View Full Version : Leaking where roof runs down a wall

10-07-2004, 04:23 AM
I have a colonial house. The garage and family room share a roof. This roof butts up along a vinyl sided wall. One side of the roof is leaking into my attic, and running down the sheathing, and settling on the drywall ceiling of my family room. I noticed this during remnants of Hurricane Ivan.

I went up on the roof during the storm and noticed immediately that the 2 peices of J-Channel the run the roof/wall line were joined incorrectly. The lower peice sits on top of the upper peice where it is joined, thus water is getting under. No big deal because the step flashing should take care of it.

This past weekend, I ripped out the lower peice and noticed that stones from the shingles, dirt, and debris were built up in 2 areas. I cleaned it up and installed new J-Channel the right way.

Last night, I took a garden hose up to the roof and turned it on. I went into the attic and the leak is now worse. I also took a garden hose up to the roof before I did anything to see where the leaks are coming in. As a comparison of the two "hosings", the second one shows leaks only further down the roof. This probably means that the debris was a problem and is solved.

The only thing I can think of is how the lower end of the J-Channel is installed to the corner post. The J-Channel's lower end runs right smack into the post, therefore, excessive water will pool into the corner. The other issue could be flashing. I did look at this as I installed the J-Channel. I saw nothing wrong. However, I don't do this for a living and only think I know what I am looking for.

Do I have a vinyl siding issue, or a flashing issue. I know its hard to answer without seeing, but any advise is much appreciated. The house and roof are 6 years old.

Thanks for your help in advance

10-07-2004, 04:29 AM
My first inclination would be a flashing issue at the lower end of the roof. It could be a problem with the J-Channel and the flashing. Could you post some images by chance?

10-07-2004, 05:22 AM
I will try to post some pictures tonight.

Can somone give me some guidance on how to install step flashing and shingles correctly? If I can't solve this leak by this weekend by testing with the garden hose, I am going to take the siding, J-channel, shingles, and step flashing off and re-install new flashing and shingles.

Here are some questions that I have:

1) What size flashing should I use? I have 3 tab 5 inch exposure shingles. I have been reading that 5" X 7" is typical. This yields a 3" horizontal leg and a 2" vertical leg with a 2" lap. Shouldn't I go wider on both legs?

2) How do I install the step flashing? Everything I read says to install on top of a shingle just above the shingle seem by nailing it in. I have read various nailing techniques like 1) one nail at the top corner furthest from the wall, 2) one nail at the bottom corner furthest from the wall to avoid the shingles from buckling up.

Is flashing that simple.....put it in place and nail? What about also cementing it in place? If so where and how would I do this?

3) How do I install the shingles? Right now there is about a 1/2" gap from the wall to ends of the shingles. Is this correct?

4) How do I install the lower end of the j-channel into the corner post? I'll verify tonight, but I think the water is pooling where the lower end of the j-channel ends in the coner post channel. This may be backfilling and getting behind the flashing.

5) Is water getting behind the siding? Whoever installed the siding, has the siding ends touching the bottom of the j-channel. I tried to move these out, but some are still touching. Could this be a problem?



10-07-2004, 02:21 PM
Here is a picture......I hope it uploads. I took the garden hose up again and had the water going primarily on the roof and not into the J-Channel. In the picture of the corner, the leak is happening right below this point. It is coming in like a faucet.

Before I installed the new j-channel, water was also coming in at a higher point due to the debris. This seems to not be a problem anymore. However, the leak at the corner is worse......really worse. There is a major difference in the amount of water coming in since I installed the new J-Channel.

Please help.



10-07-2004, 03:41 PM
Looking at the image it doesn't look like the flashing runs past the corner (i.e. wraps the corner). IMO - this would allow the water to run down the sidewall to the corner and then enter into the house. Right at the corner the flashing should extend past the corner and on top of the shingle. The trim at the corner should be held up a 1/2" or so to allow the water to pass by and back onto the roof.
Grumpy - any other ideas?

10-07-2004, 04:08 PM
You said it.

Whoever installed that corner molding and put it down on the roof was asking for trouble.

I would also check that the flashing extends around the corner and is properly installed.

