ICC - International Code Council
 
Cart                                                                   
Skip to main content
 
Membership

Your ICC Account

Email:
Password:
Bookmark and Share
Green Building Certification

Codes & Standards Discussion Forum 

Welcome to the ICC Codes & Standards Discussion Forum

The Code Council has revisited how best to provide an online, professional Discussion Forum and area within the website that has a sense of community – where Members and nonmembers can provide input and exchange ideas with their peers in the industry. The new Codes & Standards Discussion Forum does just that, as it allows Registered Website Users and ICC Members to discuss the I-Codes in an online community.

Members Area Codes & Standards Discussion Forum

Note to Nonmembers: If you join the ICC you can have access to important building safety information!

Members Area Codes & Standards Discussion Forum

As an ICC Member, you have access to the Members Area of the Codes & Standards Discussion Forum. Follow the link to discuss the Membership Councils and other benefits of being an ICC Member.


20 post(s) First 1 2 > Last
Search 
Rafter to Ceiling Joist connection
This forum is under moderation. Your reply will appear when it is approved.
Re: Rafter to Ceiling Joist connection By  ToolguyinDE

Posts: 0

10/25/2006 5:31:00 AM

Here''s what I would do. Put up your TJI''s. Wrap the ends with a band board and plywood the whole thing (flush with your wall sheathing. Place a 2X4 at the outer edge of your rafter tails and cut the appropriate birdsmouth. Connect your rafters with a hurricane clip on each rafter. (Now you just got back your height). If you set your rafters next to your TJI''s on the top of your double wall plate, I''m afraid you''d have to cut them back too far and you''d weaken them.
You will have to use a ridgebeam, but remember to make it 1 demention larger than your rafters. Also by doing it this way, you have more insulation to help with ice damming.


   

Re: Rafter to Ceiling Joist connection By  Uncle Bob

Posts: 0

10/25/2006 6:05:00 AM

Hurry, before the 2006 comes into effect; change number 4,001; 2003; R802.3.1 allows "SUBFLOORING" attached to the rafters; to be used to provide a continuous tie across the building. Check Simpson strong-tie for connectors. 2006 IRC changes that.

Have not had my tea yet; I may be wrong.

Rosso


   

Re: Rafter to Ceiling Joist connection By  engineerguy

Posts: 0

10/25/2006 8:39:00 AM

I don''t know about particular code sections, but what toolguy is proposing is how it''s commonly done. I don''t know why you need a ridge BEAM though (is this an IRC thing?), a ridge BOARD should be fine (2x covering the full depth of the rafter cut).


   

Re: Rafter to Ceiling Joist connection By  tsmith

Posts: 0

10/25/2006 9:34:00 AM

2003 IRC allows subflooring or metal straps to be used to tie the ends of the rafters together. This is required when the joists are not parallel with the rafters, but there''s nothing to prevent the same method from being used when the joists are parallel. You could also use 1x4 crossties. It''s very apparent that the whole intent of R802.3.1 is "to provide a continuous tie across the building" between opposing rafters. If this is the case, then a nominal 1x ridge board can be used.

engineerguy, the residential codes (IRC and CABO) have always required the ridge to be designed as (or supported by) a "beam" or "girder" whenever the rafter tails aren''t tied together in this sort of manner. The idea is to prevent the walls from spreading apart due to the rafters'' thrust. It will be quite a beam, too, since it has to be stiff enough for the rafters to hang from, thereby supporting half the roof''''s area. For a garage of this size, without the rafter/joist tie, it''s not unusual to see a 3-1/2" x 18" LVL specified.


   

Re: Rafter to Ceiling Joist connection By  constructionarbitrator

Posts: 0

10/25/2006 10:22:00 AM

Weyerhaeuser has bought out TrussJoist but you may want to consider the original open web joist instead of I Joists, they drop down into your building instead of sitting on the plate. Weyerhaeuser is moving them to commercial since residential is usually price driven, but the higher quality is worth the difference in price.


   

Re: Rafter to Ceiling Joist connection By  engineerguy

Posts: 0

10/25/2006 11:25:00 AM

tsmith - thanks for the reply. I understand the tied vs. not tied logic and when ridge beams are required. I guess my question is, in IRC, is having parallel joists and a sheathed floor all the way across and the rafters hurricane clipped to it not acceptable for a no ridge beam situation??


   

Re: Rafter to Ceiling Joist connection By  Uncle Bob

Posts: 0

10/25/2006 1:29:00 PM

Engineerguy,

2003 IRC:

R802.3 Framing details.
Rafters shall be framed to ridge board or to each other with a gusset plate as a tie. Ridge board shall be at least 1-inch nominal thickness and not less in depth than the cut end of the rafter.

