The History and Evolution of Building Fasteners

The History and Evolution of Building Fasteners

By Tom Hulsey

Fasteners and fastening systems have evolved steadily over time.  History has led us from the use of nails as the fastener of choice to today’s self-drilling screws as the most versatile means of securing one piece of material to another in the steel building and post framed building industry.

Nails, as a means of fastening wooden objects, date back to approximately 3400 BC in ancient Egypt.  The term “penny” probably originated in medieval England to describe the price of 100 nails.  The “d” that is used as abbreviation for penny is derived from Latin for the name of the Roman coin, Denarius. 

Until the early 1800’s, nails were made by hand.  Around 1800, cut nails (square nails) were made from wrought iron.  Around 1860’s, wire nails were introduced and by early 1900’s, 90% of all nails were wire nails.

Screws, on the other hand, date back to 3rd Century BC in Greece.  By the 1st Century BC, screws were commonly used throughout the Mediterranean area in screw presses in the processing of olive oil and grapes. 

The spiral thread has proven over time to be an effective means to provide the force needed in order to perform specific tasks.  Just as nails were originally made by hand, screws were likewise made by hand for use in the assembly of materials to form a secure attachment of one piece to another.   Originally, there were no standards to guide the making of the screw.  Consequently, there was no chance of having screws to be interchangeable from one application to another.  The screw, therefore, was a custom fabrication for one specific application.

The development of screws and screw thread forms occurred around 1800 with the development of a modern screw cutting lathe.  Screws could be made more precisely and therefore could be produced much faster than before.  Consequently, the development and standardization of thread forms became important for reproducibility and interchangeability in use.

In the late 1860’s and early 1870’s, the US Standard Thread was created.  Thread designs and thread forms continued to evolve.  Sometime around 1916, the SAE Standard (Society of Automotive Engineers) was established in order to augment the US Standard.  This standard defined thread forms and specifications for threaded fasteners for general use. These standards were later adopted by ANSI (American National Standards Institute).  IFI (Industrial Fasteners Institute) is also a standards publisher that defines thread forms for fasteners.

My first involvement with threaded fastener standards was in the mid 1960’s.  At that time, the most common fastener used in the metal building industry to attach roof and wall sheeting to the girts and purlins was a #1/4-14 Hex Head Type B self-tapping fastener.  The roof sheeting side laps used a #14-10 Hex Head Type A fastener to secure the laps.  Both fastener types required a pre-drilled hole in the assembly in order to be installed.  Installation required two tools and often two workers to install the fasteners; one to drill the holes and a second worker to install the fastener. 

By the late 1960’s, self-drilling fasteners were making their way into the metal building market.   Self-drilling fasteners were new and were also relatively expensive as compared to the self-tapping Type A and Type B fasteners that were commonplace at the time.  The first self-drilling fastener to be introduced was described as a “milled point” self-drill.  That name described the operations required to create the drill point on the end or the screw.  A typical metal building self-drilling fastener required a minimum of four cutting (milling) operations to produce the drill point geometry. 

By the late 1960’s and early 1970’s, a new technology self-drilling point was introduced to the metal building industry.   It was described as a “pinched point” (cold forged) self-drill.  This new point required only one operation to form (pinch) the point on the end of the fastener.  That process employed the use of a machine equipped with hardened dies that were configured to match the desired shape of the point.  As the fastener passed into position, the dies were closed and the point was cold formed on the screw in one operation.  This process was faster and more consistent in production of the self-drilling screw.

The obvious advantage of using the self-drilling fastener was the reduction in the overall time and cost of installing the fastener.  The self-drilling fastener did not require a pre-drilled hole to be installed.  It was still a hard sell in the early years because the self-drilling screws were considerably more expensive to purchase.  Eventually, the economics of a one-man operation to install a fastener became evident. Today, the self-drilling fasteners are used almost exclusively for securing wall and roof sheeting to girts and purlins in the metal building industry. 

