Note: Descriptions are shown in the official language in which they were submitted.
Description
ROOFING SYSTEM H~VING LIGHTWEIGHT BASE SHEET
Technical Field
The present invention relates to roofing systems and,
more particularly, to weatherproof roofing systems of the
type which incorporate a base sheet between the roof deck
and the roof surface secured to the base sheet.
Backqround Art
It is welL known in roofing construction to utilize
a roofing base sheet in the form of a product known as
"asphalt paper". Asphalt paper is normally constructed of
a non-woven fiberglass web to which a heavy asphalt
coating has been applied. Although the asphalt paper is
very heavy and difficult to handle, it generally serves to
prevent the phenomenon known as "strike-through" which
occurs when a layer of hot asphalt is applied over the
base sheet and seeps through to the deck below in the
construction of a built-up roof and the like.
Strike-through is undesirable since it allows a built-up
roof to adhere to the roof deck and thereby can result in
substantial difficulty and great expense in later efforts
to repair or replace the roof. As is known to those
familiar with the roofing art, a roof should normally be
able to be easily removed from the roof deck if the
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strike-through phenomenon is avoided during construction
of the original roof.
Although capabl~ of preventing strike-through, it is
well known that an asphalt-coated substrate (such as
fiberglass but also including other natural or synthetic
textile substrates) suffers many other shortcomings when
used as a base sheet in roof system con~truction. The
shortcomings include the unwieldy nature of asphalt paper
as well as high storage and shipping costs which are all
due to its relatively great weight. Also, asphalt paper
has a tendency to "mat" to the roof deck and thereby
create difficulties in removal, and it has an inherent
tendency to tear during roof construction or subsequent
settling o the roofing system due to its relatively low
tear strength.
Thus, there has long been a need for a new product to
replace asphalt paper in the construction of roofing
systems, particularly built-up roofs, bitumen capsheet
roofs, water-shedding sloped roofs and the like. The
product would need to be capable of preventing
strike-through during roof construction as does asphalt
papar, but it should not possess the many shortcomings
inherent to heavy asphalt paper.
Disclosure of the Invention
In accordance with the present invention, applicant
provides an improved roofing system which utilizes a
lightweight and high strength polymer latex coated
polyester web as a substitute for the traditional asphalt
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paper-type of base sheet. The roofing system of the
invention comprises a roof deck, a hot bitumen impervious
base sheet thereover comprising a non-woven polyester web
having a polymer latex coating on at least one side
thereof and which is mechanically fastened to the roof
deck, and a roof structure secured to the base sheet for
rendering the roofing sy~tem water impermeable. The
roofing system may be any of those known in the art which
have previously utilized asphalt paper in the construction
lo thereof and particularly is contemplated to include
built-up roofs, water-shedding steep roofs, and bitumen
capsheet roofs.
Generally speaking, a built-up roof system as
contemplated by the present invention comprises a roof
deck, a hot bitumen impervious base sheet comprising a
non-woven polyester web having a polymer latex coating on
at least one side thereof and which is mechanically
fastened to the roof deck, a layer of bitumen applied over
the base sheet, a reinforcement sheet applied thereover,
and a protective surface layer such as gravel thereon. A
bitumen cap roof system as contemplated by the present
invention comprises a roof deck, a hot bitumen impervious
base sheet co~prising a non-woven polyester web having a
pol~mer latex coating on at least one side thereof and
which is mechanically fastened to the roof deck, a layer
of bitumen applied over the base sheet, and a protective
bituminous membrane which is applied over the bitumen
layer. A water-shedding sloped roof system as
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contemplated by the present invention comprises a
water-shedding inclined roof deck, a hot bitumen
impervious base sheet comprising a non-woven polyester web
having a polymer latex coating on at least one side
thereof and which is mechanically fastened to the roof
deck, and a protectiva surface secured to the base sheet
consisting of a material such as clay tile, concrete tile,
asphalt shingles, slate shingles, metal shingles, wood
shakes or preformed metal panels. It is further
contemplated that the roof may be applied to either a wood
deck or a metal deck and, if the roofing system includes
a metal deck, a layer oP insulation may be provided
between the metal deck and the polymer latex coated
polyester web base sheet.
