The 7 Commandments of Roofing

If I were the Roofing God for a day, what would I change? Oh, where do I start? First of all, there would be none of this “you should,” “can,” “may” or “it is recommended” nomenclature. I would have commands: Thou shall do the following.

Freezer Buildings and Block Ice Insulation

Photos 1 and 2. When moist exterior air is pulled into the roof systems of freezer buildings, the moisture condenses and freezes. Here gaps in the insulation are filled with ice. On the interior there are icicles more than 10 feet long. The cause? Air intrusion at the roof edge under the membrane and wood blocking. Images: Hutchinson Design Group Ltd.

I have never opened up a roof over a freezer building that wasn’t solid ice between the insulation joints. How does this travesty occur? Ignorance? In part. Naiveté? Yes. Who is guilty? Whoever is the roof system designer. Most designers should know that there is an enormous moisture drive from the exterior to the interior. This drive is not a passive movement, but a huge, sucking pressure. It’s like there is a shop vac in the interior trying to pull in outside air. But designers fail to realize that the first sources of interior moisture intrusion into the roof system are moisture migrating out from exposed soil until the concrete slab is poured; moisture coming from the interior concrete floor slab; and latent air moisture (relative humidity) in the interior air before the freezer is operational.

We in the roofing industry are very good at keeping water out of the building. It’s the influx of air that is destroying these roofs shortly after bringing the freezer online. So how is the air getting in? Oh, let me count the ways: (1) though the unsealed membrane at the roof edge; (2) past beveled precast concrete joints at the roof edge; (3) below perimeter wood blocking at the roof edge; and (4) up through metal wall panel joints.

Photo 2.

Stopping air transport to the interior is key. Most designers believe that the roof membrane performs as the air/vapor barrier. In the field of the roof, perhaps, but their lack of knowledge about roof material characteristics and proper installation methods often leads designers astray. The perimeter becomes the weak link.

Let’s look at some common design mistakes:

1. In recent years, designers have revised roof membrane selection to reflective roof membranes, in part to garner a LEED point. The trouble is that these membranes are substantially ridged/stiff and can be difficult to turn over the roof edge, adhere and seal, so they are often barely turned over the edge and nailed off. The lack of a positive seal (that would be achieved by adhering the membrane to the perimeter wood blocking and wall) allows air to move up below the membrane.

2. When precast concrete panels are used at the walls, the joints are often beveled. What happens at the roof edge? The bevel extends right up to the perimeter wood of the coping that is straight and parallel to the outside wall face. The bevel becomes a gutter to channel wind up the wall to the underside of the gutter, gravel stop or coping. In a situation like the one outlined in No. 1 above, the wind can move in below the roof system.

3. When perimeter wood blocking is placed in a horizontal position at the roof edge, the underside of the wood blocking needs to be sealed. A non-curing, gun-grade butyl, applied in several rows, works well, such that when the blocking is secured to the wall, the underside of the blocking is sealed. Be aware of uneven substrates that will require additional sealant.

4. Metal wall panel joints are another potential problem spot. Ask a metal wall panel installer why they are only sealing one of the two exterior male–female joints and you are likely to hear, “because the exterior joint completes the vapor retarder” (which is on the exterior of the building when perfect). Technically they are correct. However, getting a perfect sealant joint to create a complete vapor retarder is not so easy. Think of how sealant is applied. The installer squeezes the caulk gun handle and the sealant oozes out in a thick bead, which can vary in thickness as the gun is drawn along. As the trigger is squeezed and the gun moves, the sealant bead decreases in diameter, and then the gun handle is squeezed again and a thick bead oozes out, and so on. At the end of the sealant application, the thinned-out bead is often not sufficient to properly seal the panels where they are engaged. Condensing water weeps out of the joints in the interior in cold storage areas and results in interior ice on freezer buildings. The sealant, whether factory applied or field applied, is not located at the exterior plane of the panel, but recessed in the outer tongue and groove joint, leaving the potential (almost a guarantee) that there will be a vertical “chimney” of about 1/16 of an inch that can channel air up under the membrane turned over the wall panel.

A quality vapor retarder (those of you thinking polyethylene, think again) placed on the roof deck will protect the thermal layers from vapor intrusion from the interior humidity, latent construction moisture, and ground moisture that accumulates before freezer draws down. It also prevents exterior air infiltration, which can result in interior “snow” and the huge icicle formations. (See Photos 1 and 2.)

Commandment #1: Thou shall place a vapor barrier at the roof deck on freezer/cold storage buildings and seal roof edge perimeters, drains and penetrations through the vapor retarder and all perimeter conditions to be airtight.

