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Old cedar roof shingles with asbestos coating?

sb1616ne | Posted in General Questions on

Old cedar roof shingles with asbestos coating?

I am tearing apart a 1910 vintage roof on our home and stumped on what I am dealing with for a material that was used to treat these cedar shingles back in the day. I am hoping someone can shed some light and maybe someone has ran into a similar material?

I have had two individual shingle samples analyzed by a local lab and one sample the coating contained 3% Chrysotile Asbestos where the other shingle contained zero %. As of this moment I have a dozen more shingles in route to the lab for further analysis to get this figured out. The lab manager has never seen an asbestos containing material such as this!

The roofing layers are as follows:
1. Newer corrugated light gage roof that was installed in 2002. The only reason we are removing some of this is due to a big addition project.
2. Older corrugated thick gage roof installed with ring shank nail with lead heads on the nails. This layer is in very bad condition(rust). I am thinking 1950’s or 60’s vintage.
3. White cedar shingles nailed right to the sheathing boards, no tar paper. These were nailed on with small smooth shank round nails only about 1″ long. Much smaller than the siding nails we use today.


So… The interesting thing here is the light and dark stained coating on these shingles. When intact on the back of shingles it looks and feels like an oil based polyurethane with some darker hues in spots(which did not exist 100 or more years ago). The front side of the shingles that were exposed to the elements, the coating is nearly non-existent. Another observation is this finish was applied much after the original install as it weeped around the nail holes extensively.
I am very familiar with roofing tar products and this does not look like any of the typical tar products that to my knowledge would be much thicker.

I have been chatting with some old timer carpenters I know and they said we used and they have seen creosote used back in the day and from what they can see it looks like a creosote wood preservative.

Has anyone seen anything similar or know what might have been used on these?

Thanks!

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Replies

  1. Expert Member
    BILL WICHERS | | #1

    It might be some kind of adhesive residue. I know from my asbestos remediation classes years ago that some types of glue used for linoleum floors was asbestos containing, so you ended up with the unexpected situation where the tiles were OK but the glue was a problem. I'm not sure if asbestos was ever used in wood glues, but it's always possible someone used the wrong stuff, or maybe just dropped a batch of cedar shakes on a partially finished floor and got some glue on them by accident. My guess is you have some kind of adhesive residue that has some asbestos in it. I'll be interested to hear what others may think about what you're seeing.

    Bill

  2. DCContrarian | | #2

    My guess is a fire-resistant coating. Cedar shingles burn very easily. In the first half of the 20th century asbestos was sold as fire-proof siding, in some places you could build closer to the lot line with asbestos shingles. That's my guess.

  3. DCContrarian | | #3

    What possessed you to send the shingles off for testing? I would have put them in the dumpster without a second thought.

  4. Expert Member
    AKOS TOTH | | #4

    I've seen cedar shingles installed over asbestos paper, in one of the pictures it looks like that in the background.

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