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EXTERIORS of buildings
ADHESIVES, EXTERIOR CONSTRUCTION
AGE of a BUILDING - how to determine
ALGAE, FUNGUS, LICHENS, MOSS
ANIMAL ENTRY POINTS in buildings
ANIMAL ODORS IN buildings
ARCHITECTURE & BUILDING COMPONENT ID
ASBESTOS IDENTIFICATION IN buildings
ATTIC CONDENSATION CAUSE & CURE
BARK SIDE UP on DECKS & STEPS
BASEMENT WALKOUTS & COVERS
BEST CONSTRUCTION PRACTICES GUIDE
BRICK VENEER WALL Loose, Bulged
BRICK WALL DRAINAGE WEEP HOLES
BOOKSTORE - EXTERIORS
BUILDING SAFETY HAZARDS GUIDE
CAULK GUN TYPES, CHOICES
CAULKS & SEALANTS, EXTERIOR
CHIMNEY INSPECTION DIAGNOSIS REPAIR
COLUMNS & POSTS, DEFECTS
CONNECTORS, FASTENERS, TIES
DECK & PORCH CONSTRUCTION
DECK COLLAPSE Case Study
DECK FINISHES COATINGS PRESERVATIVES
DECK FLASHING LEAKS, ROT Case Study
DEFINITIONS of ENGINEERED WOOD OSB LVL etc
DRYWELLS, FRENCH DRAINS for FLAT SITES
EARTHQUAKE DAMAGED FOUNDATIONS
EIFS & STUCCO EXTERIORS
EXTERIOR WALL SIDING TRIM & FINISHES
EXTRACTIVE BLEEDING STAINS
FLASHING MEMBRANES PEEL & STICK
FLASHING for METAL ROOFS
FLASHING ROOF WALL DETAILS
FLASHING ROOF-WALL SNAFU
FLASHING SIDING DETAILS
FLASHING WALL DETAILS
FLASHING WINDOW DETAILS
FLASHING WOOD ROOF DETAILS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FOOTING & FOUNDATION DRAINS
FOUNDATION CRACKS & DAMAGE GUIDE
GALVANIC SCALE & METAL CORROSION
GLUES ADHESIVES, EXTERIOR CONSTRUCTION
GRADING, DRAINAGE & SITE WORK
GUTTERS & DOWNSPOUTS
HEAT TAPES & CABLES on Roofs for Ice Dams
HOUSE PARTS, DEFINITIONS
HOUSEWRAP / SHEATHING WRAP
HOUSEWRAP INSTALLATION DETAILS
HOUSEWRAP PRODUCT CHOICES
HOUSEWRAP at SILLS, SOLES, TOP PLATES
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INSECT INFESTATION / DAMAGE
KIT HOMES, Aladdin, Sears, Wards, Others
LEAD POISONING HAZARDS GUIDE
LEAD TEST KIT for HOME USE
LEED GREEN BUILDING CERTIFICATION
LOG HOME GUIDE
METAL LATH, PLASTER & STUCCO
MOISTURE CONTROL in BUILDINGS
MOLD DETECTION & INSPECTION GUIDE
MVOCs & MOLDY MUSTY ODORS
ODORS & SMELLS DIAGNOSIS & CURE
PAINT & STAIN GUIDE, EXTERIOR
PAINT FALURE, DIAGNOSIS, CURE, PREVENTION
PAINT FAILURE DICTIONARY
PAINT LAB SAMPLE PREPARATION
PAINT SURFACE PREPARATION
PORCHES & Sunrooms
PORCH CONSTRUCTION & SCREENING
RAILINGS, DECK & PORCH
RETAINING WALL DESIGNS, TYPES, DAMAGE
RETAINING WALL GUARD RAILINGS
ROOF ARCHITECTURAL STYLES - PHOTO GUIDE
ROOF CLEANING RECOMMENDATIONS
ROOF COLOR RECOMMENDATIONS
ROOF DORMER TYPES - PHOTO GUIDE
ROOF VENTILATION SPECIFICATIONS
ROT RESISTANT LUMBER
ROT, TIMBER FRAME
ROT, TIMBER ASSESSMENT
SEARS KIT HOUSES
SHEATHING, Gypsum board
Sheathing Celotex Homasote & Other
SHEATHING, FOIL FACED - VENTS
SIDING TYPES, INSTALLATION, DEFECTS
SIDING, ASBESTOS CEMENT
SIDING ASPHALT ROOF SHINGLES on WALLS
SIDING ASPHALT SHINGLE or SHEET
SIDING DAMAGE by SPLASHBACK
SIDING EIFS & STUCCO
SIDING, FIBER CEMENT
SIDING, WOOD PRODUCT CHOICES
SIDING, WOOD INSTALLATION
SIDING WOOD, FAILURES OVER FOAM BOARD
SIDING WOOD, FLASHING DETAILS
SIDING WOOD SHINGLE INSTALLATION
SINKHOLES, WARNING SIGNS
SOUND CONTROL in buildings
STAIN & BIODETERIORATION AGENT CATALOG
STAINS on & in BUILDINGS, CAUSES & CURES
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on ROOFS
STAIN DIAGNOSIS on STONE
STAINS on INDOOR SURFACES: PHOTO GUIDE
STAIRS, RAILINGS, LANDINGS, RAMPS
STONE CLEANING METHODS
STONE VENEER WALLS
STRAW BALE CONSTRUCTION
STUCCO WAll FAILURES DUE TO WEATHER
STUCCO WALL METHODS & INSTALLATION
STUCCO OVER FOAM INSULATION
STUCCO PAINT FAILURES
SURFACE GRADING, SITE DRAINAGE
TEST KITS for DUST, MOLD, PARTICLE TESTS
Thermal Expansion Cracking of Brick
THERMAL EXPANSION of MATERIALS
THERMAL IMAGING, THERMOGRAPHY
THERMAL IMAGING MOLD SCANS
THERMAL MASS in BUILDINGS
TREES & SHRUBS, TRIM OFF BUILDING
TRIM, EXTERIOR CHOICES, INSTALLATION
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in BUILDINGS
VINYL CHLORIDE HEALTH INFO
VINYL Siding or PLASTIC Window ODORS
Volatile Organic Compounds VOCs
WALL CONSTRUCTION BARRIER vs CAVITY
WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in buildings
WIND ENERGY SYSTEMS
WIND TURBINES & LIGHTNING
WINDOWS & DOORS
WINTERIZE A BUILDING
Skylight leaks: this article explains how to find the cause of skylight leaks and other sloped glazing leaks. The article continues with simple suggestions for skylight leak repair and leak prevention. Our photo of a leaky roof skylight that has suffered repeated and non-durable repair attempts using roofing cement can be seen at left.
