Tag Archives: weather resistant barriers

Steel Roofing and Siding Over Purlins

There is just plain a lot of bad (and scary) information floating around out there on the internet. For whatever reason, people will believe a random unqualified answer from a stranger, rather than going to a highly educated expert (e.g. Registered Professional Engineer).

Reader DYLAN in BEDFORD writes:

“I am building a 50×60 using 2×6 stud frame walls. Trusses 4’OC. The garage area (30×60) will have around 12’ceiling. The living area (20×60) will go back and stick build ceiling rafters 2’OC to make 8’ceilings. 12’ ceiling on the living area is just more to heat and cool – not necessary. My builder right now plans on putting 2×4 purlins and 2×4 girts on roof and side walls. Then wrap the whole thing with tyvek and out metal on. 

My question starts with is this ok? 

Should I consider plywood/osb on the roof or walls in lieu of 2×4 purlins/girts?

Are 4’oc trusses ok if I am going back to the living area and building ceilings 2’oc?

Are 2’oc rafters ok assuming I finish the ceiling with 5/8” drywall or wood tongue groove or similar?

I will probably spray foam insulation in the living area. This should help with noise during rain on the metal roof.”

Mike the Pole Barn Guru responds:

My recommendation would have been for you to erect a fully engineered post frame building, rather than spending tens of thousands of extra dollars in an attempt to make a stick framed house look like a pole building.

Ultimately how your building is assembled structurally should be up to whatever engineer you (or your builder) hire to provide your home’s engineered plans. Building Codes do not allow for stick framed walls taller than 11’7″ without engineering, so you should be there already.

Steel panels should not ever be screwed into OSB only and even plywood only would only be on roofs if you are using a standing seam (concealed fastener) steel. I (and most likely your engineer) will specify 2×4 or even 2×6 girts and/or purlins in order to provide a proper surface to screw steel panels to. Your trusses every four feet may be adequate in your living area, it will depend upon how your engineer designs structural attachment of your furred down ceiling, as well as weight supported by it. Rafters 24 inches on center will provide sufficient support for 5/8″ drywall.

You should not place Tyvek between roof framing and roof steel – as Weather Resistant Barriers (WRB) allow moisture to pass through. This could allow condensation to be trapped between your home’s WRB and roof steel, causing premature deterioration.

Stick Frame and Some Limitations

Stick Frame and Some Limitations


Perhaps stick built construction’s biggest advantage is builders and tradespeople are very comfortable working in and around stick framing. All registered architects and most building inspectors are very familiar with stick framing. The International Residential Code (IRC) provides a prescriptive ‘cook book’ to follow for adequate structural assembly, within certain limitations. These limitations include, but are not limited to, no story height of greater than 11 feet 7 inches (R301.3), no hurricane prone areas with a design wind speed of 130 mph or greater located south of Virginia, or 140 mph elsewhere (R301.2(5)B), and no ground snow loads over 70 psf (R301.2.3).

IRC802.10.2.1 further limits truss spans to a maximum of 36 feet and building lengths to 60 feet (measured perpendicular to truss span). Trussed roof slopes must be at least 3:12 and no greater than 12:12.

Wood is a very forgiving building material and, even when miscut, replacement material is usually only a short drive away. America’s home building industry has built traditional, wood stick framed homes, on site for decades.

Many builders, architects, carpenters and other subcontractors prefer to work on stick built homes as compared to alternative building systems.  Because traditionally framed houses are so popular, dimensional lumber and stick built framers are readily available.

Another advantage of stick built homes is they allow for a great level of design freedom.  You can design your barndominium with various ceiling heights, angles and curves, niches and other details. Stick framing one to achieve those unique details at a fairly affordable cost.

Despite its popularity, stick framing does have some drawbacks. Because stick built homes are assembled outside, over several weeks, framing lumber is subject to outside moisture.If lumber gets too wet, it can shrink and warp as it dries and cause cracks in the attached drywall.  This shrinking and warping can also make it difficult to properly insulate. To decrease  risks of potential moisture problems, ensure exteriors are covered with an appropriate and well-sealed Weather Resistant Barrier and lumber is properly dried before drywall and insulation are installed.

