How to replace metal roof screws

Learn how to choose the optimally sized fastener when replacing metal-to-metal self-tapping screws and related tips.

Metal roofs are a practical, long-lasting, and eco-friendly roofing choice. While the lifespan of a metal roof is projected between 40-70 years, they aren’t indestructible. Leaks can happen when improper installation occurs, as a result of damage to the roof surface, and in some cases when materials are defective. 

When such scenarios occur, your first instinct may be to buy the exact same screw as previously utilized. However, this would be the wrong approach. The screw would be unable to create its own threading, causing a dangerously loose connection. Therefore, when replacing a screw for metal roofing, seek a fastener that is one size wider than what was previously used in order to create new threads in the existing hole.. 

This would mean that, if theoretically you previously employed a #14 Type A Self-tapping screw, you’d want to replace it with a #17 Type AB Self-tapping screw. 

SFS offers an array of metal-to-metal self-tapping screws and metal building fasteners to ensure you find the right roofing screw based on your individual needs.


Common Causes of Leaks in Metal Roofing 

Improper screw technique

Roofing screws use a rubber washer at the base of the screw head to prevent moisture from penetrating the metal. The performance of these fasteners are dependent on their installation. A screw that is driven too deeply compromises the rubber washer which causes it to bulge out the sides of the fastener and allows water to leak in. A screw that is driven in at the wrong angle doesn't create a complete seal allowing for moisture to break the washer barrier. An under-driven screw doesn’t allow for the screw to properly seat allowing water to leak in. 

Failing flashings
Stack flashings are the flashing around pipes and vents that come out of a metal roof. They waterproof these areas using a rubberized material that sits flat on the metal roof as well as gathered up around a pipe or vent to create a barrier against water seepage. These flashings are challenged by the expansion and contraction movements of the metal roofing. The sun also degrades these rubber flashings.

Worn or faulty sealants 

Similar to flashings, the sealants used on roofing surfaces are also degraded by the sun and tested by the movement of the metal roofing. These sealants under trims, around roof transitions, reglets, and pitch pans will need to be reapplied to maintain the integrity of the seal. 

Failing at seams and overlaps

Seams are where two parts of the metal roofing overlap. At these intersections the capillary action of water allows water to be drawn into tight spaces until it penetrates the roofing surface. The phenomena of capillary action can actually draw water uphill between two pieces of metal. 

Signs a Metal Roof Needs to Be Repaired

Metal roofs may need repair if they are not properly installed or they become damaged by severe weather. While periodically inspecting your commercial roof for signs of damage or deterioration remain vigilant for the following signs of damage:

  • Leakage

  • Fading or discoloration

  • Tears, gouges, or punctures 

  • Loose fasteners

  • Lifted fasteners

  • Loose Panels

  • Signs of oxidation and corrosion

  • Finish coming off panels 

  • Openings in seams and flashing 

Inspection Tips for Metal Roofing

SFS recommends that your roof should be inspected twice a year and after any extreme weather event, like hail, snow, or wind. Water stains and mold are signs you need roof repair or replacement. Other signs of damage like rust mean you have a leak or might get one soon. A leak in your metal roof does not have to be a catastrophe. Regular inspection is vital to spot the signs of damage early.

Your metal roof screws should also be inspected for potential movement or sealant failures. It is possible for the movement of the metal roof to thrust screws out of their seat or damage the rubber washer allowing for water to penetrate the roof.

Impact of Screw Selection

The longevity of a roof is determined by the quality of materials, installation, and regular maintenance done over time. The importance of quality materials does not stop at the metal roofing sheets. A quality fastener ensures that your roof will live up to its projected life expectancy by performing equally well with the metal roofing sheets. Using a high corrosion-resistant sheet with a screw that offers little to no weathering resistance will negate the advanced coating properties on the metal sheet. SFS as a worldwide leading supplier of fastening systems utilizes coating and layering technologies to enhance weather resistance to ensure your roof is in peak condition year-round. 

Other Considerations When Choosing Metal Roof Replacement Screws

Why the original screws fell short - the need to replace the screws can be described by one of two reasons: the passage of decades led to natural aging or the original screw did not fully meet the needs of the application. If it’s the latter, now is the time to improve upon the previous purchasing decision. 

Screw failure caused by fastener back out 

Fasteners in the field can become loose or back out. If backing out occurred, consider choosing a replacement screw that better meets the application needs.

For additional learnings, read Fine Thread Versus Coarse Thread or How to Choose the Correct Screw Length.

Screw Failure Caused by Improper Installation

Metal roofing screws are designed to seal out water. When screws are installed incorrectly they are unable to create a proper seal between the metal roofing and the screw head. Contractors should always ensure their teams are fully aware of proper installation procedures and tools for metal panel applications. If fasteners failed due to improper installation, consider correct installation procedures.

Screw failure caused by formation of rust 
If rust formed due to prolonged exposure to moisture or dissimilar metal connections, consider choosing a replacement screw with greater corrosion-resistance properties, such as the Bi-Met 300® stainless steel bimetal collection

For a deeper explanation, please refer to our article How to prevent corrosion.

Not Sure if You Need to Repair Your Metal Roof Screws?

Once your metal roof screws are older than 20-years old, assume that the fasteners are on borrowed time (most won’t safely make it past 30-years). However, even before this major milestone, you should examine your metal roof fasteners multiple times a year. Keep a close eye out for signs of rust, leaks, or loosened hold.

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