Roof leak diagnosis & repair questions & answers:

Diagnostic FAQs about finding and repairing the cause of roof leaks that show up inside or outside of buildings. Our page top photo illustrates the importance of careful inspection of roof leak clues both on the roof surface and from inside the building. A small flashing error or the wrong roof edge flashing type might alone explain leaks into the building below.

This article series provides an extensive catalog of sources of leaks in all types of building roofs, this article describes procedures for finding and fixing all types of leaks in roofs, figuring out the actual spot where a roof leak is occurring, and methods for tracking down the source of water or wet spots on ceilings or in attics. 

The first part of this article describes different types and causes of roof leaks - clues about how and where to look for the causes of a roof leak. The second part of this article discusses how we track an actual roof leak backwards to its probable source or entry point on the roof.

Questions & answers on how to diagnose and repair leaky roofs

These roof leak questions & replies were posted originally

at ROOF LEAK DIAGNOSIS & REPAIR - home . Be sure to see the advice given there.

On 2017-03-25 by (mod) - Critical in all membrane type roofs is just how well the seams are sealed -

Anon:

Silicone is often described as a "50-year" material, though of course how long a specific roof lasts depends on more than the materials, since workmanship, weather exposure, roof construction, slope, maintenance, drainage, etc. are all factors.

Critical in all membrane type roofs is just how well the seams are sealed - that seems to me to be the achilles heel on many flat and low-slope membrane roofs.

In fact some of the most irritating failures on EPDM roofs that I've worked-on and maintained have been in the seam tapes and flashing tapes that are sold to seal EPDM junctures at roof edge flashing - often those products deteriorate in less than ten years.

EPDM, or Ethylene Propylene Diene Monomer roofs are warranted by the manufacturer often for as much as 40 years. Industry gives typically a 22-35 year life expectancy as we discuss

at EPDM, RUBBER, PVC ROOFING

Also see EPDM ROOF SEAM REPAIR TAPE

Let's apply the same guesstimate math to your Silicone roof and your EPDM roof option, JUST using the warranty offering, with the caveat that roofing warranties are often more of a marketing text than a surefire guarantee: read the fine print.

Or see this example using asphalt shingle roof warranties WARRANTIES for ROOF SHINGLES - home

Annualized roof cost per square foot based on materials warranty = COST-sqft / WARRANTY LIFE

Silicone 14 / 50 = 0.28 - 28 cents per square foot per year (pretending that nothing goes wrong before the material wears out)

EPDM 10.5 / 40 = 0.2625 - 27 cents per square foot per year (pretending etc).

On an annual cost basis alone the two materials look about the same.

But then if you hired a professional to do this analysis you'd factor in probable roof life, your specific roof complexity, flashings, contractor reliability, workmanship, and the trouble of having to go through re-roofing sooner with one product vs. another.

On 2017-03-25 by Anonymous

Another question for my condominium: One roofer has proposed applying a layer of "silicone roof system" on top of the two layers of modified bitumen (dated 1995 and 2009) as the best fix for one of the building's leaky roofs.

The silicone roof system will cost about $14 per square foot. It has a 50-year materials warranty and a 20-year labor warranty.

The board is wondering about this option versus the less expensive (but shorter life?) full tear-out and replacement with EPDM, costing about $10.50 per square foot. Which option would you choose?

On 2017-03-25 by Caroline

My condominium's 20 buildings have roofs consist of a layer of modified bitumen installed in 1995, followed by a second layer of modified bitumen "overlaid" in 2009. First, what do you think the life expectancy is for an overlaid roof? Second, three of the buildings have had recurring leaks over the last two+ years.

This past year, for one of these problem roofs, some interior removal of the ceiling was done to try to find the source of the leak. Silicone sealant was applied to patch the leaks. We are waiting for rain to see if this fixes the problem.

Second question: What do you think of tracking down leaks by cutting out ceiling drywall and so on to find the source of the leak?

