Water-resistive barrier, flashings and window installation

[Robert Ellenberg]

703.2 describes the Water-resistive barrier as a layer of 15# felt or other approved (which means the local building inspector OKs it). In the past I was using Tyvek or similar but am going to start doing a full layer of 1" foam over the studs to increase the insulation and the thermal bridges created by the studding. I can't find it spelled out in the code, but assume the foam with T&G or properly taped joints should meet the local inspectors approval as a water-resistive barrier as I have seen it done this way (I am covering it in 4x8 Hardi and using thin shims to create a drainage plane between the foam and the Hardi). So far, I think what I have described is good practices--if any of you see any problems, point them out.

However, the code specifically says to follow the window manufacturers installation instructions. Every set I have seen now shows the Tyvek type paper being cut in the X pattern with the top taped up temporarily, etc. and the flashing pan and sides being installed over the turned back edges of Tyvek type paper. I have talked to two manufacturers for directions on installing in a foam sheathed wall without paper. Both have said if relying on the foam sheathing for the barrier, to follow their retrofit instructions. When I look at them, neither is appropriate as they are not fin windows. My thoughts are to install the pan, wrap a wide seal tape from the foam in against the framing on the other 3 sides (as shown in most install diagrams), nail in the window and add a sealing layer of tape over the fin and on to the foam. However, this doesn't give an install that matches up to the manufacturers diagrams, which in turn, makes you non compliant. Any thoughts?

My secondary question is whether or not a fin window creates a top flashing in and of itself as described in 703.8. If you have a vinyl window fin at the top with a sealing tape over it, does adding another flashing on top of it serve any purpose?

 

[Mule]

Re: Water-resistive barrier, flashings and window installation

I have a document saved to my computer called "Installing Windows with Foam Sheathing on a

Wood-Frame Wall". I'll try to find a www link to it however if you wish, email me and I'll send it back to you.

OR I'll print it, scan it, and post it if needed. The easiest would be for me to find a link.........hmmm better get to looking huh!?

EDIT!! Found it!!!

Installing Windows with Foam Sheathing on a Wood-Frame Wall

 

[Mule]

Re: Water-resistive barrier, flashings and window installation

Thinking about this a little more. When OSB is used we require some type of weather resistive barrier to be installed over the OSB. This is usually some type of wrap. The windows are installed over the wrap with the upper portion of the wrap cut so that it will overlap the top flange of the window. Then the window is flashed with that super sticky tape. Bottom first, sides overlapping the bottom, then the top overlapping the sides.

Now my thoughts. A lot of the builders are now using "Green Board" around the perimeter. With this type of installation we don't have a "wrap" to lap over the top flange. We require the builder to flash as described above.

After reading the information I posted on foam board, the specifications indicate flashing the opening before the window is installed....install the window, then flash over the window as described above.

Now the question. Since the foam board is basically the same as the green board, both water resistive barriers, should you double flash as described in the foam board installation article??

 

[Rider Rick]

Re: Water-resistive barrier, flashings and window installation

Mule,

Thank you for the article.

Rick

 

[Robert Ellenberg]

Re: Water-resistive barrier, flashings and window installation

Mule--Thanks. I had this at some time in the past and lost track of it. I am a avid reader of Building Science Corp stuff as well.

Yes, I think you have to have the "double" layer. The first one is sealing the edges of the foam and the wood in a similar way the cut pieces of house wrap would do. The 2nd layer is sealing the window fins to the foam. One thing I want to explore further is tape-foam compatibility. The tapes designed for this are expensive but you could still have a chemical incompatibility where it turns loose after a few years (BSC cautions this in the article).

 

[Robert Ellenberg]

Re: Water-resistive barrier, flashings and window installation

Mule or Uncle Bob,

Do you have any thoughts about my last question, "My secondary question is whether or not a fin window creates a top flashing in and of itself as described in 703.8. If you have a vinyl window fin at the top with a sealing tape over it, does adding another flashing on top of it serve any purpose?"

 

[brudgers]

Re: Water-resistive barrier, flashings and window installation

Mule or Uncle Bob,Do you have any thoughts about my last question, "My secondary question is whether or not a fin window creates a top flashing in and of itself as described in 703.8. If you have a vinyl window fin at the top with a sealing tape over it, does adding another flashing on top of it serve any purpose?"

Yes, the second flashing would be a counter-flashing.

 

[Uncle Bob]

Re: Water-resistive barrier, flashings and window installation

Robert,

In the 2006 IRC, the ICC put the responsibility for correct flashing requirements, of windows squarely on the manufacturer;

2006 IRC, R613.1 This section prescribes performance and construction requirements for exterior window systems installed in wall systems. Windows shall be installed and flashed in accordance with the manufacturer's written installation instructions. Written installation instructions shall be provided by the manufacturer for "each" window.

"Each" window should have the manufacturer's flashing installation instructuctions attached to it. There should also be a note on the instruction packet stating "READ CAREFULLY-DO NOT REMOVE THIS LABEL UNTIL AFTER FINAL INSPECTION". The installation instruction are required to be on site at time of inspection.

