Tag Archives: floor joists

Beyond Code: Preventing Floor Vibration

Beyond Code: Preventing Floor Vibration
by Frank Woeste, P. E., and Dan Dolan, P. E

Floor vibration, or bounce, is not a safety issue — it’s a performance issue, and one that’s likely to be impor- tant to homeowners. No one likes to hear the china rattling in the cabinet when they walk across the room. But at what point is the floor stiff enough, and how can a builder predict how the floor will perform?

Unfortunately, there’s no clear-cut rule for a builder to follow, and the physics of vibration are so complicated that it’s no easy matter to design a guar-anteed bounce-free floor (see “Sizing Stiff Floor Girders,” Practical Engineering, 8/97). Also, “acceptable” floor perfor- mance is highly subjective: What’s good enough for one homeowner may not be good enough for another.

The building codes don’t help much in this regard. They’re primarily con- cerned with safety — in other words, the strength of the beam rather than its stiff- ness. The most stringent code limit for joist deflection is 1/360 of the span: For example, a joist with a clear span of 15 feet must not deflect more than 1/2 inch under live load (people and furniture). The dead load — the weight of the floor materials — is not typically included in calculating deflection.

And yet it has been known for decades that a span/360 live-load deflection limit will not necessarily yield floors that are acceptable to everyone when it comes to vibration.

The purpose of this article is to pro- vide some simple rules of thumb for tak-ing the annoying vibrations out of floor systems, whether you’re framing with solid-sawn joists, metal-plate-connected floor trusses, or wood I-joists. There’s no guarantee that every customer will be satisfied if you follow these guidelines, but they should prevent the vast major-ity of complaints.

Some Quick Rules of Thumb
Before looking at specific types of joists, here are some general guidelines for controlling bounce.
✔Shorten the span. In general, shorter spans make for stiffer floors. For exam- ple, if the L/360 span table tells you a joist of a given size, grade, and species will just barely work for your span, shorten the span by adding a girder near the center of the original span. The resulting floor will vibrate less.
✔Increase the joist depth one size. If the code requires a 2×8 at 16 inches on- center, then use a 2×10 of the same grade and species. Or use a 14-inch- deep floor truss when a 12-inch deep truss would meet code requirements. This may not be the most cost-effective solution in every case, but it’s easy to remember and will save time and worry.
Probably the least efficient way to improve floor performance is to reduce the on-center spacing — 16 inches to 12 inches, for instance. Occupants feel “bounce” as a result of a foot impacting an individual joist. But even at 12 inches on-center, the joists are not close enough for the shock of a foot to be car- ried by two joists.
✔Glue and screw the sheathing. Floor sheathing should always be glued down. Screws work better than nails for long- term bounce control.

Design for Solid-Sawn Joists
Our recommendation for stiffening solid-sawn floors is a simple modifica- tion of a rule that was published in 1964 by the FHA: For floors up to 15 feet, limit live-load deflection to span/360; for spans over 15 feet, limit the live-load deflection to 1/2 inch (see Table 1, page 69). In adopting this rule, we encourage builders and designers to ignore the reduced live load of 30 psf for sleeping areas, and instead use the standard 40 psf live load for all rooms. After all, a bedroom can become a study or home office, and the traffic may be heavier than in a living room.

Metal-Plate-Connected Floor Trusses
Floor trusses are a unique product in that they accommodate effective strong- back bracing (see On the House, 7/98, for more on strongbacks). The consensus among wood truss professionals is that strongbacks are effective in minimizing annoying vibrations, and that they are well worth the time and money it takes to install them.
Table 2 illustrates the expected perfor- mance of various floor truss designs, using a 40-psf live load. Table 3 gives guidelines for sizing and installing strongbacks. For best performance, strongbacks should be installed near the center of the span (versus two at the third points) in upright position and attached to a vertical web. The strong- back should also be located at the bot-tom of a vertical web. To be effective, the strongback must be snugly attached to each web, as indicated by the nailing recommendations in Table 3.

When, for whatever reason, the verti-cal webs don’t line up, you can attach a 2×4 or 2×6 scab to the top and bottom chords for attaching the strongback to the truss (see illustration). The total number of nails used to attach the scabs to the truss chords should match the number used to attach the strongback to the vertical web.

Some of the truss professionals that we interviewed when developing Table
2 had more restrictive rules to offer, but none had less restrictive design advice. Again, no design criteria is guaranteed to totally eliminate vibra- tions, but we believe that following the recommendations in the table will minimize complaints.

Wood I-Joists
When using wood I-joists, a simple way to get good results is to always use the tables designed for span/480 deflec- tion. Any I-joist stamped under the new APA standard for performance rated I-joists is automatically designed to meet the span/480 limit. The stan- dard also uses 40 psf as the minimum live load for any floor. The APA stan- dard is now being used by some I-joist manufacturers to make selection of I- joists easier. The allowable spans for various spacings are printed right on each joist.
Another design system for control vibration in wood I-joist floors is Trus Joist MacMillan’s TJ-Beam software. Trus Joist has done extensive testing of floor performance and has developed its own rating system. Using the software, a user can select a number between 20 and 70, with 70 offering the greatest level of protection against potential floor prob- lems as judged by an occupant. For example, a design that is rated at 55 is expected to be judged as “Good to Excellent” by 96% of the population, while 2% should judge such floors as “Marginal,” and 2% should judge the floor to be “Unacceptable.” This system allows the homeowners, through their contractors or architects, to select the level of floor performance to meet their expectations.

