Slate Type

Anyone care to take a shot at identifying the slate on this 1922 roof?

I need to know the type so I can estmate the life expectancy. The picture is poor. It appeared to have some red in the color.

Is it Unfading red slate? This is only mined in NY and is rare. I cant seem to find any other types with red in the coloration.



Anyone own the slate roof bible?

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New York Red Slate

Life Expectancy 150-200 years.



Take a look at the front porch picture where the roofer installed asphalt over the slate. The house had 4 roof types. The slate looked good. The roll/asphalt looked like ****. The flashings have been tarred.



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Why would someone install asphalt over slate? I’ve inspected some here with slate over asphalt, but not asphalt on slate. Is there some reason for this?


It makes no sense to install a 20 year shingle over a 100+ year slate.

I dont think most roofers specialize in slate & instead of properly repairing the slate the sell the home owner a asphalt roof. I see this quite often.



Does one have to drill for each nail? :shock:

My market area has many older Pennsylvania and Vermont grade Slate Roofs

Roofers specialize in Roofing.

Slaters specialize in Slate Materials.

The Two Professions are not Interchangeable.

Asphalt repair to a Slate Roof is a Defect that needs to be noted and reported as such.


Asphalt Shingle over Mineral Slate is a Defect that warrants Replacement of the entire Roof.


A slate roof specialist from PA (Joe Jenkins) says that the roof is definetly not NR red slate. He says that it appears to be vermount sea green but couldnt be sure because my photos are poor quality.


I think we all know that slate roofs will last for a 100 years plus if applied correctly. If anything, the fasteners would let go first and force the slate roof to fail in areas.
To try and estimate the age of a slate roof, to me would be impossible.
To ask what type of slate it is, I think is irrelevant, I know it will be around when I am pushing Daises.
To Inspect a slate roof with an installed roofing shingle on top, is ridiculous and asinine.
Commen sense would tell me that is completely wrong and that is the way I would write it and would write it hard.
How stupid can people be in building.???

Marcel :slight_smile: :slight_smile:


I agree with you on installing over asphalt.

Where I differ from your opinion is Identifying the slate is most important.

I am in no way an authority on slate.

In recent readings and from specialist that identifying is very important.

If I can learn to identify the type it will go a long way in assisting my client.

I think I have inspected about 6 slate roofs so far. It looks like there are about 8 types of slate. I know it is hard for anyone looking at these photos as they are lousy.

It looks like the life expectancy of this roof is 100-150 years. I believe the problem is when the owner inquires he seeks just a roofer and not a slate roof specialist who would repair and restore the slate and flashings.

I do value you opinion




Value your opinion also, but have to think that how many clients would actually need to know where or what type of slate is on the roof? Playing ignorant here for a bit, if I where a home owner, I don’t think that if it were Vermont slate or anyother, would make to much difference. JMHO. Isn’t slate, slate? Whether it last 100 Years or more make any difference?
I can appreciate the information for your own knowledge, just trying to install a common loggical conclusion. If you know what I mean.

Good work on your part if you go that far.

Marcel :slight_smile: :slight_smile:

Joe Jenkins is a recognized expert.

The difference with the type of slate is the life expectancy. You will still need a review by a Slater (Not Roofer) to properly assess the roof.