Tag Archives: Building Length

Switching Post Sizes, Structure Length, and Fire Damage

This week’s ask the Pole Barn Guru answers reader questions about switching post sizes from a 6×6’s to 6×4’s, how long a structure can be built with 15 trusses with 2×4 chords, and if it is possible to rebuild on a slab that was part of a fire loss.

DEAR POLE BARN GURU: I am about to buy my post for a residential post barn using 6 x 6 x 12 post in Sottsburg, Indiana. A neighbor suggested instead of using 6 x 6 x 12, to use 4 x 6 x 12 in substitution for some of the post that would be none corner or door support post. My question would be can it be done and meet building code being it will not have an attack or vaulted ceilings? LEVIA in SCOTTSBURG

DEAR LEVIA: In most instances a 4×6 #2 will be stronger than a 6×6, however switching out columns should only be done with approval from your engineer who sealed your building plans.

For extended reading on this subject: https://www.hansenpolebuildings.com/2019/04/when-size-or-lack-thereof-matters/


DEAR POLE BARN GURU: 2 x 4 Truss spacing question, how long do you advise to build a Pole barn with 15pcs of 2 x 4 x 24′ engineered trusses? 🙂 The fires got 8 of them so I’m refiguring my length, but wanted some help on the truss spacing? Thanks, MARSHALL in PORTLAND

DEAR MARSHALL: The engineered truss drawings will provide maximum on center spacing of trusses. With 2×4 chords, I would suspect this to be 24 inches. With 15 pieces, you could build a 28 foot length building.


DEAR POLE BARN GURU: I’m working on a fire loss to a post frame building that was converted to multi-unit apartments. The building shell is post frame on slab with interior walls framed. My question is could we demo the building saving the slab rebuild utilizing standard residential stud wall and truss framing. Thanks CHRIS in FLOYDS KNOBS

DEAR CHRIS: Heat from a fire can result in concrete chemical composition breakdown. Other effects include concrete spalling, seen as large pits. Concrete may have protected substrates below, but further investigation is probably required. Water used on fire can also adversely affect soils below. Have an engineer familiar with concrete test for strength. Sometimes it may look like concrete is okay, but then later it begins to crumble.

Outside of this, slabs for post frame buildings do not have continuous footings and stem walls, or edges thick enough to provide protection from frost heave and to support imposed loads from building dead weight and imposed loads.


Pole Building Layout for Drilling Holes

Building Layout for Drilling Holes

Reader ROGER in LISBON asks: “What is fastest way to layout a building for drilling holes?” From Hansen Pole Buildings’ Construction Manual:

Building Layout

The building layout establishes exact reference lines and elevations. Care in layout makes construction easier and helps keep building square. 

REMINDER:  Building width and length are from corner column outside to corner column outside!  

After installing all framing, finished framework will normally be 3” wider and longer than ordered or “call out” dimensions. Ignoring this will result in more effort during construction.

Calculating Diagonal Lengths

Example: building is 50 feet wide and 84 feet long. 

Explanation: A picture helps greatly with this problem, so we begin with a rectangular post frame building.

Distance (drawn in red) is diagonal of our rectangle, or k. We should also note this diagonal divides our rectangle into two congruent right triangles. We can therefore find the length of our diagonal by focusing on one of these triangles and determining hypotenuse. This can be done with the Pythagorean Theorem, giving us:

50^2 + 84^2 = k^2

2500 +7056 = k^2

9556 = k^2

Taking square root gives us

k=97.754795 feet or 97’ 9-1/16” 

See Table 4-1 below.

Feet Inches Feet Inches
      0.9167 11 0.0781 15/16
      0.8333 10 0.0729 7/8
      0.75 9 0.0677 13/16
      0.6667 8 0.0625 3/4
      0.5833 7 0.0573 11/16
      0.5 6 0.0521 5/8
      0.4167 5 0.0469 9/16
      0.3333 4 0.0417 1/2
      0.25 3 0.0365 7/16
      0.1667 2 0.0313 3/8
      0.0833 1 0.0260 5/16
0.0208 1/4
0.0156 3/16
0.0104 1/8
0.0052 1/16

Table 4-1

To start, stake out a “base” line string.  This will become either building front or side. If trying to align a building with an existing structure, roadway or property lines, have the first wall line parallel to reference point. See Figure 4-1 

Figure 4-1: Base String Line

Locate and set front corner stake “A” along the baseline. Drive a nail partially into the stake top as a reference point.  See Figure 4-2

Figure 4-2: Placing Stakes

Hook a tape measure on nail at Stake A. Measure building length along base line from Stake A and set corner Stake B.  See Figure 4-3

Use a construction level (transit) and drive Stake B in so Stake A and B tops are level. Drive a nail partially into Stake B top at exact building length (as measured from column outside to column outside). 

