Process and cost factors
What actually causes a bathroom job to overrun
The moving parts
Point 1
Waiting on a customer decision, a tile choice, a tap finish, stalls a trade who then has to move to another job and come back later.
Point 2
Items ordered without confirmed lead times can arrive after the fitter has reached the stage that needs them.
Point 3
Structural surprises such as rot, an undersized waste pipe or old lead pipework found once tiles or boarding come off need time to resolve properly rather than being rushed.
Point 4
Access issues, parking restrictions, shared hallways, lift bookings in flats, can quietly add days that have nothing to do with the bathroom itself.
Worth checking on site
Waiting on a customer decision, a tile choice, a tap finish, stalls a trade who then has to move to another job and come back later.
Your questions answered
How can I reduce the risk of delays?
Confirm every material choice and have items on site, or with a confirmed delivery date, before the job starts rather than during it.
What happens if something unexpected is found mid-job?
A competent fitter should stop, explain what's been found and agree the way forward with you before continuing, rather than pushing on regardless.
Not sure which option suits your property?
Most of these decisions come down to what is behind the wall and under the floor. A site visit settles it quickly.