Seattle Home Inspector's Blog


Sometimes it is the little details that make all the difference---know when to be flashy and when not.

Today’s post is about one such little detail.  In this case the risk of its being a “big deal” is small but I have seen similar installations where, over time, considerable damage does occur.

This is a typical lead flashing common on houses in the Northwest. 

Lead Pipe Flashing 

The flashing is made of lead.  It is designed to fit over the pipe and be lapped by the shingles on the plane of the roof.  The cap you see on the top is a nice way to finish off the installation and is quite common when the roof portion of the flashing is not quite tall enough to extend to the top of the pipe.  When it is tall enough, the excess above the pipe is simply folded inside the pipe.  When the top is “counter-flashed” with this type of cap it is designed to lap both the outside of the lead flashing and the inside of the pipe.  Without the cap, any water that hit the pipe would run down the pipe behind the lead flashing.

Now you might ask, well how much water could that amount to really?

If you look at this next picture you can see where the blue arrow points to two water lines that show how water hitting the inside of the cap is still finding its way outside of the metal flashing.  The red arrow points to a water line that is clearly running down the pipe and into the roof/house structure.

Lead Pipe Flashing 

In this next picture we can see “why” this is happening.  When they installed the nice counter-flashing the piece that is supposed to be inside the pipe got scrunched and no longer directs water inside the pipe.  While the blue arrows show where they have been “lucky,” the red arrow show where they have not been lucky.

Inadequate Lead counter-flashing

In our area of the world, where it can rain or drizzle for weeks on end, it actually can result in a fair amount of water getting into the roof/house structure.  Sometimes these vent pipes make an immediate right angle below the roof line to move over to where the pipe actually comes up through the house.  There are lots of reasons why a plumber might do this.  For example if the pipe would end up coming through the roof on the “street side” of the home, they will often run it to the back of the house where the pipe would not show.

At any rate, even a half a cup of water a day---or any amount that would not dry in 24 hours would keep ceilings below the leak wet and eventually cause damage to the ceiling.  As a Licensed Structural Pest Inspector, this lack of attention to detail is what we would consider a “conducive condition.”  A condition that if left un-repaired could result in wood decay/rot or promote infestation by wood destroying insects.

I have found several damaged ceilings with “unexplained” past/ongoing water damage from improper flashings around pipes.  Repairs are a very easy fix, but certainly worth noting. 

This defect, I might add, could likely not be determined from a ladder at the edge of the roof---another important reason for the home inspector to walk the roof when it is safe to do so. 

Charles Buell, Real Estate Inspections in Seattle


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Comment balloon 20 commentsCharles Buell • February 16 2012 11:06AM


Whoa, good illustration. A little water becomes a lot of damage as the drip drip drip causing mold, rot, discolored ceilings in places running down roof rafters and making the home owner wonder "where the frig is that water coming from and like Chinese water torture, how do I just stop it and the damage. To make it stop."

Posted by Andrew Mooers | 207.532.6573, Northern Maine Real Estate-Aroostook County Broker (MOOERS REALTY) over 7 years ago

Charles, The longer we're in the business the more important we realize good flashing and sealing is.  We had a small leak around our stove pipe.  Called a roofer out and for $70 the problem was addressed by someone that knew what they were doing.  I could have stuck a bunch of goop up there and maybe gotten lucky, but I like the looks of their work better :)  Bill

Posted by Liz and Bill Spear, RE/MAX Elite Warren County OH (Cincinnati/Dayton) (RE/MAX Elite 513.520.5305 over 7 years ago

Charles...Thanks again for sharing your knowledge...I learn something in every post...Enjoy your day.

Posted by Ernie Steele, Call me, let's get started!!! 717-273-3774 (Berkshire Hathaway HomeServices Homesale Realty) over 7 years ago

Charles -- looks like they might have gotten one size too big on that unit.  Then again, why did they not notice that the cap didn't seat properly?  Hmm?

Posted by Steven Cook (No Longer Processing Mortgages.) over 7 years ago

Andrrew it is surprising what a "little" leak can do sometimes

Bill, with everything in our homes there are "best practices" and then there is duct tape and tar :)

Ernie, you are welcome---thanks for stopping by

Steven, in this case it is the proper flashing/cap---someone just wasn't "paying attention":)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

Very informative, Charles.  I can tell you are thorough in your home inspections, I imagine buyers appreciate that about you.  I have to say, in our dry climate, I've never seen moss like that growing on a roof, either.

Posted by Mary Douglas, REALTOR, Red Feather Lakes, Colorado (United Country Ponderosa Realty, Red Feather Lakes, Colorado) over 7 years ago

That is a really interesting, and excellent, installation and explanation of it!  I have never seen such a vent tube.  Everything here is plastic, except for very old homes where it is copper.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Thank you.  I always learn something from your posts.  We don't get that much rain here in Phoenix, but I can see where it could be a problem even for us.

Posted by Debora Nichols, Realtor Anthem,Phoenix,Scottsdale,Glendale,Peoria (Residential Sales, Purchases, Investors, Vacation Homes) over 7 years ago

It looks just like they were trying to make a fashion statement rather than the workable system... 

Posted by Paul S. Henderson, REALTOR®, CRS, Tacoma Washington Agent/Broker & Market Authority! (RE/MAX Northwest.) over 7 years ago

Charles - Looks like a "perfect" example of not quite good enough. The installer seemed to have started on the right track but got a bit careless.

Posted by John Mulkey, Housing Guru ( over 7 years ago

Water is just not something to take chances with. The expense of repairs is do much more than the cost of just doing it right the first time. 

Posted by Mark Delgado, Benicia and Vallejo, Property Management, rental h (houses for rent, Solano County & Glen Cove) over 7 years ago

Charlie, I like those lead flashings but not installed right they can be an issue just like anything else done wrong. Great example MR Buell.

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 7 years ago

Mary, yes the NW is proud to be the "original green roof":)

Jay, I am surprised, these lead flashings have been around for a long time.  I know that in some areas of the country there are actually insects that ruin them---perhaps that is the case in your area?

Debora, I would not want to risk leaking in any part of the country.

Paul, perhaps so :)

John, exactly

Mark, one has to wonder if when they crammed this cap on they asked themselves: "How much water could actually leak in----good enough!?"

Don, thanks

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

I love the detail of this post Charles.

I liked what you said about the importance of getting on the roof for the inspection, so important!

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 Mobile - 916-765-5366) over 7 years ago

I had never seen  a flashing like that until I came out yyour way a few years ago. Much better than the rubber boot type used around here.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 7 years ago

Tom, thanks---the devil is in the details as they say :)

Jim, yuppers---I like them quite a lot.  When the rubber one on my own roof failed I changed it to lead type. 

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

But what if you had a very, very, very nice set of binoculars, and a nice optical zoom lens on your camera?  Surely you could see down the vent with those, right?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 7 years ago

Reuben---you forgot the helicopter :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

No Guys, what you forgot was the 'Eye-Stick' , see everything with your feet on the ground.

A rolling stone may gather no moss, but those roofs surely do.

As for the flashing we use that shape here, but in galvanized sheet metal. Lead is becoming passe.

The width and interior depth of the top cap also functions as  a limiter to snow penetration down the stack.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) over 7 years ago

Robert, I have seen the eye-stick.  I would love to see how it performs on a two story 5,000 sq ft house in a 20 mile an hour wind :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago