A Photo Guide to Worn Out Slate Roofs

Photo Guide to Wear Indicators on Slate Roofs
- Photo library of slate roofing materials & slate conditions helps determine the condition of a slate roof and helps estimate its remaining life
- Standards or rules of thumb define worn out slate roofs.
- Examples of worn-out slate roofs - when is it no longer economical to repair a slate roof?
Questions & Answers about wear indicators on slate roofs - how do we conclude that a slate roof is worn out or is beyond economical repair?
References

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Worn-out slate roof indicators: how do we decide that the roof is beyond economical repair? Here we provide photos of worn-out slate roofs that are beyond repair. This slate roofing photo library shows various kinds of roofing slate, slate roof colors, slate roof patterns, and roofing slate defects. This photographic dictionary of roofing slates is a supplement to our detailed article (links at Related Topics ) describing procedures for evaluating the condition of slate roofing. How to inspect, identify defects, and estimate remaining life of slate roofs are addressed. The article also references slate repair procedures, repair slate sources, and slate quarries. The main article reviews types of slate, common defects, inspection topics, and some repair tips. Also see How to Inspect & Repair Slate Roofs for a detailed article about evaluating the condition of slate roofing and repairing worn or damaged slate roofs.

Photo Guide to Slate Roofs in Poor Condition or Worn Out

Roofing slates that are "rotted", soft, delaminated, worn out, crumbling, beyond repair

At a slate roof class organized by the author and conducted in New York in the 1980's a slate roofer referred to "rotted roofing" slates - which made sense to him but not to the rest of us.

Slate is essentially a complex mineral or stone product - so how could slate actually "rot".

Well it doesn't. Not quite anyway. (Though slate, as a naturally occurring mineral, can include soft inclusions, even organic debris, slate is basically stone. Minerals don't rot.)

But depending on their composition (each slate quarry has a unique chemical signature that identifies its slates), slates can become soft, crumbling, or delaminated that on touching a slate it is found to be completely softened and thus completely at or past the end of its life.

Below I illustrate this condition in three photographs.

Photograph of soft roofing slates that are worn out

Photograph of worn out rotted roofing slates

As we discussed in more detail at SLATE ROOF INSPECTION & REPAIR, determination of slate condition other than by direct up-close inspection is highly unreliable. Slates may look fine from the ground, but be found soft and at end of life on close inspection.

By direct inspection we mean looking at slates from a few inches, either from a ladder or some other point of view such as an attic window. We strongly advise inspectors not to walk on slate roofs whether they look soft or not. Soft Deteriorated Roofing Slates may not be obvious from the ground but mean the roof is at end of life.

Rules of Thumb for Determining that a Slate Roof is "Worn Out" and not economically repairable

Here is a slate roof that is in poor condition, probably beyond repair. What can we see that argues that the roof is at or past the end of its useful, reliable life and that it is beyond economical repair?

Even from a distance the home inspector or slate roof inspector can see that while many slates have been replaced (darker slates in the photo), the remaining roof slates show white mineral efflorescence which has formed almost all the way to the center of each slate.

The rust-colored slates in the photo were badly delaminated, thin, and soft, having no remaining predictable life. This slate roof is too fragile to inspect by walking-on. For a closer look, check out the next two photos, below.

Because of the fragile nature of slate roofs, accessing the roof to perform repairs requires extra effort and care, and thus extra costs are involved. Most slate roofers opine that if more than twenty five percent of the slates on a roof are lost, damaged, broken, delaminated, or leaking, the roof is beyond economical "patching" and should be replaced.

In our experience, when we begin to work on a slate roof in the condition of the homes shown in these photos, invariably we find many more damaged slates than first met the eye, making that 25% number more credible than ever.

Examples of slate roofs in poor or worn-out condition

Poor condition slate roof, many loose slates, efflorescence almost fills upper slates, many thin delaminating slates, more than 25% of this roof is bad, beyond economical repair.

Watch out: don't confuse superficial or light surface delamination that appears on the surface of roofing slates that remain in good condition with delamination that indicates that the whole slate is soft and shot.

It often requires an up-close look and probably some gentle "touching" or probing for a roofer or roof inspector to conclude with confidence that slates are in good condition with surface delamination versus in poor condition and worn out. See DELAMINATING for clarification. This point of confusion is another argument that a "roof inspection" performed only from the ground is, of necessity, incomplete.

Poor condition slate roof - close up, of a roof beyond economical repair (using slate) - a patch and struggle policy may be tolerable.

The dark colored slates are areas where bad slates have been replaced.

We'd love to see this replacement pattern continue. Many roofers opine that when more than 25% of the slates have to be replaced in a short period, the roof is beyond economical repair.

Worn slates at or near end of life, in the upper roof - note the efflorescence on some slates and the delaminating slates. Some slaters inform us that when they see the efflorescence marks on slates having nearly completely covered the slate they guess that the slate is near the end of its life.

Some slates, such as the red slates shown in photos above, do not show this efflorescence pattern, probably because the composition of that stone resists moisture absorption better than the darker slates shown in this photo.

Worn slates at end of life, lost slates, delaminated slates, broken slates on this small roof make re-roofing necessary

Worn out slates and sliding slates, on a slate roof beyond economical repair

Sliding slates, failed nails, and rotted roof sheathing show that this roof has not been maintained for a decade or more. Thin delaminated slates are worn out.

This roof is already leaking and is covered by slates that include so many soft, loose, lost-fastener & broken, or missing roof slates over soft rotted roof decking (more visible from the attic side) that the roof is beyond repair.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. 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:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
  Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
  Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon.
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
Concrete Folded Plate Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author), Butterworth-Heinemann, 1998, ISBN-10: 0340662662, ISBN-13: 978-0340662663
Copper Roofing, Master specifications for copper roofing and sheet metal work in building construction: Institutional, commercial, industrial, I.E. Anderson, 1961 (hard to find)
Handbook of Building Crafts in Conservation, Jack Bower, Ed., Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of Congress Catalog Card Nr. 81-50643.
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
Historic Slate Roofs : With How-to Info and Specifications, Tina Skinner (Ed), Schiffer Publishing, 2008, ISBN-10: 0764330012 , ISBN-13: 978-0764330018
Low Slope Roofing, Manual of, 4th Ed., C.W. Griffin, Richard Fricklas, McGraw-Hill Professional; 4 edition, 2006, ISBN-10: 007145828X, ISBN-13: 978-0071458283
- Roof failure causes in depth (and specific methods for avoiding them)
- Roof design fundamentals and flourishes, based on voluminous industry research and experience
- New technologies and materials -- using them safely and correctly
- Comprehensive coverage of all major roofing systems pecifications, inspection, and maintenance tools for roofing work
Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs],
Patio Roofs, how to build, Sunset Books
Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502
Slate Roofs, National Slate Association, 1926, reprinted 1977 by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It has gone in and out of print on occasion.)
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).
Slate Roofing in Canada (Studi4es in archaeology, architecture, and history),
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.


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