We tested the software for a 16-foot clear span supported by 2×4 walls (16 ft. 7 in. outside-to-outside), with I-joists 16 inches on-center and a residential load of 40/12 (live load/dead load). Using a 9.5-inch TJI Pro-250, the rating was 35. Increasing the depth to a 14-inch TJI Pro-250, the rating was a 53. Tightening up the spacing of the 9.5-inch I-joist to 12 inches on-center increased the rating only to 42 — illustrating that going to a deeper joist at the same spacing is a bet- ter solution.

The TJ-Beam software also provides a relative cost index that tells the user how much extra an improved floor will cost. Often an improved performance design can be obtained with the same or even lower cost than the original design.


NEW Hansen Pole Buildings’ Floor Systems

NEW Hansen Pole Buildings’ Floor Systems

I admit to having become easily enamored, early in my prefabricated wood truss career, by floor trusses. To me, they were not only things of beauty, but also made framing a very quick process.

But, I had been exposed to them even before then. My 16th summer, I spent framing (with my father and his brothers) two commercial medical professionals buildings, with a courtyard between each side. Both buildings were 50 feet in width and used floor trusses! Yes, they were very deep (somewhere around five feet), as they were designed to carry not only office live loads, but also an inch and a half of lightweight concrete.

Other than my own personal barndominium (more like a shop/house), with its 48 foot floor trusses, Hansen Pole Buildings rarely had buildings engineered utilizing floor trusses.

Most raised wood floors – whether over crawl spaces, for second or third floors, or lofts and mezzanines, were based upon using interior columns, beams and dimensional lumber floor joists. Beams often ended up being LVLs (Laminated Veneer Lumber), not only costly, but also heavy to work with. While this system was overall cost effective from a material’s stand point, it involved a plethora of pieces to have to move, cut and put into place.

As we began providing more and more fully engineered post frame homes, our clients looked to us to design systems where utilities (HVAC and plumbing) did not hang down below floor systems. Also important, was having a constant ceiling height, without need to finish around beams and floor joists, not equal in depth dimension.

Prefabricated wood floor trusses were an apt decision. They easily out span dimensional lumber or I-joists and due to their open webs, holes do not need to be strategically placed for plumbing and electrical. Until pre-COVID, they generally made for a quite affordable floor. With larger spans, came greater loads at floor truss ends, resulting in more use of LVLs, so it was not a perfect system.

When you read my recent article about prefabricated wood roof trusses, well – floor trusses experienced similar availability and pricing challenges.

No different than us now fabricating roof trusses, floor trusses have been added to our tool belt. We found, by producing ourselves, we could cut prices by half or, in some instances, 2/3rds or more! Back to being an affordable option.

Moreover, having invested heavily into very high grade materials, we are able to span farther, with less depth required. For residential loads, with typical L/360 deflection limitations, clearspans work out to be about one and a half times (in feet) what floor truss depths are (in inches). A 24 inch deep floor truss, can span approximately 36 feet. We have run engineered designs up to 48 foot spans and have this information incorporated into our proprietary Instant Pricing system. Should greater lengths be needed – we can accommodate, at least up to 60 feet!

Other benefits are, we no longer are forced into a situation where our only design solution for support of floor truss ends is LVLs. We can either utilize our ultra high grade MSR lumber, or provide prefabricated wood truss “beams”.

Looking at a multilevel post frame building? Our engineered floor systems are your answer – reliably strong, cost effective and quick to install.

Oh, I almost forgot to mention….looking for a column supported floor system (especially practical over crawl spaces)?

We have even made it easy to quickly identify lumber to be used as floor joists – one end will arrive spray painted ORANGE. If you (or your erector) need to trim a board, please trim unpainted end, as this makes it easy for you (if you hired a builder) or an inspector, to quickly identify wood as being properly utilized!

Call 1.866.200.9657 TODAY to participate in “The Ultimate Post-Frame Building Experience”. And, don’t forget to watch for our next article!

Adding a Second Floor to an Existing Pole Barn

Adding a Second Floor in an Existing Pole Barn

Reader ROBERT in HOLLIS writes:

I have a 24′ x 32′ pole barn with enough roof pitch and headroom to frame out the 2nd floor. Floor joists spanning 24′ with no support columns (clear span) is too expensive and 2×14 joists would take up precious headroom on the 2nd floor. So, my plan is to split the span with beams (scabbed 2×10’s) supported by 4 evenly spaced columns. That will allow joists to be 2×10 or maybe even 2×8 16″oc. Need advice on the size of columns 6×6 or 8×8 Spruce. 2nd floor would be a man cave with a possible pool table centered on 2nd floor (800lbs 4×8). I am not a structural engineer but know that loads and span dictate beam and joist size. Barn is made with 6×6 posts every 8 feet. Two 14″ laminated rim joists are notched onto tops of the posts surrounding perimeter followed by roof rafters and metal roof. Siding is shiplap 1″ pine vertical boards. Many thanks.”

Lots of considerations to be taken into account when adding a second floor to an existing post frame building, especially if connecting to current structural framing members.

Most important, is the dimensions of footings under columns. Assuming a residential floor load of 40 psf (pounds per square foot) and a 10 psf dead load, with your proposed center columns, each existing sidewall column will now be carrying another 8′ (on center spacing of sidewall columns) x 6′ (1/2 distance from sidewall to center columns) x 50 psf, totaling 2400 pounds! To safely carry loads to include a second floor, most engineers are going to recommend poured concrete footings under any columns supporting the second floor and roof system to be no less than eight inches thick. Chances are excellent footings are also lacking in adequate surface area to resist these added loads.

