BUR Rebounds From Exaggerated Death Report; Low-Fuming Asphalts Contribute

May 15, 2003

August 2003 Interface • 21
As Mark Twain did years ago, built-up roofing (BUR) can
assert that the report of its death was an exaggeration. The
roofing system, composed of three or four layers of roofing
felts embedded in a bitumen, is enjoying a revival despite threats
from other systems over the last few decades.
Annual market surveys by the National Roofing Contractors
Association (NRCA) show that BUR has held a 20 percent or more
share of U.S. low-slope roofing sales over the past several years,
adding to the 50 billion square feet of BUR in service.
Experienced contractors with a heavy stake in BUR continue
to thrive. “The average age, experience, and asset levels of BUR
contractors and their roofers are substantially more than the
average of single-ply roofing system contractors,” said Scott
Wagner, a third-generation contractor from M.G. Wagner Co., Inc.,
in Yakima, Washington. “I’ve got BUR roofers who’ve been doing
this for 25 years.”
Wagner is among a number of contractors who point to the
durability of BUR as a prime reason for its continued popularity.
“I can show BURs that my company put up over 25 years ago that
are still going strong, and lots of BUR squares that have performed
great in our cold climate. We had a major snowstorm in
’96-’97. BUR showed it could take as much punishment as any
other kind of roof.”
Wagner is not alone in pointing out that the redundancy of
plies plays a major role in tolerating thermal shock by giving
cohesive strength and minimizing the effects of cracking from
expansion and contraction of the material.
Contractors Attest to Durability
Another contractor, Gary Ramsburg of Roof Engineering Corp.,
Norfolk, Va., said, “We’re just now replacing built-up roofs that we
put on 31-32 years ago.”
“I have some built-up roofs that are approaching 20 years
old,” said Harry Bruton of Bruton-Gomez, Corpus Christi, Texas.
“In my experience I’ve never had a product failure, even under our
severe heat, as well as frequent high winds.”
“We install built-up systems as well as single-plies and metal
roof systems,” said Malcolm Nunn, Jr., Roof Systems of Virginia,
in Richmond. “Built-up roofs hold up much better in high traffic
industrial environments than other systems.”
Larry Scroggins of Hankins Roofing, Kansas City, Mo., who
applies most types of low-slope roofing systems, said, “We feel that
the four-ply, gravel-surfaced, built-up roof system offers our
clients the best return for their investment, on the basis of cost
per year of service. One reason is that BUR is repairable in its
later years. It gives plenty of warning to the building owner before
it goes out. Owners have time to budget repair or re-roofing costs
and nurse the roof through until they’ve got the money.”
“In our firm’s 40-year history, we haven’t once been in the
courthouse with any BUR failures,” said Gary Wilson of HEC
Roofing in Dallas.
Photo 1: BUR has held a 20 percent or more share of
U.S. low-slope roofing sales over the past several years,
adding to the 50 billion square feet of BUR in service.
By
Richard T. Janicki
and
David Trumbore,
Ph.D.
BUR REBOUNDS FROM
EXAGGERATED DEATH REPORT;
LOW-FUMING ASPHALTS CONTRIBUTE
22 • Interface August 2003
These reactions represent a significant turnaround from a few
years ago, when the lower initial costs of some other roofing systems
attracted owners. But today many major companies, especially
those in high-tech areas, are realizing that even a quarter of
a million dollars for a roof is minimal, compared with the potential
cost of damage to the work that’s going on beneath that roof.
Century-Old Technology Goes High-Tech
These owners recognize that today’s BURs – descendants of a
technology developed in the 19th century – are themselves “hightech,”
because they’re based on state-of-the-art research and
development that will assure proven, long-term, leak-free performance.
BUR materials and application procedures are continually
upgraded. Improved guidelines include National Bureau of
Standards NBS #55 on tensile properties for adhered systems and
the NRCA document, “Quality Control in the Application of Built-
Up Roofing.”
As for materials, “Built-up systems took a nose dive years ago
when they were using organic felts,” said Ramsburg. Introduction
of the two-ply coated organic felt system in the mid-1960s seemed
like a reasonable way to save labor costs. But, recalled Ramsburg,
“The rag content started disappearing from the felts and was
replaced by paper. But then you had the advent of fiberglass felts,
some of which have worn like iron. We have a fiberglass-felt BUR
on the Colonial Williamsburg [Va.] Inn that is 11 years into a 20-
year warranty, and other than debris from a tree, it looks like
new.” (See Photo 2).
