Ok, so let’s say collar ties installed in upper 1/3 of roof help keep ridge tied all together nice and strong. This in some small way probably does help with wall spread, but not entirely. Anyway, then if you *had* to use cross ties as a means of preventing wall spread in vaulted ceiling, but also wanted to keep that open look as much as possible, how would you guys do it??
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Depends on the building style. Steel cables or steel rods, or even chain.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Someone would have to evaluate the situation.
Lots of things to consider - The loading requirements, pitch of the roof, wall to wall span, height of the horizontal member, species and grade of framing material, etc.
Well, From what I've been reading, it seems that you could use cross ties every 4ft at plate level as a bare minimum.
Do you mean that you "could use" them or that you NEED them?Every situation is different.
Here lies one who knew how to get around him men who were cleverer than himself. [tombstone of Andrew Carnegie]
Need them.
Well, like I said earlier - It depends completely on the situation. If you're stick framing a house in Michigan with a wide span and a low pitched roof, it's a heck of a lot different than one in Arkanses that's a short span and high pitched roof. It needs to be considered on a case by case basis.
Hope to the end. [I Peter 1.13]
rakuz66
Scissors braces, buttress braces, Hammerbeams, or King posts.. come quickly to mind but then I have my own perspective on things..
Well, I believe that the code has changed in that rafter ties must now be used on every rafter pair, where it used to be every 4 ft minimum???
Situation is 15 x 22 ft garage that the owner wants an open ceiling but can't use a ridge beam. I thought that ceiling joists every 4 ft( maybe double them) nailed to rafters would satisfy code and tie outside walls together.
Why can't you use a ridge beam?
Situation is 15 x 22 ft garage that the owner wants an open ceiling but can't use a ridge beam. I thought that ceiling joists every 4 ft( maybe double them) nailed to rafters would satisfy code and tie outside walls together.
Which is the ridge dimension? What is the roof pitch?
If the rafter ties go in the 15' dimension, then you might be able to get away with this with a steep roof. Just make sure there's at least doubled top plates and that there are no plate splices in between rafter ties.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
roof width is 22 ft - overhangs= 21 ft. 11 ft from plate to ridge. Building length is 15 ft. There is a partition wall 8 ft out from outside wall to splice ceiling joists.
roof width is 22 ft - overhangs= 21 ft. 11 ft from plate to ridge. Building length is 15 ft
Hip roof why no structural ridge?
Or is this a spiffy deal like a 4/12 meaning no room for the structure?Occupational hazard of my occupation not being around (sorry Bubba)
You can utilize a structural ridge beam and eliminate any need for collar ties. This is not entirely a code issue. Much of this is dependent on what your engineer will approve.
Bruce
rafter ties
Caution, Terminoloy alert.
"Rafter tie" is not equal to "collar tie" (different thirds of the rafter 'triangle').
This can cause the discussion to break down no small end.Occupational hazard of my occupation not being around (sorry Bubba)
This can cause the discussion to break down no small end.....
you say that like that matters......
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!Forget the primal scream, just ROAR!!!
What I learned today. Roof slope has a lot to do with cross ties. The lower the slope, the less thrust placed on the outside walls, ( more on the rafter) the higher the slope, the more thrust on the walls, and less on the rafter. Ergo: engineers. And I'm ok with what I plan( cross ties 4 ft on ctr in a 15 ft span.)
You have it backwards.
The amount of thrust on walls increases geometrically as the roof slope diminishes.
Tension on Rafter Ties<!----><!----><!---->
T= W (L x OC x Load) x Span / 2 Rise
View Image
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 2/26/2008 3:14 pm ET by Riversong
How does that equation work?? Here's my data. 11 ft from wall to ridge. 5/12 slope. 60 lb live load. 24 in on ctr.
11 ft from wall to ridge. 5/12 slope. 60 lb live load. 24 in on ctr.
If you're saying 11' rafter span (horizontal), and 4'-7" rise. 60 psf live load and let's assume 10 psf dead load...
