3 Subdomains - Can their authority or ranking affect each other?

[danialniazi]

HI,

We have 3 different subdomains that target completely different industries.
a.example.com - school reviews
b.example.com - healthcare reviews
c.example.com - car reviews

Q1: If any of the above subdomains gets demoted or penalized by Google would that affect the other subdomains?

Q2: Moving forward with all the new changes in SEO, penalties, etc; would it be wise to utilize 3 subdomains for different industries or should we consider getting separate domains?

[danialniazi]

Thank you all for your response.

[BrianJGomez]

I have a different opinion based on my extensive experience working with subdomains. The big advantage to working with subdomains, is that they all benefit from the Domain Authority of the root url.

If you owned tacobell.com (with a DA of 80) and decided to create a web site on a subdomain for each location like tambabay.tacobell.com, that subdomain would benefit immediately from the root.

In my experience is the same is true for penalties, regardless of how the subdomains are linked, if in the example above, tacobell.com begins the spammiest seo campaign of all time, tampabay.tacobell.com absolutely will incur some, if not all of the wrath.

[ReferralCandy]

I agree with Chris, it depends on how "closely connected" your subdomains are. If you are sharing a lot of links in between the subdomains, then its likely that all the sites will be affected once detected by Google. However, do note that Google treats subdomain separately. This means that if you ensure the content in each of your subdomain is unique and perform different linking activities on them, it shouldn't be an issue.

On top of SEO concerns, if you are aiming to establish a review community under a common brand name, it would certainly be a good idea to use subdomains. For example, if a visitor looking for car reviews is impressed with your car review site, it is likely that he/she will look for healthcare reviews from your healthcare review site. One good example of this is Tutsplus, which has several subdomains under the giant umbrella of web development.

[Chris.Menke]

Daniel,

If you are linking to any large degree between the sites, or if the sites share a lot of links in their back link profiles, are part of joint manipulation effort such as link networks or link wheels they could all get penalized at the same time or the penalization of one could lead to the penalization of another.  If they share a link from a single strong site that gets penalized and they loose the value of that link, all three could loose domain authority.

But if their linking activities are completely separate and above board, they should be fine residing on subdomians.