On 2016-08-04 by (mod) - Roofing tar is dripping over the edge of my roofline.

I am sorry to hear that. Sure there's always a solution; the question is how much trouble and at what cost.

If the wrong material was applied it's going to continue to heat up and drip in hot weather; the solution may be to remove and re-do that roof section; you could try redirecting the tar with edge flashing but I worry that such a step will cause ponding and thus make leaks more likely.

On 2016-08-03 by shelton

Roofing tar is dripping over the edge of my roofline. This is an area that was added on to existing structure as an uninsulated cover over my deck. Is there any solution?

On 2017-02-18 by (mod) -

It depends, Barbara on the roof materials and what repair is being done. Generally if we're going to use a sealant or mastic (a temporary repair) the surfaces have to be dry - below 18% moisture. That determination is made by observation or measurement, not just time, as different roof areas and materials, slopes, in and out of sun, etc. will dry at different rates.

On 2017-02-18 by Barbara

How long after the rains does the roof/leak area have to dry out before repairs are ddone

On 2017-02-12 by Joe

Just had new addition added on this summer inside of gable ends are all wet and iced up the both ends vented with 12 in x12in vents also soffit are vented real bad ice build up on roof there is no insulation in celing yet could this be the cause the room is also heated

On 2017-02-04 by Jim Maher

I just had my house reroofed. They took off the old shingles first. Now whenever there is a frost I can see the outline of the rafters when looking at the roof. It eas not that way before. What would cause that? Did ghe roofer do something incorrectly. How can this be corrected?

On 2016-12-17 by Jeff

Let my dogs out just a bit ago and I noticed water slowly/barely dripping from the roof onto my back porch. I checked the walls, ceiling and attic- no inside condensation or water build up. My landlord is out of country so I wanted to ask the professionals if they had any ideas for me? Thanks Jeff

On 2016-10-04 by Steve

Just fitted a new roof on our house through a licensed roofer, have noticed some leaks just wondering if there is some type of inspection report we can get off a tradie so we know if it's poorly installed

On 2016-05-30 by (mod) -

Patricia your question is over where you posted it at

https://inspectapedia.com/roof/Roof_Drip_Edge_Flashing_Specifications.php

On 2016-05-19 by Patricia

I'm sorry the roof is flat only unit that happens to. Can I get advice on how to repair

On 2016-03-19 by (mod) - approaches to repairing a leak that only occurs when there is a sustained heavy rain compounded by a brisk wind

You need to find the point of leakage, cover the open seam or hole with a suitable membrane or fabric that is sealed in place and coated - for best results. Just applying a sealant on top of a crack may have short life.

Details are at EPDM ROOF SEAM REPAIR TAPE

On 2016-03-19 by maurice p.

Have been researching many approaches to repairing a leak that only occurs when there is a sustained heavy rain compounded by a brisk wind.

Now, I have tar and gravel roof that is more than 15 yrs old. Have done seam repairs, but an ongoing 'drip' occurs under the conditions described above.

If fully tarped 10 feet on either side of the area evidenced from my 'cathedral ceiling, we have no issue.

My wife is ready to spend our hard earned money to redo the roof, but i'm not and willing to go up and solve the problem.

Now, if it's an undetectable fissure/crack could I solve the problem with a liquid tar, and if so, which product?
Permit me to thank you in advance for your suggestions

On 2015-12-28 by (mod) -

Brian

I don't have a clear understanding of what we're discussing here; If you mean you re-roofed (shingles and felt on the outdoor side of your roof) and the roof is actually leaking then something is very wrong with the roof installation.

However it is also possible that you're seeing condensation in the roof space if the roof is not properly vented and moreso if there is a significant indoor moisture source.

On 2015-12-27 by Brian

I have just replaced the roof joist graded lath and breathable felt and it is leaking on every rafter any ideas

On 2015-10-13 by Anonymous

Want to write an application about about repair of roof

Question: the insulation contractor cut a hole in our roof then "patched it" - is this a leak risk?

