Hi all,
Can someone educate me on window sill height? I have some very big windows going into my house and want to know the minimum window sill height that is allowed by code. These are non-egressable windows. I’m sure there should be more to this question but I don’t know enough to ask more. Am I missing something else here?
I seem to recall something about 18″ or so and the windows having to be safety glass. Is this correct? So, if that’s the case, I could have windows all the way to the floor as long as they have safety glass?
Thanks for the help
Rob Kress
Replies
Not sure where ya live, but if it's MA then you got it right on. 18" from finish floor to glass is the minimum. Anything lower has to be tempered glass. As long as it's tempered, yes, you can run 'em floor to cieling.
There's a number of factors that go into the equation - the 18" height is one. If a window is within a certain distance from an exterior door, square footage of glass (I believe over 9 it must be tempered). I don't recall the distance from door, only that mine is separated from the door by four studs, ergo, tempered glass. But yes, if it's tempered, your base and case can kiss each other goodnight.
"The child is grown / The dream is gone / And I have become / Comfortably numb " lyrics by Roger Waters
You haven't described any of the structural nature of your project...
If this is a remodel and you're working outside of an approved set of plans, you would be wise to ensure that your large window openings are not compromising any shear values or other structural factors in the wall(s).
Otherwise, to your question, the other guys have nailed it.
Thanks for the responses guys.
Notchman.... this is my house that I am building. And yes, I have considered what these large windows may do to my wall strength and have taken appropriate steps to beef up the walls (2x6 studs and mamoth headers). Thanks for chiming in.
Rob Kress
2x6 and headers don't do much of anything for shear, and only a little for wind, unless studiously applied. Some window manufacturers can help with design and load values for wind. Unless done right, a whole window wall can be a sail on a windy day, flapping in the breeze..
Excellence is its own reward!
Piffin,
Can you please go into more detail about shear. Yes I do have a lot of window in the wall. No, they are not floor to ceiling but they are big. I did have an architect make up the plans. And I am not a complete solo job here building a house (or completely unknowledgeable). I have a complete gang of qualified professionals working with me on the project. But of course I don't know everything (I haven't had enough years in the trades to see so many things).
I would like to know more about shear though..... Do you mean racking of the wall? I can understand what you mean when you say that the windows can become one big sail in heavy winds. Luckily, I am loaded with trees on the lot and it doesn't seem to get that windy at the back of the house where the windows will be.
Thanks for any more advice.
Rob Kress
Well, let me dream up a little primer here.
Have you ever seen one of those small one car garages from about 1920-1940? The kind where it has gable roof over the end with the gargae door and that door takes up nearly the entire end wal of the little garage?
Remember how the place is leaning one way or another?
That is because the little bit of wall space on either side of the openning is insufficient to resist racking from lateral forces of wind on the walls or uneven stresses of snow loading on the roof transmitted throgh the structure.
The back wall often remains squared up and plumb while the front end wal shears.
When we build most residential frame houses, we use at a minimum a 4x8 osb or plywood at all corners to preven this racking. When foam is used instead, metal angle bracing is let into the framing. An older method was to let in a 1x4 at corners.
None of this counts for squat in seismic zones like California or some hurricane locations where engineered shear panels are part of the package.
For you, this means that the windows do not provide shear resistance. If the entire wall is a window wall, special metal hardware at wood connections is one way of overcoming the problem. If you have four feet or so of solid wall on either corner and don't live in a seismioc or high wind location, you are probably OK.
Excellence is its own reward!
If, you are planning on running your windows down tight to the floor, then, I would make certain, that you have proper flashing around those windows. then of corse, I know that you would want proper flashing, regardless of their height. Best of luck Jim J
Potentially, the windows can run from the common head height (where ever you have set that), to the height of the base board plus the height of the window apron (or just the base, if you want).
In some (many) juridictions, that will then require a window with some sort of "safety" glass (tempered, laminate, whatever). Like as not, when you get to the 6' or so heights in the window tables, the manufacturer has already specified safety glass in those units, as most applications would require that.
It's your house, if you like tall windows, use them. There are considerations, but, that's also part of both design and construction. Ok, in some places, you may need to glue & screw plywood over the outside of the studs to get proper stiffness (i.e., shear strength). Not that unusual, similar things happen when a person wants a wide, short row of windows, too.
This presumes some things, too. Like we are not talking about a wall of 4-0 x 6-0 at an 8" sill ht. with a 4-0 x 6-0 transom over . . . (I've seem on too many plans with a far too casual note of: "Balloon frame Wall" grrrr)
Capn,
Can you go into a little more detail please?
>>>>>Ok, in some places, you may need to glue & screw plywood over the outside of the studs to get proper stiffness (i.e., shear strength). Not that unusual, similar things happen when a person wants a wide, short row of windows, too.<<<<<
This is some more about that shear stuff that I don't know anything about yet. But I'm learning.
Rob Kress
A large window in a wall is pretty darn good looking.Remodeling Contractor just outside the Glass City.
Quittin' Time
Indeed!
Can you go into a little more detail please?
Sure, some will reiterate what Piff has already stated.
The old "Dade County" rules require a let-in diagonal brace in the corners for additional stiffness that prevents racking of the entire wall. An alternative is to apply 1/2" plywood in the 4 feet closest to the corner. The wind resistance (and/or shear) rules usually specify a fastener schedule--nails or screws at X distance, which sometimes also requires glue. In seismic areas, codes may also require metal strapping. OSB can be used, if its strength exceeds that of equivalent plywood, in some (most) juridictions.
Worst example I can think of was an 18' wide wall with three 4' wide, 6' tall windows. each with a 6' "transom' over it (this in an 18' high wall). Whoever had drawn the plans had left a generous 3" between the finish jambs, too. Calling the wall out as 2x6 balloon frame wall did almost nothing to help the rigidity of the wall--in any of the directions.
That wall probably ought to be built like an odd-sized garage door, with a continuous header across all three windows. That has the best success for even creating shear strength in the wall. The envelope strength (pushing the wall plane in and out) is even more suspect. (Doubt that the spec builder worried about these considerations.)
Once again, the real question is: What do you like/want/need? If you like a narrow, tall window, then that's what you should have. After that, it's just a consideration of engineering.
Hope that helps. If not ask more questions.Occupational hazard of my occupation not being around (sorry Bubba)
Capn and Pif,
I totally get what you guys are talking about. You are talking about the wall racking under load. Yes, indeed I understand that the exterior sheathing has everything to do with the wall not racking or shearing. And again, I have to apologize for not being so clear as in the other post...... It is really not an entire wall of window. There is a lot of glass but the sill height is near 20 inches. Plus I do have plywood on either side of the windows (though in this case it seems like more is better).
I think I will check out some of the metal strapping options as well. That seems like almost nothing to do to add a measure of insurance to the wall integrity.
Thanks again for the advice.
Rob Kress
It is really not an entire wall of window.
I kind of figured that, but some of the previous posts had reminded me of a potential failure point in a mcmansion <g>. The example sticks in my mind, too, as it is a perfect example of "lateral forces" effects on a wall that are less-than obvious. That 18' tall wall probably needs to be in 2x8 or 2x10 framing to give rigidity perpendicular to it's face. The poor detailing leaves little in parallel to the wall rigidity, either (not that being next to a hip-gabled end wall will help much, either).
Back in the seventies, coming up, I worked with an old framer. He always doubles the king studs when ever the window was taller than it was wide. As 2-0 x 5-0 SH windows were very popular, this made for an odd looking detail at times. Especially with the windows upwards of 6' apart.Occupational hazard of my occupation not being around (sorry Bubba)