Hi Joomla experts, I have a site i want to upgrade but don't want to lose the custom layout it currently has. can anyone tell me if a straight upgrade from 1.5.2 to 3.6? will actually retain existing custom design? please advise, if anyone is a joomla expert here feel free to PM me if you think this is something you can help me with
create a subdomain, put a copy of the site on it and run the upgrade. If the theme is ok, then repeat on the live site, if it's not, then don't.
Upgrading from version 1.5.2 to 3.6 without losing the custom layouts is something very challenging. There are many changes since version 1.5.2. However, it is not impossible. As what @sarahk suggested, you can create a subdomain to test it before upgrading. Another thing you can do is to install the Joomla version 3.6 on your local drive, then try to activate your old template.
I recommend step by step upgrade. You " WILL " lose some customization, however just like any other CMS, be prepared to start debugging.