The resulting roofing system incorporates a base
sheet which is only a fraction of the weight of
traditional asphalt paper and yPt possesses inherently
greater tear strength. This results in lower storage and
shipping costs of the base sheet as well as greater ease
of application during construction of a roofing system
which incorporates the base sheet.
Accordingly the present invention seeks
to provide an improved roofing system which utilizes a
lightweight and easy to handle pol~mer latex coated
polyester web as a substitute for traditional asphalt
paper as a base sheet.
Further the present invent~on fieeks to provide
an improved roofing system construction which utilizes a
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polymer latex coated non woven polyester web as a base
sheet so as to reduce storage and shipping costs of the
base sheet material and to provide enhanced base sheet
performance qualities during construction o~ a roofing
system as well as enhancing long term performance of the
roofing system itself.
Some of the aspects o~ the invention having been
stated, other aspects will become evident as the
description proceeds, when taken in connection with the
accompanying drawings.
Brief Description of the Drawinqs
Figure 1 is a top plan view, with parts broken away,
of a roofing system in accordance with the present
invention;
Figure 2 is an exploded cross-sectional view of a
representative built-up roof over a plywood deck
constructed in accordance with the present invention;
Figure 3 is an exploded cross-sectional view of a
representative built-up roof over an in~ulated metal deck
constructed in accordance with the present invention;
Figure 4 is an exploded cross-sectional view o~ a
representative bitumen capsheet over plywood deck roo~
constructed in accordance with the present invention;
Figure 5 is an exploded cross-sectional view of a
representative bitumen capsheet over an insulated metal
deck roof constructed in accordance with the present
invention; and
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Figure 6 is an exploded CX065 sectional view of a
representative water-shedding steep roof constructed in
accordance with the present invention.
Best Mode For Carryinq Out the Invention
Referring now to the drawings, Figure 1 illustrates
a representative built-up roof construction utili~ing a
polymer latex coated non-woven polyester web (such as
spun-bonded polyester web) as the base sheet in
substitution for conventional "asphalt paper" (asphalt
saturated fiberglass web)~ The roofing system, generally
designated 10, includes a plywood deck 12 such as is
typically found on many flat roof commercial buildings, a
polymer latex coated base sheet 14 applied over plywood
deck 12, a layer of bitumen or asphalt 16 (including Type
I, II, III and IV asphalts, cold tar pitch, cold processed
adhesives and mastics and other suitable asphaltic
products), a reinforcement ply sheet 18 (such as bitumen
saturated polyester, bi-tumen saturated fiberglass, bitumen
saturated organic felt, non-bitumen saturated polyester,
and non-bitumen saturated fiberglass), a second layer of
bitumen 16, and surface layer 19 applied over bitumen
layer 16 which may be an aggregate such as gravel or a
smooth coating of asphalt or other protective coating such
as asphaltic emulsions. Although not shown in the
drawings, polymer latex coated base sheet 14 is attached
to plywood deck 12 by conventional means known to those
familiar with the roofing art such as barbed or ring
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shanked nails either with or without fastening plates or
screws used in conjunction with fastening plates.
Although any suitable polymer latex coated polyester
web base sheet 14 may be utilized in roofing system lo as
a substitute for asphalt paper, a preferred construction
utilizes LUTRADUR brand spun-bonded polyester web
manufactured and sold by Freudenberg Spunweb Company of
Durham, North Carolina. The polymer latex coating applied
to base sheet 14 may be applied to either one or both
sides thereof so long as the coating provides a sufficient
barrier of polvmer latex thereto to render the web
impervious to hot bitumen which would normally be applied
thereover during the construction o~ built-up roofs or
related roof constructions utilizing base sheet 14 between
a deck and a roof surface secured thereover. The polymer
latex coating may include but is not limited to one or a
combination of the following comonomers: styrene, vinyl
acrylic, vinyl chloride, vinyl acetate, vinylidene
chloride, and butadiene. The preferred coating is vinyl
acrylic which is applied by conventional technique known
in the textile related arts such as foamed application.
Also, possible additives to the coating include inorganic
fillers, foaming agents, synthetic thickeners, melamine
resins, catalysts, water repellents, W inhibitors, and
~5 fire retardants. The primary criteria for the resulting
coated polyester web is that it be hot bitumen impervious.