This full second floor, also is creating a diaphragm – it will reduce wind shear forces being carried by roof, however increases shear forces transferred to endwall columns at level of second floor. This could result in overstressing endwall and/or corner columns.

For these reasons, it is generally best to consider erecting a second floor independent of your existing building shell.

Moving forward….2×14 floor joists would probably not be an option due to structural challenges.

Checking just for bending:

[50 psf x 12″ on center x 24′ span squared] / [8 * 43.89 (Section Modulus of a 2×14) * 1.15 (Repetitive member factor for joists 24″ on center of less) = 855.9 (this is required fiber stress in bending or Fb). Southern Pine lumber strength tables only go through 2×12, however a #2 2×12 only has an Fb of 750. Even at 12 inches on center, they would fail in bending, and deflection would most likely be a limiting factor.

Getting on to your question about column dimension for interior supports, wood columns are very strong in compression (resisting gravity). For practical purposes, they can be checked for L/d ratio (unsupported length of column divided by least dimension of column). L/d must be less than 50, so without adjustments for end fixity a 5-1/2″ x 5-1/2″ column is good for 275 inches (obviously full calculations are much more complex than this, however unless you have an incredibly tall building a 6×6 should be adequate).

For your central beam (again checking only for bending):

[50 psf x 144″ x 8’^2] / [8 * (3 * 21.3906) x 1.15] = 780.5 <= 800 (allowable Fb of 2×10 #2 SYP)

When checked for deflection, you will likely find this proposed solution of three 2×10 to not make L/360 deflection criteria. Better plan upon using three 2×12 with any splices directly at columns.

IRC (International Residential Code) Table R502.3 gives floor joist spans. 2×8 #2 SYP 16 inches on center is good up to a span of 11’10” or 2×10 #2 SYP 24 inches on center can span 11’5″ (depending upon beam placement, you might be within this limit).

In summary – I would recommend you engage a Registered Professional Engineer to evaluate what you have and devise a proper structural design solution.

Pool Insulation, Span Tables for Floor Joists, and Post Brackets

Today the Pole barn Guru addresses reader questions about the use of 2″ Dow Styrofoam sheets to help insulate and above ground pool, advice for a structurally sound 20×40 room with a loft in a building, and if post can be set onto a cinderblock wall.

DEAR POLE BARN GURU: I live in Minnesota and wanted to insulate my above ground pool. I cut sheets of 2” Dow styrofoam to fit in between the legs of the pool. I want to use pole barn steel to surround the pool frame to hide the styrofoam, any ideas? SHERRIE in MINNESOTA

DEAR SHERRIE: Maybe I should also be known as “Pool Barn Guru” LOL. All joking aside, if top and bottom edge of your pool support system are wooden, you could order steel panels to your pool’s vertical dimension (I’d probably hold top edge down somewhat to avoid folks being cut from top edge of steel) and screw panels directly to top and bottom supports. You could also reach out to your pool provider for suggestions. Best of success.


DEAR POLE BARN GURU: My 40’x60’x16’ shop is almost done being built. I’m wanting to do a 20×40 room in the back wall for a man cave type area, I can build the room no problem. The only thing I’m wondering is about the loft above the room. I’m having trouble figuring out what I need to do to build that 20×40 loft that will be structurally sound. What do I need to span 20’ for the floor without putting posts in the middle of the man cave. VINCENT in EAST ALTON

DEAR VINCENT: Luckily there are readily available span tables for floor joists. 2×12 #1 on 12″ centers https://www.southernpine.com/app/uploads/SPtable2_060113.pdf

DEAR POLE BARN GURU: Can you put the posts on a cinderblock wall that has enlarged footers under the block wall. I have a 30×30 continuous footer under the cinder block wall where I want to put the posts. The cinderblock wall is filled with concrete. Let me know your thoughts please? And thanks in advance. TAMI in MADISON

DEAR TAMI: Provided footings beneath your CMU wall are adequate in dimension, probably. In areas of your existing wall where ICC ESR approved engineered wet-set brackets for columns will be placed, existing blocks will need to be removed and replaced, so brackets can be properly poured into wall. https://www.hansenpolebuildings.com/2019/05/sturdi-wall-plus-concrete-brackets/



Loft in a Weld Up Steel Building

Loft in a Weld Up Steel Building

Reader CINDY in TYLER writes:

“I am constructing the interior of a welded metal house that’s 20x18x12. I am trying to figure out how to add a loft. The building framing is constructed of I-beams and the walls have 2 rows of heavy 8” C-channel per wall, Though the lower C’s will have to be cut for window installation. But the upper C is about the right height for the floor. I only want the loft to be 20×9. I’m going to give you my ideas and would like your response, ideas, thoughts and recommendations please. I have a 20’ piece of steel 8” C-channel that I could run across the building that would finish the square framing, though I don’t weld ad not sure how to best attach it to the walls. After that I can install, with screws, 2×8 along the inside of all the C’s. That will give something to attach joist hangers to which will be installed parallel to the C that was just installed. Does this sound doable and any ideas on how to properly attach the C channel? I was thinking I could cut the top and bottom part that curls, and bend it out of the way and attach some heavy duty angle pieces, but can only attach with 1’s onto the top and bottom of one channel and to the center of another. I would attach with bolts and nuts. Any help will be greatly appreciated. Thank you for all that you do for so many people with your blog.” 

Mike the Pole Barn Guru says:

If you are a regular follower of my blog posts, you will find I am a fan of weld up steel buildings only when they are fabricated from engineer sealed site specific plans with assembly done by a certified welder. While this may not be as important on a low risk shed, as buildings grow in footprint and complexity, it becomes significantly important.

