A ROOFING SYSTEM
The present invention relates to roofing systems
that include cladding sheets that are retained to
underlying roof support structures by concealed clip
assemblies.
The present invention is concerned with
minimising heat transfer via roofing systems from and to
the interior of buildings.
Typically, roof cladding sheets are roll-formed
from painted or unpainted steel strip and include one or
more parallel ribs, pan sections, and side edge formations
that enable the sheets to be positioned side by side in
overlapping relationship.
It is known to secure cladding sheets to an
underlying roof support structure, such as roof purlins,
by fastening the sheets directly to the underlying
structure using fasteners, such as roofing nails, that
pierce the sheets and penetrate the underlying structure.
It is also known to secure cladding sheets to an
underlying structure by using clip assemblies that include
clips that are secured to the structure by fasteners and
are formed to extend into the ribs and engage re-entrant
portions of the ribs and thereby retain the sheets to the
clips. These clip assemblies are often preferred over
nails because they enable concealed fixing of cladding
sheets to an underlying structure.
There are a number of known concealed fixing
retaining clips. The clips include a so-called WG clip
disclosed in Australian patent 457099 in the name of
Comalco Limited, a clip disclosed in UK patent application
in the name of Stramit Industries Limited, and a clip
disclosed in Australian patent 685102 and other Australian
patents and patent applications in the name of Stramit
Corporation.
In warm climates there is considerable cost in
keeping the inside of buildings cool compared to the
outside.
Many modern buildings are air-conditioned and the
cost of air-conditioning is an important cost
consideration.
In cool climates there is considerable cost in
keeping the inside of buildings warm compared to the
outside. Many modern buildings are heated and the cost of
heating is an important cost consideration.
By far the largest amount of heat transfer from
and to the interior of a building is through the roofing
system of the building. Thus, a roofing system that
minimises heat transfer is one option for reducing airconditioning
and heating costs.
The present invention is concerned with providing
a roofing system for a building that minimises heat
transfer via the roofing system from and to the interior
of the building.
The present invention is also concerned with
providing a clip assembly of a roofing system for a
building that minimises heat transfer via the clip
assembly from and to the interior of the building.
The present invention provides a roofing system
for a building that includes: a plurality of roof cladding
sheets in overlapping relationship, each cladding sheet
having at least one rib and pans; and a plurality of
concealed clip assemblies that retain the cladding sheets
to an underlying roof support structure, each clip
assembly including:
(a) an elongate strap member;
(b) a plurality of clips mounted to an upper
surface of the strap member and engaging
re-entrant portions of the ribs of one or
more sheets; and
(c) a plurality of spacer members made of
thermally insulating material mounted to a
lower surface of the strap member in
alignment with the clips and spacing the
clips above the underlying structure.
The present invention also provides a roofing
system for a building that includes: a plurality of roof
cladding sheets in overlapping relationship, each cladding
sheet having at least one rib and pans; and a plurality of
concealed clip assemblies that retain the cladding sheets
to an underlying roof support structure, each clip
assembly including:
(a) a clip that engages re-entrant portions of
the rib; and
(b) a spacer member that spaces the clip above
the underlying structure.
Spacing the clips above the underlying structure
by means of the thermally insulating spacer members
prevents direct contact between the clips and the
structure and this of itself increases the thermal
resistance of the clip assembly per se and the roofing
system as a whole.
Spacing the clips above the underlying structure
also has the effect of spacing the cladding sheets further
above the underlying structure than would normally be the
case. The additional space may be filled with thermal
insulation material or left as an air gap. In either
case, there is a contribution to the thermal resistance of
the roofing system.
Preferably the roofing system includes:
(a) a. layer of thermal insulation material,
such as batts of fibreglass insulation, on
the underlying structure; and
(b) an air gap between the layer and the
cladding sheets.
The spacer member may be any suitable member for
supporting the clip above the underlying structure.
Suitable members include members that have C-shaped and Zshaped
transverse sections and are formed by folding metal
sheet material.
Preferably the spacer members are blocks of
thermally insulating material.
