Licensing, insurance and references are necessary and they do not distinguish anyone — every contractor worth considering has them.
What distinguishes them is how they talk about the parts nobody sees.
1. "Which waterproofing system do you use?"
The answer should be a manufacturer and a system — a named sheet or liquid membrane meeting ANSI A118.10, used throughout rather than mixed.
"We use a waterproof membrane" is not an answer. "We use the red one" is closer. A specific system with specific corner details is what you want.
Follow up: "Do you flood test the pan?" The answer should be yes, for 24 hours, before tiling.
2. "How will you size the fan, and where does it vent?"
Look for a CFM figure derived from the room rather than a default, rigid duct rather than flexible, and a termination outside rather than into a soffit or attic.
This is a small item that reveals whether the contractor thinks about moisture at all.
3. "What do you expect to find behind the walls?"
On a house of any age, the honest answer names possibilities: rot at the toilet flange, missing or improvised venting, galvanised supply, no blocking, wiring that will need bringing up to code.
A contractor who says they expect no surprises on a fifty-year-old bathroom has either not looked or is managing your expectations rather than informing them.
4. "How is a change handled?"
Written change orders, priced before the work, signed. That should be the answer and it should already be in the contract.
Verbal changes agreed on site are the single most common source of dispute in renovation.
5. "Who is actually here each day?"
Whether the person quoting is the person working, or a project manager, or a rotating set of subcontractors.
None of those is wrong. Knowing which it is sets expectations about communication and about who to ask when something needs deciding.
6. "What is the timeline, and what are the gaps?"
A realistic answer includes waiting — permits, inspections, membrane cure, tile set, grout cure, glass fabrication after measurement.
A contractor who quotes a bathroom in a week without mentioning any of that is quoting working days rather than elapsed days.
What to check independently
Licence and insurance, verified with the issuing body rather than by looking at a certificate.
References from jobs two or three years old, not last month. Bathroom problems surface with time, and a reference from a job finished in the spring tells you the tile looked good.
Permits pulled under their name, which most jurisdictions make searchable.
The payment schedule
A deposit, progress payments tied to milestones, and a meaningful final payment held until completion and inspection.
Large payments demanded up front, or a schedule that is fully paid before the work is finished, removes the incentive to come back for the small items — and the small items at the end are what a bathroom is judged on.
The signal worth trusting
A contractor who asks more questions than you do at the first visit, particularly about how the room is used and what is behind the walls, is planning the job.
One who quotes from the doorway is quoting a product.
Getting comparable quotes
Give every contractor the same written specification: the same layout, the same fixture list with model numbers, the same tile area, and the same waterproofing requirement.
Without that, three quotes describe three different bathrooms and the totals are not comparable. With it, the difference is labour, overhead and margin — which is what you were trying to compare in the first place.
Where one contractor proposes something different from the others, ask why. It is occasionally the only one who noticed something real.
The contract
It should name the scope, the fixtures, the waterproofing system, the timeline, the payment schedule, the change-order process, and who is responsible for permits and disposal.
A one-page quote with a total and a start date is not a contract, and the items missing from it are exactly the items that become arguments.