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Window flashing on T-111??

rce | Posted in Construction Techniques on November 12, 2005 08:12am

I’m looking for a better way to flash vinyl windows that are installed on top of T-111. Currently we are caulking the flange around the perimeter and filling the grooves in the T-111 along the top. After applying 5/4×4 prime trim around the window the painters are then caulking the outside edge of the trim. Luckily I’m in a dry climate but I’m not comfortable with relying on caulk only. Is there a better system for this type of appication?

Rob

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Replies

  1. davidmeiland | Nov 12, 2005 09:25pm | #1

    You are installing the windows on top of the plywood?? No way to make that work. You need to install them to the framing and flash them into the tyvek or felt, and then install the plywood.

    1. rce | Nov 13, 2005 05:29am | #2

      Yes, The windows are being installed directly on top of the T-111. This is common practice for starter to mid range homes in my area where the T-111 is on three sides and lap siding on the front. It is the reality, now for a flashing detail that might be effective. Any thoughts out there?

      Rob

      1. davidmeiland | Nov 13, 2005 05:36am | #3

        If you are using windows with nailing fins, you cannot flash them correctly on the outside of the siding. You have to install the windows before the siding, along with the weather barrier. There is no other way to do it.

      2. User avater
        Huck | Nov 13, 2005 06:04am | #5

        That's interesting. Are they installing the lap siding before the windows also? Should make for a challenging caulking job! If they install the windows before the lap siding, why couldn't they install them before the t-1-11 siding also? Just curious.

    2. IdahoDon | Nov 13, 2005 06:00am | #4

      I'll have to agree with Dave.  T-111 is notorious for leaking at joints that aren't flashed correctly so putting the window on top of the sheeting makes it vulnerable to caulking leaks around the window as well as leaks in the sheeting above the window.

      If attaching windows on top of the T-111 is unavoidable something you may look into is making an angled, shallow saw kerf directly above the window (under the trim) which would then allow a "Z" flashing to direct water out between the trim and top of window. 

      Out here in the rocky mountain states, especially in the mountain communities, "western style" rough siding and trim is very popular so we end up with a lot of completely square trim, usually rough cedar.  Typically I'll cut a very small angle (5 degrees) on the top and bottom edges of all square trim to help shed water away from the sheeting/window and it provides somewhat of a drip edge.  Most people don't realize there's an angle there at all since it's so slight, but it does help a great deal.

      Good flashing,

      Don

      1. davidmeiland | Nov 16, 2005 07:00pm | #6

        A kerfed-in flashing is better than nothing, but won't address any moisture that's behind the siding. Obviously you get a z-bar behind the weather barrier if possible.

  2. PenobscotMan | Nov 16, 2005 07:14pm | #7

    As everyone will tell you, windows over T111 is a bad idea.  Nevertheless, this is not uncommon.  Where I summer, all but the fanciest houses have this detail at some time in their lives (often they start out this way, then years later cedar shingles are added.)

    This has worked reasonably well for me:  run caulk into the grooves of the T111 over the top piece of 5/4 trim, then a bead lengthwise, then attach a piece of quarter-round, ensuring that as you nail down the quarter round, a bit of caulk oozes out, indicating a good seal.  You should probably check it every couple of years to make sure all is well.

  3. blue_eyed_devil | Nov 16, 2005 08:06pm | #8

    Rce, I've installed windows on top of siding for my own house and I know for sure it works fine, assuming you have, and use quality caulk. I did use a z style flashing at the head. It has to be custom made unless you can find a stock flashing that measures 5/8" + 1 1/4". The flashing tucks under the siding and covers the window drip cap.

    If the window tucks up tight to a frieze, which is typical, and you have a sufficient overhang, which again is typical, you might not have to be so paranoid about adding the z flashing at the head. If you insist on adding a flashing in this situation, you'll only need a stock 1 1/4" flashing. It will tuck under the frieze, but be installed over the siding. I'm assuming that in this situation, the siding extends behind the frieze.

    If your window is installed in a larger wall, that exposes the head jamb and is wrapped in window trim, you might consider flashing on top of the window trim. For this scenario, you are trying to prevent water from getting in behind the overlaid 5/4 trim board, which is probably a good thing to think about. If you can prevent water from getting under the trim board, it most likely won't be able to get in behind the window because the trim stands proud. For this, you would need a custom bent flashing (5/4" + 5/8"). When I do remodeling, I tend to do a lot of custom flashing bends. I prefer to use a much bigger flashing up under the siding/trim boards and I also like to bend it to create a 15 degree sloped surface to shed water before it gets a chance to "pond".

    I've also done a lot of wood drip edges over some exposed windows. I slope these at 15 degrees and rely on caulk to keep water from entering behind the trim piece.