Preferably the thermally insulating material has
a high density to provide support against downward loads.
Preferably the height of the spacer members is at
least 3 cm.
More preferably the height of the spacer member
is at least 4 cm.
Preferably the roofing system includes a
plurality of fastening assemblies that secure the clip
assemblies to the underlying structure.
Preferably each fastening assembly includes a
fastener, such as a screw, that has a head and a shank
that extends through aligned openings in each of the clip,
the strap member, and the spacer member of one of the clip
assemblies and into the underlying structure.
Preferably the fastener has a small diameter
shank.
Preferably the clip has a base and the clip
opening is in the base and the fastening assembly includes
a washer formed from a thermally insulating material that
is positioned between the fastener head and the base of
the clip.
Preferably the washer includes a downwardly
depending sleeve that extends into the opening in the base
of the clip and separates the fastener shank from the
base.
Preferably each clip includes a pair of cladding
sheet retaining members that extend upwardly from opposite
sides of the base.
Preferably each cladding sheet retaining member
includes an outwardly-turned top flange that has a central
upper section and two outer sections that extend
downwardly from opposite ends of the upper section,
whereby the outer sections of the top flanges of the
retaining members contact the re-entrant portions of the
rib of the cladding sheet and secure the sheet to the
clip.
includes a main wall element that extends upwardly from
the base and terminates in the top flange.
Preferably the main wall elements extend
transversely to a longitudinal direction of the rib.
Preferably the base and the retaining members
define a generally U-shape.
Preferably each outer section of the flanges of
the retaining members has a free edge that contacts one of
the re-entrant portions of the rib and secures the
cladding sheet to the clip.
Preferably each outer section of the flanges of
the retaining members extends downwardly and outwardly
beyond an upper section of one of the main wall elements
and the outer section includes a downwardly facing
shoulder that connects the outer section to the main wall
element.
Preferably each cladding sheet includes a
plurality of ribs separated by pans.
The present invention also provides a clip
assembly of a roofing system for a building as described
above, which clip assembly includes:
(a) an elongate strap member having an upper
surface and a lower surface, the upper
surfaces including a plurality of platforms
for clips for engaging cladding sheets; and
(b) a plurality of spacer members made of
thermally insulating material mounted to
the lower surface of the strap member at
locations that are aligned with the clip
platforms on the upper surface.
According to the present invention there is also
provided a clip assembly for a roofing system as described
in the preceding paragraph and a plurality of clips for
engaging cladding sheets mounted on the platforms.
The present invention is described further by way
of example with reference to the accompanying drawings, of
which:
Figure 1 is a partially cross-sectional side
elevation of part of one embodiment of a roofing system in
accordance with one embodiment of the present invention;
Figure 2 is a side elevation of an embodiment of
a clip assembly of a roof assembly of the type shown in
Figure 1;
Figure 3 is a top plan view of the clip assembly
shown in Figure 2;
Figure 4 is an exploded section of the part of
the clip assembly of the roofing system shown in Figure 1;
Figure 5 is a perspective view of the cladding
sheet of the roofing system shown in Figure 1;
Figure 6 is an end elevation of the cladding
sheet shown in Figure 5; and
Figure 7 is an end elevation of the central rib
of the cladding sheet shown in Figures 5 and 6.
The roofing system shown in the figures includes:
(a) a plurality of roof cladding sheets 7 (only
one of which is shown in the Figure 1);
(b) a plurality of concealed fixing clip
assemblies (only one of which is shown in
Figures 1 to 4) retaining the cladding
sheets to roof support purlins 5; and
(c) a layer of fibreglass insulation material
57 (Figure 1 only) occupying part of the
roof cavity defined by the cladding sheets
7 and the roof purlins 5.
Each concealed fixing clip assembly includes:
(a) an elongate strap 71;
(b) a plurality of clips 3 mounted to an upper
surface of the strap 71 and engaging the
cladding sheets 7; and
(c) spacer members in the form of high density
polystyrene blocks 55 mounted to a lower
surface of the strap 71 and spacing the
clips 3 above the purlins 5.
