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CERTIFICATIONS for ROOFING CONTRACTORS CHOOSING A ROOFING CONTRACTOR ASBESTOS CEMENT & FIBER CEMENT ROOFING ASPHALT ROOF SHINGLES BUILT UP ROOFS CERTIFICATIONS for ROOFING CONTRACTORS CHIMNEY INSPECTION & REPAIRS CHOOSING A ROOFING CONTRACTOR CLAY TILE ROOFING CONCRETE ROOFING CORRUGATED ROOFING ENERGY SAVINGS in BUILDINGS FIRE RETARDANT PLYWOOD FLAT ROOF MOISTURE & CONDENSATION HEAT TAPES & CABLES on Roofs for Ice Dams LOW SLOPE ROOFING MATERIALS MASONITE WOODRUF FIBERBOARD ROOFING MEMBRANE & SINGLE PLY ROOFS METAL ROOFING TYPES MODIFIED BITUMEN ROOFING ROOF INSPECTION SAFETY & LIMITS ROOF VENTILATION SPECIFICATIONS ROOF VENTING ENERGY SAVING DETAILS 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 SOD ROOFING SIDING WOOD STAIN DIAGNOSIS on Building Exteriors STAIN DIAGNOSIS on Roofs STANDARDS for ROOFING STONE ROOFING THATCH ROOFING THERMAL EXPANSION of MATERIALS THERMAL MASS in BUILDINGS THERMAL MASS in UPSTAIRS TILE ROOFING WARRANTIES for ROOF SHINGLES WOOD SHAKE & SHINGLE ROOFING WORKMANSHIP & WIND DAMAGE More Information InspectAPedia Blog - News Updates Air Conditioning & Heat Pumps Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Privacy Policies Contact Us |
Here we discuss various factors that help determine the quality and thus life expectancy of a slate roof. This series of detailed slate roof inspection and repair articles describes procedures for evaluating the condition of slate roofing. How to inspect, identify defects, and estimate remaining life of slate roofs are addressed. The article series also references slate repair procedures, repair slate sources, and slate quarries. An earlier version of this article appearedin the winter 1991 issue of the ASHI Technical Journal - the content has been edited and updated for this online version - July 2007. Copies of the ASHI Technical Journal are available from the American Society of Home Inspectors - ASHI at ashi.com. 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. Slate Roof Installation quality, Fasteners Used & Slate PatternThe following may all be indications that the roof is failing from the condition of the slate nails:
In our opinion, galvanized flashings (or too-thin thin copper or painted steel) are a mistake on slate roofs. The flashing is very likely to wear, rust, and fail before the slates. While replacing flashings is quite possible and appropriate, it's often expensive and if not done by an experienced slate roofer, there is risk of costly damage to the roof. We had a client this year whose slate roof was damaged by the mason working on the chimney. He accepted a low-bidder for roof repairs. We found asphalt shingles nailed over and around the area of damaged slates. To say that the roof leaked was the least aggravating observation concerning this work. Inspecting from the attic interior may also give clues to fastener age, type, and condition if some nails are visible. You may see tips of nails, depending on the length of fasteners used. Slate Roof Installation Pattern as a Factor in Slate Roof Life
More holes and more nails may be used to hang thicker heavier slates. Where battens or spaced roof sheathing are used the spacing of the battens will affect where the holes are punched in the slates. Slates punched too close to their centers or too low in the slate are more likely to leak when water seeps down in a fan-shaped pattern from the vertical abutment of the sides of the slates in the next course up the roof. If you are inspecting a roof which frequently leaks following prolonged rains, and if the slates and flashings look pretty good, and if leaks are everywhere, you might look for improper punching or nailing errors. Don't rush to condemn the roof - how often and how badly does it leak? Under what conditions? What is being damaged? Where is water going? Nail tightness: Slates should hang loosely on the nail. Nails too tight may break the slate as they're pulled through it as wood shrinks. Nails not driven fully are likely to break the slate above. Other signs of poor installation include inadequate side laps. Side Lapped slate pattern. Side laps on slate roofs should be not less than 3" and each side-joint should be as near as possible to the center of the slate below. Particularly where improper repairs have been done you may find violations of this rule. Inadequate side laps risk leaks as a result of wind-driven rain. Inadequate side laps might be suspected on roofs which use varying-width or graduated width shingles. However some experienced roofers and inspectors commented that graduated, random-width, graduated width slate roofs were more costly than other slate systems and were often installed by more skilled roofers. Do not mistake graduated or random slate sizes for necessarily improper application. ... Technical Reviewers & References
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06/30/2009 - InspectAPedia.com/roof/SlateRoofsATJ6.htm - © 2009 - 1988 Copyright Daniel Friedman All Rights Reserved - InspectAPedia® is a Registered U.S. Trademark