Lofts can prove to be of special concern. They tend to be under designed (unless engineered) and over loaded, resulting in distinct possibilities of catastrophic failure leading to potential injuries (if not fatalities).

Trying to attach steel beams to steel framing members should not be done without an engineer’s design. There is an easier option:

Provided your concrete slab is sufficiently thick, my recommendation would be to frame 2×6 stud walls along each 20 foot side of your proposed loft. Use a pressure preservative treated 2×6 bottom plate. Studs can be 24 inches on center with a double 2×6 top plate.

Proper anchorage for stud wall to a slab has fasteners penetrating at least an inch into concrete. You could use 2-1/2″ Ramset nails.

Personally, I prefer using Tapcon screws 

What you’ll need:

Tapcon screws – Be sure to get 3/16″ x 2-3/4″
ones with hex heads. Don’t try to use a flat-head screwdriver to drive them! 

A hammer drill

Several concrete drill bits

A hex head bit for drill fitting Tapcon head size

How to attach walls using Tapcon screws

Drill pilot hole

Drill a hole through 2×6 bottom plate center, every 16″ to 20″ inches.

Hold the bottom plate in place by standing on it if possible.

Use firm pressure, but don’t push too hard. Save your body, drill will do the work!

If using 2 3/4″ screws, put a piece of tape on bit 3″ from tip. (Drill 1/4″ deeper than depth of anchor plus 1 1/2″ for bottom plate.)

Attach screw

For best results use a hex-head attachment on your power drill to secure screw. (Even the correct size flat-head screwdriver attachment will slip off frequently.)

Start off slowly until you’re through the bottom plate.

Speed up drill and drive anchor deep enough into concrete so the screw head is flush with bottom plate. 

Make sure you have enough drill bits on hand. You’ll go through several as tips eventually wear

Another method of attachment entirely avoids penetrating your concrete – construction out or break off. Repeat this process with each wall section adhesive. Make sure the slab is thoroughly clean and use a polyurethane adhesive. Polyurethane works if there is any moisture in the concrete or bottom plate and it has gap filling properties.

Assuming you will have no loads on loft greater than a 40 psf (pounds per square foot) residential load, 2×8 #2 floor joists can be spaced on top of walls 24 inches on center.                                                                                https://www.southernpine.com/app/uploads/SPtable2_060113.pdf

Use 3/4″ OSB (Oriented Strand Board) or CDX plywood for your floor decking. 

Saving a Poorly Designed Crawl Space

Saving a Poorly Designed a Crawl Space

Reader GEORGE in VIENNA writes:

“I am substantially replacing rotted parts of an existing building set on short 6×6 treated posts which are in good condition. above the posts it is conventional platform construction, and untreated. Unfortunately, the original builder set the building partially into the side of a hill in an attempt to use thermal mass and reduce energy use in its off-grid location. The uphill side was backfilled to a height of approximately 30″ above the interior floor, which is OSB over untreated 2×12 beams and untreated 2×6 joists. Skirting to keep out moisture was untreated plywood, poly sheet, and Styrofoam block insulation. In 6 years, there is substantial rot of the perimeter plywood, perimeter 2×12 rim joists, some 2×6 floor joists, some areas of the OSB flooring, the untreated sole plate and a few studs above. Otherwise the building walls, windows, doors, roof trusses, metal roof, insulation, etc., are well made and in good condition. We are temporarily supporting the building from below and removing the failed materials all the way around. We are removing the backfilled dirt on three sides to expose the posts and provide airflow underneath. All rim joists, beams, and floor joists will be replaced with treated materials. I am looking for advice in two areas (1) floor insulation, either under or over the OSB, and (2) treated skirting around the perimeter which would allow partial backfill and maintain ventilation.” 

Mike the Pole Barn Guru says:

You really have two options:

You could condition your crawl space – this would require a 6mil or thicker, well-sealed vapor barrier to cover underlying soil and up perimeter walls to floor joists. There would be no vents with this method, however an air-circulating device must be provided. Perimeter walls should be insulated using either closed cell spray foam or rock wool batts. 

From Building Code Section 308.3, Unventilated Crawl Spaces

The air-circulating device must move at least 1 cubic foot of air per 50 square feet of crawl space area. The crawl space floor area must be completely sealed with a vapor-retarding material. The edges of the vapor retarder must be lapped up against the inner foundation walls.

Read more about encapsulated crawl spaces here: https://www.hansenpolebuildings.com/2020/11/11-reasons-why-barndominium-crawl-space-encapsulation-is-important/
Or – have an unconditioned crawl space, where your vapor barrier would cover the ground surface. Insulation would ideally be beneath OSB – between floor joists. Again, same choices for insulation – just between joists. With this choice foundation vents would need to be added to perimeter walls.

Most building codes require 1 square foot of open ventilation area for every 150 square feet of crawlspace. Generally, Automatic Foundation Vents have 50 inches of net free area per vent. Therefore, install one vent for every 50 square feet of crawlspace.

FDN (Foundation) rated pressure preservative treated plywood will probably be your best skirting material.

What to do When the Old Post Frame Garage Has Issues

What to do When the Old Post Frame Garage Has Issues

Welcome back from Tuesday’s posting. As you may recall, when my great-grandfather W.R. McDowell built his two-car Model A garage pre-World War II, it was 16 feet wide by 20 feet deep. This garage was supported by eight cedar poles on minimal footings.

