caution is that you can never assume what level of information someone has coming in.  If you force an industry insider to start at the ground floor, you will probably lose them before they reach the relevant content.  Likewise a novice who starts at the penthouse may not know if they’re in the right building.  Always give your visitors the ability to pick their own level of expertise, and allow them the ability to move up or down freely.