The company that we used to upgrade out attic insulation FORGOT to call us to let us know they were coming. They couldn't get to the access panel for the attic, so they cut a section of our shingles and the board underneath. Is this common practice? Can it lead to roof leaks or something worse in the future? Please advise. Thanks so much! - K.B. 8/19/2013

Reply:

I guess the insulation contractor didn't want to have to argue with you about charging extra to come to the job twice, but speaking just for myself I'd have been reluctant to chop my way into a home without prior permission.

In fact IF the roof was properly repaired and sealed after the installation you should be fine. But I would not assume that an insulation contractor knows much about proper roof repair work. Why not ask a local roofer to take a look, both from inside the house and from outside on the roof surface, to see just what was done and how it was repaired.

Indeed an improperly repaired roof cut can lead to leaks later on, and un-detected such leaks can wet insulation, cause indoor mold or lead to a general mess and costly repairs. So let's make sure the repair to the roof was correct. Send along photos of the roof from inside the attic and from the roof surface and I may be able to comment further.

Question: flat roof leak diagnosis

(Aug 15, 2012) ramlakhansoni@gmail.com said:

Iintially roof was flat and cemented then water leakaged from the full roof and aroud the walls . I repaired applied the flat squire tiles on the roof and roof is flat. But water leakaging from full roof and around the walls . Please suggest me what I should do to stop this

Reply:

Sorry Ram but I don't understand from just your note what kind of roof is presently installed nor what roofing material is on the roof surface.

Use the CONTACT link found at page bottom to send me photos of the roof from outside, from the roof surface, and more photos of where you are seeing leaks and we can perhaps offer more useful comment.

Certainly from what you describe it sounds as if a do-it-yourself roof job has some problems, perhaps with improper material installation or use of the wrong material on a flat or low slope roof.

Question: corrugated asbestos sheet roof leaks

(Feb 12, 2013) Mrs M Tokley said:
My double garage is roofed with corrugated asbestos sheets, about 25 - 30 yrs old. I believe part of this is leaking. Is there any coating I could apply to leakproof it rather than re-place it?

I had the covered area between the house and the garage re-felted very recently and the roofer told me that if there are still some leaks it will be because the asbestos garage roof has become porous and leaks. He tells me it would be very expensive to dispose of old asbestos, so I would like to repair it if possible. Any advice please?

Reply:

There are several elastomeric roof coatings that can be sprayed on to a corrugated roof surface that may extend its life.

But if the cement asbestos corrugated sheets have deteriorated enough to become soft you should replace the roof or install new corrugated metal roof atop what's there.

Question: leaks showing up in lower floor ceilings

(Sept 5, 2014) Dervan Drysdale said:
My two storey house has rain water leaks in the ceiling of the first floor in the kitchen which is directly under the bathroom upstairs.This happens only when it rains so I ruled out bathroom leaks. The question is; How could rain water leaks shows up on the ceiling of main floor and not the second floor where the roof is directly above..?

Reply:

Dervan, By finding a path into the ceiling via a wall cavity, pipe chas, etc, leaks from a roof can enter an attic or wall, run down the wall interior and find a path out into a ceiling below.

But as you describe a leak in a ceiling below a bathroom, I'd check for plumbing leaks with great care.

Often cutting an inspection opening into a leaked-into ceiling will permit a view that answers the question of where the leak originates. Look for leaky toilet mounts, tub or shower traps, etc. by cutting an inspection opening in the most-water-stained area of the ceiling. Make the opening big enough to get a light and your head or at least an inspection mirror into the space.

Question: water stains around soffit vents

(Sept 6, 2014) Jarhead33334 said:
There are no visible internal leaks in the attic or eaves, however around EVERY vent soffit around the entire house,
it appears to be water stained.

Reply:

Jar: look for seasonal ice dam leaks into the roof eaves. That's the most likely source unless you live in a climate that is free of ice, snow and freezing weather.

