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-   -   Vinyl sided chimney on side of house - rotting OSB (http://www.diychatroom.com/f9/vinyl-sided-chimney-side-house-rotting-osb-87085/)

rfleege 11-18-2010 07:06 PM

Vinyl sided chimney on side of house - rotting OSB
 
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.

Tom Struble 11-18-2010 07:43 PM

Quote:

Originally Posted by rfleege (Post 536586)
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

Michael Thomas 11-18-2010 07:44 PM

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.

Michael Thomas 11-18-2010 07:56 PM

Quote:

Originally Posted by tomstruble (Post 536601)
ooo something like this perhaps?

http://www.bendtek.com/Kick_Out_Diverter.htm

We has a similar discussion here a while back: http://www.diychatroom.com/f49/refla...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.

Tom Struble 11-18-2010 08:08 PM

yes after re reading i see your point,my mistake,i think

we need a pic of your chimney

rfleege 11-18-2010 08:42 PM

1 Attachment(s)
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.

Tom Struble 11-18-2010 09:01 PM

like Mr. Thomas says a cricket is probably your best bet

johnk 11-18-2010 09:10 PM

No cricket needed there.Just proper flashing:)

Michael Thomas 11-18-2010 10:20 PM

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?

johnk 11-19-2010 12:52 AM

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.

johnk 11-19-2010 01:02 AM

Not to go on and on about it but it is a very simple detail for any real roofer.If done right also you will have no more run-off at the rakes at that point than anywhere else.

rfleege 11-19-2010 05:52 AM

Just to confirm, the whole backpan should have a slight angle inward, forcing the water to run towards the middle of the roof, or just have a bend inward for the overhanging 2-3" over the rake?

Michael Thomas 11-19-2010 06:21 AM

1 Attachment(s)
Quote:

Originally Posted by johnk (Post 536734)
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.

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?

Slyfox 11-19-2010 07:16 AM

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.

jmiller 11-19-2010 07:58 AM

Quote:

Originally Posted by Slyfox (Post 536801)
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.


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