Glad we're not the only ones freezing here, it's -3 here in the north west too!
I've just taken a quick look at barrettsteel.com and whilst there aren't any duplicate content issues listed within SERPs currently, there's nothing stopping canonical issues arising in the future. You can currently view the homepage via the following URL's:
http://www.barrettsteel.com/default.aspx
http://www.barrettsteel.com/Default.aspx (you can change the case for any of the letters, as-long as it says default.aspx (EG DEFAULT.aspx also works).
If someone links to /default.aspx for example, there's a chance that /default.aspx could get indexed. Therefore it's a good idea to add a canonical tag now before you do run into any issues. It doesn't take much to add it anyway, right?
I also like to implement a canonical tag so that if someone completely rips a page, the benefit will hopefully be given back to the site that the page was ripped from due to the canonical tag.
Also unrelated to your question but I found this within the SERPs: http://barrettsteel.netconstruct-preview.co.uk/ Whilst it now has no content, I'd recommend that you 301 redirect all pages from this site to the relevant page on the main site.