PDA

View Full Version : Colar tie bracing



mathew stouffer
03-09-2008, 02:53 PM
Any suggestions on this attic. Do color ties >than 8 feet required lateral bracing and is this the correct method for anchoring ties to TJI's. Any suggestions would be helpful.

Thanks

Jerry McCarthy
03-09-2008, 03:07 PM
This maybe be helpful?

MaMa Mount
03-09-2008, 03:22 PM
Thats someone who has more money than good sense. Why would they use TIJ's for roof rafters?
They have probably damaged them with all of the nailing used.
I would call it our to be investigated by a SE.

Jerry McCarthy
03-09-2008, 03:27 PM
Additional info:
IRC-2006 (all new section in 2006)
R802.3.1 Ceiling joist and rafter connections; Ceiling Joists and rafters shall be nailed to each other in accordance With Table R802.5.1(9), and the rafter shall be nailed to the Top wall plate in accordance with Table R602.3(1). Ceiling Joists shall be continuous or securely joined in accordance With Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building when such joists are parallel to the rafters.
Where ceiling joists are not connected to the rafters at the Top wall plate, joists connected higher in the attic shall be Installed as rafter ties, or rafter ties shall be installed to provide a continuous tie. Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Rafter ties shall be a minimum of 2-inch by 4-inch (51mmby102mm) (nominal), installed in accordance with the connection requirements in Table R802.5.1 (9), or connections of equivalent capacities shall be provided. Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practices.
Collar ties or ridge straps to resist wind uplift shall be connected in the upper third of the attic space in accordance With Table R602.3 (1). Collar ties shall be a minimum of 1-inch by4-inch (25 mm by102 mm) (nominal), spaced not more than 4 feet (1219 mm) on center.

Jim Luttrall
03-09-2008, 04:01 PM
Good info Jerry, thanks for posting.

mathew stouffer
03-09-2008, 04:17 PM
Jerry,
Thanks. That diagram was helpful and easy to understand. Sounds like the lateral bracing is missing. I am still not 100 percent sure if the colar ties have been properly secured to the rafters. Is it ok to nail into the joist chords.

Jim Luttrall
03-09-2008, 04:41 PM
http://www.apawood.org/pdfs/managed/D710.pdf?CFID=7110546&CFTOKEN=16395633

Try looking at these standards. There are many similar connections showing nailing in both the web and top and bottom chords.

Bottom line, I think they need stiffener plates between the I joist and the rafter tie.
I would love it if I could just see any sort of rafter tie.
I am just waiting for some of these fancy new McMansions that leave out the rafter ties to collapse in a big wind.
Last house I called it out and the builder said that rafter ties are not required... I told my client to get a letter from their engineer stating why it was exempt from the building code.
Unfortunately, the AHJ's seem to not understand or care around here.

mathew stouffer
03-09-2008, 04:55 PM
Thanks for the responses.

mathew stouffer
03-09-2008, 05:27 PM
Jim,
Thanks for that link, very informative and easy to understand. I see what you mean by the ties, looked like they skimped out on the size used.

Mat

Jerry Peck
03-09-2008, 06:59 PM
Bottom line, I think they need stiffener plates between the I joist and the rafter tie.

Go to page 30 on that link, the photo shows similar "backer blocks" installed where the collar ties are nailed to the I-joist.

Michael P. O'Handley
03-09-2008, 07:33 PM
Hi,

If you look closely at the photos, there are web stiffeners between the sides of the rafter ties and the center web of those I joists.

Frankly, I don't understand why they bothered with the rafter ties at all. I don't see them used with TJI's around here. Those can probably handle the weight without them. Seems like overkill.

ONE TEAM - ONE FIGHT!!!

Mike

mathew stouffer
03-09-2008, 09:31 PM
Mike,
My guess is for heavy snow build up on the roof. We have had a bad winter and I have seen snow depths in excess of eight feet on some roofs this winter. A lot of the second homes don't have snow removal on the roofs because the owners are unaware of the build up of snow.

Mat

Jerry Peck
03-10-2008, 05:53 AM
Matthew,

Would you update your profile to include your state?

Location: park city (is in what state?)

mathew stouffer
03-10-2008, 07:16 AM
Jerry I though everyone knew where park city is. It's in Utah, you know, Mormons, funny drinking laws and lots of snow.

Gunnar Alquist
03-10-2008, 08:29 AM
Wait!!! Something Jerry didn't know????

Amazing!:D

Ken Amelin
03-10-2008, 11:04 AM
Jerry,

Thanks for the pictures and reference to IRC- 2006, R802.3.1.

After reading both, I still have some confusion over the requirements for collar ties.

The sketch you provided shows ways to reduce span, - no problem, makes sense as a sizing economy issue but not a requirement

I might be confused, but the way I am reading - IRC - 802.3.1 sounds like if you have continuous ceiling joists attached to the rafters, then collar ties are not required. The last sentence says for wind uplift resistance install them blah-blah-blah, but doesn't say they are necessary.

Can you tell me when are collar ties are required?

We have tons of 70 ranches that are 4/12 pitched no collar ties but continuous ceiling joist rafters ties.

Thanks

Jerry Peck
03-10-2008, 11:31 AM
I might be confused, but the way I am reading - IRC - 802.3.1 sounds like if you have continuous ceiling joists attached to the rafters, then collar ties are not required.