Also look via the attic for signs of moisture or frost or even ice accumulation under the roof deck and at the house eaves. Interior building moisture can end up in the attic where it shows up as stains mistaken for roof leaks.

Question: water stains over the felt lining visible in the loft - how do I speed up the dry-out of this area?

(Dec 14, 2014) sam said:
I recently noticed water all over most sides of the felt lining in the loft - called a roofer out who spotted defective cement on the ridge tiles which he said was letting the water in - this has now been re-done and hopefully it is all sealed and secure. My question is, how long can I expect it to take for the water on the felt to dry out and is there anything I can do to speed this up?

I have got the loft hatch open at present to try and get air up there, will that help?

Reply:

Sam the dry out time depends on

- the amount of air movement through the loft and where that air comes from;

- the humidity and temperature of outdoor air

- loft temperatures and humidity

- the materials that are wet or damp

You can speed the process by

- using a fan that increases air movement around and inside the loft
- using a fan that increases the out-venting of the loft PROVIDED that outdoor temperature and humidity are lower and cooler than the conditions in the loft

A fan blowing "out" of the loft roof hatch might help if that's the hatch you meant. I would NOT try blowing air down from the loft into the occupied space.

(Dec 14, 2014) Sam said:

Thanks for your tips, at present it is just the felt and tops of the wooden beams where the felt is touching that are wet but I think it could take a long time to dry out. I might try a fan, vents around the side seem pretty good.

However I've just found something else up there - there is a pipe that goes all the way down to the downstairs toilet, not sure exactly what it's for but there was a flexible pipe that I am sure should have been attached to this, leading out through the roof.

The end is tatty and I can't re-attach it - could it be this that has actually caused the wetness, not a leak? If that pipe is supposed to exit through the roof and the flexible pipe came off a while ago, could it be that? I don't know if the pipe also carries anything from the bathroom or if its just for the fan in the downstairs loo, or something else? For now I have poked it into the top of the pipe but there is a gap around the edge - should I get this replaced? How serious is this?
Thanks!

Reply:

Sam the pipe is probably a plumbing vent. Search InspectApedia for "Plumbing Vents" to read about that component.

If the vent pipe is leaking into the loft or leaks where it passes through the roof those conditions should be repaired.

If you block off the vent you may find drains working poorly and if the vent leaks into the building you could have a smelly or even unsafe accumulation of sewer gases. It needs to vent outdoors.

(Dec 15, 2014) Sam said:
Thanks - I don't think its leaking as such, just that if the flexible pipe has come unattached, it means the pipe is left open so anything coming up is going into the loft, not out through the roof. But as Im not entirely sure what it's there for, I don't know if that has caused any condensation. Theres no foul smell evident. I have poked the flexible pipe into the top of it for now but it isn't sealed.

Question: how can I repair drips coming off of nails visible under the roof - in the attic or loft?

(Dec 15, 2014) hubert stoke said:
My ceiling has been dripping on and off basis for the past year, it started to drip last night,
I was able to climb up into the attic last night and saw the drips coming through a nail.

How do I stop the dripping whenever there is heavy gust of rain or when snow is melting on
the roof? Are there sprays that I can use?

Reply:

Hubert

You can make a temporary seal around a nail puncture to slow leaks into an attic using swim pool sealant, hydraulic cement, other glues that tolerate water.

BUT this is an upside down, inside out "band-aid" approach that does not bode well.

Water continues to leak into the roof sheathing - long term this means rot

Water probably continues to leak into the space between shingles and underlayment, underlayment and sheathing, and will also run further down the roof to appear elsewhere.

Ultimately the proper repair will be done from on the roof from outside.

Question: leaks in mobile home roof

(Jan 12, 2015) Anonymous said:
My mobile home has a metal roof. There is a leak on the inside of my window. We thought we had sealed the area and water still leaks in. The tiny gutter built into the roof edge seems to be one entire piece. What can I do? We thought about new metal roofing,but,worry about the cost.

