Search engines attempt to show what they consider the most useful results for a particular query. Naturally one part of that usefulness is for the page to have content relevant to the query. The words on the page aren’t always enough though. We can help search engines better understand our sites through a structure of content silos.
We need look no further than last week’s post on helping search engines find your content for an example.
In that post I used hiking trails in the mountains as an analogy for search engines crawling links. Through that analogy the post uses words like hiking, trail, and mountains several times. Does that make it relevant for those words? Not really. Most people searching for hiking trails in the mountains aren’t going to want to land on that post since it won’t offer anything useful to them.
That post is relevant to keywords around themes like information architecture, search engine spiders and crawlability. Someone searching around those topics might find the post useful.
Can we help search engines understand what a single post is really about and even more what a site as a whole is about through site structure alone? If we can do both we have a better chance of ranking for the words and phrases where our content meets what people are looking for.
One technique for helping search engines understand your site better is siloing.
The image above and the one further down the page are screen shots from the Webmaster World thread that I believe was the first to discuss the idea of theming or siloing
What is Siloing?
Siloing (or theming) is the idea of organizing your content into several high level keyword themes that become the main sections of your site.
Inside those keyword themed sections you build vertical silos (a hierarchy of related content) and then develop internal linking to control how link equity (link juice, page rank) flows within and between each section.
These silos allow you to reinforce different keyword themes in each section and make it easier for search engines to understand what your site is about. Through silos of content and internal linking you create more keyword relevant pages for search engines and just as important make your site easier for people to understand and navigate.
There are 2 kinds of silos you can create.
- Directory silos
- Virtual silos
From the outside looking in, both types of silos appear the same. The main difference is behind the scenes in how you organize the content on the server. We’ll cover both in a little more detail below.
Most of the thought about siloing comes from Bruce Clay, though I think the idea originated with Brett Tabke at Webmaster World. Below is one of the Webmaster World threads from 2001 discussing themes and a number of articles from Bruce Clay’s site.
I’d suggest reading through all of the articles listed below when you have a chance as most of the ideas about siloing probably come out of the articles below.
- Webmaster World Thread on Theming
- Theming Through Siloing
- Siloing Revisited
- Building a Web Site Theme with Silos
- Building a Web Site Theme with Silos, Part 2
- Building a Web Site Theme with Silos, Part 3: Folder/Directory Structure
- Building a Web Site Theme with Silos, Part 4B: Link Structure
- Building a Web Site Theme with Silos, Part Five: Keyword Rich Content
- Building a Web Site Theme with Silos, Part Six: Site Maps
- Siloing – How to Theme a Web Site for Clear Subject Relevance
How to Build Silos
Since we’re building silos around keyword themes, the first step is naturally some keyword research. One of my favorite PDFs about keyword research is the one provided by Pole Position Marketing on Keyword Researching and Selection (PDF).
The PDF talks about starting your research by finding core terms or themes instead of looking for specific words or phrases. These core terms will become the top of our silos. It’s how you’ll organize your content into sections and these core terms will likely become the links in your top level navigation.
Once you have your core terms you’ll dig deeper discovering longer and more specific phrases that will be used further down in the silo. In effect silos are like pyramids. Your main theme is at the top of the pyramid and you have a single page targeting the keyword. As you move down the pyramid you have additional content targeting more specific keywords around the same theme.
The further down the silo or pyramid and the more specific the keyword phrases, the less competition for each phrase and the more likely your page can rank well, pull traffic, and attract links. The equity from these links works its way back up the silo reinforcing the main theme along the way and helping your upper level pages rank for the more generic keywords targeting them.
Your upper level pages end up with the most internal links pointing to them and thus acquire more link equity, which they send back down the silo. Link equity continues to flow up and down inside each silo.
This should become clearer as we talk about directory and virtual silos so let’s talk about each.
In a directory silo the relationships between pages are created by grouping similar content under the same directory. When linking inside one silo you can link to any page within that silo (within that directory). When linking between two different silos or directories you only want to link to the main landing page (the top level page) of the silo.
For example say you’re building a sports themed site. You might have content that relates to each of the 4 major U.S. sports leagues, baseball, football, basketball, and hockey.
All your baseball content would be in a single directory named baseball. At the top of the directory would be a landing page for the section, likely targeting the generic word baseball. Inside the directory you could have additional subdirectories based on your keyword research. You might have a subdirectory of content for baseball teams and another for baseball statistics.
Similarly your football content would all be located in one directory with various subdirectories based on the keywords your discovered for that theme. Same for your basketball and hockey sections of the site.
By keeping each theme separate from the others you build silos on your site. Any page in your baseball section can link to any other page inside the same baseball section. If the page wants to link to something inside the football section it should only link to the top level football page, which is the landing page for the football section.
You link only within the silo or to the very top of a different silo.
In a virtual silo the relationships between pages are created through links alone. This is the main difference between directory and virtual silos. In the virtual silos you don’t actually need to place content from different themes in different directories. All the content can be located in a single directory or any other structure you want.
You do need to link between pages the same way you link with a directory structure. Again you can link to any page within the silo or to the landing page of a different silo. The silos though, are created through links alone and hence they’re virtual. The concept and the linking is still the same as in the directory silo.
Personally I prefer the directory silo, since it makes things easier on you. It’s easier to see what content is part of what silo when those pages are physically located together and separate from the pages in another silo. It also makes naming files easier and creates some well formed URLs practically by default.
Take the baseball section of the sports site above. You’d probably name the main folder for the section (the silo) “baseball” and inside have folders named, teams and statistics. Your teams folder might then include pages named new-york-yankees.html and colorado-rockies.html. All pretty logical and easy to keep track of. Your pages will now have URLs like.
