Curious.
As I understand it, there are no “special” framing requirements in an exterior wall if a window is more than four feet from the corner of the structure. I beleive this is true as the four feet of sheathing provides adequate shear strength. However, I have been told that special hardware or techniques are required if a window is to be placed closer to the corner.
What type of special hardware or techniques are required? And sure they likily vary by state, county, etc. Just curious as to generally what is required.
Replies
Just a bump, here, 'cause it's a great question.....
There are a number of houses near me with "corner" windows (one on each side & a very small corner post), and it would be intweresting to know what SOP is these days...
I recall seeing framing with ply sheer sheathing at the corners, and insulation board sheathing in-between.
I'm not sure why the racking strengh has to be (or is preferable) at the corners.....
If you are using structural sheathing, and going for the smallest possible corner-post (we'll leave the glass cornered cases for another discussion!) then I guess the critical detail is how you tie the headers to the post....
I don't know why you need the shear strength in the corners either. Your point about tieing the corners and headers to teh corners does seem think it would be the rub, particularly if you don't want any wall area between teh window and the corner post.
My original thoughts were about windows perhaps three or so inches from the corner.
Still curious, any takers?
don't know why you need the shear strength in the corners either
It probably comes from the original Dade County (Fla) wind rules. IIRC, that was back when 60mph was considered a high loading. It was certainly back when a "typical" house had that "cape" look of only one window per room, centered on the room.
The wind resistance rules, and window-to-room design have both become more sophisticated.
So, the point is correct, the shear strength is not required in the corners, it just used to be simpler to apply to corners. as a whole sheet of plywood to a nailing schedule than inletting a 1x4 diagonal brace.
Of course, there are a number of places now, where engineering is needed to meet the lateral forces requirments per code.Occupational hazard of my occupation not being around (sorry Bubba)
Capn: Thanks, but could you be more specific?
ARe you saying taht if you have a window say with a few inches of a corner but have some "extended windowless" area in a wall on the other side of the window in which shealthing can add shear strength, that you generally do not need anymore "fancy" stuff in the framing in the corner?
Or are you saying that you do?
Or are you saying that you do?
Well, as a matter of fact, I'm not saying, either way. That's because the requirements vary by location something fierce. Each AHJ will also require different sorts of things for the engineering, stamps, etc.
Generally, though, you want some sort of racking resistance in a building's frame. If you cut open a corner with windows to take advantage of a great view (a perfectly reasonable thing to do), the bracing that might ordinarily be in that corner "ought" to occur in the wall somewhere else.
Now, how that's done will vary.Occupational hazard of my occupation not being around (sorry Bubba)
"If you cut open a corner with windows to take advantage of a great view (a perfectly reasonable thing to do)"Beyond taking advantage of views, the same window, placed in a corner (vs. the middle of a wall)--actually provides more light to the room (by about 10%). This results from closer proximity to a reflecting surface (adjacent wall).Put a couple of windows in the corners, in the same room, and the room will have noticably better day lighting (with less wall space taken by windows and less spent on larger windows).Two windows in the same corner lessens the effect a little, as do dark wall colors, etc..
the same window, placed in a corner (vs. the middle of a wall)--actually provides more light
LoL! True enough, I was more taking a jab at the "drafter designed" tract builder plans, where rooms just get a 3-0x4-6 SH in the middle of all walls, even if the only view is a wooden privacy fence 5'-0" away.
Occupational hazard of my occupation not being around (sorry Bubba)
"the only view is a wooden privacy fence 5'-0" away."Amazing how little thought goes into most projects. I did an addition last summer on a house with neighbors just 10' away. I suggested, for lack of a better term, a "whole wall transom window"--10' high wall with the top 3' just header and glass.It let in light, left usable wall space, for a desk, and yielded views of sky & trees. Almost like a skylight. Turned out nice. On the extra light from corner windows, I was amazed by that trivia when I first read about it 10 years ago (I'm easily entertained). I thought it would be good info for this thread.
"whole wall transom window"
Yeah, I've drawn & specified just that (even just fixed 18" transoms in a row, too); just never have quite convinced anyone to "pull the trigger."
All I need is the one for the photo . . .
All I need is a winnong lotto ticket, too . . . Occupational hazard of my occupation not being around (sorry Bubba)
"All I need is the one for the photo . . ."Here is a photo of that project. You can see through the framing the part of the view that we eliminated with the high window. Kinda cool.
Here in Alachua County, FL (North Central Florida) if we have a window less than 3-0 from an exterior corner we have to specially reinforce that wall segment. This can also apply to the walls on either side of a garage door if they are less than 3-0.