The Roof Drain Conspiracy

I am convinced that there is an international conspiracy to drive me nuts. It’s called the ‘how small can we cut out the membrane at the roof drain’ contest. (See Photo 3.)

Photo 3. Believe it or not, this is not even close to the winner of “who can cut the smallest hole in the roof membrane at the drain” contest. The membrane should be cut back to within 1/2 inch of the clamping ring to allow the drain to function as designed.

When I am called in as an expert on a building collapse, the first thing I tell the attorney is, “Save the roof drains and attached roof membrane!” Why, you ask? Because I want to see if the roofing contractor competed in the contest and if the installer and the consultant/architect will be party to the repair costs. Drains are designed to create a vortex to drain water most efficiently from the roof. (Watch how a toilet flushes to gain an understanding on how a drain works with the water swirling into the drainpipe.) The shape of the water flow from the roof surface to the drain bowl to the downspout is critical. When the hole cut in the membrane is too small, it can restrict drainage. Costs often drive projects, and it is not uncommon for a roof’s structural elements to be value engineered down to the bone. With intense rainfalls (you know, the 100-year rains that are occurring two or three times per year) and on larger roof areas where large outlet pipes are used, restricted water drainage can and has resulted in structural roof collapse.

So, I’m on a roof and observe the roofing crew cutting out a small hole at the drain. Being the conscientious consultant that I am, I ask, “Can you please cut out the membrane to within 1/2-inch of the clamping ring?” The answer is almost universal: “I’ll do it later.” Usually my blood pressure rises and face turns red as I explain the importance of making sure this detail is not overlooked.

Our details call out the proper way to cut out the membrane and our field observation reports call this out to be corrected, but I am forced to remind contractors again and again — sometimes even when it’s on the punch list. So, what’s a consultant to do? I reject the pay request.

Commandment #2: Call out on your roof drain details to cut back the membrane to within 1/2-inch of the clamping ring (a cloverleaf pattern around the bolts is best), and drive home the importance of this detail to the crew members in the field.

The 12-Inch Roof Curb

Photo 4. Roof insulation thicknesses now required by code make 12-inch roof curbs obsolete. Specify 18-inch curbs. Raising this curb with 16-gauge steel was very expensive. I suggested sending the bill to the engineer.

When energy was cheap, insulation was an inch or two in thickness, and the roof was built up, 12-inch-high roof curbs worked. With the new insulation requirements and tapered insulation, 12-inch curbs can be buried. Furthermore, future code mandates may increase insulation R-value, increasing insulation heights. So, consider this a public announcement to all mechanical engineers and curb manufacturers: Eliminate 12-inch curbs and specify curbs that are 18 inches or higher. (See Photo 4.)

Commandment #3: Specify only 18-inch and above roof curbs and rails.

Flapping in the Breeze

Photos 5 and 6. The membrane left unsealed at the roof perimeter has placed this roof in great jeopardy of wind damage. It is also allowing water to flow back into the insulation.

Driving around Chicago it’s not hard to see roof edges — gutters, gravel stop, and parapets — where the roof membrane is just flapping in the wind. (See Photos 5 and 6.) This is especially a concern when the roof system is mechanically attached and the air can move directly below the membrane. The roof typically is installed prior to the installation of the windows and doors, and while the building is open, airflow in the interior can create upward pressure on the roof system from below. This force, in association with the air getting below the membrane at the roof edge and with uplift above the membrane, drastically raises the risk of wind damage. Furthermore, when the membrane is not secured at the gutter roof edge, water draining off the roof will return back to the roof edge and move into the building and insulation.

Photo 6.

Wrap the membrane over the roof edge, adhere it in place and nail it off. This will save you during the installation and prevent air infiltration once the roof is complete. The designer should also delineate the area where the air barrier meets the roof vapor retarder and/or roof membrane and define who is responsible for what. Detail this explicitly.

Commandment #4: Roof membranes shall be extended down over the edge wood blocking a minimum of 1.5 inches onto the wall substrate, fully adhered and nailed off on the day it is installed. Where applicable, seal to the wall air barriers.

Holding Roof Drains Off the Roof Deck

Photo 7. Drains held up off the deck make re-roofing difficult when a vapor retarder is called for. I have seen roofs covered with 1.5 inches of water due to high drains, with the water just waiting to relieve itself to the interior at the first vapor retarder deficiency.

Nothing is more frustrating to a roofing contractor during a re-roof than removing the old roof to install a vapor retarder and finding that the roof drain has been held up off the roof deck. (See Photo 7.) This goes back to the design when the engineer and architect have no clue as to the use of proper sump pans and roof drains with extension rings — preferably threaded.

