# New Flashing on Existing Vertical Siding



## grcummings (Feb 28, 2009)

The previous owner installed ledger board and deck without any flashing.
Since the overhang protects the deck to siding, and since the surface is skip 2 x 6 and allowed draining, didn't see any deterioration on the ledger to siding surface.

I will be replacing the 2x decking with 1 1/8" TnG Exterior Plywood on the existing framing. This framing provides adequate slope for impervious decking. 

With that covered,... 
*Please critique my proposed method of flashing.*


No existing flashing.
Siding is full length behind existing ledger.
All deck structure is solid, treated lumber
Ample clearance from wood to (red) flashing
Caulked as appropriate.
Fasteners will be through 90 (green), z (red) and the reinstalled siding strip.


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## mako1 (Jan 7, 2014)

No way in hell I would put T&G plywood on a deck regardless of the flashing.I hope I am misunderstanding your question?


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## grcummings (Feb 28, 2009)

mako1 said:


> No way in hell I would put T&G plywood on a deck regardless of the flashing.I hope I am misunderstanding your question?


The plywood will be edge banded with fir using resorcinol glue, the TnG will be joined with resorcinal glue, caulked with Gaco caulk, then taped as noted below.

I plan on using GacoDeck: a elastomeric coating designed for outdoor plywood deck. It is a 4 coat system, over two coat taped seams.
The edges and seams are wrapped with a polyester tape, bedded in two coats (over and under) 

Our current spaced 2x affords no protection to the lower patio.

http://www.gacocoatings.com/gacodeck-deck-coating.html


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## ChuckF. (Aug 25, 2013)

I would put the green piece of flashing UNDER the decking, over the ledger, and then extending an inch or so beyond the ledger. Stick a strip of flexible butyl flashing on the outside surfaces of the green one to seal nail/screw holes.

Ideally that green one would go down to the ledger, over the top of the ledger and then an inch or so down the ledger. Since the joists are already attached to the ledger you can't do that.

I'm not sure I would cut into the siding for the red one. Let's see what others say on that. 

You could also cut a smaller piece out, and angle the red one down at 45deg rather than at right angles, and not replace what's cut out. You could do it with one piece of metal, but it would have to be custom bent.

There are other ways of keeping a lower deck dry than going to solid decking. Some of the posters here have experience in those systems.


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## hotrod351 (Jun 15, 2012)

if your going to elastomeric the deck then it would be fine to put the green metal on top. either way, top or under, your going to be sealing it with elastomeric. would look better under, because you wouldn't see it.


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## grcummings (Feb 28, 2009)

ChuckF. said:


> I'm not sure I would cut into the siding for the red one. Let's see what others say on that.


I worried that for a while myself. 
But since the existing siding is ship lap rough cut cedar (looking much like a board and batten) and IS what T-111 tries to be, it has recessed gaps between every board.

I was not sure how I could adequately seal that portion.


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## Gary in WA (Mar 11, 2009)

You don't seal it, you drain it 2" above the deck. --R-703.4 "Flashing" *#7;* http://premiumaccess.iccsafe.org/document/code/272/4631024

Bend the flashing to 110*; http://www.mtcc1170.com/images/BCRainScreen.pdf

Gary
PS. I'd pull the door and add a pan...


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## grcummings (Feb 28, 2009)

Gary in WA said:


> You don't seal it, you drain it 2" above the deck.


Sure, I'm good with that... the question then still remains. 
How would you do that, given my siding. ? ?


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## craig11152 (Jun 20, 2015)

I would just cut a kerf in the siding for the red sort of like a counter flash on a brick chimney.

Likewise with the green I might run it under the deck as others mentioned and cut a small kerf for that too. :vs_worry:


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## Gary in WA (Mar 11, 2009)

As in third pic. Google for a link/picture from the manufacturer, I have one somewhere here.... Stain the ends of the cut siding to stop/slow capillary wicking; *pp4-5;* http://www.energyoutwest.org/eow_library/__past_confs/EOW_2008_Presentations/Tsongas_Damage.pdf

Gary
PS a kerf will still let water move downward to rot wood below, think of a tree; the end grain supplies the water to the leaves from the roots... and won't help drain moisture from the WRB, flash HAS to go behind that.


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## craig11152 (Jun 20, 2015)

I have a kerf cut in some T1-11 in my shed going on 15 years. So far so good. 

On a slightly different topic....Strangely enough I am doing some demo on some basement interior walls in my house and finding untreated 2X4 bottom plates looking pretty good after sitting on the cement for 22 years.


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## grcummings (Feb 28, 2009)

Gary, 
I certainly would like to avoid the kerf and the associated end grain that is created by cutting that kerf. I am concerned with 'wicking', but would paint, caulk, repaint.

I still see no way to properly flash my siding, which is real 3/4 Ceder TnG over 1/2 real plywood. My strength is in the 1/2 inch sheeting, so i am not concerned about the kerf from a structural standpoint. I am concerned about water penetration, and secondly cosmetic appearance.

I have read and reread all the material you have provided, but still nothing address my situation. 

I see two options.


 cut the kerf in some manner to get some flashing up under the siding.
 add material* in the batten groove to fill to flush with outer edge of siding.
 
*Option 2* will take time (which I have) and will avoid end grain exposure 
* I could easily use a synthetic, cut to fit from a synthetic building material. 
I have used PVC Brick Molding; Home depot sells similar dimensional stock.
This material is VERY EASY to mill.

