TL;DR -> Yes you will risk it if you don't perform a proper audit and migration from the original platform.

Any type of architecture changes can 100% ruin your SEO if you are not migrating content and topics correctly. Many people assume this is limited to URI structure but underestimate the power of Topical hierarchy and the content, internal linking and URI structure which play a crucial role into any migration effort.

If you have any questions about the migration process, give me a shout.

Decent free migration checklist: https://searchengineland.com/site-migration-seo-checklist-dont-lose-traffic-286880

No, re-designing it would actually help it because it's showing Google that you're updating your content and prividing a better experience for the user - assuming that your re-design is actually a great design. I would recommend using WordPress. It's similar to Joomla, but much better and you'll find more design options. WordPress has a lot of great themes (templates). As long as you're not deleting content and pages - then you're rankings will be fine. Just make sure you do it within a few days time. You don't want a website in progress for a month. But the link juice flows to the domain, so you're fine.

Disagree with Charles that Wordpress is 'much better' and that you'll find more design options, mostly because both are not true. Joomla is good for some things while Wordpress is good for others. Design wise, they're equal and don't let anyone tell you different. Just look at the theme providers for both.

However, Wordpress is easier to use. My 9 year old son has set up a Wordpress site and he liked it, but went back to Blogger. As Wordpress is easier, that also means Joomla is more complicated but at the exact same time, Drupal is even more complicated and Drupal beats both overall (although probably not for SEO but that mostly comes down to the extensions you can install for Wordpress and Joomla).

And if you're using an old version of Joomla, I'd guess 1.0 or 1.5, then the easiest thing for you to do would be to stick with Joomla but don't just migrate, first there are things to consider.

First, juice doesn't 'just' go to the domain, it goes throughout your site and each page will have some, so if you're moving platform or changing URL structure make sure and this is the most important part, that Google knows.

You can do this in a number of ways (there are extensions on the Joomle Extensions Directory to help) but the safest way would be to add some 301 redirects into your .htaccess file of your new site so when Google looks for the the URL and it ends up somewhere else, after following the redirect and seeing that it's a 301 (permanent) and accepts the new link as the right one, your juice follows with it.

There are also tools at Google Webmaster to help you know if anything is going wrong.

But it's also worth looking into where your juice is coming from and where it's going on your site. If the vast majority of it is going to your homepage then it might not be so critical on what platform you use (although I'd stick with Joomla), but just remember to do the 301 redirects so Google knows where the new pages are. And also go responsive (Google likes responsive design) and make sure your site is as fast as possible, as Google likes speed too.

Good luck ..

I help companies manage projects. I'm working with one client right now who is conducting a redesign of their own so I'm a good fit to answer this question.

The term "redesign" has become ambiguous and your intention by the term will affect the answer to your question.

Are you simply redesigning the layout? Are you redesigning the navigation? The site structure? Are you writing brand new text? Are you keeping the same web pages and URLs?

When you say "ground up", I interpret it as all of the above, at the very minimum.

To answer your question:

The short answer is, if done right, no. Your search ranking will not be affected by the redesign and you will continue to enjoy business success.

The long answer is, probably. There exist so many points of failure with website redesigns "from the ground up" that the likelihood is high that somebody with limited exposure to redesigning websites will make mistakes that result in traffic loss.

Case in point:

My client is a charity. It has offices around the world, each with their own website. I'm managing the redesign of the Canadian office's website from the "ground up". I was not involved in the UK or Kenya office redesigns and their results were troubling to us in the Canadian office.

The UK office lost 60% of its traffic following its "ground up" redesign. The Kenya office, managed slightly better, lost 40% of its traffic. I'm projecting the Canadian office will lose 10% of our traffic, and that's following best practices. (I admit, I'm setting low expectations for us. I actually think we'll continue to experience traffic growth at about 20% year over year but I'm a believer in under-promising and over-delivering).

This traffic loss for the UK and Kenya websites has probably impacted the bottom line--the UK and Kenya offices both appear to have less traffic to their Donate page (although I don't have specific dollar-values to support that statement).

If your business lives and dies on the success of your business, call an expert. At the very least, get in touch with me so that I can send you some Excel spreadsheets, templates, and other documents you'll find useful if you choose to do it yourself. If your website is mission-critical, the redesign is not the time to be frugal.

Hope it helps.

Sean Power
Partner, Bansal & Power
http://bansalpower.com/

It can happen if you are changing URL's , I would recommended if you are changing url's then make a list of all Url's of your website for that you could use scream frog and 301 redirect old url's to new.

Redesigning a site won't affect your ranking in the search engine results pages (SERPs) if you do the following:

1) Keep the same domain name.
2) Use 301 redirects to your new pages if you have renamed them or added content. (Example: your old page was at "www.example.com/what-we-do" and your new one is "www.example.com/services".)