Until the mid 1970”s, nails were the fasteners of choice for attaching metal sheeting to wood framed buildings.  The early nails were equipped with malleable lead heads or a loose disc of rubber under the nail head to effect a seal at the nail penetration through the metal panel.  The nails were generally placed at the high point of the corrugations to reduce the chance of leaks when the nails worked loose.  One building owner once said, “Put the nails in the top where the water doesn’t run.”  With the introduction of screw fastening and high performance EPDM sealing washers, fastening in the flat portion of the panel became the best location for both structural and weatherproofing integrity of the roof system. 

Self-drilling fasteners continue to evolve in form and in function.  Continually advancing technology in the design of heading, threading, and pointing equipment has produced cost effective solutions for virtually every fastening challenge.  Specifically designed thread forms provide higher strength structural connections at the purlin/ girt /metal panel connection.  New alloys are being developed in conjunction with innovative hardening processes to provide a new generation of self-drilling fasteners with exceptional performance capabilities. Improved finishing technology has provided exceptional corrosion protection and appearance of the installed fastener.  Enhanced UV and Ozone resistant metal sheeting finishes and “Green” technology continue to improve the overall quality of the building structure.  Proper installation tools for fastener installation are now on the forefront of the development challenge. 

Roof Talk-101 Three Key Questions About Green Roofing

by: Jim Hoff

Recently, I was asked to participate in an online Q&A session about sustainable roofing. The questions I received were outstanding, so I thought every Roofing Contractor reader could benefit from a brief recap of the session, which is available free of charge in the “test drive” section of my course titled “Commercial Roofing Boot Camp.

Q. When I talk to building owners and architects who are looking for LEED certification, the only thing they want to know about the roof is whether or not it’s white because white roofs get a LEED credit. Isn’t this a shortsighted way to design and specify a roof?

A. Yes, it is very shortsighted; and I’ll be the first to admit that changing the narrow focus on white roofs supported by the LEED heat island credit is very difficult. Probably the best tool available to improve the discussion about roof surface color is the RoofPoint program developed by the Center for Environmental Innovation in Roofing. RoofPoint recognizes the “greenness” of roofs using 23 different credits, and only one of these credits addresses roof surface color. And even the roof surface color credit in RoofPoint allows the use of darker roofs in the coldest climates and provides for other cool roof alternatives such as ballast. It’s a great program to educate building owners and help demonstrate that you can be a valuable expert on the best in sustainable roofing practice.

Q. How can I go about integrating green into my business?

A. I think it’s important to integrate green into your business in three basic ways. First, focus on one or two sustainable roofing strategies that could provide real value for your customers. As an example, if you re-roof a lot of warehouses, consider integrating daylighting (skylights) into your roofing proposals. There are many excellent design tools available to help you get started, and the payback is fast, especially if you can integrate the skylights into the lighting controls. For businesses with high hot water needs, such as laundries, car washes, etc., rooftop solar thermal can also be a profitable add-on to your next roofing project.

Next, look for ways to get your employees involved. Do you keep track of waste and scrap returned from jobsites, and do you have a plan to recycle or re-use them? Do you know how this year’s carbon footprint from your trucks and equipment compares to previous years, and do you have an incentive program to reduce fuel (carbon) usage? Finally, emphasize that worker safety is just as green as any other green practice. After all, green is fundamentally about people. Consider what you could do to help your community save energy and reduce waste. When you do this, it not only will help reinforce your in-house green programs, but it also will increase your company’s reputation as a sustainably-minded business.

Q. Are you concerned that some new “green” roofing products aren’t yet proven to be durable?

A. Yes, I do have concerns. My own roofing career started during the single-ply revolution of the 1970s and 1980s, and I know from hard experience how difficult it is to integrate new technologies into proven roofing practice. But I also recognize that time doesn’t stand still, and we need to find ways to use new green roofing products without exposing ourselves and our customers to potential risks. Here are three of my green performance tips:

1. Learn as much as you can about vapor retarders and how they need to be installed to actually work. Along with increased interest in cool roofs which tend to accumulate condensation and the use of air barriers to tighten up the building, we unfortunately may see premature roof failures due to long-term moisture damage — unless we work harder to keep the moisture out in the first place.