    Oh yes, one more important detail: inspect the cauld every year when you walk your roof and inspect your roof flashings. Sure the calking offers a ten year warranty, but sometimes your installation techiques are questionable and it's better to just re-caulk an area that shows signs of stress.

    As you can tell, I'm not that convinced that flashings are the everything and endall to window installations. I think common sense should prevail instead of simply doing what the "book" says.

    blue

     

    1. JohnSprung | Nov 17, 2005 03:15am | #9

      > ... and use quality caulk.

      Any specific brands and product names you recommend?   

       

      -- J.S.

       

      1. blue_eyed_devil | Nov 17, 2005 06:35pm | #16

        John, I've had good luck with Window and Siding Caulk by O.S.I. It is sold in all the local builder supply shops here. It comes in a wide array of colors and is intended to be applied after paint. It's flexible properties and tough texture make it a very good choice. It is paintable however and in some applications, I've re-painted over the caulk when I wasn't satisfied with the finished look.

        The caulk is so tough, that you really don't need nails to hold the window in. I've driven the nails through on window repairs and still can't get the window out without cutting all the caulk.

        blue 

        1. JohnSprung | Nov 18, 2005 09:53pm | #22

          Thanks.  I checked OSI's web site.  It looks like that product isn't sold here, though others are.  Most likely due to the AQMD (smog regulations). 

           

          -- J.S.

           

    2. donk123 | Nov 17, 2005 05:45am | #10

      Blue - In at least two of your examples you talk about the windows on top of the "siding" but you go on to mention that you get your flashings behind the siding.

      How do you stop water penetration where your window fins are on top of the siding and you can't get behind them? Just caulk the flashing flat against the wall, then down over the window head/fins? Does that pass code? Doesn't sound real reliable to me, I don't care what tube of caulk you have, especially when he's working on top of T111. I'd rather at least have a saw kerf to stick the top of that flashing into.

      Don K.

      EJG Homes     Renovations - New Construction - Rentals

      1. davidmeiland | Nov 17, 2005 09:32am | #11

        Blue is freaking me out. Lately I'm reading how he has no guards on his saw, and he's too old to lift his feet so he uses heavy rubber gun hose, but then he's saying how he destroys 1 nail puller per hour with two brutal whacks of the hammer to pull a nail, and now he's trimming out windows with nothing but caulk. This has got to stop.

        1. blue_eyed_devil | Nov 17, 2005 06:31pm | #15

          Don't get too freaked out David. I've worked 30 years as a rough framer and I've never used a guard. I couldn't imagine doing my work with one on. There's no extended table either.

          The hose issue isnt really an issue either. I simply don't allow anyone to use cords or hoses that won't lie flat on the deck or ground. I've been known to toss the guy's cords off the deck if they don't have one that lies flat. It's a safety issue. I learned in OSHA school that the average height of falls that cause death are 4'. It takes a lot of trips while walking on the ground to average out the 30 and 40, falls that you would typically think would cause deaths.

          The nail puller thing isn't too much to get excited about either. In the olden days, I could buy a $4 nail puller that contained quality steel. I could pound that as hard as I wanted and never worry about them breaking. In the last decade, most tooling is being done overseas. They can't take the abusive techniques that I've developed in order to be above average in speed. I probably extract nails twice as fast, or faster than any method mentioned in the thread about hangers. Anyone could match my speed if they simply watch and apply my techniqus. Oh yeah, incidently, my method doesn't mar wood, nor hangers. It does leave the nails bent in some weird shape. Try it one time. After you get the tool under the head of the nail, just keep whacking it. In three whacks it'll be completly extracted and you'll have to use one more swipe to clean it out of the nail puller. Once you start doing it my way, you'll probably never go back to your "old fartz" way.

          Lastly, you'll have to go re-read the post about windows, flashing and caulk. I'm fairly certain that I mentioned using deeper custom bent flashings where necessary. I'm also fairl certain that a lot of the things that you guys say you'll do, I wouldn't accept on my house. I'm not a "follow the crowd" kinda guy. I do things that make sense.

          blue 

          1. davidmeiland | Nov 17, 2005 07:00pm | #17

            Hey, I'm kidding ya' on this stuff, but one thing is true... I'm way too old to wail on a nail bar like that. If I have to pull a nail (or god forbid more than one), I roll my wheelchair over to the radio, turn up the opera slightly for some extra adrenaline, and then roll back and pull the thing out politely. No point in drowning out that aria she's singing.

            I've done many window installs of units with brick mold. Brick mold, nail fin, they're about the same. I always install them directly to the sheathing with a Z-bar over the top of the brick mold and then bring the tyvek or felt down on top of the riser leg of the flashing. Usually if it's tyvek it's already on and you need to cut it free at the top to do the lap.

            My semi-informed opinion is that a window installed without mechanical flashing will quickly lose you a lawsuit if your install leaks. If the HO wants to push the issue they will get a home inspector or some other expert witness to testify that there was no flashing, just caulk.

