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Worn damaged fibre cement roof cladding at Oamaru New Zealand (C) Daniel Friedman Synthetic Roofing Slate Asbestos
Do manufactured / synthetic slates contain asbestos?

Here we discuss the presence of asbestos in some but not all synthetic slate roofing products.

This article series describes procedures for evaluating the condition of slate roofing. How to inspect, identify defects, and estimate remaining life of slate roofs are addressed.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Is There Asbestos in Manufactured / Synthetic Roofing Slate?

Manufactured slate on a UK Building (C) InspectApeida.com  D-G MQuestion: should I be concerned about asbestos in this roofing slate?

... this particular tile (see enclosed pictures and below) looked to me like natural slate, but when I looked closer at the broken edge, I could see fibrous material embedded therein.

Could this be asbestos-containing fiber cement, do you think, and if so, what would you recommend doing with this broken slate?

Is it ok just to double-bag it and throw it away - is it considered a risk if left where it is?

Any suggestion or explanation would be much appreciated.

- Anonymous, Dorset, UK, by private email 2018/08/27

Reply: yes in some older products, not all

You're right that the slate roofing product in your photos is man-made, not a natural true-slate material - slate would be apparent as a layered material;

In most but not all natural or quarried slate you can see the layers that comprise the slate, as it was mined from a slate quarry, in this photo from our article SLATE ROOF LIFE EXPECTANCY

Photograph of soft roofing slates that are worn out

You can see the fine layers visible in the edge of any natural slate material.

Watch out: some slate, depending on its quarry of origin, may be more stone-like and may not show layering. Below is a natural slate from the Quarry Armadilla. Benuza (León) Spain and distributed also in New Zealand (cited below).

In your fiber-cement or synethtic slate product shown earlier and and in a closeup just below, I too, see the homogenous, solidified, particulate-based material with some fibers in the broken edge of your product - to be expected in a manufactured slate product, though there is at least one polymer-based synthetic roofing slate that also has a layered-look to the product's edge (described below).

Edge of a broken synthentic roofing slate shows that it is not a layered material and it may contain reinforcing fibres (C) InspectApedia.com op cit

That does not mean you'd assume the slate contains asbestos as fibers could be fiberglass, cellulose, or something else. In any event it's not a friable material.

If you know the country and city of origin of the material and its manufacture date that will place it in or out of the era when asbestos might have been used.

Furthermore, even if the manufactured-slate does contain asbestos that's no reason to be frightened of it.

Unless you're grinding or sawing the material it's doubtful that there is a detectable particle release in the air around the broken slate. You should be able to dispose of a broken slate as construction debris.

Test for Asbestos in a 28-year old Omaru New Zealand Roof

Synethetic slate roof in Omaru New Zealand (Heritage Motor Lodge) tested for asbestos (C) Daniel Friedman at InspectApedia.com and EMSL

Above, the Heritage Court Motor Lodge, Omaru, New Zealand sports buildings using an older synthetic "slate" that was, at the time of our inspection, quite worn and deteriorating. We wanted to know if these building roofs contain asbestos.

These contemporary fibre cement products use filler and reinforcement that does not include asbestos, commonly fibreglass. What about the shingles shown just above?

They were installed in 1986 and were photographed (above) in 2014, making them 28 years old. We were told by a tenant that the building owner received a settlement on this roof but has not replaced it. Lab samples of this roof cladding were tested, and results are now available.

Synthetic slate sample from the roof of a motor lodge in Omaru, New Zealand (C) Daniel Friedman at InspectApedia.com

Above: preparing our synthetic slate sample for mailing to a certified asbestos test lab.

Below: lab test results, using PLM, asbestos was not detected. [Click to Enlarge Any Image]

Synthetic Slate Roof, Omaru New Zealand tested for asbestos (C) Daniel Friedman at InspectApedia.com

This roof is also discussed at ASBESTOS & FIBER CEMENT ROOFING

 

History of Use of Asbestos in Manufactured or Artificial-stone slabs, Shingles, Plates and Roofing Slates: 1900 - 2018

Synethetic slate roof in Omaru New Zealand (Heritage Motor Lodge) tested for asbestos (C) Daniel Friedman at InspectApedia.com and EMSLAsbestos was used in fiber cement products including both roofing and siding materials - as we detail

at ASBESTOS & FIBER CEMENT ROOFING.

Focusing more-specifically on artificial slate or artificial stone such as synthetic slate we cite below some research on asbestos-slates and patents describing products that used asbestos in artificial slate or stone beginning in North America as early as 1917 and by 1978 was widely used in manufactured slate and stone products including roofing materials.

By 1979 most countries had stopped producing asbestos-based artificial slates or roof tiles.

For example New Zealand had banned the use of asbestos in such materials in 1979.

MacMillan (2018), a New Zealand slate roofing company, notes that in that country "asbestos slates" or "artificial slates" had been used from the early 1900s until 1979, followed by fibre cement artificial slates (ca 1980-1988) that did not perform well, failing after just a few years.

You can see that performance in the New Zealand synthetic slate photos shown above on this page.

Reconstituted slate tiles, or composite slate, also referred to as "man made slate" may use recycled "slate spoil" - old slates removed from buildings, mixed with a binder - were produced in New Zealand from about 1985 to 1995 when those products, too, showed early product failures leading to their withdrawal from the marketplace.

McMillan says that the resins in these manmade slates were found to be broken down by UV light exposure.

By 1997 and probably earlier, US patent disclosures for synthetic slates did not include asbestos. Resins and plastics, reinforced with fiberglass or other non-asbestos fibers were common.

At MANUFACTURED / SYNTHETIC SLATE we list current man-made slate producers and indicate what those manufacturers say about the composition of their current product lines.

Is it slate, manmade slate, asbestos slate, fiber cement slate, or something else?

Watch out: because of looseness with which people use the terms shingle, roof tile, roof slate, some discussions of asbestos-cement "Slates" may refer to other asbestos cement roofing products that look nothing like slate.

Those non-slate products are discussed separately

at ASBESTOS & FIBER CEMENT ROOFING - home

In the U.S. asbestos-based artificial slate or cement asbestos roof tile production based on the use of asbestos-cement as the primary material was winding down by the 1980s. Asbestos cement roofing shingles, tiles, or "slates" performed well for decades.

Watch out: a number of non-asbestos manufactured or synthetic slates or fiber-cement roof shingles, slate, tiles that were produced when manufacturers stopped using asbestos were made using wood fibers or other materials. A number of these products, promising a life of 50 years or longer, were found to fail early in their life in the 1990s. Just about all of these products are no longer sold (in 2018).

See details at FIBERBOARD ROOFING & FIBER-WOOD ROOFING.

Research on Manmade Slate History

Below we cite research articles and patents that help track the earliest and latest uses of asbestos in manufactured / synthetic roof slates.


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MANUFACTURED / SYNTHETIC SLATE ASBESTOS CONTENT at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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