Rooms in the school timetable: specialist rooms, capacity and how many you need

Room allocation in the school timetable means deciding which rooms each lesson may use, and then making sure the week holds enough of those rooms, open at the right times, with enough seats. Ordinary classrooms rarely decide whether a timetable works. Specialist rooms do: science labs, the sports hall, art and music rooms, workshops, the computer room. In short: give each lesson the loosest room rule that is still true (“a lab”, not “Lab 2”); record how many students each room seats and how many classes it takes at once; count demand against supply for every kind of room before you schedule; treat a change of building as a lost period; and handle a room that is out of use for a week as cover, not as a new timetable.

All of it works in any program or on paper. The “In Bildena” paragraphs say what Bildena does; what it does not do is listed near the end.

Home rooms, subject rooms and specialist rooms

A school week makes three different claims on rooms:

• Home rooms. A class has its own room and the teachers come to it. Simple for the timetable, but you need one room per class, and it stands empty whenever the class is in the lab or the gym.
• Subject or teacher rooms. A teacher keeps a room and the classes come to them. Rooms are used more fully, but every class moves every period, and each teacher's room becomes a fixed resource.
• Specialist rooms. Labs, the hall, workshops, studios, the computer room: shared by many classes, and almost always the scarce resource.

Many schools mix the three, and the mix decides which rooms the timetable has to book at all.

In Bildena a class's home room is where its lessons take place when the lesson card names no other room; the solver does not book it. That is why the setup says to add rooms only where they are scarce — labs, workshops, the gym — and that ordinary classrooms can be left out: “the solver assumes every class has its own”. A teacher's home room is different: their lessons that ask for no room type go there, and the solver books it like any other room.

Room allocation: give each lesson the loosest rule that is true

A lesson can be tied to rooms at three levels, from loose to tight:

1. A kind of room: any science lab, the gym, a computer room.
2. A short list: Lab 1 or Lab 2, because only those have the physics benches.
3. One room: Lab 3, because the fume cupboard is there.

Each step down removes options, and pinning a room is often habit rather than need. Suppose a school with four labs pins all chemistry to Lab 3. With 32 chemistry periods in a 30-period week, chemistry cannot fit — while Labs 1, 2 and 4 still have free periods. The number of labs is fine; the rule is wrong. Pin a room only where something physical in it is needed.

In Bildena a lesson card carries either a required room type or one specific room; when a room is set, the type is not used. A subject's default room type is pre-filled on its new lesson cards, and lists of rooms to choose from arrive with timetables imported from aSc or Untis. Eight room types come with a new school, from Science Lab to Workshop, and the school adds its own. The solver matches rooms by type, not by the equipment recorded on them: if “has a kiln” decides where a lesson goes, make “Ceramics room” a type.

Specialist rooms: count demand against supply first

Before any software runs, do the arithmetic for each kind of specialist room. A worked example: a secondary school with 24 classes and a week of 30 periods (six a day, five days).

A shortage in the weekly count is final: no solver puts 92 lab periods into 90. And the hall's curtain is not a detail — entered as one space, the same hall fails a timetable it passes easily as two or three.

In Bildena the Checks before a run do this count for every room type — the hours the lesson cards ask for against the type's open periods, times the classes each room takes at once — and flag a type no room has, or a single room with more fixed hours than open periods. These are critical issues, and critical issues block generation. A window shortage shows only in the run: if the rules leave no complete timetable, Place what fits places what fits and lists the rest with a reason, such as “in the periods still free for it, every room it can use is taken or closed.”

Room capacity: seats, halls and joint lessons

The second number every room needs is its seats, and practical rooms are often built for smaller groups than a class. England's area guidelines for school buildings (Building Bulletin 103) size a general classroom and a general science lab for 30 pupils, but a food room or a resistant-materials workshop for 24. A class of 28 does not fit a 24-place workshop: it has to be split, and two groups mean two teachers or two periods.

Capacity bites in three places:

• Joint lessons. Two classes of 28 and 27 taught together are 55 students in one room. That is the hall or a drama studio, not a classroom.
• Groups across classes. An option group that gathers 33 students from three classes does not fit a 24-place room, even though each class's share would.
• Divisible rooms. A hall with a dividing curtain is one room that takes two or three classes at once. Record it that way, or the timetable sees a room for one class.

In Bildena the room wizard asks for Seats and Classes at the same time, from 1 to 20 (“a hall with a dividing curtain can take 2 classes”). When the solver chooses a room, it only considers rooms that seat the lesson's students: the class size, a group's members, the enrolled students when timetabling is student-based, and for Classes attend together the students of every class taking part. A room with no seat count counts as unlimited and a class with no size as unknown, so enter both. Before the run, the Checks flag a fixed room too small for its class or group, and a room type with no room big enough. Two limits: those Checks count a lesson's own class or group, not the classes joining it; and when no room of the required type seats a joint lesson, the solver leaves the lesson without a room rather than squeeze it in. Look at joint lessons in the room timetables after a run.

Several buildings and the time between them

A second building turns rooms into distances. Group each teacher's lessons per building onto the same days; when a change is unavoidable, put a break or a free period between the two lessons; keep a class in one building per half-day where possible. Every forced change mid-morning is a gap in a teacher's day (see Teacher gaps and student gaps).

An example: a teacher has 26 periods, at most six a day, 19 of them in the main building and 7 in the annex. The main building needs four days (19 ÷ 6, rounded up), the annex two (7 ÷ 6, rounded up): six days in a five-day week. On at least one day this teacher changes buildings, and that day carries a free period.

