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Re-roofing a 1960’s Pole Barn

Re-roofing a 1960’s Pole Barn

Reader JEFF in GRESHAM writes:

“I have an older (built in the 60’s?) pole building that needs a new roof. It is a typical metal over 2×6 purlins (Purlins 2′ on center, trusses 12′ apart). Current roof is corrugated metal attached with ring shank nails with rubber washers and it leaks (unsurprisingly). The roof had a spray on coating 15 years ago which helps, but again, it leaks and it needs a new roof. I would like to do standing seam roof but since the roof needs to act as a shear diaphragm If I tear off the old metal, I need to sheet the whole thing so those are two substantial projects in their own right (#1 tearing off and then #2 re-sheeting…) . I tried taking a pry bar to find out the difficulty of removing the old nails and it was stuck so securely I ripped the head off the nail rather than nail of the roofing and I estimate there are about 6000 of them! Thinking about it and doing some research, I think it’s possible to go over the existing corrugated roofing with standing seam using wood strips over the corrugated. I’m still concerned about things like condensation occurring if I do that and not sure if it would be unlikely, infrequent, or maybe much worse than what I see now. Obviously frequent and substantial condensation is just going to lead to rot and problems. I’ve looked at the added weight and its about 1.4 lbs per square foot using 24Ga standing seam = pretty trivial compared to snow loads so I think it’s unlikely to be an issue. I’m interested in knowing what advice, experience, and tips the Pole Barn Guru can offer for this situation. Please see attached .pdf for a visual of the scenario at hand. Thanks!?”

Yes, those old nails are tough to remove. Most standing seam steel is not stiff enough to span between purlins, so it is nearly always recommended to install over solid sheathing. Even if it will carry this span, it is likely to droop between purlins and if stepped upon, by accident, between purlins expect it to buckle.

Next challenge – those roof trusses are probably not designed to carry more than bare minimum loads. You want to add as little weight as possible. It might behoove you to have them inspected by a Registered Professional Engineer to insure they will be structurally adequate to handle any added weight.

Assuming trusses are structurally adequate, I would pull out every nail I could and, for ones where heads break off, once old roofing is removed, pound them in. Sheet roof with 19/32″ CDX plywood, install 26 gauge standing seam over a synthetic underlayment. There is no real reason to go to 24 gauge, other than a salesperson’s commission. Make sure to vent ridge and have adequate air intakes and condensation should then be a non-issue.

This entry was posted in Barndominium, Pole Barn Design, Roofing Materials, Trusses, Rebuilding Structures, Budget, Professional Engineer and tagged , , , , on by .

Easier to Ask Permission, Than Beg for Forgiveness

Easier to Ask Permission, Than Beg for Forgiveness

Our actual client writes:

“I need you to please help me. I need a letter from engineering that states that the ceiling can withstand tongue and groove plywood being hung on it. We decided to keep part of the ceiling vaulted and open and are going to do blue pine tongue and groove wood there. The county is fine with it. As long as they have a letter from engineering that stated the ceiling will be ok with it (insulating with spray insulation under the tongue and groove).”

Had client expressed this desire initially, it could easily (and likely less costly than what they did order) have been engineered.

Here is my response:

Your building is designed, as ordered by you, with ceiling loaded trusses, designed for a 10 psf (pounds per square foot) dead load, including ceiling joists 24″ on center. This is reflected in your engineer sealed structural building plans.

This provides for load carrying capabilities and appropriate framing across your roof truss bottom chords.

Your building’s roof truss top chords (and subsequently purlins between) are designed for a 3.3 psf dead load. This is adequate only to carry weight imposed by roof steel, roof purlins and truss itself.

Loads not used on one chord, cannot simply be transferred to another chord. From experience of designing trusses for nearly five decades, I can attest to this.

In order to have a finished ceiling, supported by roof purlins (with slope of roof), a truss repair would be required to support this additional top chord load. Repairs would be detailed by engineer who sealed your roof truss designs. This could result in one or more of several outcomes – including (but not limited to) plywood gussets being added to some or all truss faces where steel connector plates are currently placed, “scabs” (dimensional lumber) being added to face(s) of truss members, or even another truss being added to what currently exists.

Beyond this, deflection criteria dictate roof purlins must be “stiffer” when supporting materials other than just roof steel. This is typically solved by adding another purlin half-way between each existing roof purlin.

Without ceiling joists installed between truss bottom chords, additional bracing will be required in order to properly brace trusses.