Well….sure enough some of those cedar post footing settled. Some settled more than others, resulting 50 years later in what was appearing to be some sort of carnival fun house. Wood floor parking surface was up and down and the stick framed walls above had developed a serious lean.

By 1946, my great grandparents (W.R. being 74 and Mary Elenis 66) found hiking up and down stairs to be not as much to their liking (much like Mr. Lillequist 10 years before). They sold their cabin to their son Boyd and his wife Jerene.

44 years later, in 1990, Boyd and Jerene had reached their 80s. Having spent my summers at Newman Lake and having developed a strong affinity for it – they gifted this cabin to me, my wife and our young daughter Bailey.

I had recently sold my first business, in Oregon, and returned to Spokane. My intention was to remodel our cabin, so it could become our primary residence. To start with, something had to be done with its garage. Even had it remained structurally sound, while two Model A cars may have fit in it comfortably,  we needed more width and depth for two more modern vehicles.

My solution – build a new 22 foot wide by 24 foot deep post frame garage around what was there.

First step was to tear down the old garage to parking deck level.

A couple of trees were too close for comfort and had to be forcibly removed.

Once offending trees were removed, pressure preservative treated posts were set around outside of the existing floor (and a few through holes chainsaw cut through the floor).

After posts were in place, the old floor was removed and framing began. Being it was early December, in Northeast Washington State – we got to deal with snow.

In order to support weight of a concrete slab and vehicles 14 feet above ground, 2×14 #2 Douglas Fir floor joists were placed 12 inches on center, with 2×8 Tongue & Groove decking over top. Raised heel bonus room attic trusses with a 7/12 slope were utilized, in order to allow for a home office space above parking level.

On Super Bowl Sunday Eve of 1991 near tragedy struck our still under construction project. On Friday, our electrician had energized power. When wiring had been run, he had neglected to install protective steel plates at crucial points where sheetrock screws might penetrate wiring. One screw hit a wire in an attic space and smoldered for a day. Around midnight, one of our neighbors got up to get a drink of water and noticed flames coming out of our garage. Their quick thinking and fast response from our local fire department saved this building, with only minimal fire damage, but everything was coated with black soot.

Profuse quantities of Kilz™ were used, however a smoke smell still persisted. We added temperature controlled powered vents in attic spaces, with corresponding air intakes, in order to exhaust burn odors on warm days.

Note: smoke stains on siding above overhead doors and cutouts in endwall for ventilators.

As you may recall – there was some significant grade change at this site. Space below garage floor level, was utilized to create a studio apartment with over 400 square feet of space (current owners rent it out as an AirBNB https://www.airbnb.com/rooms/665906592425731485?source_impression_id=p3_1667315547_%2BXfm5XMqvopowtF%2B).

Pole Barn Garage Wood Floor

Pole Barn Garage Wood Floor

Reader CLIFFORD writes:

“Hello,  I found where you had answered a question about a wood floor in a garage while I was searching the web asking “Wood floor in a garage?”.  Let me explain, I am a disabled veteran living on a fixed income.  I have a blood cancer as a result of being exposed to the toxic smoke of the burn pits in Afghanistan and Iraq.  I was told that once I started treatment I would live 7 or 8 years, 10 if I am lucky, I have been on treatment now for about 3 years.  I bought my farm from my dad.  I have a double wide home that is set up on a basement (with garage door), the problem is it is only 7’ tall with a 6 and ½ ‘ door.  I don’t have anything that fits.  I plan on building a 24 by 24 workshop/garage.  I will build it much like a pole barn, for the simple reason I can build in phases.  One pole at a time so to speak, as money allows.  I am looking at wood for the floor, I know in the really old days wood floors were common.  The problem I am concerned about is the weight limit.  I have a Mack Truck that was given to me, basically a toy, but a subsidiary of Mack Trucks rebuilt it so it is real nice.  I need the floor to be able to support this.  My plan is this:  2×8 treated floor joist, 12” on center.  Topped with 2×8 lumber, then topped with ¾” T&G plywood – to get it smooth.  To be honest I will probably have treated plywood on the bottom of the joist and fill in between the joist with what they call around here waste rock.  Then top it off with the 2×8’s and plywood.  The joist would run from front to rear, allowing a chance for the load to be right on a joist.  I expect it would be about a 10,000 to 12,000 pound load spread on 6 tires, I am guessing about a 10” x10” patch for each wheel, the heaviest load would be the front wheels.  I am not asking for official specs, just a professional opinion.  I realize cost wise it could probably be built with concrete cheaper, but I have to build it a piece at a time, and to be honest it may never get finished.  Thank You.”

Thank you for your service sir.

There is an even easier method (plus more cost effective) and if you are not going to climate control, you can omit directly under plywood insulation: https://www.hansenpolebuildings.com/2022/03/post-frame-plywood-slab-on-grade/

How to Properly Design a Barndominium Wood Floor Over a Crawl Space

How To Properly Design a Barndominium Wood Floor Over a Crawl Space

Reader JERRY in HAWESVILLE writes:

“If one were to build a post frame home on a crawlspace and the floor joists were sitting on a 3 ply 2×10 center beam on post spaced 8-10 feet apart, how does one support the joists at the outer walls? Do you need another 3 ply beam on each side and how would you attach those to your posts? If you could show a diagram, that would be great. Thanks.”

Well Jerry, a simple answer is yes, you need to support floor joists at the exterior wall. Beyond this things begin to get more complex and should only be done with a Registered Professional Engineer being involved.