10-07-2004, 04:22 PM
Hold on, let me go out on the roof and check................ok, I'm back :lol:

The first step at the corner is installed like this. The vertical leg is wrapped around the corner and runs up the vertical wall. The horizontal leg is installed normally. I'm inexperienced, but I think this is installed ok.

What do you mean when you said, "Right at the corner the flashing should extend past the corner and on top of the shingle". Also, is this the horizontal leg of the first step I mentioned above. Lastly, I do not see any of the step flashing.....they are covered by shingles.

Tomorrow morning, I am going to do another gardern hose test. I am going to put the nozzle 5" up from the corner to be absolutely sure that this is where my problem is. I will let you know of my findings. I find it amazing that this has just happened out of the blue. You wouldn't believe the amount of water coming in.

Thanks for your help. I appreciate it. I have been building a 4th bedroom in the attic since April where this leak is occuring. Fortunately, the leak is past where the room ends in the attic. I also have a newborn coming in 3 weeks. So, I really appreciate the help.

Thanks Rich and Dragon,


10-07-2004, 04:56 PM
Yes - the vertical leg should wrap the corner and the horizontal leg (per standard step flashing) should be on top of the shingle right past the corner. Where it wraps the corner (flashing I mean) you should be able to see it - or have 2 layers of shingles where the flashing is between the 2 layers.

10-07-2004, 06:43 PM
Another question.

How is that j channel installed? From the looks of your picture it is nailed on through the step flashing.

You might want to seal those nails.

10-08-2004, 04:26 AM
The the original J-channel and the peice I replaced are nail into the vertical leg of the flashing. I did not seal them after I nailed them in. I guess you just put some caulk right around the nail head?

As promised, this morning I put the garden hose 1 foot up from the corner. I went into the attic and saw NO WATER. I went out and moved the hose 2 feet up from the corner, went in the attic, and saw WATER.

I think I have a flashing problem along the entire wall. I is worse after I install the peice of J-Channel. Maybe it is leaking in through the nails holes?

How much do you think a professional will charge to come out to fix this? It is a 20 foot run.

10-08-2004, 05:58 AM
I would imagine a 1 to 2 day job if they have to remove the siding and flashing and possibly some shingles. Cost would most likely range from 250-750 for labor, depending on duration.

10-08-2004, 08:21 AM
I think I am going to throw in the towel. I inspected the flashing when I took the J-Channel off and it looked good. None were missing, their was about a 2" lap. It may be something else. Maybe the way the shingles were layed........who know's.

Thanks for all of your help.

See you at the next crisis,


10-08-2004, 12:14 PM
I'm picking up in the middle of this post, and it looks like everyone has suggested many good ideas. I will summarize.

I always try to put ice shield where the roof meets the wall, for these reasons.

Second your siding should always be at least 1/2" above the roof 3/4" preferred. Your siding sits ON the roof.

Next if my guys installed this, they would have slit the corner post and extend the baby tin (steo flashing) through the corner.

10-08-2004, 03:37 PM
Ok........I didn't throw the towel in just yet. I took off the vinyl siding, shingles, and flashing. I posted various pictures.

Here are my inexperienced findings.
1) It didn't look any water ever flowed under any of the horizontal legs. I didn't find any traces of water.
2) The vinyl was pretty wet on the back side.
3) The vinyl was touching the bottom of the J-Channel in several places.
4) The sheathing looks like it is warping, but nothing major.
5) Some of the plywood has delaminated. I don't think they need to be replaced. This delamination has occurences 2 to 3 feet out from the wall as well as at the wall.
6) I expected to see more evidence of water under the shingles. In fact, they looked good.

I'm lost

1) I am guessing that the water is coming down the J-Channel and going into the vinyl siding. Once it fills up, the water is spilling out the back, down the wall, and into the various gaps between the sheathing and plywood deck. Is this even possible?
2) Possibly the water is getting into the keys of the shingles and then under the flashing.

I am leaning towards #1 because I see water stains close to the wall only. They are 1" to 1 1/2" at most from the wall. Also, the vinyl is touching the bottom of the J-Channel.

However, why is this not happening on the other side? The vinyl seems to be touching the bottom of the J-Channel there also.

1) Step flash and shingle.
2) Flash the side of the house.
3) Cut the vinly back so it doesn't touch the J-Channel.

4) Call someone with more experience?? Plus, I probably saved a couple hundred just with what I did today?

