Key takeaways
- A metal deck roof is a system: roof sheet, fixing method, support spacing and the structure below are chosen together.
- Support spacing is product-specific. Lysaght's 2025 Malaysian catalogue for TRIMDEK OPTIMA lists 2,500 mm internal but 1,900 mm end spans for 0.42 mm sheet on 1 mm supports.
- Thickness can be quoted two ways: Lysaght lists the same TRIMDEK OPTIMA sheet as 0.42 mm base metal thickness (BMT) and 0.47 mm total coated thickness (TCT). Compare quotations on BMT.
- Design wind pressure for a Malaysian roof is derived under MS 1553:2002, and a structural engineer should confirm it for the roof's edges, corners and general area.
- NS BlueScope Malaysia's COLORBOND ULTRA datasheet asks buyers to seek specialised advice within 1 km of salt marine locations and to check they hold the current datasheet.
What decides the right metal deck roof for a Malaysian building?
The right metal deck roof for a Malaysian building is decided by the site before the catalogue: the building's use, the roof pitch and length, the distance between purlins or truss top chords, the corrosion exposure and the design wind pressure. Heat, condensation, rain noise and any future solar array come next; thickness or colour alone never settles it.
The Malaysian Meteorological Department (MetMalaysia) describes the country's climate as having "uniform temperature, high humidity and copious rainfall", and reports that the maximum daily average relative humidity, little changed from place to place, is over 94%. A Malaysian metal roof is judged on drainage, coating and condensation control as much as on strength.
Who should confirm each metal deck roofing decision?
Each metal deck roofing decision should be confirmed in writing by the party below.
| Decision | What to establish for this building | Who confirms it |
|---|---|---|
| Coating and substrate | Distance to the sea, industrial fallout, surfaces not washed by rain | Supplier's written material selection advice |
| Fixing method and profile | Roof pitch, sheet length, end laps, penetrations | Manufacturer's product literature and the designer |
| Thickness and spacing | Purlin or top-chord centres, end and internal spans, overhangs, foot traffic | Manufacturer's span table, then the engineer |
| Wind | Site exposure, building height, edge and corner zones under MS 1553 | Structural engineer |
| Heat, condensation and noise | Insulation, vapour barrier, ceiling, finish colour | Designer and supplier |
| Warranty | Eligibility, environment limits and maintenance conditions | Supplier's written terms |
Which coating suits a metal roofing sheet in Malaysian conditions?
A common choice for a Malaysian metal roofing sheet is aluminium-zinc alloy-coated steel such as ZINCALUME, supplied bare or pre-painted, with the paint system matched to the exposure. NS BlueScope Malaysia rates its COLORBOND ULTRA steel for moderate to severe marine or industrial environments. The right coating depends on distance from the sea, industrial fallout and whether rain washes every surface.
Brands here are examples; compare any other mill's product on the same documented basis. NS BlueScope Lysaght Malaysia's Selection Guide (October 2019) describes ZINCALUME steel as "composed of 55% aluminium, 43.5% zinc and 1.5% silicon". Lysaght's 2025 Malaysian catalogue for TRIMDEK OPTIMA lists a minimum coating class of AZ150 and G550 steel. NS BlueScope Malaysia's COLORBOND ULTRA datasheet (revision 18 July 2024) names ZINCALUME AZ200 as its preferred substrate and lists MS 2383 C5 for the paint coating and MS 1196 for the substrate. A quotation should state the coating class and paint system, not just a brand.
When does a site need specialised coating advice?
NS BlueScope Malaysia's COLORBOND ULTRA datasheet asks buyers to contact BlueScope before using the product "within 1km of salt marine locations, severe industrial or abnormally corrosive environments; in areas not washed by rain". Lysaght's Roofing & Walling Installation Manual, Malaysia edition (2023) says areas not cleaned by natural rainfall, such as the tops of walls sheltered by eaves, should be washed down every six months. The COLORBOND ULTRA datasheet also advises using the product "promptly (within 6 months) to avoid the possibility of storage related corrosion".
Pierce-fixed or concealed-fix: which metal deck profile suits the roof?
