Rebuild a website when the platform underneath it stops you fixing problems that cost you customers: pages that stay slow on phones whatever you try, a CMS nobody can edit without breaking something, plugins that no longer get security updates, or a structure that no longer matches what you sell. If the problems are a dated look, weak copy or a buried contact form, a fix on the existing site will usually do, and the age of the site tells you very little either way.
The distinction matters because the two cost very different amounts. If you want the numbers first, our guide to website redesign costs in the UK has them. This one is about deciding whether you need to spend that money at all.
Signs the site needs rebuilding
1. It is slow on phones, and the fixes have run out
Run your homepage through PageSpeed Insights on mobile. Google's Core Web Vitals set three targets: the main content visible within 2.5 seconds, a response to taps within 200 milliseconds, and a layout that does not jump around (a shift score of 0.1 or less). Missing them is common and often fixable with image compression, caching and dropping a few scripts. The rebuild sign is when someone has already done all that and the page is still slow, because the theme or page builder loads its weight on every page whether you use it or not.
2. It was designed for a desktop
Google has indexed the web by its mobile version since it finished the switch to mobile-first indexing in 2023. If your site shrinks a desktop layout onto a phone, with tiny text, menus you have to pinch and buttons too close together, that is what Google sees too. A retrofit can patch a few pages. A layout built for desktop throughout usually needs starting again.
3. The plugins have stopped getting updates
This one is about risk rather than looks. Patchstack logged 11,334 new vulnerabilities in the WordPress ecosystem in 2025, and its 2026 security report found 91% of them in plugins and 46% with no fix from the developer at the time they were made public. A site that depends on a page builder or booking plugin whose author has gone quiet is carrying a hole that nobody is going to patch. Replacing one abandoned plugin is a normal repair job; when the site depends on five of them, replacing the platform is usually less work than replacing each piece.
4. Nobody can edit it without breaking it
You want to change opening hours and the footer falls apart. Adding a page means paying a developer, every time. The last person who understood the setup left two years ago. When simple edits need a specialist, the site is costing you money on every change, and that adds up faster than most owners notice.
5. Your developer keeps saying that will be difficult
Ask for something ordinary, like online booking, a second language or a page per service area, and the answer is that the platform does not really support it. Hearing that once is normal, since every platform has limits. Hearing it for most of your requests over a year means the platform is setting the limits of what your business can do online.
6. What you sell has changed, and the structure has not
The site was built when you offered three services and now you offer nine, or you moved from selling to consumers to selling to companies. New pages bolted onto an old menu leave visitors unable to find the thing you most want to sell, and rewriting copy page by page does not change the menu they are lost in.
7. You cannot see what visitors do
No analytics, broken conversion tracking, a form that sends to an inbox nobody checks. On its own this is a fix. Combined with any sign above, it means you have no baseline to protect, which makes a clean rebuild with proper tracking from day one easier to justify.
Signs that look like rebuild time but are not
It looks dated. A new colour scheme, better photos and a modern font can be done on the existing site. If the site is fast and works on a phone, a visual refresh covers it.
Traffic is low. A rebuild does not bring visitors. If few people arrive but a decent share of them get in touch, the site is working and you have an SEO problem. The redesign cost guide walks through the quick analytics test that tells the two apart.
A competitor just launched a new site. Their redesign tells you about their budget, and your own enquiry numbers tell you about your site, so look at those before comparing screenshots.
It is five years old. Plenty of five-year-old sites load in a second and convert well, and replacing one puts its existing rankings at risk with nothing measurable to gain.
Fix or rebuild: a quick way to decide
Write down every complaint you have about the site, then sort each one into one of two columns. In the first, things that live in the content: words, photos, the order of pages, the contact form, colours. In the second, things that live in the platform: speed you cannot improve, editing that breaks layouts, unsupported plugins, features the system cannot do.
If the first column is long and the second is empty, fix the site and keep your money. If the second column has two or more entries, a rebuild is probably cheaper over the next three years than paying to work around it. If you are on Wix or Squarespace, the question is slightly different, and our comparison of Wix or Squarespace against a custom site covers it.
If you do rebuild
The main job is keeping the rankings and enquiries you already have while the platform changes underneath them. Our website redesign page sets out how we run a rebuild with that in mind.