InspectAPedia ^®

Porch & Deck Ledger Flashing to Buildings - Construction Details to Avoid Leaks & Rot InspectAPedia®  -     Deck Flashing Details to avoid building leaks & rot Deck & Porch Construction Materials Choices Deck & Porch Construction & Structural Fasteners Deck & Porch Construction Details for Safety Poor Construction Details and Improper Connections Can Lead to Dangerous Collapse of Decks and Porches

Here we discuss critical deck flashing details for decks in order to avoid rot and leaks at the deck ledger board and at the building to which a deck is attached, and we provide deck or balcony design and construction details for waterproofing at door jambs and sills. Also see Deck & Porch Connections to Building. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. Also see our review of that book. Also see DECK FLASHING LEAKS, ROT Case Study for an example of an older deck with rot and collapse due to improper construction and missing building flashing.

© Copyright 2009 Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Photos & Construction Details Show How & Where to Install Flashing between a Deck and the Building

Details of Proper Flashing & Waterproofing at a Deck or Balcony Ledger Board

Details of Proper Flashing & Waterproofing at a Deck or Balcony Doorway

Flashing details at doors opening onto decks & balconies: In addition to the copper or galvanized steel flashing shown in the sketch at left, additional flashing is almost certainly going to be needed below the door or sliding door that gives access to the deck from the building. Our photo (left) shows a balcony door sill that has rotted away at a 20 year old sliding door opening onto a rooftop deck (the website author's). While the peeling paint and rot at the bottom of the brick-molding door trim (photo left) shows that there has been little maintenance at this door opening, the rot below the door is due to omission of flashing of any sort when the door was installed. The aluminum sliding door track was simply caulked to the pine door threshold. Best Practices Guide to Residential Construction explains: Some contractors build their own custom door sill flashing on-site using a bending brake, but pre-fabricated sliding door flashings and water tight door pans for use at balconies and decks are available from building suppliers as well. When installing flashing below the sliding or hinged door opening onto a deck, be sure that: The door flashing pan is bent up and caulked under the door sill so that water will not be directed into the building by the flashing The door flashing pan extends outwards over the deck ledger just as the simpler flashing is shown in the sketch above The door flashing is constructed of copper or galvanized steel, or you use an adhesive flashing membrane in order to avoid corrosion through the aluminum flashing where it touches pressure-treated wood used for the building rim joist, sill plate, or deck ledger board. A water-tight flashing membrane (Moistop®) is set in place around the door sill and lapped over the metal deck ledger flashing discussed above The deck doorway rough opening is sealed with caulk as the door frame (jamb, header, sill) is set into the R.O. Building paper above and around the door opening should lap over the opening between the door jamb set and the rough opening. If deck flashing and door jamb sealing steps are omitted at this connection, failure of the deck ledger can be caused rot and decay in the ledger or band joist. Lags or bolts provide little support when fastened to rotted wood. So proper flashing of the ledger and band joist area is critical. Deck Collapse Case Study includes additional photos of improper connections between a residential deck and the building that led to a catastrophic deck collapse.

Leave an Air Space or Gap Between the Deck Ledger and the Building to Avoid Rot and Leaks

Some deck builders prefer to leave an air space at the ledger to assist with drying if the area gets wet. Flashing details are shown in the figure at left. Spacing the ledger away from the house helps prevent decay in the sheathing and band joist if the area gets wet, but this requires more bolts. A bituminous membrane across the band- joist area offers an extra layer of protection, useful in very wet or snowy regions. Caution: Do not use aluminum flashings with pressure- treated lumber unless a durable barrier material, such as a bituminous membrane, separates the aluminum from contact with the wood. Preferably use membrane-type flashings, G185 galvanized steel, or copper. However, copper flashings should not contact galvanized hardware or fasteners. Also, when using a spaced ledger as shown in the sketch, the connection of ledger to building should be made using through-bolts to the building rim joist (as shown). Lag screws are not recommended.

Free-Standing Decks: an Alternative to Using a Deck Ledger to Attach a Deck to the Building

-- Adapted with permission from Best Practices Guide to Residential Construction.

Also see DECK FLASHING LEAKS, ROT Case Study for an example of an older deck with rot and collapse due to improper construction and missing building flashing.

Share this Article      

...

Technical Reviewers & References

Search InspectAPedia

• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

EXTERIORS of BUILDINGS
STRUCTURAL INSPECTIONS & DEFECTS
ADVANCED INSPECTION METHODS
AGE of a BUILDING - how to determine
BEST CONSTRUCTION PRACTICES GUIDE
CHIMNEY INSPECTION DIAGNOSIS REPAIR
Cracks, Checking or Splitting Beams & Log Homes
CRAWL SPACES
DECK & PORCH CONSTRUCTION
  Deck Piers & Posts
  Deck & Porch Connections to Building
  Deck Flashing at Building
  Deck & Porch Structural Fasteners
  Deck & Porch Steps or Stairs
  Deck & Porch Railings
DECK COLLAPSE Case Study
DECK FLASHING LEAKS, ROT Case Study
DEFINITIONS of Mobile Home, Doublewide, Modular, Panelized
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DISASTER BUILDING INSPECTION & REPAIR SAFEY
EARTHQUAKE DAMAGED FOUNDATIONS
ENERGY SAVINGS in BUILDINGS
FLOODS IN BUILDINGS-priorities
FOUNDATION BULGE or LEAN MEASUREMENTS
FOUNDATION CRACKS & DAMAGE GUIDE
FOUNDATION WATERPROOFING
FRAMING DAMAGE, INSPECTION, REPAIR
FRAMING DETAILS for BETTER INSULATION
FRAMING DETAILS for DOUBLE WALL HOUSES
FRT PLYWOOD
LOG HOME GUIDE
PANELIZED CONSTRUCTION & KIT HOMES
MODULAR HOME CONSTRUCTION
MOBILE HOMES, DOUBLEWIDES, TRAILERS
MOISTURE CONTROL in BUILDINGS
ROOFING INSPECTION & REPAIR
ROT, FUNGUS, TERMITES
  TERMITE SHIELDS vs TERMITICIDE
ROT, TIMBER FRAME
SINK HOLES

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

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Wiley.com and also at Amazon.com. See our book review of this publication.
• Manual for the Inspection of Residential Wood Decks and Balconies, by Cheryl Anderson, Frank Woeste (Forest Products Society), & Joseph Loferski, October 2003, ISBN-13: 978-1892529343, $39.00 at Amazon.com or at the InspectAPediaBookstore
• Building suppliers for building flashing products such as a water tight door pan: use of a pre-fabricated balcony or deck flashing pan available from Jamsill Guard (Jamsill, P.O. Box 485, Talent, OR 97540; 800/526-7455; www.jamsill.com) is discussed and illustrated in this brief Journal of Light Construction Q&A on Making a Balcony Door Watertight
• ...

More Information on Building Diagnostic Inspections and Repairs

...

InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting

Contact Daniel Friedman for website content suggestions or for fee-paid consulting