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Recycling Of Thermoplastic PVC Roof Membranes

May 15, 2007

The old roof adage “out of sight,
out of mind” is no longer an
appropriate term for today’s
building owner or manager.
With roofing costs easily exceeding
$10.00 per square foot,
busy contractors, and a saturated market,
roofing represents an expensive and always
important part of the building asset. Maximizing
roof performance and life expectancy
require knowledge and experience with
roofing materials, as well as building and
maintenance technology.
Numerous articles on roof
maintenance have been written
over the last few years, including
many by this author. The topic of
this dissertation, however, spotlights
a different area of roof
maintenance than is usually
explored: protection from birds,
especially particular species (see
Photo 1).
The popularity of exposed
SBS modified bitumen roof membranes
in commercial, industrial,
and institutional buildings has,
in certain locales and conditions, revealed a
unique limitation with these materials.
Concentrations of bird droppings can contribute
to the rapid removal of the granule
cover. The surface granules on the top ply
or cap sheet supply the UV resistance to the
membrane assembly and are a critical item
in the long-term performance and life
expectancy of the roof membrane assembly.
Degradation caused by bird droppings can
expose the asphalt beneath to localized UV
deterioration (see Photo 2).
This phenomenon has been recognized
for a number of years in the Victoria, BC,
area, but changing weather patterns
(longer, drier summers) and a lack of attention
by building operators have brought
new focus to the problem.
The case study presented here is based
on a real-world investigation recently performed
by Wells Klein Consulting Group
(WKCG) on a building on the west coast of
British Columbia. Brief portions of the
report are excerpted and italicized herein.
Photo 1 – Gulls are sociable birds.
They like to roost on a place
higher than their nests, where
they can see the nesting area. In
this case, the area is below and
to the right on a nearby building.
Unfortunately, this “sociability”
includes another function.
MA R C H 2007 I N T E R FA C E • 5
The building referenced is
a new addition connected to a
renovated, older public building
and was only six months
old when WKCG was retained
to investigate. The building is
a concrete structure, four stories
in height, and about 8,700
sf (815m2) in roof area.
“Bird roosting and droppings
problems are common
everywhere in the
world and particularly in
seaside locations or near
any sources of food. The
problems are specifically
caused by the acidic feces
deposited by flying, roosting,
and nesting seagulls
(specifically herring gulls)
on this building.”
“This new roof exhibits one
of the most severe bird
dropping problems that this
consultant has viewed.
Significant and severe damage has
occurred to the membrane and its protective
In many spots, the effects of the droppings
had actually not only removed granules,
but softened or affected the top portion
of the asphalt membrane proper, similar
to hydrocarbon or oil contamination. In
limited locations, membrane reinforcing
had been exposed, indicating the erosion
(removal) of granules and perhaps 1.5mm of
asphalt sheet! (See Photo 3.)
“Seagull feces contain high concentrations
of uric acid and the effects of the
droppings on many surfaces, including
steel and paint, is well known.”
The other (and just as significant) side
to the fecal contamination is the potential
for serious health problems. Seagull droppings
are a proven source of a variety of
bacterial, viral, mycotic, and protozoal diseases.
Bird droppings in sufficient volume
may be considered hazardous waste.
Direct contact or contact through airborne
sources must be considered. A direct
source can be something as simple as
tracking fecal matter on shoes from innocent
contact on the roof. Airborne sources
are through air handling and HVAC equipment
(see Photo 4).
“Gull feces could be a major contributor
of E. coli (105-109 CFU g1) and enterococci.
1 However, another concern is the
transmission of human pathogens such
as salmonella, which gulls have been
known to carry.2 Dust and soil contaminated
by bird and bat droppings may
cause an infectious lung disease, according
to the National Institute for
Occupational Safety and Health (NIOSH).
Roofing was listed as one industry that
may be affected.”3
The specific problem appears to affect
only exposed, granulated membranes. All
roofing in the region and localized area is
6 • IN T E R FA C E MA R C H 2007
Photo 2 – The amount of fecal matter and damage discovered on the first
site visit was quite astonishing… and the smell wasn’t great either!
Photo 3 – This picture demonstrates damage to the membrane that
almost reaches the reinforcing mat. Granular degradation is
devastating; the asphalt blend is softened and contaminated.
subject to similar conditions.
Traditional, built-up roofing with
gravel cover seems to break up
and distribute the fecal matter
without a visible effect on the
membrane. Inverted roofing systems
offer similar break-up, but
in time, the residue filters down
to the membrane level and causes
an odiferous and bacterial
soup. Exposed, single-ply PVC
and TPO membranes seem to
offer a relatively impervious surface,
as does EPDM, but the
physical properties of these
membranes bring their own
unique circumstances, including
many instances of birds (gulls
and crows specifically) actually
penetrating the membrane and
removing the insulation below.