Low-Fuming Asphalt Overcomes BUR
Objections
Another deterrent to BUR use had been objections of building
owners and occupants to smoke and fumes from heated asphalt,
the weatherproofing bitumen usually used to adhere reinforcing
plies to each other and to substrates. Today, development of lowfuming
asphalts has overcome these objections. The asphalts,
such as trademarked TruLo®, TruMelt® and PermaMop®, from
Owens Corning, contain a polymer additive that when heated to
the surface creates a skim layer on the kettle that traps the fumes
and odor inside, without affecting the asphalt or disrupting kettle
operation.
“Low-fuming asphalt enables contractors to get the advantages
of BUR – redundancy of the multiple-ply effect, toughness of the
membrane system, ease of repair, and modification – without the
smell,” said Ray Corbin of Johns Manville’s Better Understanding
of Roofing Systems Institute (BURSI).
Reducing the fumes – as well as innovations in workable packaging
– also boosts worker morale. “Workers sense, ‘The bosses
Photo 2: Gary Ramsburg of Roof Engineering Corp., Norfolk, VA, walks along the gravel surface of the BUR system his firm
installed on The Inn at Colonial Williamsburg.
recognize we’re out here busting our
tail and they’re trying to make things
a little better for us,’” Wagner said.
In addition, “There’s a significant
amount of garbage generated from a
conventional carton of asphalt,”
Wagner notes. With the new asphalts
that come in pre-made cartons,
“there’s zero garbage,” he notes.
“Because there’s no packaging to dispose
of, it takes up less space, so we
can use it in situations where we have
limited access to the building.”
Also, since the packages weigh 60
pounds, compared with conventional
100-pound cartons, workers can
break them by dropping them against
a hard surface into 30-pound blocks
instead of having to chop them with
an axe into small chunks to be
dropped into the kettle (Photos 3 and
4). The packages also withstand heat
in storage, even in 100-plus degree
temperatures.
Low Fuming Restores BUR
to Applications
Low fuming has put BUR back into the running for applications
that for a while were seemingly ruled out; for example, reroofing
of occupied mid-rise schools, hospitals, and apartment,
cooperative, or condominium buildings.
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August 2003 Interface • 23
Photo 3: This worker for Hankins Roofing has just broken a 60-pound package of lowfoaming
asphalt into two 30-pound blocks.
24 • Interface August 2003
School officials also find useful the protection afforded by
BUR’s ply redundancy against the foot traffic of trespassing students.
Atop high-rise buildings, the thickness and stiffness of the
BUR membrane enable it to distribute wind loads to help resist
uplift.
BUR provides a durable, easily maintained choice on low-rise,
large-area, limited access structures such as shopping malls. An
experienced contractor can install three plies of Type IV BUR glass
felt and a gravel surface for initial costs competitive with single-ply.
Asphalt Choice is Key
Contractors quoted above agree that choice of asphalt is a key
factor in the durability their BURs have achieved. Most of their
BUR work is with asphalt that has been developed to meet and
exceed American Society for Testing and Materials (ASTM) standards,
with softening points in the top range of the specifications
to minimize the risk of slippage and reduce “fallback.” The asphalt
is made with high flash point raw materials to provide added safety.
It has a wide spread between equiviscous temperature (EVT)
and the flash point to support application, adhesion, and waterproofing.
It is tested against standards twice – at a plant laboratory
and at one of the few technological laboratories certified by the
American Association of State Highway Testing Officials.
Wilson said HEC has used asphalt meeting these standards
and its predecessor products on “probably 98 percent” of its jobs.
He said HEC recently received a commendation letter from the
manufacturer of its roof systems pointing out that since 1987,
HEC “installed 13.8 million sq. ft. of the manufacturer’s roofing
systems without a single workmanship related problem.”
Ramsburg, whose firm has also used the high quality asphalt
and its predecessors for close to 50 years, observed that it “doesn’t
dirty the kettles like other asphalt does. It just holds up better.”
Harry Bruton, another user, warned against asphalt that doesn’t
stand up well in the 100-degree-plus
temperatures in southeast Texas. That “is
the frothing of the asphalt when you heat
it, and the coking [settling of solid materials
to the bottom] of the kettle. You’ll have
to chop the coke out of your flues so that
the kettle heats properly.” Users of lowfuming
asphalt find that it virtually eliminates
this coking and frothing.
