According to several professional organizations, slate roofs have a life expectancy of 100 years or more. However, there are many homeowners in Canada who start having problems, like leaks, with their slate roofs far before the 100-year mark is reached. Some might even have their slate roofs replaced after just a few decades! Slate shingle metal roofing is more expensive than other roofing options, so you should be happy to hear that most of these early replacements and early leaks are not the fault of the roof itself, but rather a result of poor roof care and a lack of precautions. If you want your slate roof to last a century, avoid these three common mistakes.

Walking Over the Roof Tiles

Slate tiles are impervious to moisture -- until they crack. And the most common reason they crack is that someone has walked over them. Professional slate roof installers know never to walk on a slate roof. Instead, they use a system of ladder jacks and hook ladders to allow them to "hover" over the roof as they work on it. The problem comes when a homeowner hires a less-scrupulous handyman or contractor to come repair the roof -- and such person does not know any better than to walk directly on the tiles.

Tiles are almost certain to crack when someone walks over them, but homeowners don't always make the connection between the walking episode and the damage since the resulting leaks can take a while to appear. For example, a contractor may walk on a roof and crack the tiles, but the cracks only widen enough to let water leak in after three years of freeze-thaw cycles.

If you want your slate roof to last, only hire a company experienced with slate roofing to work on it. Do not let anyone walk directly on the tiles, and never walk on them yourself, either.

Choosing The Wrong Flashing

The metal flashing around chimneys and vents is the weakest part of a slate roof. If you choose a less durable metal, like stainless steal or aluminum, the flashing will erode and begin leaking long before the slate tiles themselves start failing. Some homeowners mistakenly assume failed flashing means it's time to replace their slate roof, when really only the metal flashing needs to be replaced.

You can minimize problems with flashing by choosing copper flashing. Copper lasts a lot longer than steel or aluminum, and though it will turn green after a decade or so, it won't quickly corrode and does not need to be painted.

Using Poor Quality Nails

Nails are another common reasons for premature slate roof failure. If the nails are of poor quality, they will deteriorate long before the slate tiles themselves start looking pitted or worn. With no nails to hold them in place, the slate tiles will start tumbling from the roof.

It's important to use heavy-gauge, galvanized roofing nails when installing a slate roof, and whenever repairs are made to a slate roof. The tiles should each be installed with two nails, and the next tile should cover the nails completely. Sometimes less knowledgeable contractors may "top nail" a slate tile, which means that they drive a nail straight through the tile, and that nail is not covered by another tile. This can lead to leaks and premature roof damage.

If you want your new slate roof to last as long as possible, make sure you avoid walking on it, use durable nails and install them properly, and choose copper flashing. Working with an experienced slate roofing company will go a long way towards ensuring these and other mistakes are avoided.