2. Given the significant increase in code-mandated insulation thicknesses, cover boards are almost mandatory to protect all that expensive R-value from damage. And the same goes for thermal barriers beneath the insulation, which can serve as a very effective platform for installing air barriers and vapor retarders.


3. With reductions in the VOC content of roof adhesives, cold weather application of fully adhered roofs is very, very tricky. So, invest in insulated “hot boxes” to store adhesives and keep them at a decent temperature on the roof. And make sure your crews are up to date on the latest technical bulletins about cold weather construction from your suppliers.

ROOFTEC-LLC and ROOFGUARD-LLC has been installing commercial roofing systems for over 30 years. We have the solutions you are looking for if you desire a new commercial roof or need a re-roof. ROOFTEC-LLC only uses the best products and installation practices to insure you have a worry free commercial roof. For more information visit us at. www.rooftec-llc.com and we also invite you to Like Us on our RoofTec-LLC Facebook Page .

Recently, I was asked to participate in an online Q&A session about sustainable roofing. The questions I received were outstanding, so I thought every Roofing Contractor reader could benefit from a brief recap of the session, which is available free of charge in the“test drive”section of my course titled“Commercial Roofing Boot Camp.”To view it, just log on after clicking this link:  http://bit.ly/roofingtest.

Q. When I talk to building owners and architects who are looking for LEED certification, the only thing they want to know about the roof is whether or not it’s white because white roofs get a LEED credit. Isn’t this a shortsighted way to design and specify a roof?

A. Yes, it is very shortsighted; and I’ll be the first to admit that changing the narrow focus on white roofs supported by the LEED heat island credit is very difficult. Probably the best tool available to improve the discussion about roof surface color is the RoofPoint program developed by the Center for Environmental Innovation in Roofing. RoofPoint recognizes the“greenness”of roofs using 23 different credits, and only one of these credits addresses roof surface color. And even the roof surface color credit in RoofPoint allows the use of darker roofs in the coldest climates and provides for other cool roof alternatives such as ballast. It’s a great program to educate building owners and help demonstrate that you can be a valuable expert on the best in sustainable roofing practice.

Q. How can I go about integrating green into my business?

A. I think it’s important to integrate green into your business in three basic ways. First, focus on one or two sustainable roofing strategies that could provide real value for your customers. As an example, if you re-roof a lot of warehouses, consider integrating daylighting (skylights) into your roofing proposals. There are many excellent design tools available to help you get started, and the payback is fast, especially if you can integrate the skylights into the lighting controls. For businesses with high hot water needs, such as laundries, car washes, etc., rooftop solar thermal can also be a profitable add-on to your next roofing project.

Next, look for ways to get your employees involved. Do you keep track of waste and scrap returned from jobsites, and do you have a plan to recycle or re-use them? Do you know how this year’s carbon footprint from your trucks and equipment compares to previous years, and do you have an incentive program to reduce fuel (carbon) usage? Finally, emphasize that worker safety is just as green as any other green practice. After all, green is fundamentally about people. Consider what you could do to help your community save energy and reduce waste. When you do this, it not only will help reinforce your in-house green programs, but it also will increase your company’s reputation as a sustainably-minded business.

Q. Are you concerned that some new“green”roofing products aren’t yet proven to be durable?

A. Yes, I do have concerns. My own roofing career started during the single-ply revolution of the 1970s and 1980s, and I know from hard experience how difficult it is to integrate new technologies into proven roofing practice. But I also recognize that time doesn’t stand still, and we need to find ways to use new green roofing products without exposing ourselves and our customers to potential risks. Here are three of my green performance tips:

1. Learn as much as you can about vapor retarders and how they need to be installed to actually work. Along with increased interest in cool roofs which tend to accumulate condensation and the use of air barriers to tighten up the building, we unfortunately may see premature roof failures due to long-term moisture damage — unless we work harder to keep the moisture out in the first place.

2. Given the significant increase in code-mandated insulation thicknesses, cover boards are almost mandatory to protect all that expensive R-value from damage. And the same goes for thermal barriers beneath the insulation, which can serve as a very effective platform for installing air barriers and vapor retarders.