The straps 71 are a convenient means of mounting
a plurality of the clips 3 and the spacer members 55 and
thereafter locating the clips 3 at required spacings for
engaging the cladding sheets.
Each strap 71 is formed from sheet steel and
includes a flat central section 77 and downwardly folded
sides 79. Each strap 71 includes a series of spaced apart
mounting platforms 81 for the clips 3. The mounting
platforms 81 are flattened sections on which the clips 3
can be mounted.
The high density polystyrene block spacer members
55 are mounted to the lower surface of the straps 71, for
example by means of adhesive or adhesive-backed tape. The
spacer members 55 are positioned to be aligned with the
clips 3.
The spacer members 55 provide support for the
cladding sheets 7 against downward loads and have
substantially the same insulating properties as the
surrounding fibreglass insulation material. Thus, the
spacer members 55 provide resistance to heat transfer.
In addition, the spacer members 55 space the
cladding sheets 7 above the layer of fibreglass insulation
material 57 so that the roofing system further includes an
air gap 59 (Figure 1 only) in the roof cavity between the
cladding sheets 7 and the fibreglass insulation material,
and thus further improves the resistance to heat transfer
provided by the roofing system.
The roof system also includes fastening
assemblies securing the clip assemblies to the purlins 5.
Each fastening assembly includes a fastener in
the form of a small diameter screw 51 that secures a clip
3 to a purlin 5. The shank of the screw 51 extends
through the clip 3, and then successively through the
underlying mounting platform of the strap 71 and the
aligned spacer member 55, and then into the purlin 5.
Each fastening assembly also includes a washer 65
that is formed from a thermally insulating material, such
as rubber. The washer 65 prevents direct contact between
the clip 3 and the head of the screw 51.
In addition, the washer 65 includes a downwardly
extending sleeve 69 that extends into the opening 63 in
the clip 3 and separates the shank of the screw 51 from
the clip 3.
The applicant has found in experimental work that
the combination of the above-described features of the
spacer members 55, the air gap 59, the small diameter
screws 51, and the washers 65 formed from thermally
insulating material reduces heat transfer from the
cladding sheets 7 to the purlins 5 and thereby to the
interior of a building and vice versa.
Each cladding sheet 7 is roll-formed from sheet
steel and includes a leading edge 8, a trailing edge 10, a
central lengthwise extending rib, generally identified by
the numeral 11, and pair of lengthwise extending pans 13
on opposite sides of the rib 11.
The cladding sheet 7 may be of any suitable
length and width and may include any suitable number of
ribs 11 separated by pans 3.
The rib 11 of the cladding sheet 7 includes an
upper clip retaining section* generally identified by the
numeral 15, and two downwardly extending shoulders 17 that
interconnect the upper clip retaining section 15 and the
pans 13.
With particular reference to Figure 7, the upper
clip retaining section 15 includes a flat upper section 19
that separates two sides, generally identified by the
numeral 21. Each side 21 includes a first section 41 that
extends outwardly and downwardly from the upper section
19 / a second section 43 that extends downwardly and
inwardly from the lower edge of the first section 41, and
a third section 45 that extends downwardly and outwardly
from the second section 43 and merges with the shoulder
17.
The second sections 43 of each upper retaining
clip section 15 define opposed re-entrant portions of the
rib 13 and are hereinafter referred to as "re-entrant
portions 43".
Each shoulder 17 includes a first part 17a that
extends upwardly from the pan 13 and a second section 17b
that extends from the first section 17a to the clip
retaining section 15. The first part 17a has a steeper
slope than the second part 17b. In overall terms, the
shoulders 17 are a significant component of the total size
of the rib 11.
The leading and trailing edges 8, 10 of the
cladding sheet 7 are formed as partially-completed ribs in
order to facilitate interlocking of successive cladding
sheets. These partially-completed ribs are hereinafter
referred to as "leading edge formations 8" and "trailing
edge formations 10".
Each clip 3 is formed by folding a flat metal
blank into the configuration shown the Figures.
