A room size is only the beginning
Two bathrooms with similar floor areas can require very different work. Keeping the current fixture locations, changing the shower footprint and moving plumbing are different scopes. Begin with a sketch of the existing room and the changes you want to make.
Describe what is not working: storage, cleaning, lighting, access or the way the room feels. This helps separate the problem to solve from a finish preference. A concept image can show a direction, but it cannot establish the cost of your existing room.
Existing conditions affect the work
The condition of walls, floors and concealed services may only become clear after investigation or removal. Share known leaks, past repairs and unusual movement or damage before the scope is prepared. Ask which assumptions are included in the estimate and what happens if the work reveals a different condition.
Discuss waterproofing, ventilation and the intended finish as a connected assembly with the relevant qualified trades. A tile selection alone does not define the preparation or installation needed underneath it.
Selections change more than the shopping list
Tile format, layout, niches, edges and transitions all affect the work. Fixture dimensions, shower fittings, lighting and vanity details need coordination before installation. Compare complete selections, including their installation requirements, instead of comparing only the product price.
Separate items supplied by you from items supplied by the renovation team. Record who checks compatibility, delivery dates, missing components and damage. Late changes or unavailable products can affect both the sequence and the agreed scope.
Compare written scopes on the same basis
Ask each proposal to state removals, preparation, trade work, finishes, waste handling and exclusions. Clarify whether product allowances are provisional and how selections above or below them will be reconciled. A lower total is not directly comparable when it covers a different scope.
Tell the team whether this is your only bathroom and which times the home must remain usable. Before committing, confirm the written scope, conditions, responsibilities and schedule. An accepted design direction or estimate is not evidence that a contract, payment or start date has been confirmed.