You can probably see just by the URLs how the keyword theme for the section is being reinforced. Imagine each of your specific team pages (30 in all) will link back up to the top of the section with the anchor text “baseball teams” reinforcing that phrase for the main baseball teams page. Your team pages and statistics pages link back up to the main baseball landing page, reinforcing the main keyword and theme.
Additionally you can leave a breadcrumb trail on the specific team pages that might look something like:
Sports > Baseball > Teams > New York Yankees
This way every page inside the silo links back up to the top reinforcing the main keywords in the silo as they do. Your most competitive phrases will end up with the most internal links pointing to them sending them the most link equity. Those links will also have optimized anchor text again helping them to rank.
Tight Linking in Silos
When all your pages are grouped appropriately in directories or linked to appropriately to create virtual directories, you have a tighter silo. If you allow linking between silos, from one of your baseball team pages to one of your football team pages, the silo becomes looser.
The tighter the silo the better the chance of ranking for your theme specific keywords and phrases. You can target your more general keywords by consistently linking back up the silo.
Sometimes it might make sense to link directly between pages in two different silos. maybe between teams playing in the same city. You don’t however want search engines following those links or passing link equity through them. You want the link equity to stay inside the silo as much as you can or send it to the very top of another silo. We’ll discuss one way for doing this in a moment.
By maintaining a tight silo you make it easier for search engines to understand what every page inside the silo is about and what keywords are relevant to those pages.
PageRank Sculpting became the thing to do a couple years ago when Google seemed to endorse the practice. SEOs would use rel=”nofollow” to control the flow of link equity (PageRank) within their sites. In some ways this could be seen as an advanced form of siloing where you weren’t necessarily as strict with where you linked, but you were strict with your use of rel=”nofollow”
The use of rel=”nofollow” was one way to deal with the problem described above, that of linking across silos when it made sense for people, but not sending any link equity to the other silo.
Unfortunately Google changed how rel=”nofollow” works. Originally it was assumed that adding it meant all the PageRank on the page would just be divided by the links that didn’t have nofollow applied. Google later changed it so that some PageRank did flow through the nofollowed link, only it didn’t go anywhere. In essence you now lose some link equity by using rel=”nofollow”
Better not to have the link at all from an seo perspective
If you do want to try siloing I wouldn’t recommend using rel=”nofollow” for PR sculpting. You’ll likely do more damage than anything else. You can try using other methods for conserving and controlling the flow of link equity in your site, but do know these are advanced tactics that may or may not work quite like you expect and may cause more harm than good if you’re unsure what you’re doing.
Below are some articles that discuss the good and bad of PR sculpting.
- Matt Cutts on Nofollow and the Siloing Solution – Bruce Clay post
- PageRank sculpting – Matt Cutts post
- Google Says: Yes, You Can Still Sculpt PageRank. No You Can’t Do It With Nofollow – offers additional ways to sculpt PR that don’t involve nofollow
- Expert SEO Testing: Usually Worthless – Why it’s pointless to be sculpting PR at all
- How To Get More Pages Indexed With Nofollow
- Dynamic Linking & Nofollow – Practical Examples, Diagrams, + FAQs
Do Silos Work?
That’s the key question isn’t it? If silos have no benefit why bother going through the trouble of setting them up? I wish I could give you a definitive answer about their effect on search engine ranking, but I can’t. The seo community is split on the subject as a simple image will show.
Above are the results from a Bruce Clay survey earlier this year. When asked if siloing was an important seo tactic the responses were split between the 2 extremes of it being important and not important.
I’ve yet to see anyone perform a test or study to show whether or not silos are effective. They certainly sound like they should be effective, yet in all I’ve read about them the one thing always lacking is evidence.
Then again when someone as knowledgeable about seo as Michael Gray runs a series on siloing your website and begins the series with the following quote I tend to take notice.
One of the more powerful tools an SEO can use when setting up or fixing an existing website is siloing or theming.
Proof or no proof I think it makes sense to consider siloing. First it’s hard to see how they could hurt. If there’s even a chance they help why not use them if there’s no associated risk?
However the main reason I think it makes sense to set up themes or silos in your site structure is they’re user friendly. They make it easier for real people to understand and navigate your site and in the end it’s real people who are most important.
Think about what you’re doing when you create silos on your site. You’re organizing content around related themes and linking to related content. Isn’t that something you want to do anyway? Siloing will just make you think a little more about the words people might use when searching for your content and make you a little more disciplined in regards to internal linking.
Below is Michael’s 5 part series on siloing your website. This series will be less on the theory (though it’s still there) and more on the practical advice. Definitely worth reading, though I suggest you first read some of the posts listed above and understand the theory.
- How To Silo Your Website: The Masthead
- How To Silo Your Website: The Breadcrumb Trail
- How to Silo Your Website: The Content
- How To Silo Your Website:The Sidebar
- How To Silo Your Website: The Footer
Helping search engines understand what your site is about and helping them understand what content on your site is relevant for which keywords should be one goal of information architecture. You can accomplish both through the tactic known as siloing or theming.
The idea is to organize your site at the highest level around several keyword themes. Each theme becomes a section of your site and you build a hierarchy of content inside each section as a silo. Silos freely link within and link only to the top of neighboring silos.
The seo community is still divided about the effect of silos. Some swear by them and others think they aren’t so important. If you have an existing site structure in place I wouldn’t necessary tear it apart to rebuild it as a series of silos. On the other hand if you’re designing a new site or planning to restructure the content of a site anyway you may want to consider a silo approach.
There really isn’t a downside to organizing your content in silos and they serve a major upside in that they’re user friendly. Regardless of how search engines see your siloed site, your audience will likely find it more usable. That alone should be enough to consider using them as a structure on your next site.
Have you used silos? Have you found them to be effective?