Engineers will go about designing their shear walls in different ways to meet the necessary strength requirements. One engineer makes us use southern yellow pine instead of spruce for the outside corners and kings of the header in a designated shear wall. Then we have to put a 2x12 at the top, middle and bottom of the wall in between the OSC and kind studs for the header.
Another engineer makes us run zig-zagged doubled 2x4 between the OSC and the kings in the shear wall segments. Other times we'll have to sheathe interior walls, anchor those walls to the floor and then tie the trusses into the interior shear wall.
Tim Uhler posted this link once, recommending this book. I've never read it, because I didn't buy it...but I know I should do both.
http://www.shearwalls.com/frm_main.html
Thank you. Excuse my ignorance, but what is OSC?
Sorry, I was abbreviating outside corner.
Just got off the phone with the county inspector before I got on here. I asked if we needed "hold downs" (like Simpson HT5 etc) on the corners. Nope,he said as long as the corner is 4 feet or wider. Fine with me. I dont see why you couldnt have good shear panels outside the 4 foot rule. What about those corner windows that dont have any post at all ? How does that work? By the way ,I have found articles regarding sheathing done vertically vs. horizontal. If you dont block ,vertical is stronger.
It's a Regional thing. Where I'm from you can frame 4-1/2" off the inside corners. I framed a house right across the street from the ocean and the wall was all doors with 4x6's in between using no hardware or special bracing.
What are the three foot round holes in the ceiling?
Nice birthday party, by the way. LOL!
Do you suppose the 4 1/2 inches you mentioned is to give you a full 10 inches (the 4 1/2 inche plus the 5 1/2 ajoining wall) to nail the top plates too, in order to tie the corners together?
"What are the three foot round holes in the ceiling?"Those were 5' diameter holes for three ceiling domes."Nice birthday party, by the way. LOL!'I don't know how that birthday picture got in there."Do you suppose the 4 1/2 inches you mentioned is to give you a full 10 inches (the 4 1/2 inche plus the 5 1/2 ajoining wall) to nail the top plates too, in order to tie the corners together?"No, that's just the way it laid out with the rough openings.Joe Carola
Did you frame that fancy place before or after the birthday party? Nice family!
I just finished a copy of the house shown in these pics. Each photo shows a room with casement windows coming both ways into outside corners. The mainfloor had six such corners, and the upper floor had two.
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All such window corners were framed with 4x4 TrusJoist Parallam posts outfitted into 2x6 wallframes. Solid headers were buttjoined above the posts, with the header end not bearing on the post fastened to the other header with an array of 1/2" through lagscrews.
The architect wanted the windows as close to the corners as possible, with a minimized post size between, thus the 4" post in a 6" wall. Look close at the pic in the bath tubdeck area and you can pick up the minimal trim at the corner, as compared to the between-windows mull trim adjacent.
The pics are of the prototype house, built in Stowe, VT. The copy we finished here is in Lake Placid, NY. Neither of these locations have codes requiring anything special at exterior corners for shear.
Pretty work, Mr. D......
So, how was the bearing header strapped to the post....and isn't lagging into end grain a no-no?
The attached CAD rendering should help explain how we did it.
The headers are not solid sawn timber, but instead are either two plies of either LVL or sawn lumber, or an engineered product like TrusJoist's insulated header. The TJM product is a sandwich of 1-1/2" LSL (laminated strand lumber, as is used in rimboard) with a rigid foam core. If we do it with LVL or sawn lumber we do a centerpack of rigid foam.
At the ends where we will want to lag in, we replace the last 10 inches of foam with a solid block of VG doug fir. We have a timberframer that's local that always has a nice pile of cutoffs outside his shop. That block has its grain vertical, so we are thru-screwing it into its faces and lagscrewing into its edge, thus no endgrain screwing happens.
The 2x6 cleats that run along the tops of the ROs adjacent the post have one which reaches out and sits atop the 4x4 corner, and it is lagged down into the PSL post. Two half-inchers are banged in with the impact gun, and I have no concerns about the integrity of this fastening detail
Handy drawing - how did you do that? - is it ACAD exported to .pdf?
Forrest
It's Cadkey 97, much like the ACAD of its same vintage. Print file exported to .pdf.
Gene,
Thank you very much for the post!
You said "Solid headers were buttjoined above the posts. . ."
Seems to be inconsistent? buttjoined but above?????????
You said "Solid headers were buttjoined above the posts, with the header end not bearing on the post fastened to the other header with an array of 1/2" through lagscrews."
What "other header"
If you look close at the .pdf file I attached to the earler post, and use the blow-up feature of Adobe, you can see that one of the two intersecting headers has bearing over the 4x4 post.
