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  1. #1
    Join Date
    Sep 2005
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    Default Why Not Angle The Window Sill?

    I was reading the flashing details of a popular tape and WRB company, and it seems every procedure for setting windows these days wants to incorporate some means of directing moisture/water back out of the window opening.

    Install some sort of material that will give the (rough) window sill positive slope to the exterior.

    Install something to create a back-dam, then wrap the flashing tape to it.

    Use a pan, but again, with positive slope.

    Etc...


    First off, I firmly believe it is quite possible and relatively easy to keep water out of the window area from the installation standpoint. My own take on all this is that if water gets into that area, it's coming from a deficiency in the window itself, not the installation (if done properly.)

    Problem I see is that the installation instructions want you (us) to design a way to let the water out! It's kind of like..., we have to be the ones to handle the water intrusion that is the fault of the window.


    Ok, I get that. If that's how to ensure a proper warantee, then I'll do it.

    So..., how bout just cutting the window sill cripples when framing at something like a 5 degree angle? There's your positive slope.

    Tom
    1) Unconsciously Incompetent: He knows not, and knows not that he knows not. He is a fool. Shun him.
    2) Consciously Incompetent: He knows not, and knows that he knows not. He is simple. Teach him.
    3) Unconsciously Competent: He knows, and knows not that he knows. He is asleep. Wake him.
    4) Consciously Competent: He knows, and knows that he knows. He is wise. Follow him.

    May we all endeavor to progress from not knowing that we know not, to knowing that we know.

  2. #2
    Join Date
    Jan 2007
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    Louisville, KY
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    3,771

    Default Re: Why Not Angle The Window Sill?

    The guy that i used to frame for did. This was before tyvek and all the tapes.
    Louisville Exteriors
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  3. #3
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    Feb 2008
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    Northwest Indiana
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    Default Re: Why Not Angle The Window Sill?

    No reason why not to cut the cripple at an angle. As long as you can train your crew to [remember] do it.

    I believe the slope "add on" should be for retro fit where angling the cripples would not be feasible.

    I do agree with you on the water entry issue, if properly installed the water must be coming from the way the window is fabricated.

    Tom
    http://chicagocraftsmen.org/2011/06/261.html

    Check with the AHJ, what we say doesn't matter.

  4. #4
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    Jun 2004
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    St Louis, Mo for the past 25 years
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    Default Re: Why Not Angle The Window Sill?

    I used to work for a guy who had you cut the cripples straight. But he always made the rough openings an extra 1/2 or 3/4 tall. He had a bunch of tapered lap siding he would use to give some slope. Plus he always made the sills and made sure to include a drip groove on the underside of the sill. I never did really understand why he put the siding there and the topped it with a sill with a slope. Now I am guessing if rain got around the first sill the 2nd might direct it away from the house.

    this was before anyone heard of tyvek or peel and stick wraps.

  5. #5
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    Oct 2008
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    Essexville,Mi. Home of the best walleye fishing in the great lakes.
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    Default Re: Why Not Angle The Window Sill?

    Anderson double hung jambs are staight on the bottom. To make this work you may have to cut the jambs on a slight angle. I have never heard of using a pan until I found this forum. And I never yet seen a builder use a pan or even tape yet on a new constuction window. This is in my area of Michigan. I know there are builders in this state that are up to date.

  6. #6
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    Default Re: Why Not Angle The Window Sill?

    Quote Originally Posted by gman396 View Post
    Anderson double hung jambs are staight on the bottom. To make this work you may have to cut the jambs on a slight angle.
    You wouldn't need to cut them.

    I know window jambs are square-cut, but shims are tapered. So when you shim those jambs, you have to use 2 shims, right? With a sloped sill, you'd only need 1. Just match the angle of the cripple to the taper of the shim you'll be using. Still not enough slope? Then cut your own shims.

    Tom
    1) Unconsciously Incompetent: He knows not, and knows not that he knows not. He is a fool. Shun him.
    2) Consciously Incompetent: He knows not, and knows that he knows not. He is simple. Teach him.
    3) Unconsciously Competent: He knows, and knows not that he knows. He is asleep. Wake him.
    4) Consciously Competent: He knows, and knows that he knows. He is wise. Follow him.

    May we all endeavor to progress from not knowing that we know not, to knowing that we know.

  7. #7
    Join Date
    Jun 2004
    Location
    portland, maine
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    713

    Default Re: Why Not Angle The Window Sill?

    Tom, windows shouldn't leak on a regular basis, but they all leak when the wind driving the rain is strong enough. Maybe you don't get strong storms there, but they seem to be increasing in frequency here. Do you trust your siding to hold out 100% of the rain or do you use a WRB? Windows leaked in the old days too, but the walls could dry out. With our new unforgiving construction methods we need to design in backup systems, such as sill pans.

    We've been trying different methods for sill pans, and have settled on making our own from coil stock, with a back dam, and sitting them on a strip of clapboard. We were already in the habit of making the openings taller than called for so we can make fine adjustments when setting the windows so that's easy enough. We use "set blocks" under the window jambs. Ideally they are tapered but depending on the window we usually don't worry too much about it, as long as it makes contact.

  8. #8
    Join Date
    Jun 2004
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    Lake Placid, NY
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    Default Re: Why Not Angle The Window Sill?

    A little off the topic, maybe, but maybe not. It relates to windows and leaking.

    I did some time in the commercial window biz, doing installations in high rises in coastal areas. All units, windows and doors, are set atop an element called a "water tank," which is essentially a big heavy sill pan with a dam front and weep slots.

    In full scale lab tests, pressurizing units from out and under heavy water spray, all to simulate heavy storm conditions, the units will take in water, but the water drains down into the tank, where it weeps out. The higher the pressure, the taller the tank needs to be, so that the head of water can overcome the pressure and get the weep drains to flow.

    Units, both windows and glazed terrace doors, up maybe 44 floors in a NYC hotel or condo, might have water tanks as tall as eight inches.

    So, yes, those windows will leak. Build and flash accordingly.

  9. #9
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    Sep 2004
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    down the shore
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    Default Re: Why Not Angle The Window Sill?

    Quote Originally Posted by tjbnwi View Post
    No reason why not to cut the cripple at an angle. As long as you can train your crew to [remember] do it.

    I believe the slope "add on" should be for retro fit where angling the cripples would not be feasible.

    I do agree with you on the water entry issue, if properly installed the water must be coming from the way the window is fabricated.

    Tom
    Cutting the cripples at an angle will slope the sill, but won't it also throw the front and rear face out of plane? Don't know if it is enough to matter that much, but for me it's easier to tack beveled siding on top.

  10. #10
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    Jun 2004
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    Friday Harbor, San Juan Island, Washington
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    Default Re: Why Not Angle The Window Sill?

    We install cedar bevel siding for slope on rough window sills. It's a lot faster than cutting any of the framing at an angle. Just remember to lower the rough sill height by 1/2" when framing, and don't drop the header.

    I have seen new construction windows leak twice in the short time I've been looking for it. I talked to an architect this morning about a particular brand of windows that he was interested in, he was referred to me by my window salesman who knows my concerns and installation methods. The architect says he needs to completely reframe a significant area of exterior wall in his 20 y/o house due to window leaks thru the units into the framing. TOTALLY preventable by a few extra minutes and dollars per opening.
    Bailer Hill Construction, Inc. - Friday Harbor, WA
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  11. #11
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    Default Re: Why Not Angle The Window Sill?

    Quote Originally Posted by mike maines View Post
    ... Do you trust your siding to hold out 100% of the rain or do you use a WRB?
    No, I do not think of siding as the means to keep out the rain, not at all. And yes, I always use a WRB. Claddings such as fiber cement siding will act as a first line of defense of course, but I believe the building should be weather-tight before the siding is applied.

    Tom
    1) Unconsciously Incompetent: He knows not, and knows not that he knows not. He is a fool. Shun him.
    2) Consciously Incompetent: He knows not, and knows that he knows not. He is simple. Teach him.
    3) Unconsciously Competent: He knows, and knows not that he knows. He is asleep. Wake him.
    4) Consciously Competent: He knows, and knows that he knows. He is wise. Follow him.

    May we all endeavor to progress from not knowing that we know not, to knowing that we know.

  12. #12
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    Default Re: Why Not Angle The Window Sill?

    A 5 degree angle on a 2x6 cripple will give you a rise of 1/2", which is probably about the same as using a piece of bevelled siding.

    At 5 degrees, the rough sill would indeed be out of plane... 1/16" on each side-- not enough to matter. I don't agree that it would take longer than installing a piece of bevelled siding. How could it? If you cut the cripples in a productive manner, using a slide saw with a stop for example, it would take no longer than cutting them square.

    So once that wall is framed with angled cripples, it's done. The extra time (and money) will be spent installing that bevelled piece of siding.

    I'm down with building in a means to direct the water out of the opening. I'm just trying to brainstorm a bit to explore the feasibility of cutting angled cripples to simplify the process.

    I'm going to try it the next time out, because it seems to be the most economical way of achieving that required slope.

    Tom
    1) Unconsciously Incompetent: He knows not, and knows not that he knows not. He is a fool. Shun him.
    2) Consciously Incompetent: He knows not, and knows that he knows not. He is simple. Teach him.
    3) Unconsciously Competent: He knows, and knows not that he knows. He is asleep. Wake him.
    4) Consciously Competent: He knows, and knows that he knows. He is wise. Follow him.

    May we all endeavor to progress from not knowing that we know not, to knowing that we know.

  13. #13
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    Jun 2004
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    Friday Harbor, San Juan Island, Washington
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    Default Re: Why Not Angle The Window Sill?

    I don't want the framing bulging in at the sill, even if it's 1/16". That makes it harder to get the rock flat and the trim flat. It may be slightly quicker to cut angled cripples but it may also make the trim-out more time-consuming.
    Bailer Hill Construction, Inc. - Friday Harbor, WA
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  14. #14
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    Nov 2006
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    trenton, nj
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    Default Re: Why Not Angle The Window Sill?

    Quote Originally Posted by gman396 View Post
    Anderson double hung jambs are staight on the bottom. To make this work you may have to cut the jambs on a slight angle. I have never heard of using a pan until I found this forum. And I never yet seen a builder use a pan or even tape yet on a new constuction window. This is in my area of Michigan. I know there are builders in this state that are up to date.

    Or if you were using a piece of lap siding to give you the pitch, you could cut a few 1" strips of the siding and install them on top of the 1st layer in the opposite direction and be back to having a level platform for your window to sit on.
    Brad

  15. #15
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    Northwest Indiana
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    Default Re: Why Not Angle The Window Sill?

    Quote Originally Posted by David Meiland View Post
    I don't want the framing bulging in at the sill, even if it's 1/16". That makes it harder to get the rock flat and the trim flat. It may be slightly quicker to cut angled cripples but it may also make the trim-out more time-consuming.
    I have read in JLC and at the road show it was stated that an 1/8" is acceptable for rough cutting/framing. So 1/16" is more than acceptable. Before you start, I think an 1/8" may well be a mile, just stating what I have read and what was stated. There are others here who will back up how I feel about this. It takes no longer to mark and cut it right than miss mark or cut it off mark.

    As to the 1/16" proud, nothing a block plane would not solve with a quick swipe.

    Tom
    http://chicagocraftsmen.org/2011/06/261.html

    Check with the AHJ, what we say doesn't matter.

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