Let’s begin with your interior floor beams, we will check for a beam spanning 10′:

fb: bending stress from live/dead loads
P = (D + L) = 10 psf + 40 psf = 50 psf
W = 50 psf * 8′ / 12 in./ft. = 33.333 pli (8′ is tributary area being carried by 3 – 2×10 #2 SYP members)
M = (33.333 pli * 120″2) / 8 = 60000 in.lbs
S = b * d2 / 6 = 3 * 1.5″ * 9.25″2 / 6 = 64.17 in.3
fb = M / S = 60000 in.lbs / 64.17 in.3 = 934.99 psi
934.99 ≤ 800 x 1.15 (Increase for repetitive members) so over stressed in bending by 1.6%

Not a very practical design solution.

If beam span is reduced to 8′, then allowable tributary area could be increased to 12′ (e.g. 6′ on either side).

Moral is your proposed 3 ply 2×10 beam is probably not a best solution.

Beams also need to be checked to meet Code required deflection limitations of  l/360 where “l” is the span of beam between supports. In this instance, bending will dictate design.

Hopefully this alone shows a fully engineered solution is best, as an engineer will confirm all needed grades and dimensions, as well as best connection methods. He or she will also design column footings to be adequate in diameter to properly distribute added weight (both live and dead loads) being added due to your floor system.

Builder Warranty Example

Example Builder Warranty

Disclaimer – this and subsequent articles on this subject are not intended to be legal advice, merely an example for discussions between you and your legal advisor.

I cannot express strongly enough how important to both builders and their clients to have a written warranty in any agreement. 

WARRANTIES: There is no warranty applicable to the building and is expressly in lieu of all other warranties available under any State or Federal laws, expressed or implied, including any warranty of all labor, material, product and taxes will be paid for and there will be no potential lien claim against Purchaser’s property upon completion of the work and following final payment by Purchaser to Seller.

Products supplied by third party suppliers, manufacturers and sub-contractors to the project are warranted only to the extent that the suppliers and manufacturers of those products provide a warranty.

In the event that a defect is discovered in one of these products, Seller will assist Purchaser in securing repair or replacement of these products under the warranty provided by the third party supplier or manufacturer. Warranty work is work which was correctly and completely done initially, but becomes non-operational or dysfunctional following occupancy or use by Purchaser. No retainage or holdback will be allowed for warranty work.  

Seller expressly warrants to the original noncommercial purchaser(s) and only the original purchasers.  

That if any part of a Seller constructed post frame building, as covered by this warranty, proves to be defective due to materials or workmanship, under normal use and service, for two (2) years, that defective part will be repaired or replaced, subject to the terms and conditions contained in this Warranty.

Seller hereby assigns to Purchaser all rights under manufacturer’s warranties. Defects in items covered in manufacturer’s warranties are excluded from coverage of this limited warranty, and Purchaser should follow the procedures in the manufacturer’s warranties if defects appear in these items. 

 For ten (10) years.

Any solid sawn or glu-laminated (pressure treated to a minimum UC-4B) structural columns that fail due to decay or insect damage, unless said column has been exposed to animal wastes.

The original building roof structure, if damaged directly by snow loads because of the failure of any prefabricated roof truss or trusses to meet design specification. Subjecting your roof system to greater loads than those set out on the face of this Agreement, any unspecified ceiling loads, or modifying the trusses in any way voids all Warranties.

Any major structural defects which are defined as being an actual defect in a load-bearing portion of the building which seriously impairs its load-bearing function to the extent that the building is unsafe. For purposes of this definition, the following items compromise the structure of the building:

  1. Load bearing columns,
  2. Floor or ceiling joists,
  3. Beam, trusses and rafters.

For Two  (2) Years:

Any roof leaks due to defects in material or workmanship, expressly excepting where the building has been connected to an adjoining structure, in roof valleys, or at roof slope changes to which cases, no warranty applies. 

Any other building parts which prove to be defective in material or workmanship.

This warranty period shall commence on the date of the acceptance of the building by the Purchase or Purchaser’s occupancy of the building, whichever comes first.

This warranty contained wherein is void in situations where:

  1. Installation is not made in accordance with the instructions supplied by Hansen Buildings.
  2. The actual operation or use of the product varies from the recommended operation or intended use.
  3. There is a malfunction or defect resulting from or worsened by misuse, negligence, accidents, lack of or improper performance of required maintenance by the original purchaser.
  4. The building is altered or added onto, unless by Seller.
  5. Seller is not notified within twenty four (24) hours of problems due to snow loads.
  6. Purchaser fails to take timely action to or damage.
  7. Anyone other than Seller’s employees or agents or subcontractors have been on the building roof.
  8. Purchaser fails to make final payment per terms of sale.

Equipment such as fans, HVAC, gutters, downspouts, walk door locksets, other equipment not manufactured by Seller, site work, concrete, doors, windows, interior finishes, mechanical or electrical systems are excluded from this warranty.

The Purchaser expressly agrees to fully and timely pursue all available remedies under any applicable insurance agreement before making claim under this warranty.

In the event Seller repairs, replaces or pays the cost of repairing or replacing any defect covered in this warranty for which Purchaser is covered by insurance or a warranty provided by another party. Purchaser must assign proceeds of such insurance or other warranty to Seller, to the extent of the cost to Seller, of such repair or replacement.

Any claims for defects under warranty must be submitted in writing to Seller within the warranty period and promptly after discovery of the claimed defect, describing the defect claimed and date of building completion, before Seller is responsible for correction of that defect. Written notice of a defect must be received by Seller prior to the expiration of the warranty on that defect and no action at law or in equity may be brought by Purchaser against Seller, for failure to remedy or repair any defect about which Seller has not received timely notice in writing.