Thanks everyone.

10-08-2004, 03:57 PM
As far as why isn't this happening on the other side, which way does the wind blow?

I have always nailed my step flashings on the upper corner on the wall, one nail. Do not put any nails through the flashing into the decking on the roof itself. If you are going to re-use those flashings, seal those nail holes where the J channel was originally installed.

Reinstall the J-channel so that it sits approximately 1/2 to 3/4" above your shingles.

Use roofing cement or tar along the edge of the shingles (And under them) next to the wall. Again, do not nail your shingles on through your step flashing.

Seal the nails holding the J-channel on. Water can and will travel vertically with wind behind it.

Do not use caulk. If you do you will be doing it all over again in a couple of years. Use Roofing tar or sealant.

10-09-2004, 04:28 PM
As I mentioned before, I was going to flash the side of the house because I think water is getting behind the vinyl and then behind the vertical leg of the step flashing.

Can I use felt (tar paper) to do this. I was going to use aluminum, but it is very expensive. Any other alternatives?

I thought I read somewhere that you should not use felt on the side of a structure because of either moisture damage or mold could occur. I thought they used to do this back when......that is putting felt on the entire house. Why not anymore?

I have the roof shingled and step flashed. Before I did that, I put down some self adhesive flashing along the entire span of where the roof meets the wall. It sits just as the step flashing, 1/2 horizontally and 1/2 veritcally.

Thanks everyone. I'm almost there. I will do the siding tomorrow. I am going to drill weep holes in the bottom of the j-channel and raise it 3/4 up off the shingles. I will also cut the siding back a bit so it doesn't touch the bottom of the J.


10-09-2004, 05:13 PM
As far as putting tar paper on goes, Every nail you use to hold your siding on is going through it. Defeats the purpose, no?

10-09-2004, 07:21 PM
Then I guess using aluminum would be a waste as well? What do I do about the water getting behind the vinyl? I was hoping to flash over the vertical step flashing and up to the peak. This way any water that would get behind would run down the flashing and the down the step flashing.

Thanks Dragon,


10-09-2004, 08:18 PM
The only way water should be able to get behind the vinyl is if it is improperly installed.

Or if a hurricane or tornado comes along... :wink:

Does your vinyl snap into place as it laps? It should, which creates a seal. Also, don't drive the nails in too tightly. Vinyl siding needs to be able float a bit, to alllow it shrink and swell according to temperature. Or the last I used did, it has been a few years since I messed with it.

10-10-2004, 05:52 AM
Water ALWAYS gets behind vinyl siding. Vinyl siding is not water proof. This is why you need a tyvek or equivelent.

10-10-2004, 07:18 AM
Dragon - The vinyl does "snap" together and it is lapped about 2 1/2".

Grumpydasmurf - I thought Tyvek was not waterproof?

Again, I think the issue here is that water is going down the 20 feet of J-Channel that rides the roof line. Because some of the vinyl is touching the bottom of the J-Channel, water is getting into vinyl joints and filling up behind the vinyl and spilling out the back. The other evidence is the sheathing. The further you go down the roof line, the more the flakes of the sheathing show water damage.

I don't there are leaks with light rain. I'll bet it leaks just with windy and/or heavy rain.

I ripped the roof up and siding off. I'm now re-building.

So far, I applied 1 peice of self adhesive flashing (90 degrees) to the plywood deck and sheathing. I shingled and step flashed.

To cover yourself 100% to eliminate the water from getting into the vertical legs of the steps, what would you do?

I'm sure this is overkill, but I don't do this for a living and I would rather pay $100 then about $1,500 for a roofer and hope they get it right. If I do this right, I will fix all possible sources of the leak.

Thanks guys! We're almost there.


10-10-2004, 03:50 PM
Water ALWAYS gets behind vinyl siding. Vinyl siding is not water proof. This is why you need a tyvek or equivelent.

I'll defer to your knowledge in that area. TBH I detest vinyl. I can and have installed it but I'll usually try to talk people into using almost anything else.