Some of these alterations may prove difficult to achieve in an ‘as built’ situation.

This story has a moral – similar to measure twice, cut once….think it through twice in advance, build it right once.

This entry was posted in Constructing a Pole Building, Pole Barn Planning, Pole Barn Structure, Trusses, Building Interior, Professional Engineer, Lumber, Pole Barn Questions, Pole Barn Design, Barndominium and tagged , , , , , on by .

Materials for Girts, a Raised Floor, Truss Loads

This week the Pole Barn Guru answers reader questions about girt material choices for a 60’x120′ shed, Mike’s thoughts on a raised floor to compensate for a 7% grade change, and if some 4′ oc trusses can handle the load of a heater.

DEAR POLE BARN GURU: I plan on putting up a 60′ x 120′ post frame shed. I’m going to run my 6×6 posts at 8′ o.c. can I use all 8′ 2×6 material for the girts or should I have some 16′ material staggered in with the 8′ material? Will that increase the strength or do you think it would be similar? Thanks guru! JASON in NEW HOLSTEIN

DEAR JASON: Depending upon eave height, design snow and wind loads and wind exposure 6×6 may be inadequate to carry imposed loads. Using 16′ external girt material will be slightly stiffer against wind loads perpendicular to girt and will deflect slightly less. They will not impact overall building strength. Depending upon spacing, grade and species of 2×6, and again design wind speed and wind exposure, they may also prove to be inadequate.

Personally, I would look at using glu-laminated columns every 12′, double trusses directly aligned with columns and 2×6 bookshelf style wall girts. This will result in fewer holes to dig and fewer pieces to have to handle and install. It also allows for wider sidewall door openings, without requiring large headers.

 

DEAR POLE BARN GURU: I’m building a home on land that is at a 7% grade from top to bottom. I was thinking about doing a raised floor/crawlspace with the back aligned closer to grade and the front more elevated. What are your thoughts on this idea, and elevated floor pole buildings generally? I assume you would support the floor with piers instead of spanning entirely? Thanks! MATTHEW in HOUSTON

DEAR MATTHEW: Having built for myself an elevated floor post frame building (I had 14 feet of grade change in 24 feet), I feel as though they are a great solution. Unless you had enough grade change to practically utilize space below, I would use interior columns to reduce spans of beams and joists – little, short columns being far less expensive than large multiple ply beams and large dimension floor joists. My knees also prefer to live on wood, rather than concrete – making this a double win.

 

DEAR POLE BARN GURU: Hot Dawg™ heater…..just built a 40×30 pole barn. 4/12 roof, trusses are 4′ apart, wanting to hang a 80kbtu heater from trusses, with steel channels being suspended from two trusses. Will trusses handle the weight? Thank you. SHARKBITE

DEAR SHARKBITE: In order to determine if your trusses can handle weight of this unit, you would need to look at your engineer sealed roof truss drawings. If Bottom Chord Dead Load (often shown as BCDL) is less than five (5) psf (pounds per square foot) then probably not. Ideally, reach out to whomever fabricated your trusses. Give them weight of your unit, where you propose to hang it, as well as if you have a ceiling and insulation and they can give you a definitive thumbs up or down.

This entry was posted in Lumber, Pole Barn Questions, Pole Barn Design, Constructing a Pole Building, Pole Barn Planning, Trusses, Professional Engineer, Lofts, Pole Barn Heating and tagged , , , , , , , on by .

Roof Trusses 4′ o.c., Condensation Issues, and a Sliding Door

This Monday the Pole Barn Guru answers questions about roof trusses at 4′ o.c., ways to solve condensation issues, and sliding door options.

DEAR POLE BARN GURU: My question is I just purchased some roof trusses that are 32 feet long heel to heel they are constructed with 2 by 4s can I put these on 4 foot centers? Thanks. CRAIG in BELVIDERE

DEAR CRAIG: You can if you want your building to collapse in a moderate snow event. Along with your trusses, you should have received an engineer sealed truss drawing with all specifics as to what can be carried by it and spacing. If you did not, and they are prefabricated metal connector plated wood trusses, there should be a manufacturer’s stamp somewhere on truss bottom chords. You could then contact them and give them truss specifics (and probably a few photos showing lumber grades, web configuration and steel connector plate sizes. From this, they may be able to determine what you have actually spent your hard earned money on.

If you are unable to determine where they came from, another alternative would be to take their information to a Registered Professional Engineer with roof truss experience. For a few hundred dollars, you may be able to get an opinion as to their strength.

 

DEAR POLE BARN GURU: Hello, I have a 30x46x16 all steel pole barn that I am having condensation problems with. My question is what is the best thing I can install or do to help the problem? I have been told by others to install a ventilation exhaust fan controlled by an thermostat. I do have electricity in barn. I also have a wind turbine I haven’t installed yet too? Should I put both of these items in or one of them? And if so, do you guys install these items? Please help, its rusting all my tools and growing mildew in my RV!! Thanks ALYSSA in LEWIS CENTER

DEAR ALYSSA: You have found a challenge (one of many actually) Quonset steel building providers never seem to mention – condensation (read about other Quonset issues here: https://www.hansenpolebuildings.com/2011/07/quonset-huts/).

The two best things you can do are to seal your concrete floor (https://www.hansenpolebuildings.com/2019/02/how-to-properly-apply-post-frame-concrete-sealant/) and have two or more inches of closed cell spray foam insulation applied to the inside of your steel building shell. An exhaust fan might help, provided it can adequately move enough air (need to move between 3000 and 4000 CFM – cubic feet per minute) and it will require an air inlet of similar dimensions. We are not contractors, so we won’t be able to assist you with any installations.

 

Figure 27-5

DEAR POLE BARN GURU: Hi. Not really looking for a whole building. What I am looking for is an exterior sliding door to install onto a shop wall. The Shop is a timber frame unit. The opening is roughly 6 feet wide by 7 – 7.5 feet tall. I have not yet taken exact measurements. I will as soon as I can find a vendor within my price range.

I was very intrigued by your video presentation describing the “nail on” round track system. Also, this shop is in an odd location. It is a basement shop under my house, the house is built on a slope, so the wall I want to put the door onto is at ground level, but the opposite wall is fully underground. Since it is an exterior door to my basement any info on weather sealing for the cold Vt. Winters would be greatly appreciated. ANDREW in WESTMINSTER

DEAR ANDREW: Whilst I can appreciate you thinking a sliding “barn style” door might be a solution, I am doubtful as to it truly being a viable design solution. At best a sliding door will be a challenge to insulate beyond a bare minimal R value. A bigger concern is you are not going to achieve a tight air seal.

A design solution I can recommend (although it may stretch your budget) would be to go with an insulated commercial steel double entry door (six feet wide) in steel jambs. These doors will afford a secure access to your shop, are insulated and can seal air tight.

Although we typically only provide doors with our complete third-party engineered post frame building kit packages, you can message Materials@HansenPoleBuildings.com for a delivered price.

 

This entry was posted in Pole Barn Questions, Trusses, Ventilation, Concrete, Sliding Doors and tagged , , , , , on by .

Alternative Siding, Building on Slab, and Ceiling Liner Loading

Today’s Pole Barn Guru answers questions about alternative siding and roofing, whether one can build on an existing slab, and if a ceiling liner can hold insulation.

DEAR POLE BARN GURU: Can you build me a steel wall inside and vinyl siding on the outside with asphalt shingles? PAUL in BLUE GRASS

DEAR PAUL: A beauty of post-frame construction is we can design for virtually any combination of roofing and siding materials you may desire. While I am not a huge fan of steel liner panels, yes – your building can have them along with your vinyl siding. Steel liner panels end up posing challenges with trying to attach things to them, like work benches, cabinets, shelves, etc. Gypsum wallboard (sheet rock) is generally far more affordable as well as easier to make attachments to. And, if 5/8” Type X is used, affords some fire protection.

 

DEAR POLE BARN GURU: Can Hansen build the barn on top of an existing slab? CLYDE in BELLVILLE

DEAR CLYDE: Yes, we can design a complete post frame building kit package to be attached to your existing concrete slab. https://www.hansenpolebuildings.com/2014/12/dry-set-column-anchors/

 

DEAR POLE BARN GURU: My trusses are 8 feet on center will the metal ceiling liner span that 8 feet without sagging if I blow in fiberglass insulation? RODNEY in LAKE ELMO

DEAR RODNEY: No, steel liner panels will sag across an eight foot span. If your building’s roof trusses are not designed to support weight of a ceiling load, then they will sag as well – and, in combination with a snow load, may fail.

 

 

 

This entry was posted in Pole Barn Design, Roofing Materials, Pole Building Siding, Trusses, Insulation, Pole Barn Questions and tagged , , , , , , on by .