The "other header" is the one on the adjoining wall that butts to the header with post bearing.
Both headers are made "solid" at their ends with the insertion of a solid block of douglas fir. The pic shows how lagscrews bolt through the header with bearing into the endblock of the other header.
All these corners have hipped roof above, and so the load coming down onto headers is fairly minimal.
The pic, as is typical, was worth a thousand words.
I just started trimming a house in East central Florida. The corner of the living room has 12' of sliding glass doors on adjacent walls that meet diagonally at the corner. Three panels on each side slide into pockets on the pool deck leaving the entire corner open. It is awesome but I don't know how they engineered it. There is a second story above this with a balcony too. I'll get some pictures tomorrow and post them.
In the rocky mountain region the most common sheer pannel is simply well-nailed osb or plywood. To meet the codes around here a house has so have so many feet of sheer panels on each wall, depending on the local wind directions and structure of the house. Wide sheer pannels don't always need special attachement to the foundation, but sometimes do.
When a wall has a lot of windows, or is supporting a second floor, we usually have a threaded 5/8" rod epoxied in the foundation passing up through the floor and attaching to a special metal bracket in the wall that connects the threaded rod to a pair of studs in the wall on each side of the sheer pannel with 30+ 16d nails.
A quick look through the online simpson catalog will show you a dozen different connectors and methods that are used for sheer pannels.
trout:
Thanks. I have enjoyed and found all the posts here useful, but your post was what I was orignially wondering about. Not that I would ahve any desire to haslle with that method.
...your post was what I was orignially wondering about.
I figured that was where you were headed. :-)
What you are suggesting makes good sense, however,
>> I have been told that special hardware or techniques are required if a window is to be placed closer to the corner. << (than 4')
Not a code requirement here in NC, nor required by any building jurisdiction that I build in (there are 3) or by any building inspector I have had. May be required in costal counties - don't know - don't build there.
The pictures that Gene Davis posted might be an exception because those windows are really close to the corner. IN a case like that I would expect special engineering to be required (here).
The attached picture is of a master bath. I'd say at least 20% of the houses being built in NC today have something similar - with no special bracing requirements. BTW - I sheath with all structural panels, so I'm not concerned about rack resistance with the houses I build.
Here is another thought that as bothered me for some time: How can a screened porch with full screen walls like most have, or open porch, ever have adequate rack resistance on the "wall" panels? pic attached (next post)
Edited 5/9/2006 7:56 am ET by Matt
Edited 5/9/2006 7:59 am ET by Matt
Here is the 2nd pic
I suppose the issue with a porch like the one you posted a pic of, is that it is tied into the main structure of teh house via the beams. The house is the shear strength.
Great point about the open or screened porches!!! And in those case you have a hugh wind catcher which I think would make those structure particularly vulnerable to the wind!
Beautiful bath, by the way.
SIDE BAR: Do you have a picture of the top casing to those windows? Or is teh top casing the same as teh sides and mitered in?
>> Do you have a picture of the top casing to those windows? Or is teh top casing the same as teh sides and mitered in? <<
No I don't have another pic of those windows, but may have some others. Yes, the casing is mitered at the top. I'm having a brain f@#% and can't think of the model number of the casing but it is 1 1/16" thick x 3.5" wide. Really, next time I want some upscale casing, I'll probably select a different model number - that one had a problem because the center section is so thin, it tended to cup.
Here is a pic of the same casing only with backband applied to make the build-up bigger and a pediment on top. I told the HO that we needed to make the openings lower as it would be too close to crown even with 10' celing, but he wouldn't listen to me. Oh well - it was his money and he lives there.
doright... the requirement varies depending on either your seismic zone, or your wind zone
in our zone ( coastal RI ) we are zone 2.. 110 mph .. the 4' stud in from each corner has to be doubled, and any horizontal edges have to have 2x solid blocking
if a window is within the 4' area , but no closer than 2' then the 8' stud has to be doubled
if the window is closer than 2' to the corner, you need a Structural PE to design a cure... usually involving continuous LVL headers interlocking the corners, with either threaded rod tie-downs or special Simpson hardware.. or a pre-engineered shear panel
the next zone 3 miles south of us is 120 mph... much stricter in terms of requirements
Just by coincidence, there is an article in this month's JLC showing an engineered steel moment frame around a two story garage front. Side walls are a few inches wide with the maw of the garage door between.
Always more than one way to skin a cat.
What irritates me a little is the general requirement that shear resistance always be in the corners. That may be the best place to put it but not nearly the only place.
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