In Bildena, once rooms sit in two or more buildings, the solver never gives a teacher back-to-back lessons with rooms in different buildings: at least one period lies between them. The Checks raise a suggestion, not a critical issue, when a teacher's fixed-room lessons in several buildings cannot be split onto separate days, as in the example. Each building records its walking time, but the solver does not use the minutes — any change of building counts as a walk — and the rule protects teachers, not classes.

Rooms out of use: every week, all year, or this week only

Each case wants a different tool:

• Every week, at the same time: the council lets the hall to a club in the last period on Thursdays. That is a closed period on the room, entered before you schedule.
• All year: a room under refurbishment. Take it out of the timetable.
• For a few days or weeks: a burst pipe, the hall taken over for exams. Do not rebuild the timetable; move the affected lessons to free rooms, day by day, the way you cover an absent teacher.

In Bildena the room wizard has a weekly availability grid (“Not available (✕)”) and a switch for Use in the timetable; a room switched off is closed in every period. A room out of use for some days is recorded like a staff absence, under Cover › Staff absences › A room out of use: its lessons on those days need another room, and a free room of the same kind is offered first. Events and clubs that want a room in the hours the timetable leaves free go to Plan › Bookings, where a lesson of the published week blocks the slot. Bookings do not feed the timetable, though: if a club has the hall every Thursday, close that period on the room as well.

How room shortage makes a timetable impossible

When a timetable will not complete and rooms are behind it, the shortage comes in one of three shapes:

1. Too few rooms of a kind for the hours that need them — the 92-into-90 case. Found by counting.
2. No room big enough for a joint lesson or a large group. Found by comparing seats with group sizes.
3. Enough rooms, but not at the same time: option blocks, joint lessons, pinned rooms and closed periods squeeze demand into a few periods. Found by solving, or by a careful look at the blocks.

Doubles make all three harder: a double in a lab needs two consecutive free periods in the same lab (see Doubles, blocks and the Monday problem). How to find the bottleneck before you solve is in Why timetables become impossible; why a solver never trades a room clash against a preference, in Inside the scheduling engine.

How many rooms do you really need? Measuring room utilisation

Room utilisation is the share of the week a room is in use: periods with a lesson, divided by the periods available. A lab used in 24 of 30 periods is 80% utilised. The second number is how full it is when used: a 30-seat room booked all week by groups of 12 is fully used by the timetable and 60% empty by its seats.

• Measure by kind of room. 40 rooms × 30 periods = 1,200 room-periods; with 840 used the school sits at 70% — which tells you little if its 30 classrooms run at 65% and its four labs at 95%. That school needs one more lab, or fewer lab periods, not more rooms.
• Work out the minimum, then add headroom. The minimum number of rooms of a kind is the periods that need them divided by the periods in a week, rounded up: 92 lab periods ÷ 30 = 3.07, so four labs, running at 77% (79% with one closed for prep). The space up to 100% is what doubles, option blocks and closed periods use up. Before a building project it is the same sum; as BB103 puts it, the number of timetabled spaces “will depend on the curriculum and group sizes”.
• Read home rooms differently. A class that spends 8 of its 30 periods in labs, the hall and the art room leaves its home room empty for 27% of the week. That is the price of the model, not waste to be fixed.

In Bildena the Room Usage report lists every room with its type, periods used and occupancy against the week (days × periods), busiest first, and counts the rooms never used. Each room's page shows its lessons a week, utilisation, free periods and busiest day in the published timetable. Lessons held in a class's home room without a room on the card are not counted as that room's, so home rooms look emptier in the report than they are. Every room's week can be printed or subscribed to as a calendar feed.

A room checklist before you schedule

• Every scarce room is entered — labs, halls, workshops, studios, computer rooms — with its seats.
• Every class and group has its size.
• Divisible halls carry the number of classes they take at once.
• Weekly closed periods are on the rooms: lettings, prep time, other users.
• Each lesson asks for a kind of room, unless something physical ties it to one room.
• For each kind of room, the periods needed are below the periods open, with headroom.
• No option block needs more rooms of a kind at once than the school has.
• Every joint lesson has a room big enough for all its classes.
• Rooms belong to buildings, and the days of teachers who work in two buildings have been looked at.

What Bildena does not do with rooms

• It does not try to reduce how often a class or a teacher changes rooms during the day.
• It does not use walking minutes, and it does not limit a class's building changes, only a teacher's.
• It does not match rooms by equipment or step-free access; both are recorded, but the solver goes by room type, room list or fixed room.
• It does not book class home rooms. If two classes share one, put the room on their lesson cards.
• Bookings for events and clubs do not feed the timetable.

Frequently asked questions

Do I have to enter every classroom?

No. If every class has its own room, ordinary classrooms add nothing to the problem, and in Bildena they can be left out. Enter them if teachers own rooms, if classes share rooms, or if you want room timetables and utilisation figures.

What is a good room utilisation for a school?

There is no single right number. Home rooms sit well below specialist rooms by design. A specialist room close to 100% leaves the timetable no room to move, so the useful question is whether the headroom covers your doubles, option blocks and closed periods.

Rooms, room types, seats and closed periods are set per room in Bildena Scheduler, and the Checks compare each room type's hours with its open periods before every run. In the free month you can bring in your rooms from Excel or CSV, or with a timetable from aSc or Untis, and run a full timetable on your own data.