Other roofing systems contemplated by the present
invention which utili~e a polymer latex coated non-woven
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polyester web base sheet in lieu of asphalt paper may be
found with reference to Figures 2 - 6. Figure 2
~ssentially discloses a representative built-up roof over
plywood deck of the same type described in Figure 1. The
only distinction being that multiple alternating layers of
hot bitumen 16 and ply sheets 18 are applied over polvmer
latex coated base sheet 14 prior to the application of
surface layer lgo The specific construction details of
built-up roofing system 10 as well as other systems
described below is a matter of design choice and depends
on the specific needs of a particular building.
It should be noted with respect to Figures 2 - 6
that, although not shown in the drawings for greater ease
of illustration, nails or screws and fastening plates
would be used to secure the polymer latex coated polyester
web base sheet to the deck therebeneath. The use of the
screws or nails as fastening means is necessary in order
to provide protection against naturally occurring wind
uplift forces. The advantages of the new polymer latex
coated polyester web base sheet 14 over previously known
asphalt paper base sheet in preventing wind uplift damage
to a roof will be discussed below.
Figure 3 illustrates a typical built-up roof over an
insulated metal deck comprising preformed metal deck 22,
a layer of insulation 24 (which may consist of a variety
of commercially produced products having a wide range of
R values such as isocyanurate, urethane, extruded
polystyrene, phenolic, fiberglass, and perlite and wood
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fiber), a polymer latex coated polyester web base sheet 26
(which, not shown, is mechanically attached to metal deck
2~ with metal deck screws and fastener plates by placing
the fastener plates on base sheet 26 and then securing the
screws through the plates as well as the underlying base
sheet 26, insulation layer 24, and metal deck 22), a
bitumen layer 27, a layer of reinforcement ply sheet 28,
additional bitumen and reinforcement ply sheet layers, and
a surface layer 29 (which may also include any of the
suitable surfaces described hereinbefore).
With reference now to Figure 4, still another roofing
system contemplated by the present invention is
illustrated which incorporates a polymer latex coated base
sheet as a substitute for conventional asphalt paper. The
modified bitumen capsheet over plywood deck roofing system
30 comprises plywood deck 32, a polymer latex polyester
web base sheet 34, a layer of bitumen or asphalt 36, and
bitumen capsheet 38. Bitumen capsheet 38 is a
conventional bituminous roofing membrane known to those
familiar with the art such as those modified with APP
(atactic polypropylene) or SBS (styrene butadiene styrene)
as well as capsheets incorporating only oxidized bitumen
without any modifier. The capsheets may also be
reinforced with a polyester, fiberglass or a combination
polyester/fiberglass substrate~
Another embodiment of the present invention is shown
in Figure 5 which illustrate a typical modified bitumen
capsheet over insulated metal deck roofing system ~0
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comprising preformed metal deck 42, an insulation layer 44
(similar to that described in Figure 3 above~, a polymer
latex coated polyester web base sheet 46, bitumen layer
48, and bitumen capsheet 49 as described in Figure 4
above. As referenced previously, fastening plates and
screws (which are not shown in the drawings) are utilized
to secure base sheet 46 and insulation layer 44 to
preformed metal deck 42. Finally, with reference to
Figure 6, still another embodiment of the roofing system
contemplated by the present invention can be appreciated.
Fi~ure 6 discloses a typical water-shedding inclined
roofing system 50 comprising plywood deck 52, polymer
latex coated polyester web base sheet 5~ (which is
attached by roofing nails or fastener plates and screws to
plywood deck 52), and asphalt shingles 56. Although
asphalt shingles 56 are shown as the top layer of inclined
roofing system 50, other roof surfaces could be utilized
including clay or concrete tiles, slate or metal shingles,
wood shakes, and pxeformed metal panels which are
particularly suitable as a mansard cover on commercial
buildings.
As can now be fully appreciatedl the present
invention contemplates providing a new base sheet material
to replace conventionally utilized asphalt paper in a
variety of roofing system constructions. Applicant
believes that there has long been a need for a new base
sheet for built-up roofing systems and other related roof
constructions since asphalt paper suffers from so many
shortcomings including being very heavy and cumbersome to
handlel requiring substantial storage space, requiring
high shipping costs, possessing relatively low resistance
to shear tearing and thus resulting in roof leaXs due to
stresses suffered either during or subsequent to
construction of the roof, and possessing a tendency to mat
or adhere to the deck therebeneath and thus create
difficulties in subsequent roof removal and replacement.