Another drawback of a stick built home is it usually takes several weeks to complete framing.  Total amount of time it will take will obviously depend on size and complexity of house plans and size, experience and availability of any particular framing crew.

A framing crew must precisely cut, assemble and erect barndominium framing components sometimes in adverse weather conditions.  Working around adverse weather conditions is another challenge with stick framing.

Although site-built, stick framed homes clearly dominate America’s housing market, there are several other ways to build a barndominium’s structure. These include post frame, PEMB (pre-engineered metal buildings), weld up steel and concrete.

A Real Life Climate Controlled Post Frame Wall

Reader BRANDON in WICHITA writes:

“Hello Mike!  I am in the engineering field and we are just about to put up a personal climate controlled post frame building.  I have followed many of the teachings of Dr. Lstiburek on wall and roof assemblies.  I also enjoy your very detailed write ups.  I am conflicted in our assembly a bit.  Most builders here install a thin (1/8″) foam product with Aluminum foil towards the outside to act as a vapor and radiant barrier between the metal sheathing and wood frame.  That seems well and good if no additional layers are added to the wall/roof assemblies.  However, many quickly learn about the false and ridiculous R value claims of these products and add more insulation later.  Usually glass batts.  This largely concerns me because there is always another air/vapor barrier faced on the batts that would be in the interior, which creates a double vapor barrier.  

Due to this, and realizing it is nearly impossible to totally eliminate ‘some’ condensate from forming on the underside of the sheathing, we were going to use Typar house wrap on the walls AND roof between the sheathing and purlins/girts.  The product has a perm rating of about 11.  What we are targeting is an ‘air’ barrier, that is liquid proof, but still has ‘some’ permeability since some vapor would eventually get in the cavity and we need a way for it to escape.  Our assembly would follow up this building wrap with unfaced glass batts to roof/walls, then covered with the same reinforced white facing they typically use that is a vapor/air barrier and has an aluminum facing towards the outside.  

One issue faced here is the big question about climate!  Our state, as with many, have both hot/humid summers AND cold dry winters.  

I am not an advocate of Typar but selected it due to it’s toughness during install, and very low perm rating.  Not to be confused with big box store ‘generic’ wraps which are just perforated plastic! 

I have a test piece sitting with water on it right now on a paper towel and after hours, it still has not penetrated the product.  Our intention with its use is to create an air barrier on the outside as all the metal seams and corrugations can create wind washing through the glass batts, and to shed water droplets.

Your thoughts would be greatly appreciated!  We have the columns currently up so a timely response would great!”

Thank you for being a loyal reader. Your views on usage of Radiant Reflective Barriers for wall applications are spot on. Other than if people are 100% certain they will never, ever add insulation to their walls (and who can be certain about future building users/owners?) it is just an incorrect product to be used. A good, well-sealed Weather Resistant Barrier would be appropriate to use, followed by filling your insulation cavity with unfaced batts. For interior face, there is really no benefit to going to the expense of an aluminum faced product. A well-sealed 6mil clear visqueen will do everything you need it to do.

For more information on this subject, please read my Ultimate Guide to Post Frame Building Insulation https://www.hansenpolebuildings.com/2019/11/post-frame-building-insulation/.

Barndominium: Building Kit or Building Shell?

Barndominium: Building Kit or Building Shell?

This was a recent post from a Barndominium discussion group I am a member of:

“Kit vs shell; I’m defining a kits as coming with everything like insulation and metal studs (the next step would be mechanical trades) whereas shell would be dried in with nothing. Kit companies would accept owner floorplans or have some stock floor plans and provide CAD to guide builders. Shells would perhaps provide instructions or rely on the knowledge of builders. Kits would have customer service and a modern web site; respond to emails and be familiar with barndominiums. Shells would be a business that sells barns and commercial buildings, expecting owners to know what they want. Kit metal and studs would be pre-cut in the factory. All window openings would be accounted for. Shells would be metal has to be cut on site. Shell would be all decisions are made before building begins via email; drawings back and forth. Shell would be last minutes decisions during building. Are these definitions even close to being accurate? If not what are the industry definitions? By my definition, I’m looking for a kit, not a shell. If kit is not the right word, what is the correct term? What are the top ten companies that provide what I call a kit? In this Barndo group, there are clearly differences in skill and knowledge levels. Recently on this site, a vendor posted a shell drawing and price. Some people posted questions that indicated they wanted to shop for what I call a kit; there was some misunderstanding, I think. It would be helpful to me, and perhaps others if these concepts were defined, I think. Please point out the fallacies in my thinking, if any, before I move from drawing floor plans into shopping for kits/shells.”