            The problem area is when a HO wants a window where there was none, and just wants you to punch a hole thru the wall and glue a window in. My response is that I will not do it. They will not maintain caulk like you will on your own house. I strip back enough siding to get at the tyvek and tie into it, install the window, and then repair the siding. I am doing an install of a large slider right now that required just this approach. Sorry about your siding, lady, but look, I got matching stuff and ya' don't want a leak, do ya'?

          2. blue_eyed_devil | Nov 17, 2005 07:51pm | #18

            My semi-informed opinion is that a window installed without mechanical flashing will quickly lose you a lawsuit if your install leaks.

            Ahhhh Yessss, we have to cover our selves in case of lawsuit. To heck with logic!

            I've yet to be sued for a leak-only time will tell.

            blue 

  4. rl36 | Nov 17, 2005 02:04pm | #12

    Yes the window can be flashed properly and installed over the T1-11. I was trying to solve the same problem and encountered an article by Blazer Industries from Aumsville Oregon. Living on the Oregon coast I wanted a sure fire way to seal out the rain on my new shop I am building. Following is the website with the article rather than trying to reiterate it all here. <http://www.mbinet.org/web/magazine/water.html> Hope this helps Russ

    1. donk123 | Nov 17, 2005 02:37pm | #13

      rl36 -

      The article essentially says after installation, rout out the piece of wood above the window to install the flashing over the top of the widow, then push it back in. If one is going to go through the trouble to do that, why not just cut it and flash it while the T111 is on the ground?

      I still think the better way is to put the fins behind the siding. They talk about wicking in that situation. I think you are better off trying to prevent a little wicking than trying to prevent wholesale water infiltration by setting the open jamb in caulk. I don't see where there's any benefit to putting the window on top. You still have to cut the siding around it, so put it where it belongs - under the siding.

      The other alternative is to get a window with a built in J channel around the perimeter.

      Don K.

      EJG Homes     Renovations - New Construction - Rentals

      1. blue_eyed_devil | Nov 17, 2005 06:13pm | #14

        Don, not everyone uses windows that have fins. 90% of the windows that I've installed have been wood windows with a wood brick mold that measures 1 1/4" .

        That article explains a way to install windows over the t-111. I wouldn't do it the way he shows it, but the concept is similar. The point is: it is POSSIBLE to install windows over the siding as long as you properly seal out water, if water has a way to get in.

        If the window are tucking up under a 12" overhang, then flashing the head jamb is a useless exercise and actually makes a good caulk job harder, thus making it more likely that bugs and air will infiltrate. I wouldn't allow anyone to put metal flashing over my windows if they are tucked up under an overhang.

        Window flashing techniques is just another example of how some things in our  industry become automatic and if you actually put some thought into each application and figure out that you might do it different, you will be looked down upon, even though your way might be superior and their way problematic. I've questioned every detail of our work since I started in the trades and this is just one more example of stodgy building practices that don't make sense.

        blue 

        1. donk123 | Nov 17, 2005 11:37pm | #19

          Blue - Questioning stogy building practices is fine. Questioning in general is fine, and I know you could probably argue that you have forgotten more about windows than I know. That said, your answer really did not fit the question raised by the original poster. I just went back and read the post. He talked about fins being caulked and covered with trim. He said nothing about overhangs either. If he had mentioned brick mold or wood windows, I would have responded accordingly. The bottom line is that if someone is going to put in windows without drip cap of some kind, on an open wall, it's an invitation to a water problem, caulk or not.

          Don K.

          EJG Homes     Renovations - New Construction - Rentals

          1. blue_eyed_devil | Nov 18, 2005 02:56am | #20

            The bottom line is that if someone is going to put in windows without drip cap of some kind, on an open wall, it's an invitation to a water problem, caulk or not.

            I agree. A drip cap of some kind should be installed, on a window that is installed on an open wall.

            blue 

  5. MikeCallahan | Nov 18, 2005 05:20am | #21

    Ugg ....T111. There is no accounting for taste. I hate that stuff and if I had my way, anyone using it would go to jail and be executed. (Just killing... I mean kidding.) That's just my personal opinion though. I hope you are just satisfying the shear requirements and will put some more beautimous siding on later. In the meantime. You will have to cut away the siding so that your window will install on the framing. Pry back the ply and tuck in some Z flashing and then caulk the bejeezus out of it. The top fin of the Z flashing should go under the tarpaper or Tywhatever. Furr it, fill it back to flush. Then install the trim. Your trim should have a nice beveled sill and an apron and crown at the head would be nice and a cornice too. If you use flat 1X then you will have to go to jail.
    I don't care if it is a common thing to do it wrong. Stupidity is very common. Just look at who the people elect and you might understand.

    Mike Callahan, Lake Tahoe, Ca.

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