Tag Archives: osb sheathing

Consideration for Future Building Length Additions

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

Nope.

Long time reader ROB in ANNAPOLIS writes:

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

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

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

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

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

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

The Ultimate Post Frame Building Experience

Hansen Pole Buildings is on a mission to provide “The Ultimate Post Frame Building Experience™”. (Read about “The Ultimate Post Frame Building Experience™” here: https://www.hansenpolebuildings.com/2016/06/ultimate-post-frame-experience/) In doing so, we often make what I will refer to as ‘tweaks’ to make not only our clients’ experiences better, but also their new post frame buildings better.

About Hansen BuildingsWe look for trends in questions asked by owners of existing pole barns – usually not even those we provided! There are a couple of these our team has decided to address and we have so far done a very poor job of letting our clients know we have done so.

Lesser of these items are folks who decide, for whatever reason, they would like to add either plywood or OSB between their new post frame building’s roof purlins and roof steel (https://www.hansenpolebuildings.com/2017/03/osb-steel-roofing-pole-buildings/).

Near universally pole barn builders and kit suppliers (as well as most truss manufacturers) have designed trusses with barely enough load capacity to meet minimums. In most instances, actual weight of materials (dead load) of roof truss top chords is around 2.5 psf (pounds per square foot). This is enough to account for truss weight, roof purlins, some sort of reflective radiant barrier or other minimal condensation control, as well as light gauge steel roofing. We have been using 3.3 psf just to give a little extra cushion (roughly 1/3rd more capacity).

½-inch plywood and 7/16-inch OSB both weigh 46 to 48 pounds per four foot by eight foot sheet or 1.5 psf. In order to account for possibilities of someone wanting to add one of these sheathings during building assembly, Hansen Pole Buildings has opted to increase our design top chord dead load to five psf for clearspan trusses up to and including 40 feet. This is DOUBLE minimum requirements.

Tomorrow, I will share with you a solution to an all too frequent challenge.

Stay tuned……

Do Screws Back Out of Steel Roofing?

I had a question posed of me recently which included: “Where will the water go when the screws back out of my steel roofing”? While I answered the question at hand, I didn’t actually get into the why this might happen, or the solutions.

How to avoid the potential problem completely……use the right part, properly installed and driven into the correct material. Three easy steps, should not be so difficult.

The part – most commonly used screws are a #9 diameter by one inch long. When we tested steel roofing to determine sheer strength these screws pulled out of the framing under a minimal load (so minimal the steel didn’t even have ripples in it from the applied load). You can read more about our testing here: https://www.hansenpolebuildings.com/2012/08/this-is-a-test-steel-strength/.

Going to a longer part solved the pull out issues in our testing. We also went to a larger diameter part in our testing, the shank below the screw heading being ¼ inch across, while the threads are a #12. The larger diameter screws also have deeper threads, which means they bite and grip the wood more tightly.

Proper installation – screws which are over or under driven, or driven at an angle are prone to a myriad of problems, all which end in leaks.  Over driven screws tend to damage the wood fibers, leaving little solid material to hold the screw. Use a screw gun with a clutch, so screws do not get over driven.

Driving into the right material– what could go wrong? I see folks using OSB or plywood sheathing under roof steel with the idea they can drive the screws into the sheeting and still hold, even when the screw tip misses a purlin. These screws will come back out.

Green lumber (or dried lumber which has been allowed to get wet) will cause screws to be loose as the moisture leaves the lumber once the building is dried inside. Of course green lumber has a myriad of other challenges which can be read about here: https://www.hansenpolebuildings.com/2011/09/499green-lumber-vs-dry-lumber/.

Right part, right screw, right material below – drop the mic and walk off the stage. Three easy steps for proper screw installation and keeping leaks from happening. 

 

The Look of Steel Siding

My Wife Does Not Like the Look of Steel Siding

DEAR POLE BARN GURU: I hope I’m not taking up too much of your time with this question. BTW, I’m copying Doug (Hansen Pole Buildings Designer) as we’ve briefly discussed this question.

My wife does not like the look of steel siding.  However, I’m pretty sure it’s the vertical siding that is her real issue.. i.e I agree with you that the type of material is probably not the problem. I think steel siding with a lapped siding look (Alside Satinwood for example) would be acceptable to her but I’m just not clear if such a thing is available for post frame buildings? One of your blog posts discusses horizontal steel siding but I’m not sure if it’s applicable to a post frame structure unless the panels are in multiple 2′ widths in order for the edges to line up with the girts? So, I basically have 2 questions:

1) Does Hansen have a steel, simulated lapped siding option for your kits?
2) If not but a steel siding manufacturer provided horizontal lapped siding look panels in 2′ or 4′ widths, would that siding be structurally sufficient for the wind shear loads or would the structure still require the plywood / OSB sheathing? and if the OSB is required, are we back to needing vertical stringers to attach the siding or could the siding be attached directly to the OSB?