Commandment #5: Design, detail and draw the roof drain detail showing the roof deck with a sump pan provided by the roof drain manufacturer, installed by the plumbing contractor not the guys installing the roof deck), with the roof drain now flush to the roof deck, with a reversible collar (to which the extension ring threads engage), the threaded extension ring and dome.

Fill the Void, Bury the Screw, Save the Energy

Photo 8. Often a roofing contractor will leave voids like this around penetrations. Imagine the energy loss.

With the push over the past decade for energy savings/conservation, it is amazing to me that the code bodies have ignored two very highly energy consumptive or energy loss conditions: (1) voids in the thermal layer at penetrations and perimeter conditions; and (2) mechanical fasteners with plates below the roof cover. (See Photos 8-10.)

Photo 9. This photo shows multiple problems, beginning with a stud wall and a large gap at the deck. Warm air coming up the wall will cause deterioration of the water-based adhesives on the base flashing. The insulation panels are not tight to the wall or to each other. The metal strip looks pretty thin, is not a proper vapor retarder termination and will not hold the screws of the base anchor. This is a project that will continue giving work to us expert witnesses.

Some crews work to fit insulation tight to conditions. Others don’t. Eyeballing the circular cutout at vent pipes is common, resulting in fairly large voids at vent pipes. Roof edge conditions vary and significant voids can occur there, too. All of these voids need to be sealed with spray foam insulation, which should be allowed to rise and then trimmed flush to the insulation. I recommend that the spray foam be installed at each layer as subsequent insulation layers can shift the void. We have been requiring this for years without much blowback from contractors. The only issue that arose was when a contractor wanted to use polyurethane adhesive to fill voids; that was a no-go, as the polyurethane adhesive collapses down after it rises.

Photo 10. The screws and plates seen here are costing the building owner a fortune in lost energy.

Mechanical fasteners used to positively secure the insulation and membrane have become commonplace. But as I’ve noted before, we have seen roofs covered in frost with hundreds, if not thousands, of little spots of melted frost. The heat transfer through the fasteners is substantial. Research has found that on a mechanically attached roof cover, the energy loss can be over 40 percent above that of a system without exposed fasteners. As energy requirements are defined by R-value and with the potential for thermal loss due to the fasteners, I propose an R-value penalty for exposed fasteners. For example, in Chicago where the R-value requirement is 30, if you have a mechanically attached roof cover, the R-value required would be 42. That way the thermal efficiency would be equivalent and building owners wouldn’t pay the price for the designer’s lack of knowledge. Thus, as the Roofing God, I would implement this penalty and require all adhered roofs to have fasteners buried below insulation or cover board layers.

Commandment # 6: Show and note on your details the installation of spray foam insulation at penetrations, roof drains and perimeters.

Commandment # 7: All mechanical fasteners should be covered with insulation or a cover board; if not, 40 percent more R-value needs to be added to the thermal layer to compensate for the energy loss.

So, there you have the new roofing commandments that I would bestow if I were the Roofing God for a day. Let’s all work together though to bring about positive change and increase the sustainability and resiliency of our roofs. Together we can do it.

About the author: Thomas W. Hutchinson, AIA, FRCI, RRC, CRP, CSI, is a principal of Hutchinson Design Group Ltd. in Barrington, Illinois. For more information, visit www.hutchinsondesigngroup.com.

Pancake Head Screw Approved by FM for Wall Fastening

Triangle Fastener Corporation Triangle Fastener Corporation (TFC) announces that the company’s ¼-14 DP3 Concealor Pancake Head Screw is now FM approved for wall fastening per FM Approval Standard 4881 — Class 1 Exterior Wall Systems.

TFC developed the ¼-14 DP3 Concealor Pancake Head Screw specifically to attach Insulated Metal Panels (IMPs). According to the company, the screw’s unthreaded section eliminates jacking of the insulated panel during face fastening. The screw has a #3 square recess drive that provides stability during installation, and its large diameter pancake head is designed to increase pullover strength compared to smaller diameter heads. The screws are TRI-SEAL coated for superior corrosion protection.

For more information, visit www.trianglefastener.com.

Fasteners Designed to Attach Sheeting over Rigid Insulation

Triangle Fastener Corporation expands their line of BLAZER Drill Screws with new sizes designed to attach metal panels over rigid insulation. These unique screws have two different threads with a gap in between that eliminates jacking of the panel during installation.