With particular reference to Figure 4, each clip
3 includes:
(a) a flat base 21; and
(b) a pair of retaining members, generally
identified by the numeral 23, extending
upwardly on opposite sides of the base 21,
whereby the base 21 and the retaining
members 23 form a generally U-shaped
member.
Each retaining member 23 includes an upstanding
main wall element 61 that terminates in an outwardly
extending top flange 25.
Each top flange 25 includes a central upper
section 27 and two opposed sections 29 that slope
downwardly from the upper section 27.
The downwardly sloping sections 29 terminate in
lower edges 31.
The downwardly sloping sections 29 extend
outwardly and downwardly beyond the upper sections of the
main wall elements 61. The sections 29 include downwardly
facing shoulders 57 that connect the sections 29 to the
main wall elements 61.
Each clip .3 also includes an opening 63 to
facilitate securing the clip 3 to a purlin 5.
In use, a plurality of the clip assemblies is
fastened to purlins 5 at spaced intervals along the length
of the purlins 5 using the screws 51 of the fastening
assemblies.
Batts of fibreglass insulation material are then
positioned on the purlins 5 and arranged to extend beneath
the straps 71 to form the layer 57 of insulation material
shown in Figure 1.
Thereafter, cladding sheets 7 are successively
placed over the purlins 5 in overlapping relationship. The
cladding sheets 7 are positioned so that the longitudinal
direction of the ribs 11 is perpendicular to the planes of
the main wall elements 61 of the clips 3.
The cladding sheets 7 are then progressively
engaged with the clips 3 as the sheets are successively
placed over the purlins 5.
This is achieved by successively pressing the
leading edge formations 8, the ribs 11, and the trailing
edge formations 10 of the sheets 7 onto the clips 3 so
that the leading edge formations 8, the ribs 11, and the
trailing edge formations 10 deflect outwardly and the top
flanges 25 of the clips 3 deflect inwardly.
This movement allows the leading edge formations
8, the ribs 11, and the trailing edge formations 10 to be
positioned on the clips 3 with the lower edges 31 and the
shoulders 57 of the flanges 25 engaging the re-entrant
portions 43 of the ribs 11 so that the cladding sheets 7
are secured to the clips 3.
Many modifications may be made to the preferred
embodiment of the roofing system described above without
departing from the spirit and scope of the present
invention.
In the above-de scribed preferred embodiment of
the roofing system there is an air gap 59 in the roof
cavity. The present invention is not limited to this
arrangement and extends to arrangements in which the air
gap is filled with insulation material.

WE CLAIM:
1. A roofing system for a building characterized in that a plurality of roof cladding
sheets in overlapping relationship, each cladding sheet having at least one rib and pans ; and
a plurality of concealed clip assemblies that retain the cladding sheets to an underlying roof
support structure, each clip assembly including:
(a) an elongate strap member ;
(b) a plurality of clips mounted to an upper surface of the strap member and engaging re-entrant portions of the ribs of one or more sheets ; and
(c) a plurality of spacer members made of thermally insulating material mounted to a lower surface of the strap member in alignment with the clips and spacing the clips above the underlying structure.
2. The roofing system as claimed in claim 1 comprising:
(a) a layer of thermal insulation material, such as batts of fibreglass insulation, on the underlying structure ; and
(b) an air gap between the layer and the cladding sheets.

3. The roofing system as claimed in claim 1 or claim 2 wherein the spacer members are blocks of thermally insulating material.
4. The roofing system as claimed in claim 3 wherein the thermally insulating material has a density that enables the spacer numbers to provide support against downward loads.
5. The roofing system as claimed in any one of the preceding claims wherein the height of the spacer members is at least 3 cm.
6. The roofing system as claimed in any one of the preceding claims comprising a plurality of fastening assemblies that secure the clip assemblies to the underlying structure.
7. The roofing system as claimed in claim 6 wherein each fastening assembly comprises
a fastener, such as a screw, that has a head and a shank that extends through aligned openings
in the clip, the strap member, and the spacer member of one of the clip assemblies and into the underlying structure.