A pierce-fixed metal deck profile is screwed through the sheet into the supports, while a concealed-fix profile clips onto brackets fixed to the supports, leaving no exposed fasteners. Lysaght Malaysia offers its concealed-fix KLIP-LOK OPTIMA for low-pitched roofs and describes screw fixing of its pierce-fixed TRIMDEK OPTIMA as "simple and fast". The manufacturer's minimum pitch, end-lap rules and span table for the chosen profile decide which suits the roof.
| Fixing method | Example profile | What the manufacturer states |
|---|---|---|
| Pierce-fixed | TRIMDEK OPTIMA | Screws "pass through the sheeting"; roof fasteners go through the crests "to maximize watertightness"; five fasteners per sheet per support; minimum pitch 3° |
| Concealed-fix (clip) | KLIP-LOK OPTIMA | "Concealed fastening offers excellent water tightness and control of thermal expansion"; minimum roof slope 2°; end-lapping "highly not recommended" |
The fixing method changes the minimum pitch, the end-lap rules and the insulation detail, so it should be chosen before the support layout.
How thick should a metal roofing sheet be for your support spacing?
The thickness a metal roofing sheet needs depends on the support spacing, the profile and the loads, so there is no single correct figure. A thicker sheet of the same profile can span further between purlins or truss top chords, but only on the support thickness and loading stated in the manufacturer's table. End spans and overhangs are usually shorter than internal spans.
| Base metal thickness | Single span | End span | Internal span | Unstiffened eaves overhang | Stiffened eaves overhang |
|---|---|---|---|---|---|
| 0.42 mm | 1,200 mm | 1,900 mm | 2,500 mm | 150 mm | 250 mm |
| 0.48 mm | 1,600 mm | 2,100 mm | 3,000 mm | 150 mm | 250 mm |
What does a published span table assume?
Lysaght's 2025 TRIMDEK OPTIMA catalogue states that its roof spacings are "based on foot-traffic loading", that the table assumes "supports of 1mm BMT", and that the spacings "may vary by Serviceability and Strength Limit States for particular projects". A span taken from one profile's table does not transfer to another profile, another thickness or thinner supporting steel. For the structure beneath, see our guide on choosing a steel roof truss system in Malaysia.
Why must a quotation state base metal thickness?
Sheet thickness is quoted either as base metal thickness (BMT), the steel alone, or total coated thickness (TCT), which includes the coating. Lysaght's TRIMDEK OPTIMA catalogue lists 0.42 mm BMT as 0.47 mm TCT, and 0.48 mm BMT as 0.53 mm TCT. Two quotations reading "0.47 mm" and "0.42 mm" may describe the same roof sheet. Span tables are read by BMT, so compare metal roofing quotations on BMT.
How should wind and heavy rain shape the specification?
Wind and rain decide the fixing pattern, pitch and sheet length. In Malaysia, design wind actions are determined under MS 1553:2002, the code of practice on wind loading for building structures, and a structural engineer should confirm the pressures for the roof's edges, corners and general area. Rain governs the minimum pitch, the ridge-to-gutter length and how sheet ends are turned.
MS 1553:2002 was prepared under CIDB with Jabatan Kerja Raya and the Malaysian Meteorological Department on the committee, and it includes a local pressure factor (Kl) for claddings, which raises design pressure where wind loads are highest. Lysaght's TRIMDEK OPTIMA catalogue applies a local pressure factor (Kl) of 2 for single and end spans and 1.5 for internal spans. Lysaght states its wind-pressure capacities come from laboratory tests to Australian Standards AS 1562.1 and AS 4040.2, so ask any supplier which standard its wind figures were tested to.
How does rainfall affect pitch and sheet length?
MetMalaysia records that during the northeast monsoon, exposed areas such as the east coast of Peninsular Malaysia, Western Sarawak and the northeast coast of Sabah "experience heavy rain spells". Peak intensity is what matters for a metal roof. Lysaght's TRIMDEK OPTIMA catalogue publishes maximum ridge-to-gutter roof lengths against roof slope and peak rainfall intensity in mm/hr, and notes that penetrations alter the flow of water. At its 3° minimum pitch, for example, the TRIMDEK OPTIMA catalogue allows a ridge-to-gutter length of 138 m at a peak rainfall intensity of 200 mm/hr, falling to 55 m at 500 mm/hr. A long, low-pitched metal deck roof should be checked against that drainage table, not only against the minimum pitch.