1 X or gusset plates are good to go; and yes the flooring or strap across the top of the ceiling joists makes the tie good.

R802.3.1
Where ceiling joists or rafter ties "ARE NOT PROVIDED" at the top plate, the ridge formed by these rafters shall also be supported by a girder designed in accordance with accepted engineering practice.

Rosso


   

Re: Rafter to Ceiling Joist connection By  tsmith

Posts: 0

10/25/2006 1:35:00 PM

engineerguy, I think that code section is poorly written in the IRC.

It describes nailing rafters to ceiling joists and top plate as a method of tying the rafters in a parallel-joist situation, as if this were the only way to accomplish it. Then it goes on to describe a much looser and broader range of solutions for tying the rafters if the joists are not parallel. I can''t imagine why these other methods would not be equally acceptable for parallel joists too.

The requirement for a ridge "beam" simply says:

"Where ceiling joists or rafter ties are not provided at the top plate, the ridge formed by these rafters shall also be supported by a girder designed in accordance with accepted engineering practice."

A ridge "beam" is only required when the rafter ends are not tied at their ends. When the rafters are tied across the building in the manner you describe, I can''t see why it would make any difference which way the ceiling joists run.

Since it''s so badly worded, a specific design solution might need to be run past the local officials to see whether it''s acceptable to them. Of course a properly "engineered" solution could always be substituted for the prescriptive requirements.


   

Re: Rafter to Ceiling Joist connection By  FredK

Posts: 0

10/25/2006 4:33:00 PM

Here see if the 06 IRC helps you since it''s changed in completely:

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 (51 mm by 102 mm) (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 practice.

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 by 4-inch (25 mm by 102 mm) (nominal), spaced not more than 4 feet (1219 mm) on center.


   

Re: Rafter to Ceiling Joist connection By  DRP

Posts: 0

10/25/2006 7:03:00 PM

"installed in accordance with the connection requirements in Table R802.5.1(9), or connections of equivalent capacities shall be provided."

There''s the problem with nailing to the floor or a plate on the floor, you can''t get a thrust resistant connection easily. Assuming a 30/10 load I''m coming up with 1018lbs of thrust at the rafter seat. Is there a connector?


   

Re: Rafter to Ceiling Joist connection By  George Roberts

Posts: 0

10/25/2006 10:01:00 PM

I would suggest that if the roof is designed as a diaphram, the load placed on both the ridge and the rafter seat is greatly reduced.

I think the building would benefit from engineering.


   

Re: Rafter to Ceiling Joist connection By  DRP

Posts: 0

10/26/2006 3:24:00 AM

What building wouldn''t, on a 24x24 garage? You just blew the budget though... I''d truss it or put in a ridge beam then.

I think someone had a strap that had a angle that went into the rafter seat, up each side and onto the floor. I wonder if a angled cant strip on the floor and a modified birdsmouth would do anything, kind of like the old timberframe rafter seats.


   

Re: Rafter to Ceiling Joist connection By  wvbills

Posts: 0

10/26/2006 3:36:00 AM

You guys are seeing my problem.

I''m not an engineer but as DRP says I just cant''t see how connecting the tail end of a rafter to a floor or a plate on the floor would provide sufficient resistance to outward thrust.

The code seems to say it can be done, and others say it''s common practice but I can''t find a connector in the Simpson catalog that specifically says it is for that application.

I''m going to look to see if I can use a "1 inch by 4 inch (nominal) minimum size cross tie" per 802.3.1 at a reasonable height above the floor. Failing that, I think I''m going to have to use "a girder designed in accordance with accepted engineering practice" at the ridge.

That is unless someone can suggest an appropriate Simpson or equivalent connector.

Thanks


   

Re: Rafter to Ceiling Joist connection By  DRP

Posts: 0

10/26/2006 4:08:00 AM

I saw a builder in NY using joisthangers on the floor, bobtail rafters, then sistering on 2x6 overhangs. You would about have to let in a plate under the subfloor to have something adequate to nail to. I think the strap I remember above was German.


   

Re: Rafter to Ceiling Joist connection By  engineerguy

Posts: 0

10/26/2006 9:23:00 AM

DRP -
30 psf LL on a 12:12 roof? Sigh, I guess that''s another IRC thing? (this is driving me nuts on here having so many posts not apply to me - such great, unusable info!) UBC says 12 - which would greatly reduce your thrust force - perhaps down into clip-able reach.


   

20 post(s) First 1 2 > Last
2015 I-Codes
2015 I-Codes