Mr Quyen - Santiago. Posted 03/11/2026
When a metal roof has rusted through at the laps and around the screw holes, replace the whole roof rather than patching it, because the metal next to each hole is already thin. Re-roofing with ASA/PVC sheets means measuring, stripping the old sheets, checking the purlins and closing them up to less than 700 mm apart, then laying the new sheets and fitting new ridge pieces.
Rusted old metal sheets next to new blue ASA/PVC sheets during a re-roof, Chau Duc, Ba Ria – Vung Tau
Should you patch a rusted roof or replace it?
Sealant, waterproof tape or a piece of metal screwed over the hole works only when rust shows at a few small spots. Once rust has eaten through, especially along the laps and around the screws, the metal around it is thin as well, and a patch is followed by a new leak a few months later somewhere else. Replacing the roof costs more at once and ends the leaks.
Rust running along the laps of an old metal roof, beside a newly laid blue sheet
What are the steps for re-roofing with PVC sheets?
- Measure the length of the building, the slope length of each roof face, and the ridges.
- Strip the old sheets. On a working building, do it one section at a time so the space below is never open for long.
- Check the purlins. Replace rotten or bent ones; scrape and repaint sound steel, or replace badly rusted purlins with FRP.
- Close up the purlins. Metal roofs are often laid on wider spacing than plastic needs; ASA/PVC needs purlins less than 700 mm apart.
- Lay the new sheets from the eave upwards, standing on the purlins, the wide edge of each sheet over the narrow edge of the last.
- Screw through the top of the wave over each purlin and cap every screw.
- Fit a new ridge piece that matches the profile (5, 6 or 11 waves) and close both ends.
New blue ASA/PVC sheets being fixed over the old roof frame
Which mistakes ruin a re-roof?
| Mistake | What happens |
|---|---|
| Keeping the old metal ridge | It keeps rusting and does not fit the plastic waves, so the ridge still leaks |
| Buying sheets thinner than 2.5 mm to save money | They sag; Santiago gives no warranty on them |
| Screwing in the valley | Water runs into every screw hole |
| Dragging long sheets up the roof | Sheets kink and fold; use enough people to carry them |
Which sheet should replace the metal?
Most re-roofs use the 5-wave sheet. Long warehouse roofs with a low slope take the 6-wave sheet, whose 34 mm ribs carry the most water. If only part of a roof is replaced and the new sheets must lap with old metal ones, send Santiago the profile of the old sheet first; ribs and widths differ between makers.
The finished warehouse with its new blue ASA/PVC roof, Chau Duc, Ba Ria – Vung Tau
What does re-roofing an old metal warehouse with PVC sheets look like?
The short starts with a flame put to a stack of grey and red tile sheets, then Mr Quyen crouches on grey tile sheets in the Santiago factory. It ends on a blue warehouse roof where installers are laying new sheets, with Mr Quyen standing on the roof in a white helmet.
Heat test and a warehouse re-roof with uPVC sheets (Santiago video on YouTube).
More short videos: re-roofing step by step
Three more English shorts from the Santiago YouTube channel. Each one is about a minute or less.
What does a new tile roof look like while installers fix it?
In under a minute the short goes from the Santiago factory floor to a grey tile-profile roof on site: some sheets already fixed, installers screwing down the rest, and a finished run next to the gutter.
Santiago uPVC tile roofs on site (Santiago video on YouTube).
How much rough handling can the sheet take? The truck test
Mr Quyen sets two blue sheets on the ground at the factory and a Santiago truck drives across them. It shows how tough the material is; the roof itself still needs purlins spaced less than 700 mm apart.
Truck test on Santiago ASA/PVC sheets (Santiago video on YouTube).
Why replace an old metal roof at all? Heat, noise and repairs
A one-minute short with English captions: Mr Quyen compares metal and clay roofs with Santiago ASA/uPVC tile sheets, first in the factory and then on finished red and grey roofs.
Heat and rain noise: Santiago ASA/uPVC roofing explained (Santiago video on YouTube).
Santiago – a leading exporter of ASA/PVC roofing from Vietnam
Santiago roofing is produced and loaded into containers at our factory in Vietnam. It has been exported to India since 2023, Thailand since 2024 and the USA since 2025. Every export shipment comes with a commercial invoice, packing list, bill of lading and a certificate of origin (C/O) issued by Vietnam's Ministry of Industry and Trade, which importers use to claim the duty preference of their trade agreement.
| Item | Details |
|---|---|
| HS code | 3925.90.00 (ASA/PVC roofing sheets) |
| Certificate of origin | Form D (ASEAN), Form AI (India), Form AK / VK (Korea), Form AJ / VJ (Japan), Form VC (Chile), CPTPP proof of origin |
| Shipped from | Vietnam, by container |
Certificate of origin Form AI (ASEAN–India) for Santiago ASA/PVC roofing sheets, HS 39259000, certified on 24 September 2026. Buyer details are hidden.
The Santiago team beside a loaded export container at the factory, November 2024
Loading Santiago roof tiles into an export container
Frequently asked questions
Should I patch or replace a rusted metal roof?
Patch only small, isolated rust spots. When rust has gone through at the laps and screw holes, replace the whole roof, because the metal around the holes is already thin.
Can I put PVC sheets on the old purlins?
Only if the purlins are sound and less than 700 mm apart. Replace rotten or bent purlins and add purlins where the old spacing is wider.
Can a factory roof be replaced while the building is in use?
Yes. Strip and re-roof one section at a time so each part of the building is open for as short a time as possible.
Will the new PVC roof rust?
No. ASA/PVC sheets contain no iron; use stainless screws with ASA caps so the fixings do not rust either.
Read more
- A rust-free roof from top to frame: ASA/PVC on FRP purlins
- Screws and ASA caps: fixing through the top of the wave
- PVC roofing sheet advantages and disadvantages
- ASA/PVC roofing sheet, 6 square waves
Sources for the figures in this article
- Profiles, 2.5–3.0 mm thickness and 10-year warranty: Santiago ASA/PVC product specification.
- HS code 3925.90.00: Harmonized System Chapter 39 (builders' ware of plastics), as applied in Vietnam's export tariff.
- Certificates of origin (Form D, AI, AK/VK, AJ/VJ, VC, CPTPP): issued by Vietnam's Ministry of Industry and Trade under the country's free trade agreements.
- Minimum order of one 40 ft container (about 5,000 m) and about 5 days for production and loading: Santiago export desk, October 2026.
Updated 03/11/2026. Santiago Import Export Co., Ltd, Vietnam. WhatsApp +84 935 391 495 (Mr. Quyen), hotline +84 965 437 316 (Mrs. Ly), email salessantiagoroofing@gmail.com.