These birds aren’t stupid – they
use the insulation for nesting
In this particular investigation,
certain facts seemed to synergistically
combine to cause the
severe damage. The location of
the building, the weather condi-
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MA R C H 2007 I N T E R FA C E • 7
Photo 4 – Given the amount of fecal matter, a dry weather spell, and then a rainstorm, the air intakes
can (and did!) draw some very objectionable odors into the building, to say nothing of the bacterial
tions at the time,
the type of membrane,
and the lack
of “bird control” devices
or preventative
action (and to a
lesser extent), all
appear to significantly
contribute to
the problems.
Weather Conditions
“The summer of
2004 has been a
dry period, with
no significant
rainfall for a couple
of months.
Unlike more usual
Victoria conditions,
the dry
period has allowed
the bird
droppings to build up and dry in situ and
in significant amounts. No washing or
dilutive action from rain has been available,
and this has contributed in a major
way to the deterioration of the roof membrane
There is a significant objectionable odor
on the roof, which is exacerbated after
the short (to early August) periods of rain
experienced. The odor is easily picked up
by the building air intakes and distributed
in the building. Since this report
was commenced, more significant rain
has been experienced, and dilution and
some washing have taken place. The
membrane damage has, however, been
done, and major steps to repair and protect
will be required
in order to establish
any semblance of
realistic life expectancy.”
when so-called
“normal” rainfalls
returned, much of
the fecal matter did
wash off, but the
severe membrane
damage was already
Roofing Membrane
“The roof membrane
on the building is,
generically, a 2-ply,
SBS, modified bitumen
membrane system,
with the top
ply-torch applied and the base sheet
fully adhered with hot asphalt to a wood
fiber insulation overlay adhered with hot
asphalt to polyisocyanurate insulation.
The insulation is in turn adhered to a
concrete deck with hot asphalt.”
The roofing assembly was installed by a
professional roofing contractor, inspected
by an independent roofing inspection
firm, and warranted by
a third-party roofing association,
all to the highest industry standards.
Bird Deterrent or Control Devices
“At the time of our first site visits
(the roof was some six
months in service), no bird control
plan had apparently been
considered. No devices were in
place, and as a result, the
severe build-up of bird droppings
had caused significant
damage to the roof membrane.
Some roof areas, including
ledges on the old building,
were difficult to access.
Seagulls were roosting on all
parapets, ledges, roof fall arrest
anchors, the roof membrane,
and on top of the cooling
Photo 5 – One of the attempts to “ fix” the problem was an elastomeric coating. As demonstrated, the
birds loved it. This particular coating proved ineffective.
8 • IN T E R FA C E MA R C H 2007
“Bird droppings in
sufficient volume may
be considered
hazardous waste.”
The roof drains in all locations on the
building stand slightly proud of the level
of the roof and are causing some relatively
minor water ponding. While minor,
the ponding, when coupled with the bird
problems, has created some concerns at
drains on the north side of the main roof
and all drains on the old police building.
The drains are operating, but very slowly
at this time. Algae growth is evident.
With the amount of fecal matter, it is
likely this water could be very contaminated,
and extreme caution is advised.
Successful resolution to the severe
problems identified with the roof on this
building will require a planned, integrated
approach in several categories, including
roof repairs, bird control devices, and regularly
scheduled bird control inspections (for
new nests, etc.) and maintenance (including
washing at times) by the building operator
or his subcontractor.
Membrane repairs on this building will
be extensive and expensive in order to
restore the roof to any semblance of its normal
life expectancy. Specialized elastomeric
coatings (see Photo 5), methacrylate coatings,
an additional layer of cap sheet, or
even the addition of a hot asphalt pour coat
and gravel surfacing are plausible considerations.
Regular inspection and very careful surface
washing (in dry times when rain is not
a regular occurrence) may be required in
order to keep the build-up of fecal matter to
a minimum. Even if the coating protects the
membrane as envisioned, the bird droppings
will still have to be eliminated if further
build-ups occur. Extreme care must be
taken not to remove protective granules
unless another protective measure is
identified (see Photo 6).
A planned, integrated, and
aggressive approach must be taken
to solve the bird predicament. This
may be achieved by a number of
diverse bird-deterrent and birdrepellant
systems and devices.
The products generally recommended
for gull control include
stainless steel or polypropylene plastic bird
spikes, audio or visual deterrents, netting,
etc. All can be effective – at least for a while.
In our experience, none are an absolute
MA R C H 2007 I N T E R FA C E • 9
Photo 6 – This photo was taken after
the roof had been well washed by
rain. The small, round marks are
typical of granule loss damage to
modified bitumen membrane caused
by gull droppings. The larger,
“splotchy” marks exhibit damage to
the actual membrane, down to the
reinforcing, in some locations. Some of
what these birds eat and defecate
dissolves or softens asphalt!
Ongoing Inspection and Maintenance
The last section of the proposed integrated
solution involves ongoing inspection
and maintenance of the roof and its protective
systems. Keep in mind that gulls are a
protected species and care must be taken to
recognize that fact.
