80x100 Pole Barn

Quantities, not prices, are publishable here: roof cladding runs 8,433 square feet — 5% above the 8,000-square-foot floor at a 4:12 pitch — with 148.1 cubic yards of nominal slab beneath it. Two feet of spare width reads as nothing on a plan and as a great deal when a machine is being turned.

Proportion drives cost here as much as size does: 360 ft of wall around 8,000 sq ft is 0.045 ft of wall per enclosed square foot, and a squarer plan of the same area would carry less. What moves the figure further on a two bays used for two different things under one roof is the fit-out two bay pole barn implies, along with framed openings and the height chosen for the 80 ft span.

• 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

This page is ordered around the bay, because at this size the post frame is not a background system — it is the plan, and it decides where walls, openings and divisions can go.

The footprint holds 20 bays — 5 across by 4 deep — and the remaining 7 feet is marginal: there is no partition line, so both bays share one environment and the messier use sets the condition of the whole building.

What distinguishes 80x100 is depth behaviour: 4 rows along 100 feet after 5 feet of circulation, with 7 feet unaccounted for at the end of the run. Snow, wind and site exposure change what this shape costs to build long before the interior plan does.

A 80 by 100 footprint is a mildly directional plan: 8,000 sq ft enclosed by 360 ft of wall, at a 1.3:1 length-to-width proportion. Along its 100 ft dimension it takes 4 runs of bays at 22 ft, leaving 12 ft over — the 12 ft is where the argument about this size actually happens. Two bays is the size where post frame stops being one room and starts being a plan, and the whole question is whether the structural division and the use division agree. When they do, the partition is nearly free; when they do not, it is a framing job. Permitting, setbacks and any structural provision are determined for the site by the authority having jurisdiction.

This footprint is planned as two bays used for two different things under one roof. Spent as a square 89 by 89 instead, the same 8,000 sq ft would stand 6 bays across rather than 5, and would trade this plan's length for parallel access. That is the width-against-depth decision this footprint has already made. Compared with a 80 by 80 of the same width, the extra depth here adds run rather than reach: it buys about 4 bays in line, and every position past the second is retrieved by moving what stands in front of it. A building of this size behaves like a small yard under a roof: zones need to be defined, signed and left alone, or they migrate. Two routines run under one roof at different frequencies and different levels of mess. Their separation is a wall decision, and it is cheapest at the frame stage. Openings in a post-frame wall sit between posts, so door width is a framing decision made before anything else.

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 80x100 footprint behaves when it is built this way.

The use this post-frame shell could equally be bought for is a single-bay shelter where the frame and the room are the same thing: there is no strip between posts and wall, so stored items stand in the bay itself and the bay stops being clear. Dividing the 8,000 sq ft by the 14 by 22 ft bay gives roughly 20 positions before circulation is deducted a second time for cross movement. Whether the plan keeps 20 or drops to 16 comes back to the question this footprint is really answering: does the post row fall where the division between the two uses wants to be?

There is no end zone at this footprint. 7 feet is circulation slack, not floor area with a purpose, and there is no partition line, so both bays share one environment and the messier use sets the condition of the whole building. Fire separation, egress and occupancy are determined for the specific building and can reshape this plan entirely.

Spare width is the more valuable of the two leftovers here: a continuous 10-foot strip beats the same area stranded at the end of the run, because it touches every position along the way. The mezzanine that is added afterwards is the change order that reprices the frame.

Spent as a square 89 by 89 instead, the same 8,000 sq ft would stand 6 bays across rather than 5, and would trade this plan's length for parallel access. That is the width-against-depth decision this footprint has already made. Compared with a 80 by 80 of the same width, the extra depth here adds run rather than reach: it buys about 4 bays in line, and every position past the second is retrieved by moving what stands in front of it. A building of this size behaves like a small yard under a roof: zones need to be defined, signed and left alone, or they migrate. Two routines run under one roof at different frequencies and different levels of mess. Their separation is a wall decision, and it is cheapest at the frame stage. Openings in a post-frame wall sit between posts, so door width is a framing decision made before anything else. That movement pattern, not the 8,000-square-foot total, is what decides whether the leftover 7 feet is useful here.

The 80-ft span holds 5 bays plus 10 ft — most of another position. With 4 ranks behind each other the width sets retrieval order: what goes in first comes out last.

Nothing lands in the middle of a 80-ft clear width. The 4 ranks along the 100-ft length are the only fixed geometry the plan has; every other division is furniture.

100 ft divides exactly into 10 bays at 10 ft. Over 8,000 sq ft a single 10-ft grid is the difference between a plan and an accumulation.

A 20-ft eave puts 213,200 cu ft inside and makes the upper half a planning question in its own right. The stair comes out of the 10 ft of spare width rather than out of the working floor.

100 ft is deep enough for 4 ranks and a zone behind them. Past 8,000 sq ft the plan needs zones with names, because nothing about the shell suggests them.

The 10 ft left across the width is most of another bay without being one. Given a purpose it becomes a partition line on the post row, letting one bay be closed and the other left open without adding structure; left undefined it becomes the strip everything ends up in.

One opening per position works on this gable: 5 across 80 feet, with 10 feet of wall to distribute as piers. Splitting that margin evenly is what keeps the elevation buildable. Circulation width is the first thing surrendered under pressure and the first thing missed afterwards.

Each bay wants its own opening, and their sizes usually differ — one for vehicles or equipment, one for people and daily use.

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.

Nominal bay division computes to 4 bays at about 25 feet, wider than the 14-foot module — so a position can sit inside a bay without a frame line splitting it. Storage expands until it meets a wall, so give it a wall on purpose.

Two-plus rows change the access question entirely. Every rear position at 80x100 needs either its own opening or an aisle, and 10 feet of spare width is what that aisle has to come from. Judge the plan by what has to happen on the worst day of the year, not on an average one.

A third bay in line is the natural growth and it inherits the same division logic.

Configured as two bays used for two different things under one roof, 80x100 is judged on whether the 20 bays 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 racking or work zones on both sides with a full vehicle lane down the middle, or does it need a second lane that this 80-foot span cannot give?
• Is the 100-foot length being bought for depth, or for the repeated bays — eight to ten repeated bays, which makes the layout a scheduling problem as much as a spatial one?
• 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?

Span drives headroom at 80x100: 80 feet of width on a 4:12 pitch puts 33.3 feet over the middle and 20 feet at the walls, so where a tall item stands matters as much as how tall it is. Rows that cannot be entered independently end up used as one long space.

Height on a 80 ft span is a separate decision from the 100 ft length, and it is the span that sets the frame's behavior. Raising the eave over 8,000 sq ft affects every bay along the 100 ft dimension, so the test is whether two bay pole barn genuinely needs the extra clear height or only the floor area.

Ventilation across 8,000 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.

• 40x80 moves the count from 20 to 6 bays (2 across by 3 deep), which is the reason to choose between them.
• 60x60 moves the count from 20 to 8 bays (4 across by 2 deep), which is the reason to choose between them.
• 50x80 moves the count from 20 to 16 bays (4 across by 4 deep), which is the reason to choose between them.

Because this footprint is planned as two bays used for two different things under one roof, the useful next reads are different from the ones a differently shaped pole barn suggests: two bay pole barn, partition on the post row, split use planning.