One website or one site per product line
Decide between a single site with strong sections and separate sites per product line using buyer overlap maintenance capacity and real publishing cost.
The decision you are actually making
You sell three or four reasonably different things. Someone has proposed giving each one its own website and its own domain so that each can be marketed cleanly. Or you already run four installations and three of them were last touched two years ago.
The question looks like a website question. It is really a question about how much publishing capacity you have. Every site you own is a standing commitment to keep a thing current. Businesses rarely fail this decision on architecture. They fail it on staffing.
What each extra site costs you and what is excluded
A build fee excludes everything recurring. Domain renewals hosting SSL plugin or theme licences security patching backups and the analytics setup are separate and they repeat every year for every property. So does the content. Four sites need four sets of pages written four times and nobody writes the fourth set.
The one-time cost is also multiplied rather than shared. A website design engagement carries a published rate on its service page with GST at 18% on the fee. Four separate builds are four scopes. One site with four well-built sections is one. Before choosing the split price both routes properly and include three years of recurring cost in the comparison rather than the build alone.
When separate sites are right and when they are a trap
Do not split if one person handles your marketing. A twenty person manufacturer with a single marketing executive cannot keep four sites alive. Three will go stale and a stale site does real damage because buyers read old pricing old certifications and a news page that stopped in 2023 as signs the business is drifting.
Do not split in order to chase keywords either. That is the most common stated reason and it is the weakest one. A single site with a properly built section for each product line can rank for the same terms while concentrating rather than dividing your links your crawl attention and your internal signals.
Separate sites earn their place when the businesses are genuinely separate. Different buyers different sales motions different teams and different brand names. A company selling industrial pumps to procurement managers and consumer water purifiers to households is running two businesses and the shared site will serve neither. A regulatory requirement for separation or a product line you intend to sell within a few years also justifies the split since an independent property is far easier to hand over.
How to work through it
Start with overlap. List the buyer the problem and the search language for each product line side by side. Where the buyer and the language are shared the lines belong together. Where a buyer for one line would be confused or put off by another line you have found a real boundary.
If the answer is one site give each line a top level section with its own hub page its own case material and its own enquiry path. Use subfolders rather than subdomains so the whole site accumulates authority in one place. Keep navigation shallow enough that a buyer reaches their section in a single click.
If the answer is separate sites plan the separation properly. Distinct brand names distinct contact routes and no reciprocal link network between them. Linking your own cluster of sites to each other for search benefit is a pattern search engines recognise. If you are consolidating existing sites instead map every live URL to its destination and redirect each one individually. A single redirect to the home page discards the history of every page you had.
Judging the structure later
The flattering metric is total traffic summed across properties. It flatters because it double counts people who visit two of your sites and because it has no comparison. You cannot know what the single site would have produced.
Track enquiries by product line instead and track your cost per published page. If the cost per page keeps climbing and the publishing rate keeps falling the structure is too heavy for the team you have. Time from brief to a live page on the smallest product line is the most honest number in this whole exercise.
The common mistake
The expensive error is launching the extra sites before deciding who writes for them. The build is the cheap part and it is the part everybody budgets for. Within a year the business is paying hosting on four properties while the content on three of them misrepresents what it now sells.
The reverse error costs less but still costs. Folding an acquired brand with a different buyer into the parent site strips it of the identity its customers recognised. Judge that one on buyer overlap rather than on tidiness.
A note on moving pages
Any consolidation or split involves moving URLs and that carries search volatility. Rankings commonly move in both directions for weeks while search engines reprocess the change. Nobody can promise that every page returns to the position it held because nobody controls how those systems revalue a changed site. Plan the move for a slow trading period and keep the old analytics so you can see what actually happened.
This guide explains how something works. It is not legal, tax or financial advice, and rules change. Confirm anything regulatory with a qualified professional before you act on it.