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Call us: (240) 505-6652 Virginia, Maryland & DC Areas

Slate repair and maintenance header short

The Usual Suspect: Bangor Slate

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Owners of Bangor Slate roofs:

This is US quarried slate still in production but its also called builder grade slate. In 1900-1950 it was builder choice slate as it was the cheapest and still was called slate. The problem with this slate is that the life span is roughly 80 years only. The characteristic signs are grey with color streaks, flaking and golden hues. The slate have a tendency to fall off the roof. The main cause of this short life span is its very high moisture absorption. The slate, with time, will progressively absorb more moisture and become very soft and fragile. There is a fine line, as we tell to each potential customer of ours, when the repair of such a slate roof will still be productive and when the most sensible decision is to replace it. Unfortunately, the slate quality deteriorates so quickly that many times we feel it's wasting our client's money to try to replace each slate that falls or slides off. We believe taking care of the leak at the specific source if necessary, and, only when needed, replacing the affected section of roof. Any Bangor Slate in even slightly bad shape can't be ever properly fixed without an entire roof replacement. This is a very unique situation because all other slate species will not have this problem. 

Bangor Slate is a notoriously poor quality slate quarried in Maine between 60 and 100 years ago.  These slates will only last half as long as a proper slate.

Tin Flashing issues

tin flashing problems

For owners with badly maintained slate roofs or rusted out original tin flashing:
Broken or missing slate can only be properly fixed by correctly replacing the slate with a new, undamaged piece of slate(salvaged slate of same species is also OK).
Many homes built around 1920 were built during a copper shortage and copper flashing was used only on the most expensive roofs; the alternative was to use tin flashing. This weaker flashing rusts out eventually and will degrade even quicker on the areas that are hidden under the slate because it takes longer to dry and will be exposed to the water even longer.
We do offer complete and complex flashing replacement with all-new copper flashing on all valleys, chimneys, dormers, pipe boots, and anywhere else that is flashed.

Face Nailing

Slates should always be nailed near the top end, where the hole will be covered by the next slate up.  Face nailing is when a roofer deviates from this simple, crucial rule and nails through the front or "face" of a slate.

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Face nailing only solves your roofers problem, not yours.  When a roofer repairs a roof this way, he is not only doing a bad job of repairing your roof but he is damaging it further!  A nail through the exposed face of a slate, as with anything you put a hole in, is no longer waterproof; however, he is not only ruining one slate, but also the one below it, making a hole straight through your roof. 

Another issue with face nailing is when new snowguards are installed.  As demonstrated below, the snowguard installer might just put a face nail through to get the job don quickly, despite it being an incorrect and damaging "repair".

3 face nails

If you think your home may have issues with face nails, give us a call and we'll happily come out to inspect any potential damage and give you an estimate!

Other Issues

Bangor slate is just one of many slate species quarried all over the world, but the imported slate is trend is not even 20 years old. So most slates, if they are not Bangor and either from US or Canada (North American slates are one of the best slates in the world), are safe. A quick rule of thumb is that if your slate roof is solid black, green, purple or even red, you are probably in luck. If a roofer tells you that your old slate roof is shot and you need to tear it down to install an all-new asphalt roof, give us a call!

There is a ton that we can do for you:

  • We will identify all of your problems, properly fix each one. 
  • If, for some reason, you are so fed-up with your slate roof that you really want that new asphalt roof, we will remove the slate for you and reuse it, as there is essentially money sitting on your roof.

Leska's thoughts on slate repair

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We specialize in slate, tile, and metal roofs and we do the majority of our work on historic homes. Very few roofing material will last 80 years. We install nearly all roofs that will last over 80 years: tile, slate and metal roofs.

Am i replacing

my roof too early?

Many times, when the slate is around 80 years old, the actual material is only half-way through its useful life, and the improper repairs by unqualified or unskilled roofers will only cause more roof damage than there was originally.

There are only 3 main sources of slate roof failure:

  1. Broken Slates 
  2. Rusted-out flashing 
  3. Improper head lap or slate installed on low slope without extending headlamp(this is a problem that starts at day one, a bad & incorrect install)

Are my snow guards putting my home at risk?

snow guard on slate

Snow Guard Installation:
A very small percentage of slate repairs is done by hooking the snow guards on only the nails that go through the slates. If a large amount of snow slides down the roof, the snow's force will easily rip the slate nail out, taking the slate and snow guards with it. There are many ingenious ways to eliminate this practice. Please contact us and schedule a free, no-obligation inspection.

Problems that we didn't address:

If you have slate roof with widespread or complex damages, including a Bangor Slate roof, we offer full lift and new slate relay.

We will remove all broken slate, store them on the roof, find the same reclaimed slates or buy new slates of matching or complimenting color. We will then install a brand new underlayment, all new copper flashing and reinstall slate back, per National Slate Association standards put forth in their manual. We are proud members of this wonderful organization.

Leska's Slate Options

Leska offers many other custom solutions to repairs and even entire slate systems that the homeowner can enjoy on their new slate roof:

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Greenstone Slate

Greenstone Slate

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Certifications & Credentials


Why choose us ?

  • Fully Insured/Bonded
  • Family Owned & Operated


  • 3rd Generation Craftsmen
  • European Quality