BASE METAL

The base metal is cold rolled mild steel and is indigenously available in 240 MPa grade. Standard thicknesses 0.45 to 0.80 mm. Special high tensile grade materials like 300/550 MPa are also available from abroad. Standard thickness 0.42 to 0.80 mm.

BASE METAL PROTECTION

1.Hot dipped galvanizing

Steel sheets are protected with Zinc
coating having density of 180 GSM to 275 GSM.

2.Aluzinc coating (Aluminium & Zinc alloy coating).

A special alloy coating comprising of 55%
Aluminium, 43.5% Zinc & 1.5% silicon to a coating
Density of 150 GSM or 200 GSM.
Has to be imported and is available in trade names galvalume, Zincalume.

COLOUR COATING

Choice of coating is very much dependant on the environmental conditions at the point of end use.

AVAILABILITY

Architectural Polyester (adequate for indoor and general purpose applications)

High Grade coating for industrial and adverse environmental conditions are,

1.XRW coating
2.XPD coating
3.ULTRA coating

TYPES

Pierced and fastened system

In this system, the profiled sheets are fixed to the purlin / girts with carefully engineered self drilling and self tapping screws with EPDM washers and matching colour coated UV stabilized caps.These systems are commonly used in our country.

Concealed Fixing System

Concealed clips are attached to the purlins, and the panels and the clips are integrated by snapping at the seam.The main advantage is that fasteners are fully concealed. Site roll-forming ensures minimum end laps, permitting shallow roof pitch.

INSULATED ROOFING & CLADDING SYSTEM

Built Up Roofing & Cladding System :

Roofing & Cladding can be built up layer by layer, with insulation to meet the requirements of Thermal Comfort as well as Noise Control. Combination of Fastened and concealed fixing systems are effectively utilised today in many building roofs. Double skin fastened insulated Roofing and Cladding Systems are commonly used economical building envelopes these days. Single skin insulated roofing / cladding are most commonly used for roofing and cladding system in industrial buildings.

Composite Roofing & Cladding System

Prefabricated sandwich panels with PUF / Rockwool or combination of PUF & Rockwool as core are also available today for insulated cladding for cold rooms, D.G. set rooms to reduce the heat ingress and noise transmissions respectively. These composite panels comprise of two metal skins with PUF / Rockwool core.

Prefabricated sandwich panels with PUF core and with profiled sheet on the weathering side and slightly ribbed plain sheets on the inner side are also commonly used for insulated roofings / claddings in many industrial and commercial buildings.

Special Roofing System

Mangalore Tile Type profiled sheets are available for resorts and other buildings where importance is given to Aesthetics. It is common to see designers featuring these very attractive roofs in single storey units in an industrial site to break the monotony.

ANCILLARY MATERIALS

Fasteners

Success of any roofing and cladding system is entirely dependant on the fastener selection and usage.

Self-drilling, self-tapping fasteners made of high tensile steel with EPDM washers are commonly used today in pierced and fastened system.

AS3566CLASS3 APPROVED FASTNERS Should be used

OTHER ANCILLARY MATERIALS

Profiled HDPE end closures, Flashings, cappings of adequate width, skylighting with Poly Carbonate / FRP sheets etc. have to be carefully designed and applied to make the building water tight.
Flashings and gutter material should always be chosen for compatibility with the roofing.

Insulation is an important provision in a building from the point of view :-

Thermal comfort

Acoustic / Noise reduction

Bonded Rockwool in the form of blankets/slabs with aluminium foil facing at a density of 48 Kg./m3 and in thickness of 25 mm or 50 mm are used for thermal insulation of metal roofing and cladding in buildings.

Bonded glasswool at a density of 24 Kg./m3 in 25 or 50 mm with aluminium foil facing are also used.

Bonded Rockwool in 64 Kg./m3 and 96 Kg./m3 are used in double / triple skin insulated roofing and cladding for noise reduction purpose.

Bonded Rockwool in 48 Kg./m3 density / bonded glasswool at 24 Kg./m3 density are used for acoustical applications.

PUF sandwich panels with rigid polyurethane foam core and colour coated metal sheetings on either side are used for construction of cold stores.

Prefabricated sandwich panels with PUF core and with profiled sheet on the weathering side and slightly ribbed plain sheets on the inner side are also commonly used for Insulated roofings / Claddings.

Pierced and fastened system

Single skin insulated roofing system.
Weld mesh shall be placed over the purlins and insulation material in the form of rolls shall be laid over the weld mesh prior to fixing the metal roofing sheets.

Double skin insulated roofing.

1.Internal profiled sheets shall be fixed to the purlins.
2.Z-sub-girts shall be provided at purlin locations and the insulation material shall be laid between the Z-purlins.
3.External profiled sheets shall be fixed to the Z-purlins.

Pierced and fastened system – General

1.Roofing sheets shall be crest fixed and the cladding sheets shall be valley fixed.
2.Wall cladding shall be commenced and progressed from the end which is away from the prevailing wind or most viewed direction so that the sheet overlaps are not visible.

Concealed fixing system

1.The clips shall be fixed to the purlins and the kliplock sheets shall be clip fixed on the clips.
2.The insulated system installation shall be similar to the pierced fixing system.

GENERAL

Bundles of roof and wall cladding sheets should be stored in such a way that one end is at a higher elevation than the other end to allow speedy drainage of water. Sheets should be kept covered with Tarpaulin during the times of rain. Usage of Polythene sheet cover should be avoided as it can cause vapour retention within the bundle and subsequent condensation.

The use of chalk line is always recommended for accurate drilling and screwing of sheets to the support structure. This gives better appearance and less risk of leakage due to misdrilling.
While walking on the roof, always walk on the low ribs and preferably along the purlin line. Standing on the hi-ribs can cause severe damage, which could lead to possible leakage of water. Do not walk on skylights.

Metal roofing and cladding concepts have carved for themselves an enviable position in the Construction Industry. The major advantage of the high speeds of design and construction afforded by metal roofing and cladding has contributed to their premier position.