3. With reductions in the VOC content of roof adhesives, cold weather application of fully adhered roofs is very, very tricky. So, invest in insulated“hot boxes”to store adhesives and keep them at a decent temperature on the roof. And make sure your crews are up to date on the latest technical bulletins about cold weather construction from your suppliers.

Roof Talk-101 The 10 Best Rooftop Bars In NYC

Anything that has roof in it, we are probably going to blog about it. Its' summertime and if you 

are planning a trip to New York, you might want to stop by some of these outstanding rooftop 

drinking establishments and enjoy the sights from the Rooftop. 

EMPIRE HOTEL: This sleek outdoor lounge is not the place for casual boozing—there's a dress code here (no denim!) and trying to get upstairs on a Saturday night usually requires striking some sort of deal with the devil. But the Empire Hotel's rooftop is well worth a visit on a post-work weekday, boasting lovely views of Central Park and Lincoln Center from its 12th floor perch. 

The Empire Hotel is located at 44 West 63rd Street between Central Park West and Broadway on the Upper West Side (212-265-7400, empirehotelnyc.com).

GALLOW GREEN: Gallow Green made our rooftop list last year, and we're repeating the praise once again. The McKittrick Hotel's bewitching outdoor bar boasts some pretty gorgeous decor, with vintage train tracks and boxcars, lush greenery, live jazz music and—like the sprawling Sleep No More set that lies below—an ethereal, haunting old-world ambiance. 

Gallow Green is located at 530 West 27th Street between Tenth and Eleventh Ave in Chelsea (212-564-1662, mckittrickhotel.com/gallowgreen).

(John Del Signore/Gothamist)

THE IDES AT THE WYTHE HOTEL: The Wythe Hotel is another hotspot that made our list last year, and that spectacular skyline view's landed it another mention. True, you'll probably find yourself waiting on a line winding down North 11th Street if you brave the bar on a weekend night. But once you get up there, you'll be treated to sparkling Manhattan skyscrapers lined up against a midnight blue sky.

The Ides at the Wythe Hotel is located at 80 Wythe Avenue between North 11th and 12th Street in Williamsburg, Brooklyn (718-460-8000, wythehotel.com).

Via Facebook

THE PRESS LOUNGE AT INK48: This massive elevated drinking spot's got all the fixings for a top notch NYC rooftop bar. There's a stellar, unobstructed panoramic view of the city and the Hudson River, a "dress code" (no fitted caps, flip-flops, beachwear, tank tops, t-shirts or torn clothing allowed), trendy clientele and A POOL. You cannot swim in the pool, but you can look at it and yearn to be inside of it.
The Press Lounge is located at Ink48, 653 11th Ave between 47th and 48th Streets in Hells Kitchen (212-757-2224, thepresslounge.com).

LE BAIN AND THE ROOFTOP AT THE STANDARD HIGH LINE: Another star on our 2013 list, the Standard High Line's rooftop still outshines most of the other elevated offerings around town, a suspicious bubbling pool and faux grass.

The Standard, High Line is located at 848 Washington Street between Little West 12th and 13th Streets in the Meatpacking District (212-645-4646, standardhotels.com/high-line).

Night of Joy, via Facebook

NIGHT OF JOY: For a far more casual rooftop drinking experience, this Williamsburg bar sits right next the the BQE.

Night of Joy is located at 667 Lorimer Street between Jackson Street and the BQE in Williamsburg, Brooklyn (718-388-8693, nightofjoybar.com).

POD 39: The Pod 39 Hotel's lovely rooftop bar might sit precariously on the edge of fratastic Murray Hill, but don't let that stop you from stopping in for a summer drink or two. The bar, which opened in 2012, offers a glittering view of the Empire State Building and Lower Manhattan, framed by the hotel's brick facade, twinkling lights and funky archways.

Pod 39 is located at 145 East 39th Street between Lexington and 3rd Aves in Midtown East (212-865-5700, thepodhotel.com).

