A Photo Library of Slate Roof Defects

SLATE ROOF DEFECTS - Photo Guide to Slate Roof Defects - key on-roof or at-roof-edge slate roof inspection points . Photo library of slate roofing materials & slate conditions; Slate wear indicators that you can evaluate by visual inspection; Examples of new, normal wear, and worn-out slate roofs
EFFLORESCENCE, Salts & White / Brown Deposits - separate article
STAIN DIAGNOSIS on ROOFS - separate article
STAIN DIAGNOSIS on STONE - separate article
Questions & Answers about slate roofs: slate installation, flashing, slate sources, slate roof leaks, stains, diagnosis, repair advice
References

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Slate roof defect photo library: this slate roofing photo series shows all kinds of roofing slate defects. Here we give photographs of slate roof conditions including normal wear on slate roofs, worn out slate roofs, types of slate roof wear and damage, and stains or discoloration on slate roofs. Starting at SLATE ROOF INSPECTION & REPAIR we describe procedures for evaluating the condition of slate roofing. We describe the types of roofing slate, common defects, inspection topics, and some repair tips. This article series assists home inspectors, building buyers or building owners, and roofing contractors in evaluating the condition of slate roofs by providing photos of various slate materials, patterns, defects, and conditions.

A Photographic Guide to Defects in Slate Roofs

Photo guide to Cracked, Broken Slate Roofing Inspection & Repair

Broken roofing slates

Cracked, broken slates, probably not leaking but note the diagonal crack in the slate below the course with a missing slate half

Cracked roofing slates

Cracks: Slate crack repair, copper was slipped up over a slate which had split just below the butt joint of slates in the next course

Photo Guide to Delaminating Roofing Slates

Delaminating roofing slate, if the delamination is only in the upper surface layer of the slate the material may have substantial remaining life.

Also ask how many of the roof slates are delaminating at all - note the neighboring slates on this roof are sound.

Surface delamination on slates: Notice the surface delamination on some of these slates. A close inspection is needed to evaluate slate delamination when it looks like this. We need to know if the slate is basically sound, hard, and secured to roof, or if alternatively the delaminations are throughout the slate body, making it soft.

See our photos at SOFT DETERIORATED SLATES where we show close up photos of slate that looked pretty good on the roof but when touched, disintegrated easily

Photo Guide to Slate Roof Flashing Details

Slate roof flashing defects

Flashing: Chimney in the roof valley, was a probable factor in recurrent leaks in this slate roof

Slate roof with good sidewall flashing to a brick building

Flashing: Slate roof with good side-wall step flashing, against a brick wall

Slate roof flashing defects-closed valley caulked

Flashing: Suspect copper valley in slate roof, note the attempt to "patch" the valley with roof mastic - and the cracks in the mastic - this repair is not durable

Photo Guide to Loose, Sliding, Lost Roofing Slates & Slate Nails

Repair on loose roof tiles |

Nails: sliding slates, mean the nails are lost - perhaps from corrosion.

Don't underestimate the implication of many slates which have moved only a little bit - all may have lost their nails.

Notice also the surface delamination on some of these slates.

Loose roof slates

Nails: Slate fastener failure, might be indicated by the slate at right if it is sliding down - can you move it back up?

If you can, this slate has lost its nail and is not connected. Use a slate hook or copper tab to secure the loose slate in place.

Sliding roof slates

Nails: Roof Tiles (not slate), repaired using copper strips - the strip ends holding tiles have been bent back by sliding snow - expect movement, leaks, and extensive nail failures.

This defect also occurs on slate roofs repaired using this method. This demonstrates the advantages of slate hooks in lieu of copper strips when replacing lost slates.

Slate damage at chimney and lower edge, probable leaks at chimney. Why to the slates seem loose particularly around the chimney?

Often the building framing settles away from the masonry chimney as framing ages, sags, or settles due to shrinkage or later rot or other in-building damage. But the chimney, built of masonry, tends to remain the same height.

On many old houses the framers actually connected roof framing right to the chimney. Later when the building sagged, settled, or moved, the framing pulls away from the chimney causing damage to the roofing slates and flashing, and leading to leaks in this area.

Another common source of slate roof damage around a chimney is wear and movement caused by flashing leaks and, in freezing climates, frost.

Photo Guide to Slate Roof Defects: Mineral Inclusions & Staining in Slates

Mineral inclusions in roof slates

Mineral inclusions: Slates with mineral inclusions, the wash-out of minerals in some slates can lead to holes and leaks

Mineral inclusions in roof slates can lead to holes and leaks

Mineral inclusions, holes in slates - the slates with these defects need to be replaced or patched from below with copper panels.