Again, sorry to be a pain but since our property should be ready within the next 2 months, the siding issue is the only real question I have before ordering my kit.

Thanks LONNIE in COLORADO SPRINGS

DEAR LONNIE: Our goal is to deliver the Ultimate Post Frame Building Experience – as such we prefer clients who ask lots of questions, as they end up getting buildings they are extremely happy with.

In the article you reference (https://www.hansenpolebuildings.com/2015/10/horizontal-steel-siding/), the siding being used is typical post frame building steel siding, just run horizontally. This entails having to add vertical blocking between the wall girts to attach the steel. There are some benefits to this as opposed to other horizontal sidings. It is structural, so does not have to be applied over OSB or plywood. It is going to be strong – with an 80,000 psi minimum yield point, it is pretty tough stuff – less likely to dent. With the large quantity of ribs (high ribs every nine inches with two low profile ribs between each high rib) it tends to not show waves and ripples nearly as much as other products. And – it can be ordered in relatively long lengths, which minimizes the number of splices.

We can provide a steel, lapped siding (such as Alside Satinwood®  https://www.alside.com/products/siding/steel-siding/solid-color-horizontal-siding/satinwood-select/) however keep in mind, some of the same expansion/contraction issues as with other lap sidings are likely to occur – you are probably going to see some waves. These panels are not structural, so will need to be applied over either 7/16″ OSB or 15/32″ plywood. And, although most manufacturers say you can attach the siding directly to the substrate, I personally would not do it. I’d want to have verticals no more than every two feet to attach the siding. I have read recently where installers have screwed the siding to OSB, but have no personal experience with how it performs over time.

OSB versus Plywood

Plywood or OSB; OSB or Plywood?

Oriented strand board (OSB) long ago became the market leader, in relationship to plywood. As much as 75% of all sheathing is now OSB, thanks mostly to cost conscious buyers.

OSB vs. PlywoodOSB versus Plywood Prices

Prices for commodities like structural panels are notoriously volatile, and plywood can often be nearly double the price of comparable OSB sheathing. This can result in a savings of hundreds, if not thousands of dollars on an average OSB sheathed post frame building.

OSB versus Plywood Structural Differences

APA – The Engineered Wood Association (the main trade group representing panel manufacturers) says there is no real difference between the two panels. The structural characteristics are equivalent, and they can be used interchangeably. Both are rated Exposure 1 for temporary vulnerability to the weather; they have equivalent nail withdrawal resistance; and they’re installed using the same methods and construction details. However, there are differences.

OSB has more going for it than just cost. “Green” folks appreciate it can be made from small, fast growing trees, many of which come from tree farms rather than forests. OSB boasts a more consistent density. While a sheet of plywood might be 5 to 7 plies thick, a sheet of OSB is made from as many as 50 strand layers packed and compressed into the same thickness. There’s no equivalent of the weak spots which can be left in plywood when knotholes in adjacent plies overlap.

OSB versus Plywood Moisture Reaction

The biggest difference between the two panels is how they react when exposed to large amounts of moisture over extended time periods. With the exception of projects in very arid regions, sheathing and flooring panels are routinely covered with rain, snow, and ice during construction delays. This is where plywood has the edge.

When plywood gets wet, it tends to swell consistently across the sheet, and then returns to its normal dimensions as it dries out. It dries out relatively quickly, and the swelling is usually not enough to affect floor or roof finishes.

OSB takes longer to get wet than plywood but also takes longer to dry out. When used as roof sheathing, this tendency to hold moisture means it can degrade faster than plywood when exposed to chronic leaks.

When OSB does get wet it also tends to swell along the edges, and those edges stay swollen even after the material has dried out. Swollen edges have been known to telegraph visible ridges called “ghost lines” through asphalt roof shingles (just another reason to use steel roofing over purlins for pole barns).

Manufacturers insist OSB’s moisture problems have been corrected, thanks to the development of water-resistant edge seals. But of course that edge seal is lost when panels get cut on site, as they often do.

Screw Adherence in OSB versus Plywood

For post frame applications where screws will be placed into sheathing only (rather than into roof purlins or wall girts), steel roofing manufacturers specify the use of plywood, rather than OSB, as screws have a greater propensity to pull out of OSB under a wind load.

There you are…it’s 27 of one and 14 of another, but when it comes down to it…you need to weigh the pros and cons of how the osb/plywood will be used to make a conscientious choice.