Via Facebook

Z ROOF AT Z NYC HOTEL: The Queensboro Bridge has already earned its merit as one of the city's more romantic sights, but the auroral view of it afforded by this LIC rooftop kicks even Woody Allen's creation up a notch, framed by Midtown Manhattan and a pitch-black East River at night. The hotel's elevated bar doesn't crowd up as much as some of the roofs on the Big Island.

Z NYC Hotel is located at 11-01 43rd Ave in Long Island City, Queens (212-319-7000,zhotelny.com).

(Katie Sokoler/Gothamist)

LA BIRRERIA AT EATALY: The Italian beer garden of sorts that sits atop Flatiron's famed Mario Batali food mecca is open year-round, but when the weather picks up the retractable roof comes down. And that's when the real fun starts, since there's nothing more wonderful than drinking barrels of beer above ground in the summer.

La Birreria is located at 200 5th Ave in Flatiron (212-937-8910, eataly.com).

VU ROOFTOP BAR: One of K-town's lesser known secrets, this bar located on top of the La Quinta Manhattan serves up an awesome laid-back atmosphere unbridled by the non-stop pretension at some of the other elevated offerings around town. Though the view here isn't much, minus a close-up shot of the Empire State Building, the benefit of being outdoors far outweighs a panoramic scene.

ROOFTEC-LLC and ROOFGUARD-LLC has been installing commercial roofing systems for over 30 years. We have the solutions you are looking for if you desire a new commercial roof or need a re-roof. ROOFTEC-LLC only uses the best products and installation practices to insure you have a worry free commercial roof. For more information visit us at. www.rooftec-llc.com and we also invite you to Like Us on our RoofTec-LLC Facebook Page .

The Top Eight Roofs In The World

The Top Eight Roofs In The World

1. Hospices – Beaune, Burgundy, France

People love to visit the Burgundy region in France for the wine, but equally enchanting are the roofs of the Hospices in Beaune. These hospitals and health care facilities date back to the 15th century, and their roofs provide eye-catching patterns of colors and designs.

2. Thean Hou Temple – Kuala Lumpur, Malaysia

Even though this homage to the goddess whose name means “Heavenly Mother” in Cantonese appears to be from ancient times, this temple is only about a quarter century old. Its roof adornments include multicolored tiles, sweeping curves, and lots and lots of dragons.

3. Sydney Opera House – Sydney, Australia

The curvaceous shapes atop this opera house make this structure unique throughout the world. Each of the “shells” are actually precast concrete panels covered by a total of over a million Swedish tiles. The building took 14 years to complete and cost around 102 million Australian dollars — which was 13/1/2 times its original budget. Ouch!

4. Red tiled houses of Old Town – Dubrovnik, Croatia

These roofs look pretty new for a 1300-year old settlement, right? That’s because Dubrovnik was under siege in 1991 and 1992 by Serbian forces, which mercilessly shelled the Old Town and damaged most of the buildings. The city was bombarded because forces couldn’t march into Dubrovnik, which is surrounded by thick stone walls.

5. Olympiapark – Munich, Germany

As the name implies, these buildings were constructed for the 1972 Summer Olympic Games in Munich. The roofs are not solid, but instead are made of a “skinned” material that is lightweight. Unlike many of these other historic sites, you can actually walk up the roof of Olympic Stadium — and then zipline from the top!

6. St. Stephen’s Cathedral – Vienna, Austria

The roof of the mother church of the Archdiocese of Vienna dates back to the 14th century and is covered by 230,000 multicolored, glazed tiles. In addition to geometric patterns, these tiles also form images, including coats of arms and a two-headed eagle. Plus, the roof is so steep that it only requires rainwater to wash it clean.

7. Grand Palace – Bangkok, Thailand

As you can see, the king of Thailand has some pretty sweet digs. While the palace grounds span about 2.35 million square feet, this photo portrays the top of the throne hall (known as Phra Thinang Dusit Maha Prasat). Not only are the adornments complex and beautiful, but each one is chock full of symbolism pertaining to Thai culture and history.

8. Domed roofs – Santorini, Greece

Just because you see a shiny domed roof on the Greek island of Santorini does not necessarily mean that the building houses royalty. The whitewashed limestone roofs are practical because they reflect the sun’s rays to help keep the interiors of the homes cool. And since rain is scarce, there are cisterns strategically placed near the roofs to catch runoff water (instead of gutters!)

