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How to Repair Slate Roofs InspectAPedia®  -     How to repair slate roofs - a guide How to inspect, evaluate & repair slate roofs - the basics

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

The abandonment of good slate roofs which should have been repaired is a financial shame and the destruction of a valued asset. At the same time, careless optimism about a bad slate roof which is at the end of its life risks an angry inspection client. This article reviews some slate roof repair tips. We also provide slate sources and where to buy slate roofing materials and slate roofing tools and products.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

This section deals with repairs to damaged slate roofs as compared with complete new slate roof installation. A key difficulty is presented by the fact that unlike asphalt shingles, slates are rigid. The repair person cannot easily "lift" adjacent slates to install the fastener for the new replacement slate.

Replacing Lost Slates using the Copper Tab Method

A proper slate repair involves several steps:

• Cut the concealed nails, holding the damaged slate in place. There are usually two nails.
• acquire the properly sized replacement slate. If the exposure is ten inches the slates should be twenty-three inches long. A proper slate application uses slates which are twice the exposure plus a three-inch allowance for head lap.
• slide the slate into place, use the gap between the sides of the above-course of slates to mark the location of a single holding nail.
• the nail hole is punched into the slate from the back, so that the ragged part of the hole is on the front or face of the slate. This will allow the nail to sit flush in the hole. It's a crude form of counter-sinking.
• nail the replacement slate into place with a copper nail. Sometimes the edges of the nail head have to be cut off to pass between the sides of the two slates in the covering upper course.

• Stainless steel slate hook offers a more reliable alternative than copper strips for holding replacement slates in place. The fastener end of the hook is nailed roughly 3" up from what will be the lower edge of the replacement slate. The slate is slid up over the hook and seated. The illustrations below depict this procedure.
  
  
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  Slate hook installation-1, the hook is driven in place where the missing slate is to be installed - nailed into the side butt joint of the lower slate course
  
  
  
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  Slate hook installation-2, the new slate slides over the hook, is seated, and the hook, pops up into place to hold the new slate securely

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SLATE ROOF INSPECTION & REPAIR
How to Inspect & Repair
Types of Roofing Slate
Slate Colors, Chemistry
Slate Roof Aging and Durability
Ribbon Slates
Slate Roof Installation Quality
Other factors in Condition
Slate Roof Repair history
Slate Roof Leaks
Slate Holding actions
How to Repair Slate Roofs
  Copper Tab Method
  Slate Hook Method
SLATE ROOF PHOTO LIBRARY
Slate References
Slate Sources, Repairs
SLATE ROOF INSPECTION CLASS

Slate Roofing References

• SLATE ROOF INSPECTION & REPAIR home page
• SLATE ROOF PHOTO LIBRARY Our online photo dictionary of roofing slate colors, types, and conditions has moved to its own web page
• SLATE ROOF INSPECTION CLASS presentation notes and illustrations
• 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.
• 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.
• Slate Roofing Contractors Association of North America
• National Slate Association includes list of slate testing laboratories

Slate Replacement & Repair Sources

If less than 25% of the slates on a roof are damaged or sliding down from worn out nails, slate repairs are in order. Luckily replacement slates are available from a variety of slate quarries, slate suppliers, and slate roofing companies. Slate "look alike" products are also available using cementious materials. If the building owner cannot afford to repair a slate roof where most slates are intact, holding action slate roof repairs should be followed, such as simply sliding metal flashing up under broken or missing slates on the roof.

• Vermont Structural Slate Co., PO Box 98 Fair Haven, VT 05743 802/265-4933 802/265-3865 FAX (Green, purple, unfading red, and Spanish imported black.)
• Rising & Nelson Slate Co., West Pawlet, VT 05775; 802/645-0150 (all VT colors plus Buckingham Gray from VA and blacks from PA.)
• Evergreen Slate Co., 68 Potter Ave., Granville, NY 12832; 518/642-2530. Vermont slates in 10 colors.
• Hilltop Slate Co., Middle Granville, NY 12849; 518/642-2270 (all VT colors plus imported Spanish Black)
• Structural Slate Co., Pen Argyl, PA 18072; 215/863-4145 (PA black)
• Buckingham Slate Co., 4110 Fitzhugh Ave., Richmond, VA 23230; 805/355-4351 (VA Buckingham Grey)

In addition to these slate sources there are several slate look-alike substitutes. While the application techniques, flashing and nailing concerns are similar, the wear characteristics of these materials may be quite different and were not evaluated for this paper. This paper is not an endorsement, nor a critique of any of these materials.

• Eternit, Inc., rigid fiber reinforced cement roofing slates (and board products. Village Center Drive, Reading, PA 19607 800/233-3155
• BritSlate^TM are made from 100% quarried slate particles combined with an adhesive (epoxy?) and no fillers with no questionable side effects according to the manufacturer. According to the manufacturer, they can be cut, drilled, etc. and come with a 50-year guarantee. They're less prone to breakage than slate, fireproof, and do not absorb water (like natural slate), and do not encourage organic growth (moss and lichens) because they are not porous. BritSlate North America, Inc., 647 West Boylston St., Worcester, MA 01606 508/852-4888 508/852-7224 FAX 2/90.
• Reinforced-cement shingles which "look like slate but are lighter and one-third the cost" are available from Atlas International Building Products, 5600 Hochelaga St., Montreal, Quebec, Canada H1N 1W1. [$180/square loose or $400./sq. installed, 30-year guarantee.]
• Supra-Slate "looks like slate and is manufactured in colors of real quarry slate." Tegusol is a double interlocking clay roof tile. Available from: Supradur Manufacturing Corporation, PO Box 908, Rye, NY 10580 800/223-1948 or 914/967-8230. or 122 East 42nd St., NY, NY 10168 212/697-1160
• Lifetile(R) Boral Concrete Products, Inc., produces high density extruded concrete roofing tiles meeting Class "A" requirements. Dallas, TX 214/544-2227

More Information on Building Diagnostic Inspections and Repairs

• How to Inspect & Repair Slate Roofs a detailed article about evaluating the condition of slate roofing and repairing worn or damaged slate roofs.
• Slate Roofs: a photographic library of slates, slate roofs, roofing styles
• 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)

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