Hi bosses here,

My current zinc roof is too short, so I plan to buy a longer one then stack on top of current one. will use the screw to screw current and new zinc roof together.

However, is there anyway to prevent the rain water from going below new roof? I would like the rain water to flow through the new zinc roof instead.

I guess the only way is to apply sealant on the upper edge of the zinc. The sealant meant for gutter and roof will last very long. I bought one brand (I could not remember) from Mr. DIY saying it will last 20 years (if not mistaken)

https://shopee.com.my/MAJU-Selleys-Awning-R...71-4a8df83677e8

Have more allowance for over lapping and seal the edges with silicon

What is have more allowance

Meaning one new sheet cover 75% of old sheet. So existing row now have 5 sheets but for overlapping, it needs 6 sheets.