Poultry houses and piggeries in the Philippines rust GI roofs quickly because ammonia from manure condenses with humidity under the roof. ASA/PVC roofing sheets do not rust, are about 6 – 8 °C cooler underneath than bare metal, and are about 80% quieter in rain, which reduces stress on animals. FRP purlins take the steel out of the roof frame too.
How does ammonia damage a farm roof?
Ammonia rises with warm air and condenses with night moisture on the underside of the roof. It dissolves the zinc coating, starting at screw holes and laps, and rust flakes fall into feeders and drinkers.
ASA/PVC roof on a farm building
A farm roof that lasts
| Part | Recommendation |
|---|---|
| Sheets | ASA/PVC 6-wave (34 mm ribs) for long roofs |
| Daylight | Skylight sheets, about 5 – 10% of the roof |
| Purlins | FRP SF-100 for 2.5 m rafter spacing, SF-120 for 3 m |
| Fixings | Stainless screws with ASA caps, 4 – 5 per m², more at edges |
Tunnel-ventilated houses
Closed houses with fans and cooling pads are even more humid. The roof still needs to be rust-free; a cooler roof also lowers the load on the cooling system.
Importing to the Philippines? Minimum order one 40 ft container (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 poultry house roofs rust?
Ammonia from manure condenses with humidity and dissolves the zinc on steel sheets and purlins.
Which roof sheet suits a piggery?
ASA/PVC sheets, which do not rust, with stainless screws.
Which purlin for 3 m rafter spacing?
Usually FRP SF-120, depending on wind pressure.
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.