Reply:

Anon,

You may be able to seal the leaks with a silicone sealant applied to a clean dry surface if you can spot the actual leak points. There is also a variety of adhesive membranes or sealant coatings for mobile home roofs.

Question: leaks in ceiling near a window

(Mar 3, 2015) Fran said:
Occasionally, when we have rain with wind, there is a fall of water through the ceiling near the window. It is the middle room of a town house with a dormer above it. Builder has secured flashing. Could rain be coming in through soffit vents just outside the window?

(Mar 6, 2015) leaks are new ones was suppose to replace new boards said:
I feel like it shouldn't have leaked having it done 1 year ago especially with ice and water sheets put on the whole roof. What do you think?

Reply:

Fran,

We need an accurate diagnosis of the leak source in order to make a proper repair suggestion.

On occasion wind blown rain can enter a soffit. But if that were the case we'd expect leak signs along much of Te soffit length.

So I'm inclined to look at dormer window, flashing, and roof areas above where you see the leak as likely candidates. If you live in a freezing climate look for ice dam leaks first.

Also check for wall flashing errors above the leaky window.

Question: leaks in metal-roofed factory - what's the best repair? Bostix Flexacryl?

(May 5, 2015) Kaz said:
We have a factory with metal sheeted roof but it is old now and we are getting more and more leaks, what is the best repair for this, flexacryl or something like that?

Reply:

Kaz

Bostix Flexacryl is provided by the U.K. company and is intended for "general repairs or routine maintenance" - I'm doubtful that it would be appropriate or cost effective to try to coat an entire roof with a repair sealant compound.

I'd get bids from roofers for a roof-over. Metal roofing is quite light. Be sure that any proposal for adding roof layers considers the adequacy of the structure.

...

Continue reading at LEAKY ROOF DIAGNOSIS & REPAIR - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see ROOF LEAK DIAGNOSIS FAQs-2 - more-recent questions and answers about diagnosing the cause of roof leaks

Or see these

Roof Leak Diagnosis & Repair Articles

• ROOF LEAK DIAGNOSIS & REPAIR - home
  • ASPHALT SHINGLE FAILURE TYPES
  • ASPHALT SHINGLE LIFE / WEAR FACTORS
  • ASPHALT SHINGLES on LOW SLOPE ROOFS
  • ATTIC MOISTURE or MOLD
  • CLAY TILE ROOF FLASHING LEAKS
  • COLD WEATHER ROOF TROUBLE
  • DRIP EDGE FLASHING for ROOFS
  • DRIP EDGE FLASHING for ROOF FAQs
  • EARLY ROOF FAILURE DIAGNOSTIC QUESTIONS
  • EPDM ROOF LEAK REPAIRS
  • EPDM ROOF SEAM REPAIR TAPE
  • FLASHING, CHIMNEY Mistakes & Leaks
  • FLAT ROOF LEAK REPAIR
  • FLAT ROOF MOISTURE & CONDENSATION
  • GREENHOUSE or SOLARIUM ROOF LEAKS
  • HIDDEN MOLD, HOW TO FIND
  • LEAKY ROOF DIAGNOSIS & REPAIR
  • MOBILE HOME ROOF LEAKS, DEFECTS
  • MODIFIED BITUMEN ROOFING
  • MEMBRANE & SINGLE PLY ROOFS
  • RESOLVING ROOF JOB PROBLEMS
  • RIDGE VENT LEAK PREVENTION
  • ROOF ICE DAM LEAKS
    • HEAT TAPES & CABLES for ROOF ICE DAMS
  • ROOF LEAK DIAGNOSIS FAQs
  • ROOF-WALL FLASHING SNAFU
  • SKYLIGHT LEAK DIAGNOSIS & REPAIR
  • SLATE ROOF LEAKS
  • SLATE ROOF HARDWARE
  • SLATE ROOF LEAKS, TEMPORARY REPAIR

Suggested citation for this web page

ROOF LEAK DIAGNOSIS FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ROOFING

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