Cut Edge Corrosion

Metal roofs, renowned for their durability and aesthetic appeal, have become a preferred choice for many. However, like all construction materials, they come with their own set of challenges. 

One such challenge that has gained significant attention in the industry is “Cut Edge Corrosion”. In this article, we shall delve into the intricacies of sealing metal roof overlapping and provide a comprehensive understanding of the subject.

The Implications of Cut Edge Corrosion

The installation of a metal roof and its pristine appearance is undeniably appealing. However, as time progresses, the emergence of corrosion, particularly at the cut edges, can occur. This phenomenon is called “Cut Edge Corrosion”, and if neglected, can lead to the exposed metal surface corroding and eventually perforating. Such degradation not only compromises the aesthetic appeal but also the structural integrity of the roof.

Seal or No Seal 

The roofing industry is divided on the approach to address this issue. Some professionals advocate for the application of a sealant under the overlaps of the metal sheets, stating that it effectively prevents water ingress. On the other hand, there are experts who say that the application of sealant inadvertently traps condensation from the cold metal roof, thereby facilitating corrosion.

Evidence from older roofs, where sealants have been utilised, indicates rusting stops precisely where the seal was applied. This observation suggests that moisture is not coming down the sheet, but is, in fact, rising up.

The Consequences of Coating Only

Now, you might be thinking, why not just coat the roof and be done with the sealing? However, this approach is fraught with challenges. Any movement between the roof sheets can result in the coating cracking at the joints, facilitating water ingress and subsequent corrosion. Furthermore, it is important to recognise that rainwater, along with its various pollutants, can exacerbate the corrosion process.

The Importance of Selecting the Correct Sealant

Assuming you’re now of the opinion that sealing makes pure sense, the next question is, what sealant should I use? There’s a plethora of options out there, ranging from mastics to tapes to embedding materials in a liquid medium. However, it is very important to understand that NOT all sealants, stated to “do the job”, are of equivalent efficacy. Certain variants, such as weak silicone mastics or tapes, may not adhere optimally, thereby allowing water penetration.

The Art and Science of Sealant Application

Once you’ve decided on the right sealant then the next stage is application. This requires the same amount of attention to selecting the sealing products. An inadequate application might compromise the sealant’s strength, rendering it incapable of withstanding the movement of the roof sheet overlap. Conversely, excessive application can lead to unnecessary costs and potential structural issues.

Hopefully, this article has been able to assist you with the decision to seal your metal roofs and demonstrates that the decision whether to do this or not is multifaceted, and requires a thorough understanding of the associated benefits and challenges. 

Sealprem are experts in the manufacturing of sealing products for metal roofing and cladding. Our team is always on hand to answer any questions you may have.