Stains and Wear Indicators on Slate Roofing, a Photo Guide

Staining on roofing slates: Slate edges showing moisture absorption, but generally good condition, these slates have a good remaining life

White Efflorescence on roofing slates: the white markings shown on these roofing slates, is a mineral deposit left behind as water evaporates. Water penetrating the slate material absorbs minerals and leaves some of them, probably Ca and Mg on the slate surface.

Many slate roofers and slate inspectors assert that as the white stains progress from the edges of individual slates towards their center, one can estimate the remaining roof life. If 50% of the slate remains inside of the white area, the slate may have about half of its life remaining.

We recommend that this condition be confirmed by close inspection as well since other slate deterioration factors could be at work.

Thickness of Roofing Slates, Close up Photo of Slate Edges in Good Condition

Edge of slate shows thickness and layers of minerals

Slate edge close up, showing the natural layering of mineral deposits in the original stone

Measuring the thickness of roofing slates after installation

Thickness: Measuring slate thickness, and close up inspection permits check for slate delaminating and softness

Thin worn out roofing slates

Thin, worn slates, French and conventional pattern, missing slates, tar patches, leaks. This roof is probably repairable But we 'd need a closer look at those slates to evaluate their thickness and hardness.

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Frequently Asked Questions (FAQs) about slate roof inspection, leak troubleshooting, repair or replacement

Question: long white roof stains down from chimney

We are buying a house with a slate roof on a six year old home...the roof has long white stains down from the chimney. Looks like it's coming from the flashing around the stone chimney. Thoughts? - Steve

Reply: possible sources of white stains on roofs and buildings

White stains down FROM the chimney? Steve I'm not sure and would need to see some photos (use the CONTACT link found at top, side, bottom of our pages to send me some pix) . Our photo at left shows white efflorescence on the outside of a masonry chimney - discussed at White/Light Stains on Chimneys.

Search InspectAPedia for
Chimney Stains, Discoloration, Leak, Diagnosis, Cleaning & Repair Guide
to see white efflorescence stains on chimneys themselves as well as other types of stains on chimneys themselves (photo at left).

White stains on a roof can be pigment wash down from something above, salts from flashing corrosion, and on slate, white stains that form on individual slates, beginning usually as a roundish spot at the center of individual slates, are a sign of aging and wear.

See STAINS on ROOF SHINGLES for our library of types of stains found on roofing surfaces. There we include this comment

White stains on roof surfaces may be from wash-down of pigments in paint on surfaces above the roof such as a gable end or dormer wall; white or less-black roof surfaces may also be found below copper or aluminum flashing whose salts run down the roof surface in wet weather, preventing algae or moss growth and leaving a white area on an otherwise stained roof surface. Our article at ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES includes a photograph of this condition on a wood shingle roof.

White stains on slates themselves (photo at left) as a wear indicator are discussed in the article above on this page.

To diagnose white stains that are on a roof, building chimney, or walls, and specifically around or below a chimney, I'd be alert for flashing leaks - check indoors - and I'd follow the white stains up to their point of origin on the roof to see just what materials are there, for example:

A white-painted dormer side or window above a roof section can bleed down white onto a roof surface
Mineral salt runoff from some metal flashings, particularly aluminum, may result in a "white" or "clean" area on otherwise darker building roof or even walls below
Less often white stains below a chimney could be salts leaching from the chimney interior through the masonry and onto the roof surfaces (more often these are dark brown or black and relate to combustion products)

Finally, I can comment more accurately if I can see some photos of the roof in question. Here are articles on building roof stains:

EFFLORESCENCE, Salts & White / Brown Deposits
STAIN DIAGNOSIS on ROOFS
STAIN DIAGNOSIS on STONE

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Questions & answers or comments about how to inspect & recognize defects, leaks, damage in slate roofs.

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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.
How to Inspect & Repair Slate Roofs a detailed article about evaluating the condition of slate roofing and repairing worn or damaged slate roofs.
Slate Roof Photo Library photographs of colors, types, patterns of slate roofs, slate roof wear, slate roof conditions.
Slate References page from the ASHI Technical Journal
Slate Sources, Repairs page from the ASHI Technical Journal
Roofing: Defect Recognition, Repair, Prevention for Roofing & Flashing main web page
Inspecting and Evaluating Slate Roofs Hudson Valley ASHI seminar content
Choosing a Roofing Contractor How to find and select a roofing contractor - (thanks to Jessie Schrader)
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.)
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 Roofs , Steven Trapasso, presentation to NY Metro ASHI, Inc. chapter seminar, November 1990.
The Old-House Journal , Special Roof Issue , April 1983, The Old-House Journal, PO Box 50214, Boulder, CO 80321-0214
National Slate Technology Center courses for architects, builders, etc.
Slate Roofing Contractors Association of North America
National Slate Association includes list of slate testing laboratories

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

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
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),
Tile Roofs of Alfred: A Clay Tradition in Alfred NY
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