SLATE ROOF TYPES, RIBBON SLATES - CONTENTS: Ribbon Slate Roofing: how to evaluate ribbon slates on a roof. Definition of ribbon slate roofs? Photographs of ribbon slates. What is the life expectancy of ribbon slates on a roof?Do ribbon slate roofs wear out faster than other slates? Mineral inclusions and leak risks at certain ribbon slate roofing products.
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Ribbon slate roofing:
What are ribbon slates, and do they wear out faster than other slate roofs? Slates with diagonal or striped inclusions of varying colors, or ribbon slates, include products with a very long life expectancy and other ribbon slates that are or were a low-priced slate with soft inclusions, short life, and leaks.
Here we illustrate different types of ribbon slates used in roofing and we describe how to distinguish the low-priced short-lived ribbon slate from the longer-lived very durable ribbon slate on a roof.
The ribbon slate on this
mansard roof slope may have been chosen for appearance, though it was not installed so as to use the ribbon diagonals to form any particular pattern.
[Click to enlarge any image]
In the first two photos shown here the slates have diagonal
colored stripes of mineral inclusion, but they do not show the characteristic delamination and wear we see
on classic ribbon slates.
Some ribbon slates were a cheaper and shorter-lived product because the mineral inclusions that formed the "ribbons" of color in the roofing slates were a softer material that weathered out of the slate rapidly.
However as numerous slate roofers and other readers have pointed out, ribbon slates were also selected and installed on some buildings for their aesthetic appeal and included ribbon slates from other quarries whose mineral inclusions were quite durable.
So the answer to the question of "are ribbon slates more or less durable than other roofing slates?" is "it depends" on which quarry was the source of the slate.
More slate with diagonal mineral inclusions is shown mixed with solid reds on other slopes of the same home.
Ribbons of color in ribbon slates on roofs may be in the entire shingle or in some applications, may be in the
upper or covered portion of the slates. In the photo at left a mix of ribbon slates have diagonal colored stripes of mineral inclusion, but they do not show the characteristic delamination and wear we see
on classic ribbon slates
"Slate is of medium hardness, very fine grained of low porosity, great
strength and consists essentially of insoluble and stable minerals
that will withstand weathering for hundreds of years. Some slate in
Pennsylvania contains ribbons which consist of narrow original beds
usually containing carbon, and darker in color than in the body.
is tendency for some ribbons to contain an excessive amount of the
less resistant minerals, and they should not appear on exposed surfaces." -- Dr. Oliver Bowles, Mineral Technologist of the US Bureau of Mines,
in "The Characteristics of Slate" , June 1923 paper delivered
to the American Society for Testing Materials. ASTM.
By "appear," Bowles meant that inferior ribbon slates which contain
fast-weathering mineral inclusions should not be used where exposed to the weather.
Ribbon slates are easily identified from the ground. The stripes are
accentuated because the ribbon portion absorbs more water than the
rest of the slate. Usually the ribbons are darker, often multi-colored
browns and reds. An Albany NY slate roofer
suggests that ribbons were desirable
for a pattern effect, and that they were equally durable with other
slates from Pennsylvania. -- Capital Region ASHI
chapter education seminar, fall 1990
Some roofers consider ribbon slates as less durable material.
we suspect that the durability of
ribbon slates depends on the particular minerals which make up the
visual diagonals. If the diagonals are comprised of minerals softer
than the surrounding slate, early wear is likely. In at least some
cases, ribbon slates are less durable than other Pennsylvania slates. -- Trapasso,
If these slates were actually shorter-lived than clear cut materials,
why were they used? In the 1940's one square (100 sq. ft.) of Pennsylvania
slate cost about $6.00, or about $15.00 installed. Because of these
attractively low prices and low anticipated replacement cost [boy
were they wrong!] ribbon slates were very popular and were
As slate and roofing costs rose and as ribbon slates
were less expensive than clear slates, some clever roofers used slates
which were cut so that the ribbons were only in the upper half of
the slate. As the ribbons were covered by the next course, these roofs
were more durable.
What's the bottom line on ribbon slates? Good or bad?
Really, as Florida home inspection expert Mark Cramer loves to intone, "... it depends." Some ribbon slates include mineral inclusions that weather out and lead to a short slate roof life. But plenty of ribbon slate roofs like the Poughkeepsie home shown at left are very durable, lasting many decades. So the life of a ribbon slate roof depends on the particular ribbon slates installed and thus on the quarry where they originated.
An inspector may spot this interesting material from attic view
or from outside if a slate has fallen
out of position, exposing the upper half of its predecessor course.
The cost of installing a modern slate roof makes the choice of poor
Attic view means inspecting the underside of the roof surface from
inside the building. If open or spaced sheathing was used as nailing
base for the slates you'll be able to see the backs of the slate material,
or in some cases, you'll see roofing felt, usually damaged or soft,
which may provide openings to see the slates. Where closely-spaced
board sheathing was used you'll not see slates except perhaps through
a knot hole or damaged board.
More ribbon slate photos are in our SLATE ROOF COLORS article or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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Roof Tiling & Slating, a Practical Guide, Kevin Taylor, Crowood Press (2008), ISBN 978-1847970237, If you have never fixed a roof tile or slate before but have wondered how to go about repairing or replacing them, then this is the book for you. Many of the technical books about roof tiling and slating are rather vague and conveniently ignore some of the trickier problems and how they can be resolved. In Roof Tiling and Slating, the author rejects this cautious approach. Kevin Taylor uses both his extensive knowledge of the trade and his ability to explain the subject in easily understandable terms, to demonstrate how to carry out the work safely to a high standard, using tried and tested methods.
This clay roof tile guide considers the various types of tiles, slates, and roofing materials on the market as well as their uses, how to estimate the required quantities, and where to buy them. It also discusses how to check and assess a roof and how to identify and rectify problems; describes how to efficiently "set out" roofs from small, simple jobs to larger and more complicated projects, thus making the work quicker, simpler, and neater; examines the correct and the incorrect ways of installing background materials such as underlay, battens, and valley liners; explains how to install interlocking tiles, plain tiles, and artificial and natural slates; covers both modern and traditional methods and skills, including cutting materials by hand without the assistance of power tools; and provides invaluable guidance on repairs and maintenance issues, and highlights common mistakes and how they can be avoided.
The author, Kevin Taylor, works for the National Federation of Roofing Contractors as a technical manager presenting technical advice and providing education and training for young roofers.
The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com,
143 Forest Lane, PO Box 607, Grove City, PA 16127 - 866-641-7141 (We recommend this book).
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
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