(Note: this article originally appeared in our September 2006 Newsletter
While the concept of siloing (also known as theming) has been widely adopted into SEO jargon, it's clear that the technique itself is not widely understood. It is for this reason that we chose to revisit the concept of siloing after first addressing it in an article last spring.
In its simplest terms, siloing is a site architecture technique used to split the focus of a site into multiple themes. The goal behind siloing is to create a site that ranks well for both its common and more-targeted keywords.
We developed our siloing technique after discovering that many of our clients expressed difficulty in ranking for both their site's generic keywords (i.e. jelly) and specific page terms (i.e. organic strawberry jelly). We found that by haphazardly linking to unrelated (or even semi-related) internal pages, clients were actually diluting the theme of that web site. This, in turn, caused lower rankings because the search engines were unable to identify what the site was supposed to be about. By implementing proper siloing, site owners can ensure that their pages rank well for theme-specific keywords, as well as general site keywords.
There are two distinct methods of siloing: directory silos and virtual silos. Both allow site owners to create tight themes through linking strategies, however, they approach the concept very differently.
Directory silos: Directory silos reinforce themes by grouping like content pages under one, highly organized directory. A minimum of five content pages are needed to establish the theme and each must be named to reinforce the subject matter.
Think of a directory silo like a file cabinet. In order for the file cabinet to be effective, everything must remain tightly grouped in its place and filed under the appropriate, structured heading. Every distinct category will have its own heading. This means if you are a site specializing in peanut butter, all of your creamy peanut butter pages would be grouped together and all of your chunky peanut butter pages would be grouped together. The two would never be mixed.
Your creamy peanut butter silo might look something like this:
In the example above, each page is named to help the search engines see the like theme. The directory naming system helps establish that these pages are all about creamy peanut butter. Sticking to this format will help prevent your themes from blurring and keep them unique.
Most sites will find that their topic is widespread enough that they need to separate it into multiple themes. If you find that your creamy peanut butter silo can be divided even further, don't be fearful of creating multiple sub silos, however keep it within reason. We recommend keeping the pages about 2-3 directors deep. Delving any further than that and you may run into trouble. Additional silos give you more room for keywords and keyword synonyms. The tighter your silos are, the better your chance at ranking for your theme-specific keywords. Just make sure you're not forgetting your more general terms in the process. Your silos should target both sets of terms.
Once you create your separate themes, you may find instances where you want to connect them. For example, let's say your peanut butter site has a silo about the health benefits of different types of peanut butter. If you have a page that specifically addresses the health benefits of creamy peanut butter, it may make sense for you to link the two pages. The best way to do this without diluting your theme is to link from the creamy peanut butter page to the health benefits landing page. This shows the engines that you have two unique silos and makes it easier for both pages to stand out. Linking at will can cause confusion for the engines as they try and decipher what your page is about.
Virtual Silos: Virtual silos use a vertical cross-linking structure to create subject themes. In other words, the theme of the top landing page is created by supporting pages linking to it. This form of siloing may be useful for an established site that does not have a directory file system already set up or is fearful of breaking established page links.
In a virtual silo, each supporting page is linked to the theme's landing page and also linked to the other supporting pages for that theme. The theme of the silo is created and reinforced by this type of cross linking of the pages. With virtual siloing, pages don't need to be in the same directory in order to be in the same silo; the theme is established solely through the use of links.
For example, let's say you want to create a virtual silo for crunchy peanut butter using the five crunchy peanut butter pages listed below:
To create the virtual silo, all five pages would link to the crunchy peanut butter landing page. This tells the search engines that these pages are related to- and support the topic presented in the landing page. Each page should then also include a link to every other supportive page in the virtual silo. In this case there are four other pages in the silo. The easiest way to do this is to include navigation on the page to link the pages together and basically creating a mini-sitemap on the page.
When linking out to other pages within the site, you must be very cautious about not risking the integrity of your silo. To link two related peanut butter pages found in separate directories, link the same as you would in a directory silo. Each page should be linked to your main landing page, as well as linked to one another. Linking this way will help build the theme of that silo. As mentioned earlier, when linking this tightly, beware of failing to address your general keywords.
Sticking with our peanut butter example, say your site sells a type of jelly that is particularly complimentary to creamy peanut butter. It may be fitting to link from your peanut butter page to the flavored jelly page. Since the jelly page would be a supporting page in the Jelly silo, you would want to link your creamy peanut butter page to the landing page of the Jelly silo instead of to the particular flavored jelly page. Doing this would dilute your theme of the creamy silo. By linking to the top of the Jelly silo, you not only keep the integrity of the two silos, but you also are helping to establish the Jelly landing page as the main page for that silo. If you absolutely had to link the creamy peanut butter page to the flavored jelly page you would want to do it with a rel=nofollow in the link command.
Whichever method of siloing you plan on choosing, we recommend designing your silos before creating your Web site, whenever possible. Doing it this way will allow you more options with your design process. If you're not sure what silos your site will need, you may opt to run your keyword testing to see which terms you plan on targeting. If you know you want to rank for the terms "creamy peanut butter" and "jelly hybrid", then you will need to create unique silos that address both of these themes. This will allow you to create deeper silos, while keeping your original structure intact.