Mike the Pole Barn Guru’s response:

About Hansen BuildingsWe provide custom designed engineered post frame building kit packages. As we are wood framing, we provide no metal studs. We can supply Weather Resistant Barriers and Reflective Radiant Barriers as well as batt insulation. We typically provide only structural portions of buildings – exterior shell, any raised floors (for crawl spaces, second or third floors or lofts) but can provide interior wall framing, if desired. We can work from any client supplied floor plans, elevation drawings or sketches. We do not have ‘stock’ plans, as every client’s needs are different. We expect our clients to layout their own interior rooms, to best fit with those needs and lifestyle.

We provide complete 24″ x 36″ blueprints for permit and construction sealed by third-party engineers, with full calculations. All openings, including windows are located on plans. There should be no “last minute” decisions made whilst building.

Our comprehensive (nearly 500 page) construction manual is designed for an average literate person to successfully assemble their own beautiful building, without requiring a contractor. We provide unlimited free technical support. Clients have an online portal to track progress and deliveries, etc.

Steel roofed and sided buildings come with cut to length steel panels, however some cutting will be needed in the event of oddly located openings or width and lengths of buildings other than a multiple of three feet.

At the risk of sounding redundant (I’m a proud owner of a “shouse”) go back to yesterday’s blog to see a picture of my and my wife’s shouse or barndominium.

If a post frame building is on your radar, then we are going to be #1, call us today 1(866)200-9657.

How Can I Add interior Walls to a Post Frame Building?

DEAR POLE BARN GURU: How difficult is it to add interior walls to build rooms inside the pole barn. Are more materials needed to add interior rooms and do the exterior walls need extra support? PATRICIA in McMINNVILLE

DEAR PATRICIA: The beauty of post frame (pole barn) buildings is the great majority of them are designed to be clearspan – there are rarely interior columns to avoid, so non-structural interior walls can be placed anywhere!

Home OfficeThis was a great feature for my lovely bride and I, as we moved walls all around until we came up with the configuration which best met with our needs – after the building shell was completed.

There is a caveat – if the interior of your building is going to have gypsum drywall (aka sheetrock) it is important to have the structure designed to limit the deflection. Most post frame buildings are designed with only the deflection of steel siding in mind, which would cause many drywall joints to crack under wind or seismic events.

If properly designed (better make sure an engineer was involved in those original plans) then no materials should have to be added to the exterior framework in order to add interior walls. You will, of course, have to provide the materials for the interior walls themselves.

DEAR POLE BARN GURU: Can Hansen provide a kit that will work as a picnic shelter with no walls, just the poles and the roof with the triangle gable ends covered with siding? JOE in MISENHEIMER

DEAR JOE: Yes we can provide roof only buildings. In most cases, it is less expensive to cover one or both endwalls to the ground, rather than building just a pavilion style structure. Here is a link to a previous article where I expound upon why: https://www.hansenpolebuildings.com/2015/04/roof-only-pole-buildings/

DEAR POLE BARN GURU: I am doing a barn w apartment , the whole building will be conditioned space, I am looking for the best house wrap for my barn and new home?

I am wondering if insulated Tylek or insulated panels are worth it on outside since I’m framing w 2×6 and concrete lap siding? Thanks DANIEL in WOODBINE

DEAR DANIEL: Most Building Permit issuing jurisdictions are going to require a Weather Resistant Barrier underneath siding around a conditioned space, so there is probably not much of a choice. For the most part, concrete lap siding should be installed over a solid sheathing such as OSB (oriented strand board) or plywood to prevent waves in the material and to give the building adequate shear resistance. Here is the link to the first of a three part series of articles I wrote on Weather Resistant Barriers: https://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/.