Steven L. Smith, Bellingham, WA Home Inspector (King of the House)

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Moisture and Deck-Porch Flashings

In the wet Pacific NW, missing metal flashings at critical and weather exposed locations can result in serious consequences -- rot of siding, moisture intrusion into walls, rotted flooring.

When a flat surface such as a deck or a porch attaches to the exterior wall of the home, with few exceptions, a properly positioned metal flashing should be in place at the junction of the flat surface and the wall. Caveat, if there is a highly effective overhang roof over the landing, this may be a less critical matter but typically the flashing goes over the deck ledger board.  The photo below is a wood deck that was butted tight to the wall, a very weather exposed location, and no metal flashing has been installed.


Deck flashing

The fact that the wood deck was built directly on top of soil is not helpful either. To guard against moisture, metal flashing should be in place at the junction of a weather exposed flat surface landing and the exterior wall. Sometimes a flashing is in place, but there is an insufficient gap between the landing and the wall: Proper application of flashing includes establishing a gap, 2" minimum, between decking-floor and exterior siding or wood trim. In this photo, both the wall and the deck were rotted at various locations, so repair/replacement is necessary.

In some instances, if materials are still sound, a contractor can lift that horizontal board that's closest to the wall and, without too much trouble, install a proper flashing. The repair becomes more difficult if the decking boards run perpendicular to the wall, since installing a flashing would involve removing multiple boards.

Steven L. Smith

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Comment balloon 5 commentsSteven L. Smith • February 08 2015 02:01PM

Comments

The installation of flashing is often overlooked but very important to the protection of the building.

Well done Steven L. Smith 

Posted by Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366, General Contractor, Dry Rot and Water Damage (Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366) almost 3 years ago

Thanks Tom. Glad to see your comment.

Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) almost 3 years ago

I once had a seller AND the seller's realtor call me to argue that there is no such thing as deck ledger-beam flashing.  And that my photo of moisture meter on the stains inside was obviously a different house and I was confused.

Alrighty then!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 3 years ago

Jay,

Some sellers see the inspection process as a dual of gladiators. They forget the science and just want to argue. The way I do it, it would be 99% impossible to get a photo in from the wrong house.

Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) almost 3 years ago

There were people present too!  But the photo of the meter on a stain in this house would be hard to duplicate from another house!

Once a builder's supervisor told me I made up the deck flashing thing simply to have something to comment on!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 3 years ago

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