To do a 301 redirect on a Linux server you need to edit your .htaccess file in the root directory where you site is hosted. The simplest redirects, just pointing an old page to a new one, look like this:
"Redirect 301 /oldfile.html /newfile.html"
(with no quotes and one redirect per line)

It is likely that you'll forget a few steps if you haven't done it before and if you don't have a solid website redesign SEO checklist.

If you miss out on a few critical things after you launch the redesign, these will harm the rankings:
-Forgetting to update robots.txt if you disallow search engines
-Forgetting to remove the noindex for pages you DO want in the index
-Not redirecting your important pages if you change URLs
-Letting important pages accidentally 404
-Not looking at all the elements helping important pages rank before making drastic changes

There's probably 50-100 items to check off if you're managing an important redesign for an important site.

If your site doesn't bring in much search traffic and you've got nothing to lose, then the risk is much smaller.

If your site is critical to your business, and you're making tons of changes, then there are some big risks there, so do some research or hire an expert to get it right!

Feel free to ping me or request a call if you have any follow-up questions, as I've done about 20 of these and so I have a huge checklist of my own to manage this process.

One of the biggest misconceptions among website owners is that SEO only needs to be done once. Unfortunately, this is not the case. Numerous fractions are altered during redesign including code and pages. If they are not properly handled, it can negatively impact the website’s SEO and affect the long-term growth of the site. If done correctly, however, redesigning a website can also increase your SEO strength. Here are few steps that would help you to redesign your website without affecting SEO.
Step 1: list of all pages from the old website: The first step is to download the URL structure of your website. Redesigning means a lot of changes which will also affect the URL re-structure. It is important therefore to back it up otherwise you run the risk of impacting your website ranking. You can use plugins to get the URL structure. If you are using Yoast SEO plugin, you can crawl the website and then download the updated sitemap.
Step 2: The redesign needs to be done on a temporary URL: Never do the redesign on your existing website. It can cause visitor issues and give you problems in the long run. The best approach is to copy your site and set it up into a temporary URL. Once done; you can start making changes to it. An alternative would be to switch the domain once all the required redesign changes are made. If there is a potential for you to struggle with this, you can always get help from your developer. Another option would be for a hosting company to do it for you. It is important for you to ping your hosting provider to do the setup for you as this step will protect you from unforeseen issues in future.
Step 3: Test the new website: Great, you copied your existing website into the new website. However, before you start your redesign project, it is a good idea to do an end-to-end check-up of your website. In this check-up, you should look at multiple aspects of your website including broken links, features, CSS, etc. You can also use the XENU, a free-to-use tool that will find all the broken links on your website.
Step 4: Do proper 301 redirects: The next step is to do 301 redirects between old and new URLs. For example, if you have an “About Us” page on the old website, and its URL was “www.yourwebsite.com/aboutus.html.”
If during the redesign, your designer changed the URL to “www.yourwebsite.com/about-us.html” – it is better to implement proper 301 redirects to ensure that both URLs work and you don’t lose SEO benefits gained from your previous URL. If you don’t do it correctly, the search engine will get 404 web pages not found. By doing 301 redirects, the old URL will be redirected to the new one. This is the technical way to tell the search engine that the URL has been changed. Google will not downgrade your previous SEO efforts. You can add redirects using the .htaccess file. It would look like the following code.
Redirect 301 /oldwebsite http://yoursite.com/new-url
If you are confused and do not know how to do it manually on WordPress, you can also try out redirect plugins that let you do it by filling in a form.
Step 5: Make the jump to the new website: Once everything is finalized, both design and redirection, it is time for you to switch to the new website. You can also make an incremental change in stages if your website is big.
Step 6: Run Google Webmaster tools: It is common for developers or designers to stop the search engine to crawl the website. If that is the case, then you will need to resume the crawler on your website. To check the status, you need to use the “Fetch as Google” option under crawler. Once done, click on the “Fetch and Render” option. If both tests return positive – your website is entirely crawlable. Also, it is advised to check if the redesigned website is verified. You can do so by logging into the respective webmaster’s tool provided by Bing and Google. If it lacks verification, then redo it and claim your website. And finally, re-submit your website URL into Google index by clicking on “submit to index” button.
Step 8: Robot.txt: During the redesign, there is a chance that your robot.txt file can get corrupted. To check if it has, you can use “robot.txt” option under crawl.
Step 9: Sitemap submission: As your website now has a new and modified structure, submit the website XML to Bing and Google. Once submitted, your new website will be crawled in the coming hours.
Step 10: monitor the changes: Finally, it is important to monitor the changes and look for any potential growth. Keep a close tab on the rankings of your top keywords. There are many SEO tools available that enable you to keep track of these keywords. If there is a considerable change in your SEO, then endeavour to understand why this is happening and look to find a solution if your website traffic slows down quickly.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath