50x120 Pole Barn

This page is ordered around the division between two uses, because whether the post row falls where the wall wants to be decides what the partition costs.

The footprint holds 24 open bays — 4 across by 6 deep — and the remaining 6 feet is marginal: there is no closed bay, so nothing in this building is secure and everything in it is exposed to whatever blows in.

Read this footprint through its span. 50 feet across is the fixed constraint; 120 feet of length is the negotiable one, and at 2.4 to 1 the building is long for its width, so movement runs front to back. Depth is bought cheaply and width expensively, which is why this proportion tends to be argued about before anything else.

A 50 by 120 footprint is a long corridor of a plan: 6,000 sq ft enclosed by 340 ft of wall, at a 2.4:1 length-to-width proportion. Along its 120 ft dimension it takes 6 runs of open bays at 18 ft, leaving 12 ft over — the 12 ft is where the argument about this size actually happens. Taken purely as arithmetic, 50 by 120 gives 3 open bays across the 50 ft dimension once 6 ft is reserved for movement, and 6 deep along the 120 ft dimension. Run as a a partly open building offering shelter rather than enclosure, 8 ft across is enough to be worth planning: a closed end bay for anything that has to stay dry and secure while the rest of the building stays open Post frame lengthens cheaply and widens expensively, which shapes every expansion decision.

At 50x120 the operating question is a specific one: which way does the open side face, and what does that decide about how the building can be used in winter? That is a different question from the one a pole barn of another shape has to answer, and it is why this footprint is planned as a partly open building offering shelter rather than enclosure rather than as generic covered area.

Read this page as a construction-form page, not a use page. Pole barn is a construction-form category on this platform: it describes the post-frame approach, where posts carry the roof and the walls enclose between them, and the uses it serves — agricultural, garage, workshop, storage — are applications of that form rather than definitions of it. The question it answers is how a 50x120 footprint behaves when it is built this way.

At 24-foot nominal bays the structure works with the layout instead of against it: one open bay per bay line, walls free of awkward half-positions. Service routes are cheap to plan now and expensive to retrofit through a finished shell.

Depth here creates a hierarchy: 6 rows means front positions get used and rear positions get filled. Deciding which is which up front is what keeps 50x120 workable. Every foot of width added multiplies through the roof and the frame; every foot of length mostly adds skin.

Extension is cheapest along the 120 ft dimension, where each added bay repeats work already framed; widening past 50 ft is a different frame rather than a longer one. Growing to 50 by 138 adds a 7th run of open bays — useful if the constraint is open bays rather than the 12 ft already spare at the far end.

Configured as a partly open building offering shelter rather than enclosure, 50x120 is judged on whether the 24 open bays it holds match the operation, and on whether the 2 feet of spare width leaves the route this mode depends on.

• Does the work need three lanes and a working lane, or two lanes with an interior work hall between them, or does it need a second lane that this 50-foot span cannot give?
• Is the 120-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?
• Does the intended layout tolerate interior posts, or does it genuinely need a clear span?
• Where do the openings fall relative to the post lines, and does any opening have to bridge one?

50 ft across takes 4 open bays and leaves 2 ft. Over 120 ft of run that slack becomes a continuous side aisle rather than 6 separate gaps.

At 120 ft depth stops being the constraint: 6 ranks fit and the far end is discretionary space. 6,000 sq ft needs a stated route through it; without one the middle silts up.

120 ft divides exactly into 10 bays at 12 ft. Over 6,000 sq ft a single 12-ft grid is the difference between a plan and an accumulation.

This shape buys frontage with skin: 340 ft of perimeter for 6,000 sq ft, 56.7 ft per 1,000 sq ft, 10% above a square of the same area. At 2.4 to 1 that is the trade, not an error.

The 50-ft gable clears about 42 ft after corner framing — 2 module-width openings abreast. Over a 120-ft run, openings at both ends turn the building into a drive-through rather than a dead end.

At 14 ft a 15-ft platform across 50 ft would add about 750 sq ft. Framing for it now is a drawing change; adding it to a finished frame is a structural one.

The use this post-frame shell could equally be bought for is a post-frame building built specifically around working rather than storing: there is no bench depth between posts, so benches stand proud of the wall and the working floor shrinks by their depth. Open bays for the sheltered use, and one closed bay at an end for anything needing security or dryness. Closing the middle produces two open ends and no benefit.

There is no end zone at this footprint. 6 feet is circulation slack, not floor area with a purpose, and there is no closed bay, so nothing in this building is secure and everything in it is exposed to whatever blows in. Height is the dimension people regret; it cannot be added later without rebuilding the frame line.

Width is fully committed at 50x120. With 2 feet spare, wall storage and passing room compete with the open bays directly. A wider bay is a structural decision and a longer bay is a layout decision; the two are often confused.

Compared with a 50 by 90 of the same width, the extra depth here adds run rather than reach: it buys about 6 open bays in line, and every position past the second is retrieved by moving what stands in front of it. Spent as a square 77 by 77 instead, the same 6,000 sq ft would stand 5 open bays across rather than 3, and would trade this plan's length for parallel access. That is the width-against-depth decision this footprint has already made. At this size the building becomes a shared resource, and shared resources need a written rule for who parks where and which door is kept clear. The building is used without ever being entered through a door, which is the point. Anything requiring a door belongs in the closed bay. Site drainage around a post-frame building matters more than in a slab-on-grade one. That movement pattern, not the 6,000-square-foot total, is what decides whether the leftover 6 feet is useful here.

Openings are the pinch point here. With 2 feet of spare width the gable cannot host 4 separate doors, so access is either shared or moved to the 120-foot sidewall. A building that cannot be reversed out of is a building that gets used in one direction only.

The 50 ft ends and the 120 ft sides offer very different opening budgets: 50 ft of end wall has room for one wide opening or two modest ones, while 120 ft of side wall can carry several without the openings competing. On this plan the deciding factor is whether open front pole barn or orientation and prevailing weather should be the first thing reached from the door.

Loading happens bay by bay: what can be brought in at one opening and set down in that bay is the practical unit, not the length of the wall.

The stored configuration carries a 14-foot eave and computes to 20.3 feet at the ridge on a 3:12 pitch — a 6.3-foot rise across 50 feet. Height is therefore not uniform, and the sidewall is the constraint. Cleaning, maintenance and inspection all need reach, and reach is planned in the gaps rather than in the modules.

Height on an open building drives rain penetration as well as clearance — a tall open face admits more weather. That trade-off is a site judgement.

Ventilation across 6,000 square feet at this height: post-frame buildings are frequently left partly open or lightly enclosed, so natural cross and ridge airflow does much of the work and enclosure level is the variable to settle first.

• 30x80 moves the count from 24 to 6 open bays (2 across by 3 deep), which is the reason to choose between them.
• 40x60 moves the count from 24 to 4 open bays (2 across by 2 deep), which is the reason to choose between them.
• 50x50 moves the count from 24 to 6 open bays (3 across by 2 deep), which is the reason to choose between them.

Because this footprint is planned as a partly open building offering shelter rather than enclosure, the useful next reads are different from the ones a differently shaped pole barn suggests: open front pole barn, orientation and prevailing weather, closed end bay.

At 50 by 120 the building is narrow relative to its run, so the efficient direction of growth is across rather than along: 12 feet of extra width returns 1,440 square feet against 24 feet of added wall line (60 square feet per foot), where a 18-foot module of depth returns 900 for 36 feet (25). The caveat is structural rather than arithmetic — widening changes the clear span and the frame that carries it, while lengthening only repeats a frame line that already exists.

Neither the 18-foot depth step nor the 12-foot width step changes the count: the plan stays at 24 open bays either way, so both are bought as clearance and working room rather than as capacity. That makes 50 by 120 a comfortable rather than an efficient footprint for this use — a real advantage if the operation is tight, and dead area if it is not.

The binding dimension is the depth. The 50-foot width absorbs its 4 open bays with 2 feet spare (240 square feet down the length), while the length leaves 6 feet after 6 modules and 6 feet of circulation — 300 square feet across the full width. That is too shallow to plan as a room, so there is no closed bay, so nothing in this building is secure and everything in it is exposed to whatever blows in.

Access is the constraint to design around here. Only 12 feet of the 120-foot run stays uncommitted once 6 modules of depth are placed, short of the 14 feet this platform plans a square-on approach around, so the 4 positions across the 50-foot width are entered end-on and what goes in first comes out last. Either the length grows, or the plan accepts that one position is a store and the others are working.

Quantities, not prices, are publishable here: roof cladding runs 6,185 square feet — 3% above the 6,000-square-foot floor at a 3:12 pitch — with 74.1 cubic yards of nominal slab beneath it. Noise from this floor reaches the office, the neighbours and the yard, and separation is a plan decision.

This is the cheapest post-frame arrangement per covered square foot, because a wall is missing. The saving is real and so is the limitation.

• how many sides are enclosed, and whether any stay open
• the bay rhythm relative to the openings and layout wanted
• the ground interface and site conditions at the post positions
• whether lean-tos or additions are planned onto the same rhythm
• later lining or insulation of the wall assembly between posts