8. The roofing system as claimed in claim 7 wherein the fastener has a small diameter shank.
9. The roofing system as claimed in claim 7 or claim 8 wherein the clip has a base and the clip opening is in the base and the fastening assembly comprises a washer formed from a thermally insulating material that is positioned between the fastener head and the base of the clip.
10. The roofing system as claimed in claim 9 wherein the washer comprises a downwardly depending sleeve that extends into the opening in the base of the clip and separates the fastener shank from the base.
11. The roofing system as claimed in any one of the preceding claims wherein each clip comprises a pair of cladding sheet retaining members that extend upwardly from opposite sides of the base.
12. The roofing system as claimed in claim 11 wherein each cladding sheet retaining member comprises an outwardly-turned top flange that has a central upper section and two outer sections that extend downwardly from opposite ends of the upper section, whereby the outer sections of the top flanges of the retaining members contact the re-entrant portions of the rib of the cladding sheet and secure the sheet to the clip.
13. The roofing system as claimed in claim 12 wherein each cladding sheet retaining member comprises a main wall element that extends upwardly from the base and terminates in the top flange.
14. The roofing system as claimed in claim 13 wherein the main wall elements extend transversely to a longitudinal direction of the rib.
15. The roofing system as claimed in any one of claims 12 to 14 wherein each outer section of the flanges of the cladding sheet retaining members has a free edge that contacts one of the re-entrant portions of the rib and secures the cladding sheet to the clip.
16. The roofing system as claimed in any one of claims 12 to 15 wherein each outer section of the flanges of the cladding sheet retaining members extends downwardly and outwardly beyond an upper section of one of the main wall elements and the outer section comprises a downwardly facing shoulder that connects the outer section to the main wall element.
17. The roofing system as claimed in any one of the preceding claims wherein each cladding sheet comprises a plurality of ribs separated by pans.
18. A clip assembly of a roofing system for a building as claimed in claim 1 which clip assembly comprises:

(a) an elongate strap member having an upper surface and a lower surface, the upper surface including a plurality of platforms for clips for engaging cladding sheets; and
(b) a plurality of spacer members made of thermally insulating material mounted to the lower surface of the strap member at locations that are aligned with the clip platforms on the upper surface.

19. The clip assembly as claimed in claim 18 wherein the spacer members are blocks of thermally insulating material.
20. The clip assembly as claimed in claim 19 wherein the thermally insulating material has a density that enables the spacer numbers to provide support against downward loads.
21. The clip assembly as claimed in any one of the claims 18 to 20 wherein the height of the spacer members is at least 3 cm.
22. A roofing system for a building as claimed in claim 1 wherein a plurality of roof cladding sheets in overlapping relationship, each cladding sheet having at least one rib and
pans; and a plurality of concealed clip assemblies that retain the cladding sheets to an underlying roof support structure, each clip assembly including:
(a) a clip that engages re-entrant portions of the rib; and
(b) a spacer member that spaces the clip above the underlying structure.

23. The roofing system as claimed in claim 22 wherein the spacer member is a block of thermally insulating material.
24. The roofing system as claimed in claim 23 wherein the thermally insulating material has a density that enables the spacer number to provide support against downward loads.
25. The roofing system as claimed in any one of the preceding claims 22 to 24 wherein the height of the spacer member is at least 3 cm.
26. The roofing system as claimed in any one of the claims 22 to 25 comprises a plurality of fastening assemblies that secure the clip assemblies to the underlying structure.
27. The roofing system as claimed in claim 26 wherein each fastening assembly comprises a fastener, such as a screw, that has a head and a shank that extends through aligned openings in the clip, the strap member, and the spacer member of one of the clip assemblies and into the underlying structure.
28. The roofing system as claimed in claim 27 wherein the fastener has a small diameter shank.
29. The roofing system as claimed in claim 27 or claim 28 wherein the clip has a base and the clip opening is in the base and the fastening assembly comprises a washer formed from a thermally insulating material that is positioned between the fastener head and the base of the clip.
30. The roofing system as claimed in claim 29 wherein the washer comprises a downwardly depending sleeve that extends into the opening in the base of the clip and separates the fastener shank from the base.