The pillar-to-cluster link-back gets most of the attention when people talk about interlinking a topic cluster, but it’s only one relationship in a structure that can support several. A cluster that only ever links straight up to its pillar, with no connections between cluster articles themselves, is leaving real interlinking value on the table.
The Three Link Directions Worth Planning For
Pillar to cluster (downward)
The pillar linking out to its cluster articles functions as a table of contents — it helps readers navigate from the broad overview to the specific sub-question they actually have, and it distributes some of the pillar’s own authority downward to support newer or less-established cluster pages.
Cluster to pillar (upward)
Every cluster article linking back to its pillar concentrates authority in the other direction and signals clearly which page in the group is meant to be the central hub. This is the relationship that makes the structure legible as a cluster at all, rather than a set of independently existing articles.
Cluster to cluster (sideways)
The most commonly neglected relationship: articles within the same cluster linking to each other where genuinely relevant. A “descaling frequency” article naturally connects to a “descaling solution comparison” article — both are part of the same broader sub-topic and each answers a question a reader of the other might reasonably have next.
Why Sideways Links Matter
Without sideways links, a reader who finishes a cluster article has exactly two options: go back to the pillar, or leave the site. Sideways links to genuinely related cluster articles give readers a third, often more relevant option — continuing deeper into the same sub-topic rather than being funneled back up to the broad overview every single time. This keeps readers on the site longer and reinforces topical depth at a finer grain than the pillar-cluster relationship alone can.
Building Sideways Links Deliberately
Because pillar and cluster articles in a batch are generated from a shared, mapped keyword list, you already have the information needed to plan sideways links before writing even starts — you know which cluster articles belong to the same rough sub-topic grouping from the planning stage covered in our companion piece on structuring a 40-post cluster. Using those groupings to identify two or three genuinely related cluster articles per piece, and referencing them within the content (or adding them post-generation as a “related articles” note), turns a flat pillar-and-spokes structure into a genuinely networked one.
How Nesting Interacts With Interlinking
A nested pillar/parent/child structure gives you a natural interlinking pattern for free: children under the same parent are strong candidates for sideways links to each other, since the nesting itself already signals they’re closely related sub-topics. A parent page can also serve as a secondary hub, linking to just its own children rather than every article across the whole pillar — useful for large clusters where linking every single article to every other one would be excessive and unreadable.
Avoiding Over-Linking
More links isn’t automatically better. An article stuffed with a dozen internal links to every tangentially related cluster piece reads as spammy and dilutes the actual reader experience rather than improving it. A reasonable target is two to four genuinely relevant sideways links per cluster article, chosen because a reader of this specific piece would plausibly want to read that specific other piece next — not because it exists somewhere in the same cluster.
Auditing Interlinking Over Time
As a cluster grows — new keywords added, new articles published in later batches — earlier articles won’t automatically link to newer, closely related ones added after they were written. This is worth checking periodically alongside a broader link-back audit: does an older article about “descaling frequency” now have an obvious sideways link opportunity to a newer “descaling solution comparison” piece that didn’t exist when the first one was written? Adding that connection after the fact is a small, high-value maintenance task.
A Practical Interlinking Checklist
- Does every cluster article link back to its pillar?
- Does the pillar link out to every currently published cluster article, including ones added after the initial batch?
- Does each cluster article include two to four genuinely relevant sideways links to other cluster articles, not just an arbitrary “related posts” list?
- For nested structures, do children under the same parent link to each other where relevant?
- Has the interlinking been revisited since the cluster’s last batch of new articles was published?
The Takeaway
A complete interlinking strategy for a topic cluster considers three directions, not one: pillar down to clusters, clusters up to the pillar, and clusters sideways to each other. The upward link-back is the non-negotiable minimum that makes a cluster a cluster at all; the sideways links are what turn a functional structure into a genuinely well-connected resource that keeps readers moving deeper into your content instead of bouncing back to the same hub every time.
