Can I combine existing static HTML website with new CMS site under same domain name?

I'm a member of a small society with an html website (cmyf.org.uk) built many years ago -most of the information is static and very rarely edited but we would like to add blogging and other functionality. My question is, should we set up a CMS site under a new domain name, or is there a way to combine the existing static site and a new section with modern CMS under the same domain name, without needing to import existing content into the new CMS? We are working with a very small budget so would like to save on domain hosting costs.

You can easily create a dedicated subdomain, i.e.`blog.cmyf.org.uk`, and set up any cms just for blogging purposes (e.g. `WordPress` or `Ghost CMS`). Ask your domain provider or server admin for help - by definition creating and configuring a subdomain is free (in comparison to registration a new domain).

Most of the common off the shelf CMS/blogging software can be relatively easily configured to run from a subdirectory under the webroot.

That would be one way to have both sites co-exist happily, on the same webhosting package and domain.

There may well be other or more desirable ways to accomplish the same thing but they all depend on the details (which software/blogplatform, what webhostingcompany and what kind of features they offer, etc.)