Ken,

Not 'that Jerry' but I believe you are confusing two things: "collar ties" and "rafter ties".

This: "if you have continuous ceiling joists attached to the rafters, then collar ties are not required".

Should read like this: "if you have continuous ceiling joists attached to the rafters, then RAFTER ties are not required".

I believe that is where your confusion is coming from.

Collar ties are up in the upper third and are intended to help tie the ridge together into a triangle.

Rafter ties are in the lower third to help keep the rafters from spreading apart (which is also what ceiling joists do when continuous from rafter to rafter).

Michael P. O'Handley
03-10-2008, 11:46 AM
Ken,

Not 'that Jerry' but I believe you are confusing two things: "collar ties" and "rafter ties".

This: "if you have continuous ceiling joists attached to the rafters, then collar ties are not required".

Should read like this: "if you have continuous ceiling joists attached to the rafters, then RAFTER ties are not required".

I believe that is where your confusion is coming from.

Collar ties are up in the upper third and are intended to help tie the ridge together into a triangle.

Rafter ties are in the lower third to help keep the rafters from spreading apart (which is also what ceiling joists do when continuous from rafter to rafter).I seem to recall some research years ago that showed that a "collar" tie was pretty much a waste of material and does nothing to reinforce a structure; that rafter ties do.

OT - OF!!!

M.

Jerry McCarthy
03-10-2008, 12:04 PM
EC Jerry is of course correct and I'll add some diagrams under the premise that one picture is worth a thousand words.
Download if you wish and anybody out there remember cutting a roof with only the aid of a framing square? I suspect you can add that to the growing list of lost construction skills? :confused:

David Banks
03-10-2008, 12:08 PM
I seem to recall some research years ago that showed that a "collar" tie was pretty much a waste of material and does nothing to reinforce a structure; that rafter ties do.

OT - OF!!!

M.

This from Jerry M's IRC-2006 (all new section in 2006)
R802.3.1
Collar ties or ridge straps to resist wind uplift shall be connected in the upper third of the attic space in accordance With Table R602.3 (1). Collar ties shall be a minimum of 1-inch by4-inch (25 mm by102 mm) (nominal), spaced not more than 4 feet (1219 mm) on center.

Appears to be for wind uplift more than anything else.

mathew stouffer
03-10-2008, 01:03 PM
Buyer freaked out about the attic and now want an SE to look at it....let you know what happens.

Ken Amelin
03-10-2008, 01:09 PM
Thanks all for the added clarifications.

I know the difference between a rafter tie and a collar tie, I just don't know when collar ties are required.

Can you folks help me with that one?

David Banks
03-10-2008, 02:36 PM
Thanks all for the added clarifications.

I know the difference between a rafter tie and a collar tie, I just don't know when collar ties are required.

Can you folks help me with that one?

Ken. I see no requirement for collar ties in the new State Building Code put out end of last year. It is based on 2003 IRC with amendments.

Jerry Peck
03-10-2008, 04:14 PM
anybody out there remember cutting a roof with only the aid of a framing square?

Yes, but, as you said, that's a "lost construction skills" on my part too. Do you still remember how?

Looking at those collar tie angle cuts at the 'top chord' of the I-truss and whoever cut those can't even use a Speed Square, much less a sliding T-bevel.

Jerry McCarthy
03-10-2008, 04:15 PM
Yep, I agree, check which code your state has adopted and that's what your inspection road map should be.

IRC - 2006
R802.3.1 Ceiling joist and rafter connections: Ceiling joists and rafters shall be nailed to each other in accordance With TableR802.5.1 (9), and the rafter shall be nailed to the Top wall plate in accordance with TableR602.3 (1). Ceiling Joists shall be continuous or securely joined in accordance With Table R802.5.1 (9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building when such joists are parallel to the rafters
Where ceiling joists are not connected to the rafters at the top wall plate, joists connected higher in the attic shall be installed as rafter ties, or rafter ties shall be installed to provide a continuous tie. Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Rafter ties shall be a minimum of 2- inch by 4- inch (nominal), installed in accordance with the connection requirements in TableR802.5.1 (9), or connections of equivalent capacities shall be provided. Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice.
Collar ties or ridge straps to resist wind up lift shall be connected in the upper third of the attic space in accordance with Table R602.3 (1). Collar ties shall be a minimum of 1-inch by 4-inch (nominal), spaced not more than 4feet on center.

Jerry McCarthy
03-10-2008, 04:20 PM
Jerry P, Can I still use a framing square? No doubt rusty I be, but I don't believe I've forgotten roof or stair stringer layout employing a framing qsuare. :o

Jerry Peck
03-10-2008, 04:21 PM
I seem to recall some research years ago that showed that a "collar" tie was pretty much a waste of material and does nothing to reinforce a structure; that rafter ties do.

The only way the rafter ties reinforce the structure is to keep the walls from spreading out (which is their purpose).

The collar ties, on the other hand, are there to triangulate the ridge / rafter area for strength, the higher the collar tie the better at keeping the rafters together at the ridge (with some loss of triangulation versus having the collar ties lower, of course, though, there are usually not enough nails in the collar tie / rafter connection to do a lot for the maximum triangulation effect).