Adhere to Best Installation,
Maintenance Practices
For all the improvements in BUR materials,
contractors are quick to point out
the need to adhere to best installation and
maintenance practices. The field on a
built-up roof is usually not the cause of
failures if properly installed. More often,
the causes are poor details at transitions,
base and perimeter flashings, curbs, and
penetrations. Apply extra asphalt to provide
waterproof sealing around flashings
and other vulnerable areas.
Ramsburg emphasized, “Make sure the
kettle operator is following NRCA and manufacturer guidelines for
the proper kettle temperature in heating the asphalt. If it’s too
cold, it goes down too thick. If it’s too hot, it goes down too thin.
Also, make sure you’ve got good adhesion when you’re brooming
in felts, so that you don’t leave pockets without asphalt.”
Contractors also advise that all layers, laps, sealants, and fasteners
at seams, as well as seals into the roof drains and scuppers,
should be completed for the area being constructed by the
end of the working day.
Tom Potteiger of Potteiger-Raintree Inc. in Glen Rock, Pennsylvania,
said, “The most important thing in installation is to minimize
traffic over a new roof to prevent displacing the asphalt when
it is still soft.” Potteiger advised waiting longer in the summer
than in the rest of the year because of the longer time needed for
asphalt to set in the heat. The rule of thumb is to wait 45 minutes
after application on a hot day without a cool breeze.
In discussing the longevity of his firm’s BURs, Bruton cautioned,
“That doesn’t mean they held up without maintenance,
any more than a car would go 100,000 miles without changing
the oil.”
It is suggested that building owners follow steps listed in
NRCA’s Handbook of Roof Knowledge to ensure a roof is properly
maintained:
• Keep all job records and specifications on file.
• Clear debris from the roof.
• Unclog roof drains.
• Make a thorough inspection twice a year, checking:
— Integrity of all flashings.
— How quickly water drains from a roof after a storm.
— Condition of the membrane.
— If the inspector spots a problem or potential problem,
the owner should contact the contractor immediately.
• Keep people off the roof. If the roof contains equipment
that must be serviced, walkways should be part of the
original design.
Photo 4: A worker drops a block of low-fuming asphalt into
a heating kettle on a BUR job.
August 2003 Interface • 25
And, don’t forget common sense. “Any kind of roof can get
beaten up if you try,” Wagner cautioned. “In our 1996-97 snowstorm,
BURs and single plies both suffered damage, but it wasn’t
because of the roofs. It was because of what was exerted on them.
If a guy started chipping ice with a snow shovel, it didn’t matter
what kind of roof it was. He made a hole in it.”
Mark Twain lived 13 years after his exaggerated obituary.
Following these successful suggestions for materials selection,
installation, and maintenance should enable your built-up roofs –
and the system type itself – to last a lot longer than that. ■
This article first appeared in the February 2002 issue of Roofing
Contractor, copyright Business News Publishing Co. II LLC.
Reprinted with permission.
Richard D. Janicki is president of
R&J Associates Technical
Consultants, Inc. He has 45 years
experience in roofing, petroleum
refining, and asphalt product development
and processing. He holds 14
patents for asphalt-related products
and processes. Janicki is chairman
of ASTM D 08.03 – Surfacing &
Bituminous Materials for
Waterproofing and Built-up Roofing,
and past chairman of the National
Corrugated Steel Pipe Association Coatings Committee and the
Roof Coatings Manufacturers Association (RCMA) Technical
Committee. He has received the ASTM Award of Merit and the
RCMA Martin A. Davis Award. Janicki can be reached by phone
at 708-671-1609.
David Trumbore, Ph.D., is the director
of science and technology for
Roofing Solutions Business, Owens
Corning Trumbull Asphalt. His 22
years with Owens Corning include 17
with Trumbull. Trumbore holds nine
patents and has written several publications
in the asphalt field. He has
earned two chemical engineering
degrees, including a bachelor’s from
Lehigh University and a Ph.D. from
the University of Washington. David
can be reached by phone at 708-594-6980 or by e-mail at
dave.trumbore@owenscorning.com.
ABOUT THE AUTHORS
DAVID TRUMBORE,
PH.D.
RICHARD D. JANICKI
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