Need to add 30K new pages to a 10K page website - troubles ahead? (SEO)

Google's Matt Cutts has addressed this via video:

It’s a fair question. I think we can handle it either way, so we should be able to process it. But if we see a lot of pages or a lot of things ranking on a site all of a sudden, then we might take a look at it from the manual webspam team. So if it doesn’t make any difference whatsoever to you in terms of the timing of the roll out, I might stage it a little bit and do it in steps. That way it’s not as if you’ve suddenly dropped 5 million pages on the web.

And it’s relatively rare to be able to drop hundreds of thousands of pages on the web and have them be really high quality. An archive of a newspaper is a great example of that.

But if it’s all the same to you, and it doesn’t make that much of a difference, I might tend to do it more in stages and do more of a gradual roll out. And you could still roll them out in large blocks, but just break that up a little bit.

Sure there are concerns in dumping huge numbers of pages onto your site and whether it would be considered spam or not or have a negative SEO effect. I just want to give my perspective since I feel you are within a safe range of pages and likely have fair domain trust due to domain age and stability.

My experience is this.

My site can add over 3000 pages per week. I have added as many as 100k pages in just a few months. I have about 500k pages now. I too have an older site with a fair level of trust and stability and had a fair number of pages for a long time.

I feel that it is highly likely that with your site age and likely a fairly high trust rank, I feel that dumping 30k pages will not hurt and in fact can provide a benefit. Here is what I mean.

Site stability and trust are important. If your site was a new site, then I would caution you against it. However having a well established website works in your favor. I have routinely jerked a knot in the tail of my sites (and others) by making large updates and have noticed a benefit of velocity that larger updates can bring. Again, I would not recommend this for a younger site with less trust, but for older well established and trusted sites, large updates do happen and Google seems to handle it well. Of course Google will begin to spider and index your site quicker for a period and your placement in the SERPs will take some time to settle out, but along the way there is a velocity in impressions and clicks that benefit the site owner.

If you are nervous about what I said, then roll out the update in parts. If you have 30k pages, then 10-15k pages should be okay. I would recommend 1-2 months to let it settle before making another update. Personally, I would either break it up into 2 15k updates or just update the whole thing all at once.

Again, I have not ever seen a negative effect and I think it goes to trust and the quality of the content. If your content is somewhat thin, then perhaps you should break it up. If you have full confidence in your content, then it is okay to be bold.

BTW- I have been working on large scale sites off and on for 15 years or so. I have never had an issue with a large update. Sure it can be scary. It is always advisable to be safe if you cannot afford any issues.