This tutorial explains how to diagnose and repair a roof leak caused by a cracked boot around the plumbing vent flashing.
I became aware of a possible leaky roof when I noticed water stain on the drywall ceiling. The water stain occurred during a period of record rainfalls and extensive flooding in the metro Atlanta, Georgia region. My area received about 17 inches of rain in an 8-day period! 17 inches of rain is a lot for an area that would normally less than 4 inches on average in September. With that much rain any roof leak, no matter how small, is likely to be noticed.
Water Stain on Drywall Ceiling due to Roof Leak
Finding the Roof Leak
The main attic is above the room with the water stain on the drywall ceiling. To locate the source of the leak, I got a flashlight and went into the attic. The stain is the corner next to the exterior wall, so I focused my search in that direction. The PVC vent pipe for the basement bathroom plumbing rises through the roof directly above the stain on the ceiling. The vent pipe became an immediate suspect.
Take care to walk only on the wood joists when working in the attic. The ceiling drywall will not support your weight and you can fall through! Move slowly and carefully.
PVC Plumbing Vent Pipe
This is the lower end of the vent pipe – it’s covered by blown fiberglass insulation. The dark bits on the insulation are nut shells left by flying squirrels that sometimes get into the attic during the winter. I catch them in a box trap to take them to the park and set them free unharmed. Last winter, when I opened the box trap to set the squirrel free, he ran out and turned around, sat up and stared at me for while before scampering off into the trees. Whether confused or saying “thanks!”, I’m not sure. But I digress.
Lower End of the Plumbing Vent Pipe
I moved the insulation away to reveal the bottom of the vent pipe and ceiling drywall. The insulation and paper surface of the drywall were damp. I’m getting close to finding the leak.
Insulation Pushed Aside to Reveal the Drywall Ceiling
A closer look at the vent pipe penetration through the roof revealed daylight shining through around the vent boot flashing. This is the source of the water leak! Rain water is coming in around the vent boot, running down the side of the vent pipe and dripping onto the drywall ceiling. Persistent heavy rains caused enough water to leak inside to be noticed.
On the positive side, the Oriented Strand Board (OSB) roof deck is dry and untouched by the leak. If the roof decking were rotted, the shingles would have to torn up and the rotted section of deck replaced – a major repair effort!
Roof Vent Pipe Flashing – Daylight Coming In!
More rain was in the forecast and it might a take a couple of days to get a roofer over to repair the vent flashing. To minimize further water damage, I tied a towel around the pipe just above the horizontal brace. This is only a band aide solution.
Towel Tied Around the Vent Pipe to Catch the Roof Leak
Cracked Vent Boot
Now that I know what to look for, a crack or split in the vent boot is clearly visible in this photo (red square). The vent boot must hug the pipe tightly to form a watertight seal. The roof is about 10 years old and the vent boot has cracked from a combination of the UV rays from the sun, weathering, expansion and contraction from the heat and cold.
Cracked and Leaking Plumbing Vent Boot
The 2″ PVC vent pipe with the cracked boot is shown here in perspective to the house. The roof is a steep 10/12 pitch and the house sits on a hillside. A 40 foot ladder is needed to reach vent pipe from the ground. Time to call a professional roofer to make this repair.
Vent Pipe Flashing with Cracked Boot
This repair is continued in Part 2.
Hope this helps,
Bob Jackson
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This is really helpful, thanks. I think I have a similar problem, and the roofer is quoting me $375 to change out the boot, fix some nails, and he’s not going to replace any of the decking. Sound like a deal?
Sounds a bit high to me for a single pipe boot. I called two roofers and received the following quotes:
1st Roofing Company: $225 minimum for a service call. Will replace two vent boots including materials at this price.
2nd Roofing Company: $125 minimum for a service call. Price includes replacing one vent boot with materials. A 2nd vent boot would be $50 extra.
Both companies said a lead pipe boot flashing would be extra.
Also ask about the warranty, e.g. “guaranteed no leaks for 1 year”.
I have leaking through cracked boots on the roof vent pipes on my house which is 10 years old. A roofer with 25 years experience offered two options, 1. to replace the flashing and boots (would likely breakdown in 6-8 years), 2. to buildup and cover the existing boots with polyurethane which will work just as well and last as long as the current roof before needing to be replaced in 15 years or so. Please advise.
I recommend option 3 or 4 – that is, none of the above.
Option 3 (preferred): Install a lead pipe flashing. Lead flashing lasts forever and the top is folded into the PVC pipe for a leak free union. A lead book will cost ~$35 versus $7 for the Oatey plastic boot. This is what I would have done had there been more time to buy one before the next rain storm. See the lead flashing references in the article.
Option 4: Install a new $7 flashing unit/boot like you have now but add a $5 rain collar. This is how I fixed mine. The rain collar provides extra UV protection for the plastic boot.
It’s so simple and inexpensive to replace the entire flashing why bother with the polyurethane? Do use roofing caulk to seal the nail heads.
Thanks,
Bob
I have EXACTLY the same problem. I just got an estimate for $2,225 dollars to replace the boot and to patch a bit of drywall (around a square foot) in the ceiling where the leak came through. Seeing this website is disturbing to me because I think someone may be trying to take advantage of me for being a female again.
$2,225 just to replace the boot and repair a small area of drywall sounds like a scam.
I show how to replace a water damaged section of ceiling drywall in How to Repair Drywall Ceiling Water Damage. To hire someone would cost $150 to $200 – mainly because it requires two trips to sand and apply a second layer of drywall mud.
You can find reputable contractors and businesses in your area at http://www.Kudzu.com.
Write back and let me know how your repair turns out.
Thanks,
Bob
Should this kind of repair be covered under the roof warranty?
Thanks.
Generally speaking, any roof leak due to materials or workmanship should be covered by your new home warranty (if new construction) or roof replacement warranty. It all depends on the specific terms and conditions of your warranty, so read the fine print.