Condensation Solutions, A Ceiling the Right Way, and Timing

Advice about condensation, ceilings done right, and the timing of questions

DEAR POLE BARN GURU: My deck roof is metal panels on 2×4 purlins, rafters are 2×6, like a pole barn. I am enclosing it, and need to stop the condensation. I spray foamed it with closed cell, but there is some condensation on the foam in a few places. It will be covered with drywall. Would a 6 mil plastic vapor barrier on the conditioned side work? MICHAEL in FRAZIER’S BOTTOM

DEAR MICHAEL: Provided you are able to reduce the moisture content within the building so as no vapor is being trapped between the vapor barrier and the foam, it should take care of the problem. In all reality, as long as you have no holes in the gypsum drywall, once it is painted you should have eliminated the problem of condensation against the insulation.

Now getting to the real problem – you have too much moisture in your building. If you did not place a well sealed vapor barrier under your concrete slab floor, you need to seal it. Walls also need a vapor barrier (without holes) on the conditioned side to prevent moisture from passing through.

 

DEAR POLE BARN GURU: I have a 40 x 80 pole barn with 8 foot truss spacing. I will be installing faced rolled insulation between each truss. What is the recommended ceiling product to install on the inside? Wood, metal, that will be lightweight and easy to install?? Thanks JEFF in SYCAMORE

DEAR JEFF: I see problems in your future….

Installing a ceilingFaced insulation is the absolute wrong product to use for insulating your ceiling. Any insulation placed at the truss bottom chord level should be unfaced. The best bet would be to blow insulation in above the finished ceiling.

In any case, you must adequately vent the attic space.

Now, on to the ceiling.

 

I am hopeful you have trusses designed with a minimum of a five psf (pounds per square foot) ceiling load, with 10 psf being even better. Confirm with your RDP (Registered Design Professional – architect or engineer) who designed your building, however 2×4 #2 ceiling joists at 24 inches on center between the bottom chords with joist hangers should adequately support a ceiling.

My choice of ceiling product?

5/8” Type X gypsum wallboard. It is affordable, weighs under three psf and provides fire resistance.

 

DEAR POLE BARN GURU: I’m putting up a building with a 3/12 pitch single sloped roof. radiant reflective polyethylene, vapor barrier insulation between the purlins and the metal roof sheathing. Probably rock wool batts under the 1-3″ draped barrier. Do you think the roof has to be vented, and how would this work? CHRIS in BROOKLINE

DEAR CHRIS: Yes, it would need to be vented and it is my feeling you are going about this entirely in the wrong direction. Your question is well timed, as I have just written an article on how to properly insulate between purlins, which will be posted soon. The basic gist is your best solution is to use closed cell spray foam applied directly to the underside of the roof steel.

 

This entry was posted in Pole Barn Planning, Trusses, Ventilation, Insulation and tagged , , , , , on by .

Ceiling Loads

Ceiling Loads

Considering a new pole building? An important question to ask is, “What will the cost be to upgrade the roof trusses to support the weight of a ceiling”?

Most post frame (pole) building trusses are not designed to support the dead weight (things which are permanently attached to the building) of anything other than the trusses themselves, required bracing and minimal wiring and lighting. In most cases, the necessary load carrying capacity on the bottom chord of the trusses is one psf (pounds per square foot).

Installing a ceilingBut – isn’t a ceiling fairly light? It will depend upon what the ceiling is going to be constructed of.

In the case of probably the lightest assembly – steel liner panels, the weight of the liner needs to be accounted for. A cubic foot of steel weighs 489.024 pounds. The thinnest 29 gauge steel measures .0142” thick. If the panels were totally flat, they would then weigh 0.58 psf (pounds per square foot). But liner panels are roll formed, with a 36 inch net coverage coming out of a coil which is typically about 40 inches in width. Figure a minimum thickness 29 gauge panel at about 0.65 psf.

Unless trusses are very close together (say four foot spacing or less), framing will need to be added to support the steel. Dry (19% maximum moisture content) 2×4 Hem-Fir weighs 0.98 plf (pounds per lineal foot), 2×6 1.54 plf. In case a heavier species or damp lumber is used, it is generally accepted to use 0.37 psf for 2×4, or 0.57 psf for 2×6 spaced every four feet.

Insulation is fairly light, but still must be accounted for. Fiberglass adds 0.04 psf per inch of thickness, cellulose 0.14 psf per inch.

