More truss modification info

[ms fowler]

Just as an example of what is required if you cut a "simple" truss....
I plan to cut 3 trusses to increase the ceiling height for my lift. I am talking about raising the ceiling height 2'. My engineer just got back to me. I need to sister TWO 2X12 on each of the trusses I plan to cut--one on each side. The rafter tie could be a 2X6, but the tension forces require 12 16d nails in each end--which would tend to split it up beyond use. So the rafter ties will be 2X8 just to have the room for the required nails.
"simple" truss or not, there is a LOT of force that needs to be understood.
Your mileage may vary

 

[readhead]

It wasn't that complicated to find that out was it. That is a pretty easy fix to provide peace of mind.

 

[ms fowler]

It wasn't that complicated to find that out was it. That is a pretty easy fix to provide peace of mind.

but its going to const me more than $100..........
Well, I worked in the industry for 30 years and have a number of "contacts", so maybe its easier for me than for some. Its probably more of a fear of the unknown--if you have never dealt with an Engineer before.

 

[R6 Racer]

So if I understand you... your basically going to end up with a kind of box shape up into your attic. With 4 vertical walls & a horizontal ceiling that's 2 feet higher than your existing ceiling.

Yes, No?

Steve

 

[ms fowler]

So if I understand you... your basically going to end up with a kind of box shape up into your attic. With 4 vertical walls & a horizontal ceiling that's 2 feet higher than your existing ceiling.

Yes, No?

Steve

More or less. Once I reinforce the existing trusses and then cut out the center 10' or so of the bottom chord, I will probably frame the opening into a box. My Engineer added, almost as an after thought--that I need to complete all the reinforcing work BEFORE I cut the Bottom chords. Roger that!

 

[Commendatore]

If possible, it's generally better to take the load off of it before you reinforce and cut.

 

[theoldwizard1]

I need to sister TWO 2X12 on each of the trusses I plan to cut--one on each side.

I ASSUME these will be "sistered" on each side of the top chord, correct ?

That is a whole lot of wood ! You might want to ask about using steel plate.

 

[buzz4041]

Kinda like this.

 

[mike93lx]

Did the engineer provide drawings or anything in writing, or was it all verbal? What did the consultation/answer cost, if you are willing to share?

 

[jdieter]

ms fowler am I understanding your design correctly. The three trusses are sistered on each side of the top chords with 2x12's. So effectively you'll be creating a vaulted ceiling in the area with rafter ties up two feet from the original bottom chord. What is your roof pitch and how are the 2x12's attached to the wall top plates.

 

[ms fowler]

ms fowler am I understanding your design correctly. The three trusses are sistered on each side of the top chords with 2x12's. So effectively you'll be creating a vaulted ceiling in the area with rafter ties up two feet from the original bottom chord. What is your roof pitch and how are the 2x12's attached to the wall top plates.

Three trusses. each gets a 2X12 sistered to each side of the top chord butting at the peak and going to the side walls. Roof pitch is 7/12. 2X12 will be glued and screwed.
Engineer is a friend, so I owe him some beer when I see him.
He said that when he ran the calcs with shorter 2X12s as I had proposed, the top chord always "broke" at 9" from the wall. He also said that doing just three trusses may not fail at all-even if I didn't run the 2X12 all the way to the wall. He complained how every time they update the code, the spans get shorter. He did plans for two builders who share plans and workers. One submitted his plans the end of June, the other the middle of July. The plans submitted in June were accepted. The plans submitted in July (next fiscal and code year) did not.

One other thing to remind people ----OSB in not a good structural material. You are depending of the strength of the resins that bind the wood chips together. Plywood is a much better choice.