Using trained, in-house personnel or
subcontracting the work, a planned program
of regular scheduled inspections must
be implemented. This program will be to
visually monitor the condition of the protective
roof coating and the effectiveness of the
bird control devices.
One caution: nesting and roosting birds
can be very aggressive on the roof. Personnel
should go on the roof in paris and
take precautions to protect themselves.
Birds will usually only swoop and attack
from behind. Carrying a full-sized corn or
whisk broom above one’s head is often
effective in warding off an attacking bird. A
hard hat is sometimes a good idea, as are
towels and antibacterial wipes to clean up
the effects of the dive-bombing attacks!
Nesting must be prevented. This is the
first step in controlling and protecting the
asset. If the initial control measures are not
effective and gulls are attempting to build
nests, then removing the nests and contacting
the control specialist is required. There
is no law, to our knowledge, that prevents
personnel from removing the nest prior to
eggs being laid. If nesting becomes apparent,
then additional lawful measures to prevent
and protect will be required.
A bi-weekly, walk-around inspection is
all that is required. Should problems with
birds, fecal build-up, or anomalies with the
protective coating be observed, then a
report can be generated and the appropriate
steps to solve the problem can be established.
The roof is an important, expensive, and
even critical component of the building.
Protection and maintenance of the asset
can be a challenge and only with information
and planning can this process be effective.
1 L.R. Fogarty, S.K. Haack, M.J. Wolcott,
and R.L. Whitman, “Abundance
and Characteristics of the Recreational
Water Quality Indicator Bacteria
Escherichia Coli and Enterococci
in Gull Faeces,” Journal of Applied
Microbiology, Volume 94, Issue 5,
Page 865, May 2003, doi:10.1046/
2 Manual for Gull Control at Massachusetts
Landfills, Massachusetts Department
of Environmental Protection,
Bureau of Waste Prevention,
Massachusetts Division of Fisheries
and Wildlife, May 1998.
3 “It’s No Joke, NIOSH Warns Against
Bird Droppings,” Professional Roofing,
February 1998.
John W. Wells, RRO, is the senior partner and president of
Wells Klein Consulting Group Inc. Headquartered in Victoria,
BC, Canada, WKCG also has offices in Delta, BC (Vancouver)
and specializes in commercial and institutional roofing and
waterproofing consulting. Formerly J.W. Wells Consulting
Inc., WKCG has provided professional services on many large
and challenging projects in its 15-year history
John W.Wells, RRO
10 • I N T E R FA C E MA R C H 2007
SPRI (Single Ply Roofing Industry) celebrates its 25th anniversary in
March 2007. The organization, representing sheet membrane and component
suppliers to the commercial roofing industry, has released statistics showing
the increased acceptance, growth, and enhanced field performance
of single-ply and modified-bitumen roof systems.
In 2006, SPRI member companies shipped out more than
3 billion square feet of sheet membrane roofing, more than
double SPRI member shipments in 1984.
According to independent market research from Infometrics
Inc., Duluth, MN, in 1979, single-ply roofing systems
accounted for only 10% of the U.S. low-slope roofing market.
This percentage increased to 25% in 1983, one year after
SPRI’s founding. In addition, while the use of single-ply and
modified-bitumen systems has increased dramatically over the years, field
performance for these membranes has also significantly improved.
Data from Penn & Associates, a Cleveland, Ohio-based research firm,
show that while single-ply roofing represented less than 30% of the average
roofing contractor’s dollar volume in 1984, roof failures and callbacks with
these systems were initially higher. Today, Penn estimates that single ply and
modified bitumen represent 67% of the average roofing contractor’s annual
volume. With more than twice the volume, total failures and callbacks with
these systems have dropped nearly 20% since 1984.
EPDM roofing systems fueled single-ply growth in the 1970s and 1980s.
According to Infometrics, EPDM accounted for most of single ply’s volume
early on, with a low-slope roofing market share of 19% in 1980.
In 1985, Springborn Laboratories of Enfield, CT, put single
ply’s market share at 48% and modified bitumen’s share at
12%, with EPDM still representing 60% of all single-ply sales.
Today, energy-efficient, white membranes, such as TPO
and PVC, are becoming more popular. In particular, TPO (thermoplastic
polyolefin) is the hottest product in the single-ply
market, with double-digit growth rates over the last several
years. In a 2006 survey conducted by a leading trade publication,
almost 75% of contractors said they were pleased with
the performance of TPO roofing.
The popularity of single-ply roofing systems also led to increased participation
among roofing suppliers within SPRI. By 1987, 111 member companies
had joined SPRI – 36 membrane suppliers and 75 associate members. Since
its inception on March 3, 1982, SPRI has developed scores of technical publications
and roofing manuals, as well as a number of SPRI/ANSI standards.
For more information about SPRI and its activities, visit SPRI’s Web site
at, or contact the association at