Tag Archives: second floor

Ceiling Liner, Double trusses, and a Second floor

This Wednesday the Pole Barn Guru answers reader questions about what best installed between ceiling liner and trusses and insulation recommendations in a new shop, advice on sidewall column size for use with double trusses, and the structural stability of a pole barn second floor.

DEAR POLE BARN GURU: Just built a 40x60x11 pole barn on the eastern shore of MD. Approx. 20×40 will be garage workshop, the rest will have a kitchen and bathroom etc. going to use liner panel for ceiling, what do I, if anything needs to use between the liner and the trusses? Insulation recommendation? Product recommendations are appreciated! Thank you, LYNN in SHARPTOWN

DEAR LINN: There is not a Code requirement for a barrier between trusses and liner panels in your climate zone. If you are considering blowing in cellulose, chemicals in cellulose can react with steel panels to cause premature deterioration, so a barrier should then be used. My first choice would be blown granulated rockwool, second would be fiberglass. Make sure to have adequate eave and ridge ventilation, in correct proportions.


DEAR POLE BARN GURU: Went reading your blog on double truss system, if wanting to erect a pole barn 30×78. Would using 4×6 be ok going 12 ft high post spaced every 8 foot other then 2 16 openings. BRIAN in PADUCAH

nailing trussesDEAR BRIAN: Thank you for being a reader of my articles. Even with a very low design wind speed, low risk occupancy and a well-protected site, it is unlikely 4×6 columns would be adequate to properly carry design loads, given your eave height. As you are possibly considering utilization of ganged (double) trusses, and will need larger columns anyhow, you may want to consider increasing column spacing to 12 feet on center. Fewer holes to dig, fewer columns to set and your budget will be much happier. In any case, I would encourage you to invest in a fully engineered building – any possible savings you might believe you would attain without engineering, will be quickly eaten up when you have a failure.


DEAR POLE BARN GURU: I’m wondering if this would be structurally sound with a top floor on it? It would be meant as a home/business. I work in the commercial construction industry I guess the other question is do you have any of these in New Hampshire? Please let me know what you think and Thank you. JOE in HUDSON

DEAR JOE: My own post-frame building has a 48′ x 60′ main center section. Downstairs has a clearspan floor (yes, spanning 48 feet), with a 16 foot high ceiling. Upstairs is a full living area, again with 16 foot high ceilings. A portion of this upper level also has a small mezzanine. Overall building height at peak of roof is 44 feet. So, in answer to your question – fully engineered post-frame construction lends itself very well to multiple stories (up to three stories and 40′ tall sidewalls, or four stories and 50′ tall sidewalls with fire suppression sprinklers). We have provided over 100 of our buildings to clients in New England states, including a dozen or so in New Hampshire.


Attic Space, Cost Effective Size, and Column Sizing

This week the Pole barn Guru answers reader questions regarding a 6ft attic space over a 30×44 pole barn, the most “cost effective” method to build, and the point at which a post increased from a 6×6 to a 6×8.

DEAR POLE BARN GURU: We want a decent-height (a bit over 6ft) attic space in our 30×44 pole barn (on a concrete slab foundation), can we use steel trusses or would wood trusses be a better option for this? The ground floor ceiling height is 8ft. Thnx for the help. RON in TONEY

DEAR RON: Lots of possible design solutions available. To begin with, I would recommend wood trusses – should you ever want to finish a ceiling, or if you want to have a product fabricated under strict quality control standards, then wood trusses are your best choice. On to options…. #1 My favorite. Make your building tall enough to have a full second floor. This will give you greatest usable space and best resale value. By using prefabricated wood floor trusses, you can still have a clearspan floor (no posts below) and it provides an unencumbered space below without columns to dodge. Yes, it will be a greater investment, but one you will probably never regret. #2 Prefab wood ‘bonus room’ trusses. With a steep enough slope (roughly 8/12) you can end up with an eight foot ceiling height at center and a room roughly 10-12 feet in width. For amount of space being gained, this is a fairly costly design solution. #3 Increase sidewall height and use scissor trusses to allow for a central mezzanine supported by columns. While likely to be your least expensive design solution, you will be faced with columns below (unless opting to again add in floor trusses.


