Galvanized Iron (GI) sheets have been a staple in the Philippine construction industry for decades, especially for roofing. Their longevity, affordability, and ease of installation make them a popular choice for residential and commercial construction. In a typhoon and heavy-rain-prone country, the resilience of GI sheets in the Philippines to extreme weather conditions is priceless. This article will help you through the installation process of GI sheets for roofing to keep your building safe and secure.

Importance of GI Sheets

GI sheets are manufactured by applying a zinc coating on steel, offering great corrosion protection. This characteristic is important in the Philippines due to high humidity and regular rainfalls, which tend to disintegrate weaker materials rapidly. GI sheets are also light, thus lowering the overall structural load, and affordable in terms of material and installation prices. These sheets come in different profiles and colors for customization.

Recent Standards and Regulations

More stringent requirements for GI sheets for roofing have been adopted by the Department of Trade and Industry (DTI) in the last few years. Department Administrative Order (DAO) 20-10, promulgated in December 2020, requires hot-dip metallic-coated and pre-painted galvanized coils and sheets to comply with quality standards before they can be sold in the market. These requirements include a minimum thickness of 0.4 mm of the coated steel so that consumers can enjoy high-quality materials that can resist weather conditions.

Preparing for Installation

Understanding Local Regulations and Standards

The DTI's DAO 20-10 sets minimum product standards for galvanized steel coils and sheets. This regulation ensures that all GI sheets used for roofing meet quality and safety standards, providing consumers with reliable products. When purchasing GI sheets, look for the Philippine Standard (PS) Quality Certification License to ensure compliance with these standards.

Choosing the Right Materials

GI Sheets

Calculate the required number of GI sheets for your roofing project, factoring in overlaps and necessary cuts. It's recommended to have a surplus of sheets to accommodate these.

Wooden Purlins

These structural components serve as the support for these sheets.

Zinc Screws with Rubber Washers

Secure these sheets properly to create a watertight seal.

Roof Sealant

Seal overlaps and screw points with sealant.

Ridge Capping

To seal the roof’s peak.

Essential Tools and Equipment

Circular Saw

For cutting GI sheets to size.

Drill

For drilling screw holes.

Safety Gear 

Helmets, gloves, and safety harnesses for working at heights.

Measuring Tape

For accurate measurements.

Installation Techniques

Preparing the Roof Structure

Structural Assessment

Before starting the installation, confirm that your roof structure is strong enough to hold these sheets, despite their light weight.

Remove Old Roofing

Before installing new these roofing sheets, remove the old material and inspect the underlying structure for damage requiring repair.

Install Purlins

Secure leveled wooden purlins to the roof framework with 1 to 2 meter spacing, adjusting for design and load.

Installing GI Sheets

Measure and Cut

Measure the roof length with desired overhang. Use a circular saw to cut them to the required size.

Start at the Bottom

Start the installation of these roofing sheets at the roof's lower edge, ensuring a slight overhang at the eaves.

Overlap and Screw 

Overlap GI roofing sheets by a few inches and secure them to purlins with zinc screws and rubber washers. Ensure that you do not over-tighten the screws, as this can damage the sheets.

Sealant Application 

Apply roof sealant at overlaps and screw points for a watertight seal.

Work Upward

Proceed with the installation of these sheets by arranging them in successive rows, moving upwards. Ensure a slight overlap between each row.

Ridge Capping

Finish the roof with ridge capping at the peak for sealing and extra protection.

Additional Roofing Accessories

Gutters and Downspouts

To prevent water damage to the foundation, install these.

Flashing

Apply flashing to the edges of the roof and around chimneys or vents to prevent water seepage.

Valley Gutters

If your roof has valleys, install valley gutters to manage water flow effectively.

Safety and Maintenance Considerations

Use Safety Gear

Always wear helmets, gloves, and safety harnesses when working at heights.

Stable Surface

For safety, make sure the working area is firm and steady.

Cautious on Slopes

Be cautious when working on sloped roofs to prevent falls.

Post-Installation Maintenance

Regular Inspections 

Check screws and sealant routinely.

Prompt Repairs

Replace any damaged sheets promptly to prevent water leakage.

Cleaning

Clean the roof regularly to remove debris and maintain its appearance.

Key Takeaway

Installing GI sheets in the Philippines for roofing is a manageable task when done correctly. By following the steps outlined above and adhering to local regulations, you can ensure a durable and weather-resistant roof that protects your structure from the elements. The cost-effectiveness and minimal maintenance requirements of GI sheets make them an excellent choice for both DIY enthusiasts and professional contractors. As the Philippine construction industry continues to evolve, GI sheets remain a reliable option for building safe and resilient homes and buildings.