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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 Pole Barn Design, Barndominium, Constructing a Pole Building, Pole Barn Planning, Pole Barn Structure, Trusses, Building Interior, Professional Engineer, Lumber, Pole Barn Questions and tagged finished ceiling materials, truss dead loads, truss loads, ceiling materials, engineer sealed plans, ceiling load trusses on December 12, 2024 by Rick Ochs.

Ceilings: Steel Liner Panels

In many parts of the country, a popular ceiling is to use steel liner panels. Generally the liner panels are the same rib configuration as steel roofing and siding, the difference being the panels themselves generally have little or no warranty on either the paint, or the steel themselves. As the paint is not exposed to the elements, this is really of no concern. These liner panels usually have a minimal coating of galvanization under the paint, so protection against rusting is low. Due to both of these factors, the cost of the material is lower than siding and roofing panels which require more protection from weather and sunlight deterioration.

In many cases, the steel liner panels are screwed directly to widely spaced trusses, sometimes spanning eight to 12 feet. This results in the liner panels having a noticeable sag between the trusses, especially if insulation is blown in on top of the panels.

The common reasoning in using liner panels, as opposed to say… gypsum wallboard, is they are far lighter in weight, so the roof trusses do not need to carry as high of a load. Many people seem to feel the use of white painted liner panels, contributes to the building being brighter inside, when lights are turned on. Cost is also often mentioned as a factor, however properly installed liner panels, with framing close enough to minimize sagging, and drywalled systems are fairly close to the same price.

My own objection to steel liner panels is the noise factor. Drywall tends to absorb sound, where steel liner panels reflect it.

I also wondered if condensation on the underside of the panels could ever be a problem. Warm moist air inside the building rises, comes in contact with the ceiling liner panel steel (which will often be colder in fall, winter, spring than the inside the building) and condensation should occur. Having never owned a pole building with a steel liner, I couldn’t vouch for the actual situation personally.

Well, I got my answer today, from an online forum post:

“I think it depends on how tight your building is. My metal garage has two roll up doors and there is a gap at the top of them. In the winters, I had no problems with condensation on the metal ceiling until I sealed over the doors with OSB. I have insulation stuffed in all of the grooves on the inside at the edge of the metal roof. So, that made it pretty air tight. Now in the winters, when the roof has frost or snow on it, when the sun comes out, the metal ceiling will drip water on my car. I have to cover it with a plastic tarp to keep the water off of it.”

Personally, my idea of having things inside a building is to avoid having to break out the blue tarps! Considering a steel liner panel ceiling in a new pole building? I’d recommend thinking long and hard before you jump into this one.

This entry was posted in Steel Roofing & Siding and tagged ceiling materials, ceiling drywall, ceiling liner panels on August 15, 2013 by admin.

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).

But – 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:

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.
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 truss loads, ceiling loads dead, ceiling materials, Ceiling weight, truss repairs on March 29, 2013 by admin.