How do you control heat, condensation and rain noise under a metal deck roof?
Heat, condensation and rain noise under a metal deck roof are controlled by layers chosen with the sheet: a reflective finish on top, insulation held against the underside, a vapour barrier where condensation is likely, and a ceiling below. Insulation also changes the screw length the installer needs, so these layers belong in the roofing specification from the start, not as an add-on.
Lysaght's TRIMDEK OPTIMA catalogue says COLORBOND steel carries THERMATECH solar reflectance technology "to allow for lower temperature cladding", and that "If condensation on the reverse side of roofing sheet is likely, vapour barrier should be installed". Lysaght Malaysia's Specification Guide (October 2019) writes its insulation clause as mineral wool "on 1 layer of double sided alum. foil supported by 1 layer of BRC 3316 weldmesh": a mineral wool blanket laid on double-sided aluminium foil, carried on a layer of steel reinforcing mesh. The guide leaves the thickness and density blank, so ask the supplier to state both. Lysaght's 2023 installation manual adds that with insulation "you may need to increase the length of the screws".
How is rain noise on a metal roof reduced?
Rain noise on a metal roof is reduced by damping the sheet, not just by a ceiling. Lysaght's Australian design guidance says the insulation blanket should be held "hard against the underside of the roofing to dampen the rain-induced vibration", and that "If the blanket is not hard against the roofing the noise reduction will not be as good."
Which detailing mistakes shorten a metal roof's life?
The detailing mistakes that most often shorten a metal deck roof's life are incompatible metals touching or draining onto the sheet, cutting debris left on the roof, fasteners that do not suit the coating, and sheltered areas that rain never washes. Each is preventable at specification and handover, and each is written into the manufacturer's installation instructions.
"Lead, copper, free carbon, bare steel and green or some other chemically treated timbers are not compatible with this product. Don't allow any contact of the product with those materials, nor discharge of rainwater from them onto the product."
NS BlueScope Lysaght Malaysia's 2019 Selection Guide adds that "Stainless steel fasteners are not recommended for ZINCALUME® and COLORBOND® steel." Lysaght's 2023 installation manual tells installers to "Sweep all metallic swarf and other debris from roof areas and gutters at the end of each day" and requires the high end of every sheet to be turned up on roofs pitched below 15 degrees. Solar rails and flashings need the same check: see what to check before solar mounting on a metal roof and, for an existing building, when to repair, reroof or replace a metal roof.
What documents should you ask a roofing supplier for?
Before accepting a metal deck roofing quotation, ask for the documents that make the specification checkable: the current product datasheet, span and wind-pressure tables with their assumptions, the installation manual, written material selection advice for the site, the warranty terms and eligibility, and current certificates.
- Current datasheet. NS BlueScope Malaysia's COLORBOND ULTRA datasheet tells users to "ensure you have the current datasheet for this product".
- Thickness and coating. Base metal thickness, coating class and paint system, stated separately.
- Span and wind tables. With their assumptions, checked against your engineer's MS 1553 pressures.
- Site-specific material advice. In writing for coastal, industrial or unwashed conditions.
- Warranty terms. The COLORBOND ULTRA datasheet states that "All warranties for a product, if any, are subject to eligibility."
- Certificates. Current cycles, not old scans.
- Installation method. Fasteners, laps, flashings, insulation and maintenance.
"Pastikan bahan mempunyai sijil SIRIM, CIDB, atau ISO sebagai tanda kualiti yang diiktiraf." (Make sure materials carry SIRIM, CIDB or ISO certificates as a recognised mark of quality. Our translation.)
Where does Ducero fit in a metal deck roofing project?
Ducero Sdn Bhd is Superdaya Group's roofing company, offering total roofing solutions. Superdaya's work includes roof covering, metal deck, light-gauge steel roof trusses and mild-steel portal-frame factory projects. Ducero's roofing project archive lists 94 entries from 2021 to 2025, including roof covering, reroofing, wall cladding, party-wall capping and strip ceiling work alongside truss jobs.
