1. You'd rather not share the link
Someone asks for your website and you hear yourself say "it's a bit out of date, just call me". That's the clearest sign there is. If you're embarrassed by it, visitors can usually tell.
2. It's a struggle on your own phone
Try this now. Open your site on your phone, find your phone number and tap it. Then try to book or send an enquiry. If the text is tiny, the buttons sit too close together or the menu won't open, your customers are hitting the same wall.
3. It looks older than your business
A roofing company with a long record of good work shouldn't look like it was set up in a hurry years ago. People judge quickly, and an old design can make a well-run business look careless.
4. People ring to ask things the site should answer
If customers keep calling to ask your hours, whether you cover their area or roughly what a job costs, the website isn't doing its job. Those answers belong on the page, where people look first.
5. It describes a business you no longer run
New services, a new area, a new name, a team member who left long ago. When the website lags behind the business, it confuses people and makes you look less established than you are.
6. You can't change anything yourself
Updating your holiday opening hours shouldn't mean emailing a developer who stopped replying last year. If you're locked out of your own site, rebuilding it on something you control is worth the money.
7. It isn't secure or looked after
No padlock in the browser, a warning when the page loads, or a platform that hasn't been updated in years. These aren't cosmetic problems. They put visitors off, and they're a security risk.
When your website needs a redesign, and when a refresh will do
Not every tired website needs starting again. If the layout and content still work and the real problem is speed or how the site behaves on phones, a speed and mobile refresh is cheaper and quicker. A full redesign makes sense when the look, the structure and the content all need work. I'll tell you which I think you need, even if it's the smaller job.
Don't lose what already works
A redesign shouldn't throw away useful pages. Keep the content people actually read, and set up redirects from old page addresses to the new ones so nobody lands on an error page. That includes Google.
If speed is your main complaint, start with why is my website slow?