DEAR POLE BARN GURU: What is the most cost efficient size to build (Can I save money by buying a specific width/ length/ height?) What are the pros and cons of choosing metal frame or post frame? Is it still true that you can add square footage more affordably by building up (adding a second floor)? Can you put a basement under a Barn House? ANNIE in FORT LUPTON

DEAR ANNIE: As you get closest to square, your costs per square foot will decrease slightly. This is due to having less exterior wall surface, although it does not necessarily lend itself best to layout of rooms. For post frame construction, your most efficient use of materials typically comes from multiples of 12 feet in width and length. Work from inside out – do not try to fit your wants and needs within a pre-ordained box just because someone said using a “standard” size might be cheaper. Differences in dimensions from “standard” are pennies per square foot, not dollars. Post frame will always be your most cost effective structural design solution: https://hansenpolebuildings.com/2022/01/why-your-new-barndominium-should-be-post-frame/ Two story is not necessarily your least expensive design solution: https://www.hansenpolebuildings.com/2020/02/barndominium-one-story-or-two/ And yes, fully engineered post frame buildings can include a full, partial or walk-out basement: https://www.hansenpolebuildings.com/2020/02/barndominium-on-a-daylight-basement/


DEAR POLE BARN GURU: At what point do the post size change from 6×6 to 8×8, thanks. JEFF in SOUTH HAVEN

Roof Only Riding ArenaDEAR JEFF: If erecting a roof only “pavilion” style post frame building, column dimensions are often dictated by L/d ratio as there is no wind load on totally open sidewalls. “L” is unsupported length of column (grade or top of concrete slab to bottom of truss connection), divided by least dimension of column. Playing a part in this is a factor known as Ke. Ke is determined by fixity of columns. On a roof only structure, columns act as cantilevers (think of a diving board), so Ke = 2.1. Looking at your 5-1/2″ square 6×6, 5.5″ x 50 / 2.1 = 130.95″ (or just under 10’11”). This means at an unsupported length of 11 feet, a 6×6 would fail. Obviously, truss span, spacing, and loads from dead, wind and any snow must be properly factored into equations to be verified by your building’s engineer. Adding an eave sidewall (or sidewalls) with open endwalls will cause bending forces to fail most 6×6 columns at lesser heights.

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.

Spray Foam, Up Instead of Out, and a B-Ball Court

Mike answers questions about spray foam releasing agents, Going up instead of out, and a Post Frame Basketball Court.

DEAR POLE BARN GURU: Thank you for this blog of informative words on the world of post frame construction. I am a confirmed fan of spray foam insulation. What are your thoughts on the use of a release agent when applying spray foam directly to metal, be it sidewalls and a conditioned attic? CHUCK in MERINO

DEAR CHUCK: Thank you for your kind words. I’ve become a closed cell spray foam convert over the past few years. I am seeing more and more practical applications for it as folks become more energy conscious about their post frame buildings.

Spray foam release agents are a blend of specialized parting agents, specifically designed to prevent polyurethane foam insulation from adhering to most surfaces where the product is applied.

I am far from an expert on spray foam, so I’ll have to go with the common sense answer of I want the closed cell insulation to stick. I suppose it might work on sidewalls, with the idea of perhaps wanting to replace a damaged steel panel someday – provided the insulation remained rigid enough between the wall girts to stay in place. Below roof steel, I would have some concerns about the force of gravity causing it to drop off the roof. It could also lead to a gap where moisture could collect (especially if a roof leak occurs).


DEAR POLE BARN GURU: Curiously. I’m wanting to build post frame. I know the rule of thumb is if you have the space to build bigger on the ground before going up, but my lot is limited to only 1/4 of an acre, and strict building codes only allow so much square footage to be taken up but doesn’t go against additional levels only ground floors and basements.  So my question is: Will post frame structure support a second level, and also attic trusses for a future room later down the road? Can I even buy a kit like this? JESSE in LEESBURG

DEAR JESSE: It is always most affordable to build the largest footprint one can, on a single level. It also is most practical in terms of accessibility. Even for those who are not mobility challenged, going up and down stairs gets to be old far before we are!

You can have a post frame building designed to support both a second floor and even a third if so desired. And attic bonus trusses can be incorporated into the design. Make sure to be talking with your local Planning Department, as they often have rules which may restrict heights. The building height can also affect setbacks from property lines and other structures as well.

DEAR POLE BARN GURU: We are considering a pole barn construction for a community recreation center which would include a basketball court. We want to have second story six foot wide walking track around the interior of the building. Do you have thoughts regarding the difficulty of doing the track? BILL in ALBION

DEAR BILL: Post frame construction is most certainly the way to go for basketball courts (read more here: https://www.hansenpolebuildings.com/2017/04/indoor-basketball-courts/). Having a mezzanine walking track is most certainly doable by utilization of prefabricated metal connector plated truss frames which could be connected to the sidewall columns and cantilever over the court area below. Joists can them be placed between the frames, with ¾” thick OSB or plywood on top, then your choice of floor coverings (rubberized floor matting might be an idea).

The design should incorporate some fairly significant deflection limitations, so as not to feel bouncy to those who are utilizing the space.

The track should also be placed fairly high on the walls, so the thickness of the frames does not interfere with activities below.