Pricing covering and trusses together matters because the structure sets the sheet's support spacing. One 2025 line in the Ducero archive reads "LGST + Covering – Bandar Serai Development Sdn. Bhd., Gamuda Gardens, Rawang, Selangor" (172 units). See the Ducero roofing page, Superspan's light-gauge steel profiles and trusses and the Superdaya comparison of light-gauge steel and mild-steel frames. Ask Ducero for current CIDB and ISO certificates with your quotation; the scans shown on the Superdaya site are from earlier cycles.
To price a metal deck roof and the trusses beneath it together, send your roof drawings, the approximate roof area, the site location and its distance from the coast, any solar or ceiling plans, and your programme to info@superdaya.com, call +603 3123 1348, or use the Superdaya contact page. Packages are quoted from your drawings.
Frequently asked questions
What thickness of metal deck roofing sheet should I use in Malaysia?
No single thickness suits every building. The right base metal thickness (BMT) depends on the profile, support spacing, supporting steel, foot traffic and design wind pressure. Lysaght's Malaysian catalogue lists TRIMDEK OPTIMA at 0.42 mm and 0.48 mm BMT, with different allowable spans for each. Check whether a quotation states BMT or total coated thickness, and have an engineer confirm the choice.
What is the minimum pitch for a metal deck roof?
Minimum pitch is set by each profile's manufacturer. Lysaght Malaysia lists a minimum roof slope of 3 degrees (1 in 20) for pierce-fixed TRIMDEK OPTIMA and 2 degrees for concealed-fix KLIP-LOK OPTIMA. Long roofs also need a drainage check against peak rainfall intensity, and Lysaght's installation manual requires sheet ends to be turned up on roofs pitched below 15 degrees.
Can pre-painted metal deck roofing be used near the sea?
It can, but the product must be chosen for the exposure. NS BlueScope Malaysia's datasheet for COLORBOND ULTRA steel says it suits moderate to severe marine or industrial environments, yet asks buyers to seek specialised advice before using it within 1 km of salt marine locations or in areas not washed by rain.
What affects the cost of metal deck roofing in Malaysia?
The main cost drivers are the coating class and paint system, the base metal thickness, the profile and fixing method, the roof area and its complexity (hips, valleys and penetrations), insulation and ceilings, flashings and gutters, and the truss or purlins below. Coastal exposure can change the coating needed. Superdaya quotes roof packages from your drawings.
Is a metal deck roof hot or noisy?
A bare metal sheet transfers heat and rain noise, which is why the layers under it matter. Lysaght's catalogue describes COLORBOND steel's solar reflectance technology as allowing lower temperature cladding, and Lysaght's design guidance says an insulation blanket held hard against the underside of the roofing dampens rain-induced vibration.
Can solar panels be mounted on a metal deck roof?
Often, yes, but the roof sheet, its fixings and the structure below must be checked for the added load, wind on the array and compatibility between mounting parts and the roof coating. A qualified engineer and the manufacturers' current documents should confirm each installation.
Sources
- MetMalaysia — Malaysia's Climate
- Department of Standards Malaysia — MS 1553:2002 Code of Practice on Wind Loading for Building Structure (preview)
- NS BlueScope Malaysia — COLORBOND ULTRA steel datasheet (revision 18 July 2024)
- NS BlueScope Lysaght Malaysia — LYSAGHT TRIMDEK OPTIMA catalogue (2025)
- NS BlueScope Lysaght Malaysia — LYSAGHT KLIP-LOK OPTIMA product page
- NS BlueScope Lysaght Malaysia — Roofing & Walling Installation Manual, Malaysia edition (2023)
- NS BlueScope Lysaght Malaysia — Lysaght Selection Guide (October 2019)
- NS BlueScope Lysaght Malaysia — Lysaght Specification Guide (October 2019)
- Lysaght (Australia) — Rain noise considerations for steel roofs
- CIDB Malaysia — Jom Bina Sempurna: Pemilihan Bahan Binaan