On poultry and pig farms in Laos, ammonia from manure mixes with night condensation under the roof and eats the zinc on metal sheets and purlins, starting at screw holes. ASA/PVC roofing sheets do not rust, and FRP composite purlins remove the steel from the roof structure as well. Use stainless screws so the fixings do not fail first.
Where does a farm roof start to fail?
At the screw holes and side laps, on the underside. The outside can look fine while the sheet and purlin underneath rust through, and rust flakes fall into feeders.
ASA/PVC roof on a humid building
A rust-free farm roof
| Part | Choice |
|---|---|
| Roof sheets | ASA/PVC, 2.5 – 3.0 mm |
| Daylight | Skylight sheets, about 5 – 10% of the roof |
| Purlins | FRP composite box purlins: SF-100 for rafters about 2.5 m apart, SF-120 for 3 m |
| Fixings | Stainless screws with rubber washers and ASA caps, 4 – 5 per m² |
Will animals notice the change?
Heavy rain on metal sheets is loud. ASA/PVC is about 80% quieter, and the space underneath is about 6 – 8 °C cooler than under bare metal, which helps in the hot months.
Importing to Laos? Delivery by truck from Vietnam, minimum one 40 ft load (about 5,000 m), production about 5 days, Form D included: importer and distributor guide.
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
Why do farm roofs rust so fast?
Ammonia from manure condenses with humidity under the roof and dissolves the zinc coating on steel.
Which purlin size suits a farm with 3 m rafter spacing?
Usually SF-120, depending on wind pressure; send the drawing for a check.
Do I need stainless screws?
Yes. Plated screws rust before the sheets and leak.
Related products: ASA/PVC 5 waves · 6 waves · 11 waves · ASA/PVC roof tile · Skylight sheets
Contact Santiago: Santiago Import Export Co., Ltd, Vietnam. WhatsApp +84 935 391 495 (Mr. Quyen), hotline +84 965 437 316 (Mrs. Ly), email salessantiagoroofing@gmail.com.
Updated October 2026.
