Constraint recipe
A room clash assigns one room to two lessons in the same period. Specialist rooms make fixes harder because only a few labs or workshops may be eligible. Before you move a lesson, check room type, group size, equipment, and whether one assignment is a duplicate row from an import.
Key takeaways
- One room cannot host two in-person lessons at the same time.
- Replacement rooms must match type, size, and equipment.
- Duplicate source rows can look like a scheduling clash.
- Fixing the room clash can create teacher or class clashes.
Why room clashes are serious
Two classes cannot occupy the same physical room at the same time. The problem is sharper for labs, kitchens, and workshops because eligible alternatives are limited.
Preferred rooms are a separate issue. A clash is about two lessons claiming the same space simultaneously.
What to check before choosing another room
A free classroom on the grid may still be wrong for a chemistry practical. Check type, capacity, equipment, and whether the teacher and class are also free in that period.
See restrict rooms by subject for classifying must-have room types.
What to do next
- Identify the two lessons sharing the room and period.
- Search source data for duplicate or outdated room assignments.
- Confirm each lesson's required room type, capacity, and equipment.
- List eligible alternative rooms for the less constrained lesson.
- Move the lesson only if teacher and class are also free.
- Recheck specialist-room rules after the move.
Common mistakes
- Moving a lab into a room without the required equipment
- Choosing a room that is too small for the group
- Fixing the room while creating a teacher or class clash
In Smootables
Conflicts detected
The following conflicts will occur if you proceed:
Room Lab B is already bookedChemistry practical at 13:00–14:30
A room clash means two in-person lessons need the same room at the same time. Generate timetable keeps each physical room unique on the grid. Lessons marked as remote teaching do not reserve a room, so they do not compete for lab or workshop space.
When you move a lesson manually, Conflicts detected flags the other class already in that room and period before the change sticks. Room no-conflict in the post-generation summary confirms the solved timetable respected the rule.
- Check room type, capacity, and equipment before moving a lesson to an alternative room.
- Remove duplicate room assignments in the period plan if the clash came from source data.
Quick answers
Is a room clash a mandatory rule?
Yes for one physical room and two in-person lessons at the same time. The timetable must change.
Can I use any free room as the fix?
No. The replacement must match subject needs, capacity, availability, and equipment.