Tension = (70psf x 2' x 11') x (11' /2 x 4.58') =
= 1540 lbs x 1.2
= 1849 lbs (this is tension of ceiling joists/rafter ties at walls)
Here's a more straitforward diagram (but the nailing schedule is for 30 psf live load):
View Image
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 2/26/2008 6:56 pm ET by Riversong
Ok, thanks. Now what does that mean in laymens terms?? The 60 lb live load is only during winter, and that seems an awful lot of tension.
Riversong,
Your graphs help a lot. Do you have one showing collar ties on a Grambrel roof? The second story rafters are 16" OC, 10'-6" from the plate to the ridge beam and the total width of the second floor roof is 16' and 32' ft. long.
I'd like to have an 8' ceiling.
Thanks,
Bill
Edited 2/26/2008 8:56 pm ET by BilljustBill
The gambrel is already self-supporting. If you want to add ceiling joists, they just need to be sized for the ceiling load and the span.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
I follow you so far, but didn't you forget to divide 1849 by 2 H?? The example shows T = W x L / 2 H. Which would be W (1540 ) x L (1.2) = 1849. Shouldn't 1849 then be divided by 2H??
My bad, I got it, 1849 looks correct.
Riversong, here are a few pics of my nailing on rafter to ceiling joist connection. This is a vaulted ceiling in a camp. I used 2 (2x10) cross ties every 4 ft to stop rafter/wall thrust. I will eventually box in the 2x10's.
[IMG]http://i275.photobucket.com/albums/jj296/rakuz66/DSC00360.jpg%5B/IMG]
[IMG]http://i275.photobucket.com/albums/jj296/rakuz66/DSC00361.jpg%5B/IMG]
[IMG]http://i275.photobucket.com/albums/jj296/rakuz66/DSC00370.jpg%5B/IMG]
That looks like it ought to do the job. Plenty of nails and the rafters look like they're gussetted to the studs with plywood.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Can you fix those pics? They seem not to be working...
Correxted pic links:http://i275.photobucket.com/albums/jj296/rakuz66/DSC00360.jpghttp://i275.photobucket.com/albums/jj296/rakuz66/DSC00361.jpghttp://i275.photobucket.com/albums/jj296/rakuz66/DSC00370.jpg
I need brain surgery like I need another hole in my head.
Bosshog, thanks for helping with those pics. What did I do wrong on the original post of those pics?
I'm not exactly sure what happened - You may have used the wrong link from Photobucket. Your first link looked like this:http://i275.photobucket.com/albums/jj296/rakuz66/DSC00360.jpg%5B/IMGI just took offf the "%5B/IMG" so it looked like this:http://i275.photobucket.com/albums/jj296/rakuz66/DSC00360.jpg.I do know that the "[IMG]" thingy doesn't work on BT.....
How did the man who invented cottage cheese know he was done?
How did you take the "img" thing off?
I right clicked on the links, and picked "Copy link location".Then I pasted it into my browser and figured out what it would take to make 'em work.
Successful people form the habit of doing the things failures don’t like to do
"Bosshog, thanks for helping with those pics. What did I do wrong on the original post of those pics?"
Since the [IMG] tag doesn't work on this board, it ignored the opening tag, but asssumed the closing [/IMG] was part of your URL that you typed in, since there was no space between .jpg and [/IMG]. So when someone clicked on the link, it tried to open an image titled *.jpg[/IMG] - which didn't exist.
Shawn
Well, what do you think??? Stable enough to stop rafter/wall thrust. Wall span is only 15ft.
i think it will easily work, but it's too busy
can you run the calcs with the ties every 6' ? and how does that work for the ceiling layout ?
View ImageMike Smith Rhode Island : Design / Build / Repair / Restore
Mike, I'm not educated on calculating spans, etc. I plan on boxing in those c,joists to make them look like beams. I guess if I really wanted to I could somehow find out if I could span 6 ft, but a PE came out and said it was more than enough to keep walls from spreading, so I'm letting it go. BTW, this was a repair job on vut trusses, that's why I kinda "overkilled" it.
cut trusses. If you look at the rafter to the extreme right, you can see the 2x4 top chord of the old truss.
You can use an LVL or steel ridge beam or you can use a fir 6x8 every 4-6 feet on the top of the walls. You can leave the 6x8 beams exposed or wrap them in pine/trim or sheetrock.
create a scissors with the ceiling pitch less than the roof pitch and get an engineers input
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