Purchaser must provide access to Seller, during normal business hours to inspect the defect reported and, if necessary, to take corrective action. A reasonable time should be allowed for inspection purposes. If, after inspection, Seller agrees, at its sole option to repair or replace only the defective materials or workmanship within the first three months from date of building completion at NO COST to the Purchaser. Thereafter Seller shall assume the cost of material and labor for any warranty work upon advance payment by the Purchaser of a one hundred dollar service payment for each incident under this warranty. The obligation of Seller, under this warranty, shall be performed only by persons designated and compensated by Seller for that purpose, and is subject to all other provisions of this warranty.

The provisions of this Warranty are the full and complete warranty policy extended by Seller, and are expressly in lieu of all other warranties, expressed or implied, including any warranty of merchantability or fitness for a particular purpose. These warranties may not be transferred or assigned. The liability of Seller shall not exceed the cost to Seller for repairing or replacing damaged or defective material or workmanship, as provided above, during the warranty period. 


Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above limitations or exclusions may not apply to you. This warranty gives you specific legal rights and you may also have other rights which vary from state to state. 

Purchaser shall promptly contact Seller’s warranty department regarding any disputes involving this Agreement.

Seller and Purchaser agree that this limited warranty on the building is in lieu if all warranties of ability or workmanlike construction or any other warranties, express or implied, to which Purchaser might be entitled, except as to consumer products. No employee, subcontractor, or agent of Seller has the authority to change the terms of this warranty.

A Floor Raising Exercise: I Joists

For some obscure reason people planning new buildings tend to scrimp on height. In most instances, designing a new fully engineered post frame building – whether for a barndominium, shop house (shouse), garage, shop, etc., just a little bit taller is a relatively inexpensive proposition and can save many more dollars and mental anguish than having to alter after construction.

Reader CHRIS in SNOHOMISH writes:

“I have a pole barn with a center door for Rv, above is an additional living space, the width is 12’6” depth of 41’ height of 13’, I need to shorten the truss’s so I can gain 6” height , current truss are HY floor joists, question is can I put 2×6” spaced every 8”’s and have the same weight carrying capacity?”

Mike the Pole Barn Guru writes:

HY floor joists are wood prefabricated I joists. Let’s take a look at Chris’ proposed design solution (please keep in mind, any structural design solution should be reviewed by your building’s engineer to confirm structural adequacy):



Joist span 12.5-ft.
joist spacing = 8″ o.c.

joist  live load = 40 psf
joist_dead_load = 10 psf

Fb: allowable bending pressure
Fb‘ = Fb * CD * CM * Ct * CL * CF * Cfu * Ci * Cr
CD: load duration factor
CD = 1 NDS 2.3.2
CM: wet service factor
CM = 1 because floor joists are protected from moisture by roof
Ct: temperature factor
Ct = 1 NDS 2.3.3
CL: beam stability factor
CL = 1 NDS 4.4.1
CF: size factor
CF = 1.3 NDS Supplement table 4A
Cfu: flat use factor
Cfu = 1 NDS Supplement table 4A
Ci: incising factor
Ci = 1 NDS 4.3.8
Cr: repetitive member factor
Cr = 1.15 NDS 4.3.9
Fb = 900 psi NDS Supplement Table 4-A
Fb‘ = 900 psi * 1 * 1 * 1 * 1 * 1.3 * 1 * 1 * 1.15
Fb‘ = 1345.5 psi

fb: bending stress from live/dead loads
fb = live + dead load * joist spacing / 12 / 12 * (sf * 12 – 1.5)2 / 8 / (b * d2 / 6)
fb = 50 psf * 8″ / 12 in./ft. / 12 in./ft. * (12.5′ * 12 in./ft. – 1.5″)2 / 8 / (1.5″ * 5.5″2 / 6)
fb = 1012.5 psi <= 1345.5 psi so okay in bending

Δallow: allowable deflection
Δallow = sf * 12 / 360 IBC 1604.3
Δallow = 12.5′ * 12 in./ft. / 360
Δallow = 0.4167″

Δmax: maximum deflection
Δmax = 5 * live load * joist spacing / 12 / 12 * (sf * 12 – 1.5)4 / 384 / 1600000 / b / d3 * 12 from http://www.awc.org/pdf/DA6-BeamFormulas.pdf p.4
Δmax = 5 * 40 psf * 8″ / 12 in./ft. / 12 in./ft. * (12.5′ * 12 in./ft. – 1.5)4 / 384 / 1600000 / 1.5″ / 5.5″3 * 12
Δmax = 0.423″ > 0.4167:
2×6 #2 DougFir joists will not work at 8″ on center due to not meeting deflection criteria

Chris’ options are to buy #1 or Select Structural graded 2×6 DougFir or go to 6″ on center spacing.

Designing a Dream Barndominium Loft

Designing a Dream Barndominium Loft

Reader BRIAN in PETOSKY writes:

“ Hi Mike,

Mindi told me to email you my lofted floor question for our project.

To avoid messing with truss-support floors, we were planning to build a full 26×60 main barn with scissor trusses the full length. Then on one end, we would make a 20’x26′ loft. Have the floor joists run parallel to the barn, perpendicular to the trusses, so we’d have 20′ floor joists. These would be supported by the gable end wall and interior posts 20′ in.

We live in a barn home with this configuration and it works well. Allows consistent and uninterrupted ceiling space the length of the barn but still get a 2nd floor in where we want it.