ROOFTEC-LLC and ROOFGUARD-LLC has been installing commercial roofing systems for over 30 years. We have the solutions you are looking for if you desire a new commercial roof or need a re-roof. ROOFTEC-LLC only uses the best products and installation practices to insure you have a worry free commercial roof. For more information visit us at. www.rooftec-llc.com and we also invite you to Like Us on our RoofTec-LLC Facebook Page .

Roof Talk-101 Chicago’s Wrigleyville Rooftop History

Where the Wrigley Field Rooftop phenomenon began!

Since 1914, the nearby rooftops of adjacent residential buildings have been used to view Chicago Cubs baseball games or other major events at historic Wrigley Field. The term “Wrigley Rooftops” has been used primarily by sports crazed Chicagoans for the past several decades to describe the beautiful structures surrounding the ballpark which have become an extension of the baseball and concert experience at Wrigley Field.

The rooftops had long been a unique and primitive way to experience the Chicago Cubs baseball games with informal gatherings of a few lucky fans and neighborhood folks perched atop the buildings lining Sheffield and Waveland Avenues. These fortunate fans would sit on coolers, folding chairs, garden furniture, overturned buckets or blankets to buffer the hot tar of sun scorched roofs just to see a Cubs game. Access was generally granted to guests of building owners and their tenants by climbing through the top floor attic of a residential apartment. For several decades, Cubs broadcasting legend Harry Caray would say “hello” to the familiar Wrigley Field rooftop fanatics during his televised broadcasts on WGN. Thus, getting invited to a rooftop became a coveted prize, like winning a secret Cubs fan lottery.

In the 1980’s the Chicago Cubs experienced a renaissance of sorts and with their revived popularity and renewed interest in the team, some enterprising property owners began constructing more sophisticated seating on these once crude rooftop properties. Some owners began charging “admission” to enjoy the game, which did not bode well with the Cubs organization. For nearly a decade the Cubs management tolerated these entrepreneurial endeavors until several of the rooftop structures became organized, profitable businesses that in their opinion, encroached on their business and “used the Cubs organization’s product for personal and financial gain”.

Discussions between the property owners and the Chicago Cubs continued, and progress towards a balanced relationship with the rooftop neighbors was achieved. In 2004, eleven of the thirteen rooftops settled with the club and agreed to pay 17% of gross revenue in exchange for official endorsement. The Cubs now endorse their “Official Rooftop Partners” on their team page at MLB.com.

Today, Wrigley rooftops have become a unique alternative venue to watch Cubs baseball games and summer concerts. Rooftop venues now feature bleachers, beverage service, specialty food menus, meeting space, and a unique game-day atmosphere without the huge crowds, long lines, crowded restrooms and raucous fans.

Roof Talk-101 What Is The Difference Between Architectural Shingles and 3-Tab Shingles

Roof Talk-101  What Is The Difference Between Architectural Shingles and 3-Tab Shingles

What are architectural shingles?

Architectural shingles, also called laminated or dimensional shingles, are made with a heavier base that creates a stronger, thicker shingle which gives a three-dimensional look to your roof.

What is the difference between 3-tab shingles and architectural shingles?

3-tab shingles are flatter and thinner than the architectural shingles, producing a one-dimensional look to your roof. They usually have shorter warranties and lower wind ratings than laminated shingles.

Roof Talk-101 What Are Roof Blisters And How Do You Repair Them?

Roof Talk-101 What Are Roof Blisters And How Do You Repair Them?

What causes blisters?Roof blisters can frustrate anyone who works with roofs. Their arrival is usually a surprise, their cause is often unknown, and their removal is a lot of work. In this bulletin, we offer some ideas that may be helpful in dealing with blisters.

Blisters represent a localized loss of adhesion and the lifting of roof ply or roof coating film from the underlying surface. The most common cause is water or moisture vapor migrating through from below or above the roof surface. If the volume of trapped moisture exceeds the permeability (breathability) of a roof ply or coating film, pressure caused by rising temperatures on a warm day expands the moisture below the ply or coating film, and separates it at its weakest point, forming a blister.