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For proper skylight and other sloped glazing installation details, see SLOPED GLAZING DETAILS. Additional examples of skylights are found at WINDOWS & DOORS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Our photograph (left) shows an interesting sloped window installation on the roof of a barn silo that had been converted to living space. Conventional wood-frame double-hung windows were set into the sloped silo roof - this was not a successful installation and the windows rapidly rotted, leaked, and disintegrated.
As Mr. Bliss points out in SLOPED GLAZING DETAILS, a glazing system must perform many functions. It has to shed and drain water, support and cushion the glass to avoid mechanical pressure points, and seal against air and water leakage. It should be attractive and economical.
Yet many subtle and pervasive forces are working against you: thermal and structural movement, high UV radiation, wind and weather. A pretty redwood cross batten is no match for sliding sheets of ice.
The problems inherent in vertical glazing (see VERTICAL GLAZING DETAILS) are multiplied in sloped glazing: higher levels of UV, water damming at the lower edges of sloped window frames or between the roof and the upper section of window and skylight frames, and structural loading.
Professionals in the large scale curtain wall industries, as well as residential contractors, have encountered problems with skylights and other forms of sloped window glazing. Fortunately, many new products and systems have been developed to beat the elements as well as to reduce the chances of installation errors leading to leaky skylights and related structural damage or even leak-related mold contamination in buildings.
Sloped glazing such as roof skylights probably has historically had more leaks into the roof structure due to improper roof flashing than other window failure causes.
Leaks at skylights, left unattended, can lead to costly structural damage, rotted roof sheathing, rotted roof framing, and wet, moldy insulation as well. These skylight leaks should not be blamed on faulty product design, although at some leaky skylights we find a combination of multiple failures.
Our photo of a leaky roof skylight that has suffered repeated and non-durable repair attempts using roofing cement can be seen at left. From the pattern of sealant application we suspect that the leaks at this skylight were around the window frame due to improper roof flashing at the time of installation.
Building owners, having trouble determining exactly where the skylight leak is occurring, sometimes simply slather caulk or roof cement all over everything in sight (an approach that is ugly but might work. But a roof-cement slathered skylight that is still leaking may be even more difficult to diagnose. Here are some tips that might help diagnose the actual leak point at a skylight:
If the insulating glass unit of the skylight has failed, you can seal the unit against further water leakage, but only replacing the unit will remove condensation, opaque skylight glass, and a failed window unit.
Our closeup photo of the down-roof corner of a leaky skylight (left) shows what is probably a double failure.
Leaks at the insulated-glass frame permitted water to enter the window structure where the freeze-thaw climate at this New York home continued to damage the window by forcing apart and losing the seal of the insulated glass itself. See Sealed Window Joint Failures for more on this skylight failure.
If the skylight leak is at the roof flashing, it may be possible to make temporary repairs using roof flashing cement around the perimeter of the unit, but a proper repair will require removing shingles near the skylight, installing proper head, side, and foot flashing around the unit, as you reinstall new shingles in the area.
In addition to installing skylights properly, using the methods discussed in this article and following the manufacturer's instructions, a period inspection for evidence of leaks into or around the glazing unit can avoid costly building damage by early detection and repair of any problems.
If debris collects on or around a skylight (see our photo at left) the water held in that location combined with the working action of extra winter ice (if the building is in a freezing climate) will reduce the roof life around the glass unit, leading to early leaks in this area.
Try gently brushing debris away from and off of your skylights when performing a roof inspection. Don't walk carelessly on a debris-covered roof - it's like walking on ball bearings.
Modern factory-built skylight units have been designed by their manufacturers to make the window as idiot-proof as possible, including factory-made skylight flashing kits and simple, clear instructions.
Still if the contractor is inexperienced with skylight installation, if the skylight was installed later in the life of the building as a retrofit, and especially if the installer did not read the instructions provided by the manufacturer, leaks at the skylight are likely.
Seal Skylight Flashing at Time of Skylight Installation to Prevent Future Leaks
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