If I went option 2, I would install the 'green' flashing on the ledger, under the decking. I would fully cover the exposed plywood decking, wrapping it with the Elastomeric and tape... After installing the decking, I could flash as show, without disturbing any of the residential wall.


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## Gary in WA (Mar 11, 2009)

End grain is the end of the board (exposed bottom) at 3/4" or 7/8" thick, both pieces of siding total thickness. Any flashing HAS to go BEHIND the siding and the Water Resistive Barrier; tar paper, most likely, This will drain ALL water in the wood and behind the board siding, onto a "Z" metal flashing, and out onto the deck. A reglet won't work nearly as effectively and is not code-compliant. Measure the trim piece that will set on the deck, IMO-use some 1x4 PVC board at 3/4" thick, add in the flashing and gap, 3/8"-7/16", and cut the siding above the deck and flush with the decking ply to remove the pieces. Treat/paint the end grain of the siding boards. Add your green flashing against the sheathing, under the tar paper, caulking it down to the plywood- or on top the waterproofing. Finish waterproofing the deck, add the PVC trim board, after slipping in the "Z" flashing under the tar paper. 

Picture of "skirt and bandboards" *page 9; *From; http://www.realcedar.com/wp-content/uploads/2013/06/installingsiding.pdf
Here they cut a slit in tar paper for the Z-flashing, but it *has to go behind it*.

Gary


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## grcummings (Feb 28, 2009)

I believe that this graphic represents what you described in words.
The dotted line is my best attempt at showing the tar paper.

Largely, the difference from my first proposal, is the insertion of flashing below the tar paper at two places, rather than one. My original design was intended to minimize the cuts to the tar paper. 

I do like the idea of the synthetic, pvc.. I have worked with it before and love it. 

I will need to cut that lower kerf before decking is applied, I have no tool for a flush cut, but have a great DeWalt XRP with a 1" offset... I'll rest a 3/16" spaced ON the ledger to get my correct distance to create that FLUSH cut to the decking surface.

Since the price of flashing and pvc is cheap, compared to a downstream repair.. I may z-flash below the green onto and over the ledger....


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## grcummings (Feb 28, 2009)

Note: After removing all existing deck 2x and inspecting the ledger, siding, and deck framing, I see no (none) decay, aging or any other structural or cosmetic damage. 

I am amazed; this structure was installed with the house in 1980 and remains... near as good as a new installation. I imagine arsenic in the treated wood .... and the cedar siding was probably as good as it gets. I am going to spend a few more days thinking.. I hate to cut into this siding..


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## carpdad (Oct 11, 2010)

Although I can't agree to paintable roof deck sealing (I would use rubber), you'd want continuous seal from the deck to wall. I'd have it if I cut the siding a foot and install a water table of a kind. Seal up to the water table and good wide drain cap over the seal. Caulk under the drain cap for stop possible wick up from melting snow.
Any roofing must have a good drain, that is a slope that you can see. That, however, makes it uncomfortable to walk around on.


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## Gary in WA (Mar 11, 2009)

I'm a little "amazed" also. The previous owner installed the deck without flashing and you want to do it correctly. I showed you Code requires flashing there and Cedar Siding manufacturer requires flashing there but you are going with someone who has the same viewpoint as you. The deck was not built to code minimums; 

(1) Table 5 shows- up to *15/32" sheathing* wood allowed between ledger/framing- not 3/4 or 5/8" cedar siding 

(2) after *removing SIDING- Fig.14*, 

(3) do you have *lateral restraints tied to house floor joists- Fig.22*; http://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA62012-DeckGuide-1405.pdf

If you call it a "roof" now, rather than a "deck"--- flashing is also required; 
*INTERNATIONAL RESIDENTIAL CODE 2006*​*WALL COVERING - SECTION R703 EXTERIOR COVERING*
*R703.1 **General*. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing as described in Section R703.8 The exterior wall envelope shall be designed and constructed in such a manner that prevents the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer as required by Section R703.2 and a means of draining water that enters the assembly to the exterior.
*R703.8. Flashing*. Approved corrosion-resistive flashing shall be applied shingle-fashion in such a manner to prevent entry of water into the wall cavity or penetration of water to the building structural framing components. The flashing shall extend to the surface of the exterior wall finish. Approved corrosion-resistant flashings shall be installed at all of the following locations: 
6. At wall and roof intersections.
*ROOF ASSEMBLIES - SECTON R901 GENERAL*
*R901.1 Scope*. The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies.
*ROOF ASSEMBLIES - SECTON R903 WEATHER PROTECTION*
*R903.2 Flashing*. Flashing shall be installed in a manor that prevents moisture entering the wall and roof through joints in copings, through moisture permeable materials, and at intersections with parapet walls and other penetrations through the roof plane.
*R903.2.1 Locations*. Flashing shall be installed at wall and roof intersections" 

So now you have a paper trail for your HO Insurance carrier if/when you ever file a claim on the deck/roof liability or siding rotting any lower framing later, for claim denied. Much easier not to do anything...

Gary


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## grcummings (Feb 28, 2009)

Gary.. 
Since everything is in such good shape, I want to keep it that way 
I needed a good reason to by a new tool anyway.
I'll get the flush cut offset circular saw and set it to the thickness of the cedar siding and remove it carefully. 

I still think the weak link in 'doing it right' will be that exposed end grain of the cedar siding that is above the top flashing. 
Heavy coat(s) of an oil primer followed by house paint should work fine given it is cedar.. and proper gap (clearance) between the end grain and flashing... 

I still have time to think... and plan... Like I tell my wife.... _Good things take time_


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