FredK
Gold Member
Re: Rafter ties
Engineer it.
Engineer it.
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Rafter ties
- Thread starter Par
- Start date
Re: Rafter ties
I like the WFCM, but remember the limitations of the WFCM. Chapter 1.1 Scope presents many limitations on WFCM's usage. But it does fill in a lot of blanks left by the IRC with plenty of good illustrations. Every building department and every homebuilder should have one.brudgers said:
Re: Rafter ties
From a design standpoint, some of the information is specific to the geometry limitations...generally, components of the MWFRS.
Other parts like Table 3.9 are valid beyond the geometry limitations...the distribution of forces in a rafter with a tie is the same regardless of the length of the rafter...only the magnitude changes.
My point is raising the tie a foot should not automatcially require engineering.
If you are checking the adequacy of the rafter to plate connection (which in my opinion, you should be doing particularly if whe your worried enough about it to require engineering for a slight deviation), then it's another 30 seconds to determine if it is adequate for the additional thrust.
It's just alternate means and methods.
I like the WFCM, but remember the limitations of the WFCM. Chapter 1.1 Scope presents many limitations on WFCM's usage. But it does fill in a lot of blanks left by the IRC with plenty of good illustrations. Every building department and every homebuilder should have one.TJacobs said:
From a design standpoint, some of the information is specific to the geometry limitations...generally, components of the MWFRS.
Other parts like Table 3.9 are valid beyond the geometry limitations...the distribution of forces in a rafter with a tie is the same regardless of the length of the rafter...only the magnitude changes.
My point is raising the tie a foot should not automatcially require engineering.
If you are checking the adequacy of the rafter to plate connection (which in my opinion, you should be doing particularly if whe your worried enough about it to require engineering for a slight deviation), then it's another 30 seconds to determine if it is adequate for the additional thrust.
It's just alternate means and methods.
TimNY
SILVER MEMBER
Re: Rafter ties
Second, well said.
First, the "man who draw with pencil" thing has my whole office laughing.jar546 said:
Second, well said.
Paul Sweet
SAWHORSE
Re: Rafter ties
If the tie is halfway up the rafter, the bending moment in the rafter is tripled. You may have to resize the rafter in addition to providing more nails.
If the tie is halfway up the rafter, the bending moment in the rafter is tripled. You may have to resize the rafter in addition to providing more nails.
Re: Rafter ties
That was the original question.
The one to which I suggested that requiring engineering might be unnecessary and for which I used the table a tool for assisting in making such a determination.
As I'm certain you know, for a rafter of 7 feet or more, moving the horizontal member up a foot will reduce the maximum bending.Paul Sweet said:
That was the original question.
The one to which I suggested that requiring engineering might be unnecessary and for which I used the table a tool for assisting in making such a determination.
RickAstoria
BRONZE MEMBER
- Joined
- Oct 17, 2009
- Messages
- 531
Re: Rafter ties
Be careful about the number of nails, you could run out of wood. Options may shift from a cluster of nails to a couple of 1/8" thick steel plates sandwiching the rafter tie and a 1" diameter lag bolt.minimally a 2x6 rafter tie and rafter. 2x4 (I would say 3/8" lag bolt max size. The plates are for reinforcement.
Just some loose thoughts. Sizing would need to be determined with prescribed loads.... now where is that International Performance Code.
Be careful about the number of nails, you could run out of wood. Options may shift from a cluster of nails to a couple of 1/8" thick steel plates sandwiching the rafter tie and a 1" diameter lag bolt.minimally a 2x6 rafter tie and rafter. 2x4 (I would say 3/8" lag bolt max size. The plates are for reinforcement.
Just some loose thoughts. Sizing would need to be determined with prescribed loads.... now where is that International Performance Code.
RickAstoria
BRONZE MEMBER
- Joined
- Oct 17, 2009
- Messages
- 531
Re: Rafter ties
Sure, it is a good and funny line.
Rick, would you object if I used "Be careful about the number of nails, you could run out of wood" in my signature? Thanks in advance.texasbo said:
Sure, it is a good and funny line.