120x150 Steel Gymnasium Building

This page is ordered around the working arrangement, because the 150-foot depth at 120x150 is what gives a steel gymnasium its usable sequence of zones.

The footprint holds 20 support rooms — 5 across by 4 deep — and leaves 16 feet of depth for a wide equipment store opening directly onto the floor, which is what stops equipment living in the corners.

What distinguishes 120x150 is depth behaviour: 4 rows along 150 feet after 14 feet of circulation, with 16 feet unaccounted for at the end of the run. Service routes are cheap to plan now and expensive to retrofit through a finished shell.

A 120 by 150 footprint is a mildly directional plan: 18,000 sq ft enclosed by 540 ft of wall, at a 1.3:1 length-to-width proportion. Along its 150 ft dimension it takes 5 runs of support rooms at 30 ft, leaving 0 ft over — the 0 ft is where the argument about this size actually happens. A floor without changing rooms, staff space and real equipment storage is used at a fraction of its capacity. This mode treats the support wing as the subject, because the wing is what is cut first and missed most. Doors that swing into an activity area remove floor for the whole session.

At 120x150 the operating question is a specific one: how much of the footprint should be given to rooms that make the floor usable rather than to the floor itself? That is a different question from the one a steel gymnasium of another shape has to answer, and it is why this footprint is planned as an activity floor with a support wing of changing, storage and staff rooms rather than as generic covered area.

Nominal bay division computes to 6 bays at about 25 feet, wider than the 22-foot module — so a position can sit inside a bay without a frame line splitting it. A building that cannot be reversed out of is a building that gets used in one direction only.

Depth here creates a hierarchy: 4 rows means front positions get used and rear positions get filled. Deciding which is which up front is what keeps 120x150 workable. Noise from this floor reaches the office, the neighbours and the yard, and separation is a plan decision.

Extension is cheapest along the 150 ft dimension, where each added bay repeats work already framed; widening past 120 ft is a different frame rather than a longer one. Growing to 120 by 180 adds a 6th run of support rooms — useful if the constraint is support rooms rather than the 0 ft already spare at the far end.

Configured as an activity floor with a support wing of changing, storage and staff rooms, 120x150 is judged on whether the 20 support rooms it holds match the operation, and on whether the 10 feet of spare width leaves the route this mode depends on.

• Does the work need an interior street with independent zones on both sides and turning room at each end, or does it need a second lane that this 120-foot span cannot give?
• Is the 150-foot length being bought for depth, or for the repeated bays — a long repeating bay sequence, so segment boundaries are set by bay lines rather than by walls?
• What clear height does the activity need, measured to the lowest obstruction?
• Are the run-off margins protected from storage and seating?

The activity pattern this floor could equally be planned around is a practice floor kept clear for training rather than for fixtures: there is no perimeter strip, so bags and equipment sit on the playing surface and the usable floor shrinks by more than the strip would have cost. The wing takes one end and the floor takes the rest, with the store placed where equipment is used rather than where the plan had space left. Support rooms distributed around the perimeter cost more wall than they are worth.

The 16-foot leftover depth is 1,920 square feet across the full width — deep enough to plan deliberately, and at this footprint it goes to a wide equipment store opening directly onto the floor, which is what stops equipment living in the corners. Every foot of width added multiplies through the roof and the frame; every foot of length mostly adds skin.

The 10 feet of spare width runs the whole 150-foot length — 1,500 square feet of wall strip. It earns its keep as shelving, staging or a walking route, not as another support room. Cleaning, maintenance and inspection all need reach, and reach is planned in the gaps rather than in the modules.

The longest internal travel on a 120 by 150 plan is about 192 ft corner to corner, and the shortest useful one is the 120 ft cross-run. For a an activity floor with a support wing of changing, storage and staff rooms that matters where support wing planning sits, because shortening the 120 ft run to serve it lengthens every trip along the 150 ft dimension. Changing and sanitary provision is where the per-square-foot cost of this building type concentrates. That movement pattern, not the 18,000-square-foot total, is what decides whether the leftover 16 feet is useful here.

The stored configuration carries a 14-foot eave and computes to 29 feet at the ridge on a 3:12 pitch — a 15-foot rise across 120 feet. Height is therefore not uniform, and the sidewall is the constraint. Temperature swing on a steel shell drives condensation decisions that outrank most layout preferences.

The wing does not need the floor's height and shares the frame, so planning a flat ceiling over the rooms gives somewhere for services and keeps them from feeling like partitions in a hall.

Ventilation across 18,000 square feet at this height: an intensively occupied volume with high activity levels, where air handling is planned for the occupied peak.

The 120-foot gable can carry 5 openings, one per support room, with 10 feet of wall left for piers between and beside them — the arrangement that keeps each position independently reachable. The count of working positions, not the headline area, is the figure that survives contact with the operation.

The 120 ft ends and the 150 ft sides offer very different opening budgets: 120 ft of end wall has room for one wide opening or two modest ones, while 150 ft of side wall can carry several without the openings competing. On this plan the deciding factor is whether support wing planning or equipment store sizing should be the first thing reached from the door.

• 60x120 moves the count from 20 to 2 support rooms (1 across by 2 deep), which is the reason to choose between them.
• 50x150 moves the count from 20 to 4 support rooms (1 across by 4 deep), which is the reason to choose between them.
• 80x100 moves the count from 20 to 2 support rooms (2 across by 1 deep), which is the reason to choose between them.

Because this footprint is planned as an activity floor with a support wing of changing, storage and staff rooms, the useful next reads are different from the ones a differently shaped steel gymnasium suggests: support wing planning, equipment store sizing, changing room planning.

No price appears on this page. The quantities that scale an estimate at 120x150 are 18,000 square feet of slab, 222.2 cubic yards of nominal concrete, 7,560 square feet of wall cladding and 18,554 square feet of roof cladding. Access, not area, is what makes a plan feel small once it is in use.

Changing rooms carry plumbing, drainage, ventilation and finishes, and per square foot they are the most expensive part of the building by a wide margin.

• clear height above the playing surface
• the clear span across the court and its run-off
• the support wing with changing rooms
• impact-resistant lighting and interior surfaces