Figure 4-3: Batter Boards

Next make endwall perpendicular to sidewall. Measure 12 feet along the base line from Stake A and set a temporary stake. Intersection point 20 feet from this temporary stake and 16’ from Stake A is perpendicular to the base line. Set a second temporary stake at this point. (Figure 4-3)

Measure outside building width along this line and set Stake D. Drive Stake D into ground…level with Stake A and B tops. Drive a nail partially into Stake D top at exact outside building width. (Figure 4-3)

From nail in Stake D top, measure the outside building length. From nail in Stake B, measure outside building width. At two measurement intersection, drive last corner Stake C, with top level with previous three corner stake tops. As before, partially drive a nail into Stake C top, at exact outside corner point. (Figure 4-3)

Before proceeding, make certain all four corner stakes tops are level.  Then double check, in this order – baseline length (A to B), Width B-C and A-D and then length C-D. Adjust nails or stakes B, C, or D as needed.

Diagonals AC and BD are to be equal for a rectangular building. Adjust by shifting C and D along the rear wall line. 

Do NOT move A or B. 

Keep widths B-C and A-D equal. Recheck any shifted stake levels.

Drive batter board stakes 8 to 12 feet from all corners. While specific batter board materials are not provided with building kit, girts make excellent batter boards, as long as they remain uncut and undamaged. Batter boards provide a level reference plane for building layout. Place to avoid interfering with excavation, pre-mix deliveries or construction and to remain undisturbed until columns are backfilled.

Level and fasten batter boards to stakes at same heights as corner stake tops.

Stretch building string lines between batter boards, barely touching nails on corner stake tops. Partially drive nails into batter board tops to line up string lines. 

Temporary and corner stakes can now be removed. Corners will be located where lines cross.

Photo above shows corner column in hole with batter boards in place.

Mark Column Locations 

Measuring along building lines, use small temporary stakes or nails painted with fluorescent paint to mark each column location center.  

Remember to locate column center, ½ column thickness inside string lines. (Example: 5-1/2” column, column center is 2-3/4” inside string lines.)   See Figure 4-4

Figure 4-4: Offset String Lines

Figure 4-4 shows column centers as compared to “outside” building line. 

After column centers have been located, offset (move) building line strings 1-1/2” (splash plank width), from column face outsides.  

Why offset string lines? While this may sound confusing, failure to offset string lines could result in crooked finished walls, due to columns inadvertently touching lines. We’ve seen professional builders make this error far too often, and in this case, an ounce of prevention, is worth a pound of cure.

Once offset, building string lines will now measure 3” greater in dimension than building width and length (column outside to column outside). 

Measure in from building string line 1-1/2 inches to set each column.  Rather than having to use a tape measure each time, a 2×4 or 2×6 scrap block (happens to be 1-1/2” in thickness) can be placed between column and string line.

Consideration for Future Building Length Additions

Adding on to post frame building length sounds like it should be such a simple process – unscrew sheets of steel and just build away, right?


Long time reader ROB in ANNAPOLIS writes:

“I feel like you have answered this somewhere in the past, but when I search past “Ask the Guru” I get an employee login prompt.

Due to budget and general indecisiveness, I am considering building a structure shorter than I think I will need long term. If I am sticking to the same width and truss style, how hard is it to extend a building down the road? Essentially I am planning a workshop that I would like to have an office, bathroom, covered parking area. Those are all wants and not needs. If it is not a terrible design decision to add another couple sections to the end later on, I can get the important part, shop space, done sooner.”

My first recommendation would be to construct the ultimate sized shell and only finish off interior of what you immediately need and will fit within your budget. Done in pieces doubles the number of deliveries made to your site and trucks do not run for free. 

Built in segments – even though steel roofing and siding will come from the same manufacturer, there will be some degree of fade. People will be able to tell it was not all constructed at the same time. However, over time the newer steel will fade also and the difference may be imperceptible. Pick lighter colors so the degree of fade is not as noticeable.

If you do build in segments, it should be structurally designed to take into account eventual length. Roof and endwall shear are impacted by building length and it is far easier to account for possible added necessity of materials at the time of initial construction, rather than having to do a retro fit. Beyond a certain length braced endwall panels, by use of OSB sheathing, may be needed, This is a function also of wind loads, as well as building height and width.

Finally, if you are considering adding on to an existing building – place a double truss on the end to be added onto and have no endwall overhang on this end.