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-   -   How to flash/mount new window install with only T1-11 siding, sheathing! (

Dr_Jim 02-18-2009 05:42 AM

How to flash/mount new window install with only T1-11 siding, sheathing!
OK,....greetings all.

Going to be putting in a new window into an existing wall. (no window there now).

My question is this,...I havent gone inside the wall yet,...BUT the exterior of the home is T1-11, and I fear that this is the only siding, sheathing underneath.

If this is the case,...what the heck do I flash the window to? And for that matter even attach it to?

The only thing I can think of, to do my rough opening a bit larger?...cut my exact sized hole through the T1-11, then caulk the window up good...get it in place,...and build additional studs and framing around the window nailing flange from the inside?....I mean all seems pretty sketchy to me.

If I get in there and have sheathing then im golden,....but I fear that wont be the case...

Any thoughts here?

jdougn 02-18-2009 07:50 AM

Dr Jim, help us out with some more information. What type of window are you using and how will it be fastened to the wall? Does it use brickmold or will it have a nail flange? Answers to these questions will help use give good answers.

Dr_Jim 02-18-2009 11:38 AM

Anderson basic double hung window. Was going to buy new construction with nailing flange.....

Again,.....IF I have sheathing I will just rough in the opening from the inside, cut my sheathing exact,...remove the T1-11....put the window in, nail through sheathing, do all the necessary flashing..etc..etc...
THEN, put new T1-11 back up.

BUT, if I do not have sheathing,....what the heck do I flash the window too?
I mean all I will have is studs, wrap and T1-11?
Follow me?

tinner666 02-19-2009 05:29 AM

Hopefully the window flashing details, at a link in my signature site will help give you some ideas. I did not address T1-11 in the tutorial, but a little adatation may save the day.
Possibly, cut the lower piece 3' wider that the window on each side, a sill pan, to empty over the lower piece, the sides cut back around 3", all flashing installed, and tucked behing the siding, and over the metal on the bottom.

SOme trial and error with smaller pieces to see how they will 'go together AS a system. They must work together.

Dr_Jim 02-19-2009 05:38 AM

Interesting,....I read through it all.....and I am probably missing something,...BUT it appears all your info relates to the flashing of the window to the underlayment sheathing, and then siding on top.
In my situation I do not have underlayment....I am preparing for the situation (when I open wall) that I have ONLY T1-11, then tyvek wrapped on studs. No underlayment to attach the window too.
Does this make sense? Or am I missing something from your very well put together web info?

jdougn 02-19-2009 09:49 AM

Jim, I'm not beyond being a little redneck about some things so take all this with a grain of salt and remember that your methods may vary.

If this in a finished house then hopefully there is sheathing under the T1-11. If there is no sheathing under the T1-11 then use the nailing flange directly to the T1-11. You've already read how to properly use flashings and all. I'd use drip cap across the top then simply use exterior grade trim such as 1x3 Redwood or Cedar to cover the nailing flange and caulk as needed.

If the Andersen window has wood brickmold on it then fasten the brick mold directly to the T1-11. Again, drip cap across the top of the window and caulk behind the brickmold before installing the window. Other people will have different suggestions but this has worked well for me in the past.
just my .o2, Doug

Dr_Jim 02-19-2009 11:20 AM

jd - Whoaa......are you suggesting I install the window from the OUTSIDE? With the nailing flange on top of the T1-11 (from the outside??) Then flash it and cover it all up with trim??

That seems a bit odd to me,...I just assumed this really needed to be isntalled from behind the T1-11....

hmmm.....many ways to skin a cat I suppose......

jdougn 02-20-2009 06:57 AM

Dr Jim, standard installation for a window in T1-11 and sheathing is to anchor the windows brickmold or nailing flange directly to the sheathing. A good carpenter will install a drip cap across the top and rubberized/self adhesive window flashing at each corner of the window. Then the T1-11 siding simply butts up against the perimeter of the window as close as the carpenter can fit it, probably within 1/8" or so. It is then carefully caulked and it's done. If a window is carefully installed like this then with any reasonable maintenance it will last indefinitely. Regardless of what construction method was used on your project it is not extremely unique.
Always remember, "your methods may vary" ymmv, and, this is just my .o2,
Respectfully, Doug

Dr_Jim 02-20-2009 01:21 PM

yes,...your 2nd post makes sense to me ( sure it makes sense,...I jsut might be having trouble following :-)

The T1-11 would be removed. Then the opening cut into the sheathing underneath...the window is installed onto this (from the outside)..and the flange nailed in...etc..etc.
THEN the T1-11 opening is cut, as tight as possible a fit to the window,...and the T1-11 is put back up over the properly flashed window.

IF I DONT have any sheathing....just T1-11 on over studs.....then you are saying I cut the opening in the T1-11 and put the window in (from the outside) and then nail the flange into the T1-11. How could I Flash this? There would be paper and flashing tape..etc..etc..all over the T1-11,...even with some HUGE trim I couldnt cover it all....

Damn,....I am sure you are giving me great advice,....but Im not that experienced in this,..and am having trouble following this......

inspectorD 02-20-2009 02:45 PM

Well, he has the advice correct, but this may help you understand.
After you follow this, you can cut a small groove into the t-111 above the window trim and install a metal drip cap which will tuck into the cut in the siding, and then cover the top of the piece of trim. You need to think of where the water will flow and redirect it. I'm sure you get that part. Then caulk it with 100% silicone at the top connection when it is all painted. This gives a good bond.
I would also caulk the window onto the siding when you install it. Either behind the flange or the trim, whichever it happens to be.
Good luck.

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