Blisters may occur below or between ply sheets in a built-up roof system, at the roof coating interface with the roof surface, or between coating layers when multiple coats have been applied to the roof. It is important to recognize the difference before proceeding. Blisters may be filled with water or air. Osmotic blisters can occur when moisture permeates the coating film from the outside due to continuous or frequent contact with water (i.e. ponding water). Moisture collects at the interface between roof ply, or the coating film and the ply, eventually causing a loss of adhesion and a blister. Osmotic blisters are not likely in areas where drainage is good.

Moisture can come from below the roof and through the ply system to cause blisters. Some roofing experts maintain it is impossible to build an absolutely moisture tight BUR membrane. The nature of the process always creates tiny voids. If the area beneath the roof can’t breathe, then moisture may be drawn to the roof deck. Buildings can be too air tight to breathe adequately.

Surface blisters in coating can sometimes be caused by the actual moisture in the liquid coating at the time of application. Small blisters can form when the coating dries so rapidly some of the water can’t evaporate completely before the coating surface cures.

What to do about blisters

If blistering is evident; try to determine the source of the moisture. Likely possibilities:

• Coating blisters confined to standing water areas are osmotic blisters.
• Coating blisters over asphalt emulsion or Puddle Plaster™ often mean these were coated before fully cured.
• Blisters between layers of coating (as opposed to blisters originating between the coating and the ply) are often caused by:
  
  • Thick roof coating applied over a hot surface (flash-drying that traps moisture)
  • Applying a second coat before the first coat is dry
  • Poor coating adhesion, either due to coating over a dirty/chalky surface (lack of proper cleaning) or not fully rinsing away cleaning agents such as TSP, causing areas of chemical interference

• Blisters originating at the coating/substrate interface, indicating moisture coming up from below:
  • Moisture trapped in roofing plys, insulation, or wood decking due to past or current roof leaks
  • Moisture trapped in roofing plys, insulation, or wood decking — caused by moisture from the living area being lifted by warm air that ultimately condenses on cold roof and deck surfaces — migrates through tiny passages in the ply layers.
  • Moisture trapped in voids during construction of BUR roofs where ply sheets are not fully sealed by hot mop asphalt can cause blisters between ply sheets.
  • Moisture trapped in spray-down foam due to deterioration or loss of protective coating.

What to watch for

Roof coating blisters in ponding water areas are due to moisture permeation from above. Roof coating blisters in areas of adequate drainage are usually coming from below. Consider venting.

Watch out for roofs with coatings that have blistered before. Try to determine why the blistering occurred before recoating, as the blisters may return.

Roofs over cathedral ceilings often blister because they are likely poorly vented and collect moisture from the interior.

Coatings on older foam roofs that have not been well-maintained will result in blistering (water intrudes into the foam and can’t be seen when recoating).

Look for water squishing out of small openings as you walk the roof. Water can permeate foam, asphalt, and decking and is very hard to dry out.

Coating roofs in extremely hot weather results in flash drying. The coating may separate from the substrate even before it dries but not be visible as a blister immediately. By examining the underside of a coating blister, look for numerous tiny tendrils indicating the film pulled away from the surface at application.

Recoating tinted roofs (coated with a dark color) or asphalt emulsion on a hot day also can result in flash drying and blistering.

Coating roofs too soon after heavy rains or washing leaves roofs vulnerable to blistering, as does coating roofs with frost or condensation present.

Coating roofs just before it rains is poor timing. Water in the coating that has not had time to evaporate provides an avenue for rainwater to penetrate and damage the coating.

ROOFTEC-LLC and ROOFGUARD-LLC has been installing commercial roofing systems for over 30 years. We have the solutions you are looking for if you desire a new commercial roof or need a re-roof. ROOFTEC-LLC only uses the best products and installation practices to insure you have a worry free commercial roof. For more information visit us at. www.rooftec-llc.com and we also invite you to Like Us on our RoofTec-LLC Facebook Page .