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Vinyl sided chimney on side of house - rotting OSB

40K views 55 replies 10 participants last post by  Michael Thomas 
#1 ·
We have a vinyl sided chimney on the side of the house about 6 feet or so from the top of the roof. It is cut into the overhang of the roof about 2 feet and then 2 feet extend past the rake edge of the roof. So the back (top) side of the chimney is about 2 feet wide on the roof and then 2 feet off the roof. I just noticed a wet spot from the basement on the subfloor and investigated further. I went up to the roof and noticed gaps in the siding where the water ran right off the chimney and into and behind the siding. There's a good chunk of rotted OSB on the chimney chase now.

I will have a contractor come out next week to look at it but what I am asking is to see what the best method of correcting this so it doesn't happen again once the chimney chase wall is repaired. How can you direct water so it doesn't hit the chimney side wall?

Thanks.
 
#2 ·
We have a vinyl sided chimney on the side of the house about 6 feet or so from the top of the roof. It is cut into the overhang of the roof about 2 feet and then 2 feet extend past the rake edge of the roof. So the back (top) side of the chimney is about 2 feet wide on the roof and then 2 feet off the roof. I just noticed a wet spot from the basement on the subfloor and investigated further. I went up to the roof and noticed gaps in the siding where the water ran right off the chimney and into and behind the siding. There's a good chunk of rotted OSB on the chimney chase now.

I will have a contractor come out next week to look at it but what I am asking is to see what the best method of correcting this so it doesn't happen again once the chimney chase wall is repaired. How can you direct water so it doesn't hit the chimney side wall?

Thanks.
ooo something like this perhaps?

http://www.bendtek.com/Kick_Out_Diverter.htm
 
#4 · (Edited)
We has a similar discussion here a while back: http://www.diychatroom.com/f49/reflashing-chimney-60854/

A conventional kickout flashing will work well at an chimney penetrating a eave:

Kick out flashings reduce leaks at the junctions of chimneys and roof eaves - Paragon Home Inspections Chicago/Morton Grove/Evanston

but will not work where the uphill side of a chimney partially penetrates a roof at the rake as water runs off the roof at the roof/chimney and down rake, chimney and wall below.

I've seen three methods of flashing this junction:

1) A sort of "single sided cricket" which directs water running down the roof diagonally toward the side of the chimney opposite the rake.

2) A diverter flashing which extends diagonally down the roof above the chimney, sloping down the roof from the rake toward the edge of the chimney opposite the rake.

3) Various types of "flashing" (usually ad hoc) which attempt to protect the rake and areas below it as water ruins off the rake side of the chimney.

I do not have pictures of any of them, however.
 
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#3 ·
The key is correct flashing at the uphill side of the chimney - it should be flashed like a conventional chimney part way down a sloping roof, only flashed so as to prevent water from running down the rake at the uphill intersection of the chimney and the edge of the roof. The easiest way to do this is to flash so as to redirect all the water hitting the uphill side of the chimney around the chimney at the side of the chimney opposite the rake. Unfortunately don't have a picture of this type of flashing, and could not find one on the net.
 
#6 ·
Here's an image. You can kind of see the siding stained where the water flowed. The house is 23 yrs old, we bought it in February, had a re-roof in April, and just noticed this now. Based on the completely black, flaking OSB and evidence of previous attempts at caulking this spot, it has been a problem for years. There's got to be a way to divert water around to the left (down the roof) and away from the rake side.
 

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#9 ·
Well... The question is, what is "proper flashing" at that location? You can flash the uphill side to the chimney with a conventional chimney head flashing, but if you allow water to flow out over the edge of the rake, how - exactly - do you flash rake board, chimney and wall?
 
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#10 ·
There should not be an issue with water running down siding,if the siding is installed right.A backpan extended past the rake 2-3" with a slight slope inwards should do the trick.I've done many that are exactly like that without any issues or complaints for that matter.
 
#13 ·
Are you referring to a bend at the end of the head flashing (basepan) to from a sort of reverse kick out flashing (see attached) or actually forming the head flashing so as to be wider (further from the chimney) at the rake side of the chimney?
 

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#14 ·
You install regular L 'head wall flashing' at the face 'front lower portion' of the chimney.

Install step flashing's up the side, letting the last piece of flashing & shingle wrap the top corner.

Install L 'backpan' flashing 'at the top'.
The back pan should be cut to go atleast 10" up the chimney,
atleast 12" on to the roof sheathing,
atleast 3" past the inside corner 'facing the roof',
atleast 2' past the overhang of shingles on outer corner 'rake side' and
have a slight slope to it making the inside corner the high point, thus sloping to the rake.

The back pan will set over top of the siding panel that hits roof level,
than under the panels of siding from there up.
This allows the water to run on top of the siding rather than behind it.
 
#15 ·
Install L 'backpan' flashing 'at the top'.
The back pan should be cut to go atleast 10" up the chimney,
atleast 12" on to the roof sheathing,
atleast 3" past the inside corner 'facing the roof',
atleast 2' past the overhang of shingles on outer corner 'rake side' and
have a slight slope to it making the inside corner the high point, thus sloping to the rake.