Applicant has surprisingly discovered that a
non-woven polyester web provided with a hot bitumen
impervious polymer latex coating on at least one side
thereof may be substituted ~or asphalt paper with
remarkable results. First of all, and perhaps most
striking, applicant has found that the polymer latex
coated non-woven polyester web base sheet weighs only
about ten to fifteen percent (10% - 15%) as much as the
asphalt paper which it replaces. This results in very
substantial savings in storage space as w~ll as shipping
costs. Also, the polymer latex coated non-woven polyester
web base sheet is substantially more pliable and thus
easier to use during the construction of a roofing system.
Also surprising, it has been found that the polymer latex
coated non-woven polyester web base sheet does not tend to
mat to an underlying deck as does asphalt paper, and it
possesses inherently greater tear strength and resulting
resistance to wind uplift forces and shear forces which
occur during construction and subsequent utilization of a
roofing system. Consequently, applicant has discovered a
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new base sheet product for use in roofing systems in lieu
of asphalt paper which, although weighing only about ten
percent as much as the product it replaces, possesses
greater performance characteristics as well as results in
substantial cost savings in storage and shipping.
As noted above, the preferred non-woven polyester web
for use in the base sheet is sold under the trademark
LUTRADUR. The wQight range of this web which may be
utilized in a roofing system is from about 25 grams per
square meter to 350 grams per square meter with a
preferred weight of about 100 grams per square meter. The
pol~mer latex coating applied thereto may be any one or
combination of monomers such as noted above but preferably
could be vinyl acrylic such as HYPOCH ~ R-13 manufactured
by High Point Chemicals of High Point, North Carolina, and
the coating would typically be applied by conventional
methods known to those in the textile industry such as
foam application. The polymer latex coating must be
applied to at least one side of the LUTRADUR non-woven
polyester web and the application must be such that the
product is rendered impermeable to hot bitumen applied
thereto. Although the amount of polymer latex to be
applied to the web is a matter of choice 50 long as the
resulting web is impervious to hot bitumen, it is believed
that a desirable range is about 30 weight percent to 9O
weight percent for the best results with a preferred
weight of about 60 percent. After application of the
polymer latex to the LUTRADUR non-woven web utilizing
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conventional textile processing methodologyf the resulting
product is dried and may be post-treated according to
conventional textile techniques. If only one side of the
non-woven polyester web i5 coated, it is believed that the
coated side should ~e placed adjacent the roof deck in
order to obtain the best results. This placement enhances
the adhesive attachment of an overlaying roofing layer to
the uncoated top side of the base sheet in a roofing
system construction.
An example of polymer latex coated non woven
polyester web base sheet contrasted to a conventional base
sheet is set forth below by way of example although it is
understood that many variations are possible according to
the type of roofing system being constructed and design
choice by the manufacturer of the coated web. The
specifics of the representative coated web for use in a
novel built-up type roof construction according to the
invention are as follows.
Example 1
Polyester/Polymer Latex Fiberglass/Bitumen
Base Sheet Base Sheet _
Weh: LUTRADUR (Style MANVILLE
LDH1010 and LDH2010) Fiberglass Sheet
Web
Weight: 100 grams/meter2 73 grams/meter2
Coating: HIPOCHEM FR-13 Bitumen
Vinyl Acrylic
Coating
Weight: 60 grams/meter2 1,144 grams/meter~
Total
Weight: 160 grams/meter2 1,217 grams/meter2
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In sumrnary, the very surprising aspect of the present
invention lies in the substitution of an acrylic resin
coated polyester web for asphalk paper in roofing system
constructions to achieve enhanced performance and reduced
storage and shipping costs with a lightweight product
weighing only a fraction as much as the roofing product it
replaces.
It will be understood that various details of the
invention may be c:hanged without departing from the scope
of the invention. Furthermore, the foregoing description
is for the purpose of illustration only, and not for the
purpoRe of limitation--the invention being defined by the
claims.