This gives the weight added for a steel ceiling with 16 inches of cellulose blown in above at 3.26 psf (1.66 psf for fiberglass).

With the assumption fiberglass insulation will be blown in, I would normally recommend the bottom chord loading be increased to three psf for a 29 gauge steel liner.

How about other materials?

5/8” thick gypsum drywall weighs 2.2 psf, 7/16” osb (oriented strand board) 1.47 psf. Both will often require 2×6 supports every two feet for 1.14 psf. To handle 16 inches of fiberglass insulation, add four psf.

But what if the trusses were NOT designed to support ceiling loads?

Trusses engineered to support ceiling loads are going to be more expensive than those which do not. Depending upon the span of the truss and the applicable snow loads, the cost could be minimal, to very expensive.

With trusses of large spans, it may prove impossible or impractical to upgrade them to support the added ceiling loads.

Repairs (when they can be done) typically include doing one or more of the following:

  1. adding scabs along some or all of the top and bottom chords. Scabs typically are going to be equal to or larger in size, as well as grade of the original truss material. As truss chords are often high grade materials (msr, mel, #1 or Select Structural), it is rarely lumber which can be purchased from anyone except a truss manufacturer.
  2. Adding internal web members is rarely a “fix”. The same goes with flat steel plates.  If the steel connector plates are inadequately sized for the larger loads, structurally rated plywood (usually 5/8″ or 3/4″) “plates” can be added, usually by both glue (not the “off the shelf” construction adhesive) and nailing in a prescribed pattern.

Any truss repair (such as increasing load carrying capacity) should always be designed by a registered design professional (an engineer), and a sealed drawing provided by the engineer.

It is always easier, and less expensive, to pay for the ceiling load to begin with.

This entry was posted in Trusses and tagged , , , , on by .

Truss Repair? Don’t Skip this Step

A client writes:

“I recently purchased one of your pole barn kits to use as my home garage.  We have begun construction and have all the framing and the roof on.  I recently contacted my building designer about potentially getting the metal lining material for the ceiling and walls.  My designer told me that I can’t put a ceiling in because my trusses weren’t designed to handle the extra 5lbs per sq ft required.  This has got me a little confused and puts me in a bit of a jam.  If I can’t insulate and install a ceiling in my garage it doesn’t do me any good.  I’m just curious if this information is correct and if so what are my options at this point to ensure I can finish the ceiling of my garage??”

Typically pole building trusses are NOT designed (by any provider or contractor) to support a ceiling load. The price to upgrade to ceiling loaded trusses is generally offered as an option on our quotes, and is typically fairly inexpensive. All too often, it is a case of a client trying to shave a few dollars and ends up being a case of “penny wise, pound foolish”. We do make every concerted effort to prevent truss repair issues, such as this client is now confronted with, from occurring.

It is important enough so as we specifically mention it in the terms and conditions of every purchase:

“Dead loads specified on engineered roof truss drawings include the weight of the roof truss. Roof trusses are NOT designed to support ANY hanging loads or ceiling loads other than those specified as special truss loads in the Agreement. In the case of design roof truss bottom chord loads of less than five (5) psf (pounds per square foot) the bottom chord dead load may be sufficient only to cover the truss weight itself and may not allow for any additional load to be added to the bottom chord.”

In many cases it may be possible for an engineered truss repair to be made, to upgrade the load carrying capacity of the bottom chord of the trusses to 5 psf. I’m sorry to say, this is not free. The truss company’s engineer will need to put his license on the line in designing a “fix” for trusses which were designed for a load other than is now intended.  It’s not the same as designing the original trusses.  If you think about it, redesigning and augmenting something you have built, is always more time consuming (and brain challenging!) than the first time around. His time and expertise are not without a charge.  It’s not usually “much”, like a couple hundred dollars.  Then there is our time, as changes like this are not included in the basic cost of your building kit.  Again, we don’t charge “much”, but our time is worth something as well. The cost of materials to fix it…one last cost if you are doing the truss repair yourself.  If not, a contractor’s charge must be added.  All totaled, it could run you anywhere from a couple hundred dollars to over a thousand or more, so you can see why we diligently try to get folks to “do it right the first time”.

When ordering a building from anyone, if there is a suspicion anyone might ever consider putting a ceiling in – it is always prudent to err on the side of caution, and spend the extra few dollars to include the load carrying ability in the original design. Truss repair is not my idea of “fun”.

This entry was posted in Pole Barn Planning, Trusses and tagged , , on by .
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