Features and benefits:

  • A special ¼-14 “high thread” under the screw’s head secures the metal panel tightly against the head for optimal seal
  • Unique unthreaded section eliminates the “jacking” of the panel during installation, improving the drilling and tapping performance
  • BLAZER 3 drill point for fast penetration with less effort
  • Lengths: 1-7/8-inch, 2-3/8-inch, 3-1/4-inch and 4-inch
  • TRI-SEAL 1,000-hours salt spray coating provides over 20-times more corrosion protection than screws with commercial zinc plated
  • Available with a zinc alloy cap or stainless steel cap providing corrosion resistance in harsh environments

For more information, visit www.trianglefastener.com.

Bi-Metal Drill Screws Feature Corrosion Resistance and Ductility

Triangle Fastener Corporation introduces a full line of 304 stainless steel bi-metal self-drilling screws.

Bi-metal screws have heads and threads made of 304 stainless steel providing corrosion resistance and ductility. A hardened carbon steel drill point welded to a stainless steel body, which allows the screw to drill and tap steel up to ½ inch thick.

The screws are used to attach aluminum, stainless steel, insulated metal panel (IMP) and when ductility is needed in the connection.

  • Available in #12 and ¼ inch diameters
  • Drill and tap up to ½ inch thick steel
  • Lengths up to 12 inches long
  • Head styles include: hex washer head, pancake head and button head
  • With and without EPDM Bond-Seal sealing washers
  • Can be painted to desired color

For more information, visit www.trianglefastener.com.

PrimeSource Expands Collated Fastener Offerings With Pro-Twist

PrimeSource Building Products has announced that it will start shipping a full line of collated specialty screws under its proprietary brand Pro-Twist. “The Pro-Twist brand has been selling collated screws for 25 years, but now the demand has really gone mainstream,” said Director of Specialty Fasteners Michael McFarland. “With the focus of this product line, it was clear that our customers were looking for a collated fastener under the Pro-Twist brand that is of premium quality.”

Collated screws are commonly used to install subflooring but with recent developments, builders can now apply timesaving techniques to other materials, such as drywall

“The technology for high-speed equipment has come a long way and the prices have come down. Builders know they can save time and money,” said McFarland. “We’re in that business and now we’re adding a full line of collated fasteners for a variety of material applications to our distribution network.”
 
PrimeSource is committed to focus on products that meet the need of its customers, while providing relevant brands and building solutions within the industry.
 
“PrimeSource is always looking for ways to improve the breadth and depth of our offerings,” said Building Materials Group Manager Andy Spyhalski. “We are a key supplier to the nation’s building trades, and we want to respond to our customers’ needs and simplify their buying decisions.”

Zinc Head Screws Resist Corrosion

Triangle Fastener Corp.</a> has launched a complete line of corrosion-resistant zinc head screws.

Triangle Fastener Corp. has launched a complete line of corrosion-resistant zinc head screws.

Triangle Fastener Corp. has launched a complete line of corrosion-resistant zinc head screws. Available on the high-performance BLAZER Drill Screws, these fasteners are preferred for use in many warranted roof systems. The ZAMAC-5 Zinc Alloy Head provides superior strength and will not red rust. The carbon steel shank is TRI-SEAL 1,000-hours salt-spray- coated, which increases the corrosion resistance by more than 20 times compared to zinc-plated screws. An EPDM washer seals and weathers. Sizes include #12 and 1/4-inch diameters in BLAZER-3 and BLAZER-5 drill points in lengths up to 4 inches.

Leland Industries Celebrates 30 Years of Fastener Manufacturing

Leland Industries Inc. celebrates 30 years of fastener manufacturing. In 1984, Byron Nelson, president and founder of Leland began production in a 2,000-square-foot rented space in Toronto. Beginning with two cold headers and a staff of six, Leland has grown into one of North America’s largest fastener manufacturers, offering a broad line of screws, nuts and bolts for agricultural storage, post frame and metal building construction. Leland was the first manufacturer in the industry to offer powder coating of screws to match panel colors. Leland takes pride in being a domestic manufacturer; the company does not import. All Leland products, from the earliest days were considered green. From melted scrap steel to recycled paper or plastic in our packaging, everything qualifies for LEED points.

In 2012, Leland acquired the equipment from a failed producer, allowing our offering to be expanded to include bolts to ¾ by 6 inches, nuts to 7/8 inch and A325 structural items. Following that, and still expanding, Threadall manufacturing was acquired, once again allowing a product line expansion, now including; U-Bolts, J-Bolts, Anchor Bolts, Up to 4 1/2-inch diameter studs and threaded rod and special shapes to customer specifications.

Leland Industries competes with import products every day, concentrating on quality, delivery and value for money. We are presently adding 50,000 square feet of manufacturing and warehouse space. To provide the best possible service, Leland operates from and additional seven warehouse and branch locations across the USA and Canada.