The back pan will set over top of the siding panel that hits roof level,
than under the panels of siding from there up.
This allows the water to run on top of the siding rather than behind it.
All the rainwater should be diverted into a gutter at the eave, not off the side of the house. With the pan pitched the wrong way you'll also have a gap where the last pc of step flashing meets the pan.

I'm also having a bit of trouble picturing how the j channel that runs up the fascia and along the pan would integrate with the back pan if it was partially covering a pc of siding or even sticking out further than the fascia. I can see it working with traditional siding but maybe i'm having a brain fart with the j channel.

I've always pitched mine to run back onto the roof and bent the rake edge to lap over the fascia. The rake side is a tricky intersection to waterproof so I try to make the water go the other way, which is a much easier corner to flash properly (you can't have ice/water on your fascia board), and prevents staining.
 
#17 ·
What's needed here is a Contractor, not just a roofer. I'll put my life on it that the siding is leaking, not the roof. Seen it many times just like the picture shows. Some siders think vinyl siding alone keeps water out.

A ton of work like this in the near future fellow Contractors. Too many slop jobs in the past 15-20 years.
 
#18 ·
No question attention will have to be paid to the siding and flashing detailing at that junction - for starters, there may not even be a water resistant barrier (Tyvek or similar) behind the siding. And at a minimum using slyfox's technique (where a portion of the flashing will be under the siding) the WRB will have to be carefully detailed where it is slit to fit over the vertical leg of the flashing so as to prevent water entry.

Such detailing is why I'm so skeptical that this is an "easy" problem to solve if "you "just know how" - I'm wiling to bet that when everyone has had their say and we all agree on a "best" design (if we do), that it will incorporate at least some details that each of us overlooked in our original proposed solutions.
 
#24 ·
My preference would be to keep the water on the roof.You would only need the slightest slope considering the short width of the chimney.A simple water test would tell you exactly where your peskey leak is coming from.Either way,it is a very simple fix.Even if you had to redo siding,flashings,shingles,etc.
 
#28 ·
If you are having a contractor come out to look, why don't you wait to see what he suggests for a fix, after all, he will be looking at it. Although it may be an easy fix, we are only guessing not seeing firsthand.
I would find it difficult to tell you the best approach to fixing water and leaking issues without looking.
 
#34 ·
It's good that you point them out to your customers. A lot of inspectors miss it.

In SDC's pics it looks like the water ran all the way down the outside of the siding until it hit the j channel at the bottom, which was probably pitched towards the rotted wall on both sides.



 
#40 ·
IMO, that's a "combination of ingredients problem" - the siding install guaranteed that water would enter the exterior wall wall at the bottom of the chase even absent the roof runoff above, and the lack of gutters and the missing kick out flashing guaranteed a high concentration of water from roof runoff was present to worsen the problem.
 
#41 · (Edited)
To go back a step, SDC's example is a good illustration of why I'm skeptical that when a chimney penetrates a rake, the chimney's flashings should direct water over the rake rather than back toward the roof side of the chimney.

We know that real-world, even at new construction, wall cladding details will usually be imperfect if not blatantly incorrect, and that as a result at least some water will be entering behind the water resistant barriers and flashings details.

And we know that at older buildings, there will often have been a series of modifications (siding and window installs, additions, wall penetrations for dryer and bath exhaust fans and the like, etc.) which compromise the original wall water-control provisions, often in ways we can't visually assess without removing portions of the cladding and/or trim.

We also know that the investigation and and correction of many of these defects will usually be outside of the scope of the work being performed during a re-roof or even the installation of a roof at new construction. For example, in SDC's examples few roofers are going to be pulling off siding to investigate its installation, except perhaps for a small area at the roof, chimney junction itself - even if they are aware of the potential problems, or even strongly suspect they are present, convincing homeowners to pay for the investigation and repair of such problems will be somewhere between difficult and impossible).

So the the questions confronting someone installing a roof (if they even bother to ask it) is not "Is water getting into the walls?", it's "How much water is getting in, and how fast is it deteriorating the materials it reaches?".

And real-world, given the quality of the actual work by others we see every day, the answer usually is "If it's not too much water, and it's not creating too much damage" (i.e. there is only minor deterioration, and it's going to take decades to cause problems), then "given the nature of the beast, that's about the best we can expect, but let's at least try not to make it any worse...".

And from that perspective, why would a roofer want to direct substantial quantities of water down a wall of unknown but likely imperfect water-resistance, when there is the alternative of sending it down the roof to be eventually conducted away from the rest of the structure by an appropriate roof drainage system?
 
#44 ·
even if they are aware of the potential problems, or even strongly suspect they are present, convincing homeowners to pay for the investigation and repair of such problems will be somewhere between difficult and impossible).
I disagree, I don’t think I’ve ever had a customer that didn’t want the root cause of the problem detected and resolved. What’s the point of a new roof or siding if it’s still going to leak. Although not always the case, more times than not it is a simple flashing or wb detail that is the problem and correcting it is usually a small additional charge compared the cost of the job.
 
#43 ·
good call Mr.Miller,vinyl siding can handle a surprising amount of water intrusion,but even it has its limits

if that was wood or fiber cement,i'd imagine the damage would be much worse if installed with the same level of expertise

side wall water protection should not depend on one system for ''waterproofing'',but should be attacked with a multi layered approach
 
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