2009 IRC, has moved this section to R612.

Here is JELD WEN instructions;

http://www.jeld-wen.com/_pdf/resources/ ... JII001.pdf

Many window manufacturer's defer to AAMA 2400-02 for installation instructions;

http://pro.milgard.com/_doc/products/in ... 400-02.pdf

"Ours is not to reason why; but, to insure that they comply." Rosso

Hope this helps,

Uncle Bob

 

[Mule]

Re: Water-resistive barrier, flashings and window installation

Robert Ellenberg wrote:

Mule or Uncle Bob,

Do you have any thoughts about my last question, "My secondary question is whether or not a fin window creates a top flashing in and of itself as described in 703.8. If you have a vinyl window fin at the top with a sealing tape over it, does adding another flashing on top of it serve any purpose?"

For a while window manufactuers were calling their windows "self flashing" windows. No such window exists so by the ICC putting the flashing requirements directly on the window manufactuer they have changed their tune a little.

Now on your last question.......the tape across the top fin is all that is required by almost all of the window manufactuers I have seen. Adding the other flashing on top of the tape does not hurt anything but does it serve a purpose......not really. You could just keep on going and going and going..........fin, tape, flashing, tape, flashing, tape..........where would it end?

 

[TJacobs]

Re: Water-resistive barrier, flashings and window installation

Check the Evaluation Report for the foam that you are using. There will be requirements in the report on how to install the foam as a water-resistant barrier. Some also have penetration flashing guidance.

Here is an example:

http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2142.pdf

Here is a link to the report list:

http://www.icc-es.org/reports/index.cfm?csi_num=07280&view_details=yes

Regarding flashing, it is in what order the flashing is installed. No self-flashing windows...

 

[Robert Ellenberg]

Re: Water-resistive barrier, flashings and window installation

These sites were interesting.

Jeld Wen’s has only the pan installation wrapping a sealant from the face of the wall in to the frame prior to nailing in the window. In other words, the side flashings go over the fins and the sheathing/house wrap but there is not a layer below wrapping in on the framing.

American Architectural Manufacturers Association shows installing the bottom flashing pan and sides to the face of the unsheathed studs wrapping in on the jacks, installing the window, the head flashing, the wall sheathing and then the building wrap. I can’t recall ever seeing window fins buried under wall sheathing but maybe I’ve had my head in the sand.

TJacobs—Thanks, excellent references. On the list of evaluation reports, Owens Corning was visibly absent except for their house wrap product—it appears their foam has not been approved as a barrier like most of the Dow Styrofoam products. Out of ignorance I would have assumed if one could be used—so could the other. The individual Dow report you referenced shows the window install like the Jen Weld instructions. It also has a good detail on proper flashing of a through-the-wall pipe.

I was aware of the code reference to following the window manufacturer’s instruction (but most don’t show a method where the foam is the house wrap). However, 703.8 spells out the requirement for flashing in a way that seems to be totally independent of the reference to how the window manufacturer says to install the window. Since all window instructions I have seen refer to the last adhesive strip over the top as flashing, I would assume it would meet it. But 703.8 specifically says it has to be an “approved” corrosion-resistant flashing and “approved” by definition means what is acceptable as flashing material to the local code official.

Sometimes trying to meet the letter and the intent of the code can be difficult.

 

[peach]

Re: Water-resistive barrier, flashings and window installation

Most sytrofoam sheathing is pretty water resistant.. so you shouldn't necessarily have to add a second WRB.. however, flashing the windows to prevent leaking is still required.. you flash just like you do a roof.. from the top down.. over lapping to prevent water intrusion.

A "self flashing" window doesn't exist.

 

[brudgers]

Re: Water-resistive barrier, flashings and window installation

Robert Ellenberg wrote:Mule or Uncle Bob,

Do you have any thoughts about my last question, "My secondary question is whether or not a fin window creates a top flashing in and of itself as described in 703.8. If you have a vinyl window fin at the top with a sealing tape over it, does adding another flashing on top of it serve any purpose?"

For a while window manufactuers were calling their windows "self flashing" windows. No such window exists so by the ICC putting the flashing requirements directly on the window manufactuer they have changed their tune a little.

Now on your last question.......the tape across the top fin is all that is required by almost all of the window manufactuers I have seen. Adding the other flashing on top of the tape does not hurt anything but does it serve a purpose......not really. You could just keep on going and going and going..........fin, tape, flashing, tape, flashing, tape..........where would it end?

If you don't flash over the top fin, water coming down the wall will be directed behind the fin and into the building.

BTW, you want to flash under the the bottom fin.

Flashing once is theoretically enough.

Counter flashing is good practice.

 

[peach]

Re: Water-resistive barrier, flashings and window installation

under the bottom fin.. not over it...

had a contractor rip tape off just yesterday... if water gets in around the window flanges, gravity will take it back out .. it needs to escape.. or you've just added a whole new problem.

I worked in a jurisdiction where the "senior" inspector absolutely positively made them tape the bottom of the window... see how that works for them in the future.

Same thing goes, in my opinion.. for the house wrap.. don't tape the horizontal overlap... let the water out...

"Let my water go... "

wait, was that PC enough for this group?

 

[Uncle Bob]

Re: Water-resistive barrier, flashings and window installation

The ICC dropped a definition from the IRC when they wrote the 2009;

"UNUSUALLY TIGHT CONSTRUCTION"

Next deletion will be to completely remove the use of asphalt-saturated felt (overlaped), as a water-resistant/resistive barrier; because it allows air to inter the wall and dry up any moisture that may have gotten into the wall.

Seal'um up,

Uncle Bob