The question is, I guess, what, if anything needs to be conveyed to the engineer for this design? Does it influence anything on the gable end wall? How far apart can the posts be on the interior end? Can stairs be free-standing next to this loft?

Thank you!”

When I used to call on Home Depots, Petoskey was one of my stops. Every time I was there the weather was gorgeous, making it difficult to get motivated to move on to my next appointment!

There are some challenges with running dimensional lumber floor joists to span 20′. Even using #2 & better 2×12 Douglas Fir joists, they would need to be 12 inches on center! Other popular specie of framing lumber has lower MOE (Modulus of Elasticity) values, so will not even begin to approach being able to span 20’. Chances are good there will be both a fair amount of spring to this floor, as well as a non-uniformity in deflection from joist to joist.

For extended reading on floor deflection, please read https://www.hansenpolebuildings.com/2015/12/wood-floors-deflection-and-vibration/

This would be my recommendation – we can use prefabricated wood floor trusses to span 26′. Doing so would allow there to be no interior supports within this 26′ x 20′ area. As long as stairs run perpendicular to the floor trusses, no columns would be needed where they attach. When you and Mindi have your building details finalized, she will relay this information forward on your Agreement with us, so everyone will be on the same page. Further, we send plans to you for a final once over prior to engineer sealing them, just in case.

Wood Floor Trusses

When I was first in the metal connector plated wood truss industry back in 1977, my employers – Dutch Andres and Tom Vincent at Spokane Truss, had just invested in a machine which would fabricate what would be called a 4×2 floor truss.

These trusses revolutionized the way floors could be constructed – freeing up areas below them from the need for load bearing walls and columns in all of the most inconvenient places!

Rick Ochs is new to the inside team at Hansen Pole Buildings, and earlier this week, he posed a question:

“Hey Mike,

No rush… I have been viewing tutorials from WTCA (Wood Truss Council of America) on trusses and structural building components.  I was wondering why we don’t spec floor trusses instead of the traditional 2×10 with hangers.  Cost I presume.


Here is my response to Rick:

Floor trusses will be significantly more expensive.

Let’s say you have a 2×10 at .6285m (current price at The Home Depot®) so a 12′ would be $12.57.

(“m” happens to be lumber people’s secret code for 1000 board feet)

If they were even 16″ o.c., you are talking 0.79 per square foot for the cost of joists.

Floor trusses are going to run around $4.40 per lineal foot, spaced 2′ on center, this makes the cost per square foot for the joists at $2.20.

For a floor span of over 24′ trusses are certainly the way to go.

To which Rick responded:

“I’m thinking it would take a little more math on the builder/customer part to compare against labor cost savings of setting floor truss vs time required to set hangers, cut and nail joists.”

Personally, I have metal connector plated wood floor trusses in two of my personal buildings – in one case spanning 30 feet and the other 48 (yes a 48 foot clearspan floor).

Here are some of the benefits of using wood floor trusses:

  • Larger sheathing attachment, with 2×3 or (usually) 2×4 nailing surface,
  • Spacing up to 24” o.c. maximizes efficiency, decreasing installation time.
  • Each unique truss is engineered to proper codes and loading.
  • Speeds up mechanical installation (think heat ducts) with the open webbing thus saving dollars.
  • Span longer distances than conventional lumber or I-joists.
  • Special bearing, cantilever, and balcony details are easily built in.
  • Less pilferage, it is unlikely a 20’ truss is going to walk off the jobsite.
  • Faster jobsite build times, saving jobsite labor, construction loan interest, vandalism, and environmental damage.

Wood floor trusses can also be designed to limit the deflection and vibration, read more here:


In the global scope of life, having a wood truss supported floor is a fairly economical upgrade, which is certainly something worth investigating.

Scary Pole Barn Design

Scary Design

A one-time potential Hansen Pole Buildings’ client, who is a friend of mine on Facebook, didn’t invest in one of our engineered post frame buildings. Most likely it was due to price – people so easily believe they have gotten a great deal, when instead they set themselves up for nothing but potential grief.

He proudly posted the photo above on Facebook of the progress of his new building.

Disclaimer – in case you, gentle reader, were unsure – his new building is NOT a Hansen Pole Building.

I will let you in on a secret which truly frightens me about this building…….

loft floor framingIf a load approaching what the loft should be designed to support is placed upon it, I venture to wager it will fail. Do not stand underneath it, by any means.

As near as I can tell from the photo, the columns which support the second floor are spaced roughly 12 feet on center. It appears the floor joists are 2×12 spaced 16 inches on center and each end of the joists are supported by what seems to be another 2×12.

Building design and construction are only as good as the weakest link.

The building is in the deep south, so we will go with the premise the lumber being used is Southern Pine.

The floor joists are not a problem – they would easily support double the normal design floor live load of 40 pounds per square foot (for residential loading). The problem comes from the beams which support them at each end.

Here is the formula for design of the beams:

(Live plus dead loads) X ½ the distance to the next beam X Beam span^2  /  8 X 31.6406 (the Section Modulus of a 2×12) X Fb (for 2×12 Southern Pine 750) X 1.15 (Cr – repetitive member increase)

(40 + 10) X (72”) X 12’^2 / 8 X 31.6406 X 750 X 1.15 = 2.37 when it has to be less than or equal to one to work.

The floor, as built, is overstressed by 237%!! Or – think of it this way, it will only support 42% of what it should support by the BuildingCode!!

In either case, it is frightening.

Don’t construct (or have constructed for you) any post frame (pole) building which has not been designed by a Registered Design Professional (RDP – architect or engineer). To do so is scary pole barn design and nothing short of playing Russian Roulette.