10-11-2004, 01:36 AM
Don't use any sealants. Step-flashing (min 4"w x 4" h.) ( bent 80 degrees and pushed into place for tight wall fit) can only be nailed in roof deck, upper center ot each piece. It should exactly cover the hidden part of each shingle. It's suppposed to be behind any felt or tyvek. ALL siding needs to be 1" above roof deck AND 'hidden' upper corner where it fits into j channel must be cut off, vertically to direct excess water downwards instead of along top of siding. This applies to all siding. Also, be sure bottms of all vinyl siding is cut like factory ends where it hits any corner piece or window j channel.

10-11-2004, 05:11 AM
I will install a 6" inch flashing over the vertical steps and apply Tyvek. I hope to be done today.

I'll let you know how I make out.

Thanks everyone.

10-11-2004, 08:15 AM
Tyvek is a vapor barrier much like your skin is a vapor barrier.

It allows water to transfer out, but not in. It's not 100% water proof but at a 90 degree angle (up and down)the water can't penetrate.

10-11-2004, 12:52 PM
I am half finished with the Tyvek and re-siding. What a pain in the A. I am relying on the previous holes so everything lines up. So, I have a crayon to mark the Tyvek for where the holes are. Also, don't hang this stuff by yourself on a windy day, you'll just discover plenty of new curse words.

I had to take a little more vinyl off today. I did not take it all off previously. I only took off from the peak (of the roof that I am working on) down.

I have a problem with the rake (the one at the top of the vertical wall). I can see water damage on the sheathing. Water is getting in at the rakes and running down the sheathing. The problem is that wind driven rain is blowing across the siding, and into the J-Channel, and down the back. This may have been a big part of the problem. How do I fix this without ripping the siding off to the peak and Tyveking and flashing the whole thing? I was only going to tyvek to the peak of the roof I am working on.

Next house I buy is going to be underground or in a bubble.



10-12-2004, 03:55 PM
I finished today. I hope this fixes the problem(s). I flashed under the j-channel that is against the rake and tyveked the side of the house. I can't imaging having a leak, but who knows. We are supposed to get heavy rain Thurdsday.

Thanks to all. I don't think I could have tackled this without you.

See you next project,


10-12-2004, 05:46 PM
Have you tried the water hose yet?

10-13-2004, 02:43 AM
I never saw picture and forgot to ask if there were any windows there. If so, siding men never flash windows and they require special consideration.

10-13-2004, 09:03 AM
Good point tinner. If the window capping was done improperly, or if there is no capping, that may be the problem!

10-13-2004, 04:37 PM
Rich - I have not tried the water hose. I probably should. I just wanted to enjoy that past day believing that maybe I fixed it :wink: . I also want the roofing cement to cure. I'll try it tomorrow and post my results. FYI, for the first peice of step flashing I installed, I let it protrude the corner about 1/4" so that it can get up in the corner.

grumpy and tinner - There is no window on the vertical wall, but there is a vent for the attic. This was j'd all around, no flashing. I flashed over the Tyvek. Just to recap my tyvek job from the top down. I flashed at the rake and over the tyvek. I Tyvek'd all the way down to the roof/wall line. The tyvek here is on top of 8" flashing I installed over the step flashing. Below the step flashing is 6" self adhesive flashing that is installed 90 degrees. If this leaks, I'm burning the house down!

After thinking and absorbing this. I think the big problem is at the rake. During windy rain storms, the rain is being blown across the siding, into the j and down the back. You can see the evidence on the sheathing. It is slightly wavy and some of the flakes are peeling. The wind is definitely hitting this area. I noticed it whenever I walked up the peak. A gust of wind would hit me. I had a great time hanging the Tyvek. With the flashing, Tyvek, and caulking of the j to rake, this should not be a problem anymore.

Thanks guys.

10-14-2004, 11:09 AM
If it's the vent, you will need to put metal from behind the J to locking piece of highest siding. It would terminate flush with LOWEST part of lock strip so as to dump water in next piece of siding.
Go to any window on house and look down J into that big hole at each lower corner of any window. LOTS of water goes there, behind siding.
What on earth did you caulk??

10-15-2004, 05:35 PM
Rich - I haven't taken the garden hose up to the roof, but we got a heavy rain tonight. I checked the attic and saw no signs of water. Let's keep our fingers crossed.

Tinner - I caulked the j to the rake. My rake is covered with aluminum. The j is butted right up to it. I caulked the seam to prevent water from getting behind the j.

Thanks guys,