When To Replace Your Slate Roof

How To Know When To Replace Your Slate Roof

A natural stone slate roof can be a long-lasting, aesthetically-pleasing feature of any home.   A slate roof can generally last at least 80 to 100 years, with many lasting much more than that.  There are a number of factors that will extend or limit the lifespan of a slate roof.  The type of slate, the quality of the slate, roof pitch, and weather conditions are some factors that can affect how long a slate roof will last.  These factors also may affect how much maintenance a slate roof will require.

A big question homeowners with slate roofs often have is if their slate roof should continue to be repaired, or be replaced.  Roofers will argue about when a slate roof has come to the end of its life.  Roofing contractors that specialize in asphalt shingles may be more prone to recommend a roof replacement sooner than necessary in order to get a roof job.  Home inspectors may also not be able to give a proper analysis about the true condition of a slate roof.  Inspectors tend to lean toward the negative when assessing a slate roof.  It is important to get an assessment from a qualified slate specialist to more accurately determine the condition of a slate roof.

Here are three basic ways to help in determining the condition of your slate roof, and to help decide if your slate roof needs to be replaced.

Are the rows straight?

Uneven, wavy rows, or a large amount of sliding slates usually show that the nails are failing.  This is generally an indication that steel nails were used.  Over time, the steel nails will rust and eventually break, allowing slates to become dislodged.  A slate roof in this condition can be possibly maintained, but there may be a tipping point when the amount of slates sliding doesn’t warrant repairs any longer.

Do you have excessive flaking and/or broken slates?

Slates can flake for quite a while without causing problems.  At a certain point, the slate will become too thin, and will either be porous, or easily break in poor weather conditions.

If you have many slates breaking at diagonal angles, you probably have “ribbon” slates.  These are a lower quality slate that have a “ribbon” mineral inclusion that weakens the slate.  These types of slate can often be spotted from the ground.  A ribbon slate roof is not necessarily a bad thing as the quality of some ribbon slates is better than others.  At a certain point in the life of a ribbon slate roof, the slates may start to break at a faster than normal rate.  This may be the time to consider replacement.

When to replace a slate roof

What are your maintenance costs from year to year?

Depending on the size of your roof, location, weather, trees, roof age, and other factors, you may be spending hundreds or thousands of dollars yearly or every other year in slate roof maintenance.  Several hundred dollars a year to maintain an older slate roof is to be expected.  When that number jumps to over a thousand dollars every year, you may need to consider the costs for continued repair versus the cost for replacement.

Slate can be quite expensive compared to shingles, although a new slate roof will last much longer, and be more aesthetically pleasing, and complement a historical home much better than shingles.  If you wish to keep slate on your roof, but the high replacement costs are a factor, one cost-effective option may be to replace a failing slate roof in phases.  Concentrate on the worst side first.  Replace other areas as the budget allows.