Small offices often start by hiring a cleaner directly, and it can work well. But once you count sickness cover, equipment, supervision and everything else that comes with employing someone, the comparison is closer than it looks.
What you take on with an in-house cleaner
You become the employer: contracts, pay, holiday, sickness, pensions and insurance. You also supply the equipment and products, and you're responsible for training and for checking the work.
The hidden cost is cover. When your cleaner is ill or on holiday, the office isn't cleaned unless someone arranges it.
What a cleaning company adds
A company provides trained, insured staff, its own equipment and products, and cover when someone is away. There is a named person to call, and someone checking the standard. Our office cleaning is set up this way, with the same small team on your building.
It usually costs more per hour than a direct hire, but you're buying reliability and not having to manage it.
When each one makes sense
An in-house cleaner suits a single small office that wants someone on site during the day and is happy to manage them. A company suits most others, especially if you need out-of-hours cleaning, cover for absence, specialist work like windows or carpets, or a supplier who handles consumables.
Some offices use both: a part-time in-house tidier during the day and a company for the deeper evening clean.
The cost of a cleaner isn't the hourly rate. It's what happens on the day they're not there.
The short answer
If you want to manage cleaning, hire directly. If you want it managed, use a company. Whichever you choose, write down the standard you expect.