Author Topic: Trusses....did we mess up? Maybe time to fix?  (Read 1074 times)

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Offline brandywine

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Trusses....did we mess up? Maybe time to fix?
« on: August 06, 2017, 12:56:33 PM »
 ???
We designed our home and researched on the internet for a long time. My husband has built several homes but this is the first time he has built a house like this with beams and a tall ceiling, big pitched roof. He usually site built his trusses.

Foot print is 32'x48'. Half the house is open to the ceiling, the other has a second floor loft room. He researched on the internet and somewhere read that KING POST beams would work. But, now I am looking and cannot find where he found that info. I was wondering why every picture had struts on their king post beams and I wanted to know why. The more I read, the more I got worried. Our trusses we built are King Posts without the strut posts.
My understanding is the struts are to keep the rafter beams from sagging. But when are they necessary?

     /|\
   /  |  \   22.3ft
  /_ |__\
/    22ft  \
   
  32' span

So here is the info.
SPAN  32'
Rafter 22.3ft.
Chord is 22 ft
The chord is 1/4 of the way up from the bottom of the rafters.
Roof pitch 12/12 (45 degrees)
Beam size 4x8" Doug fir
We used 1/4" steel plate for the brackets and 5/8" bolts
The trusses are sitting on 2x6 walls with no overlap.
48" on center
We are in TN...typically no snow loads but sometimes we do get a little bit of snow, melts same day or next.
All ceilings are exposed. Tongue-n-groove, metal roof.



Half the house is going to have a loft area so we only did a /\ with no chord. it will have a knee wall connecting in from the upstairs floor.

The chord is just 2x4 to stabilize.

Is this incorrect? If yes, what do we need to do to fix it?
« Last Edit: August 06, 2017, 01:33:26 PM by brandywine »

Offline Don_P

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Re: Trusses....did we mess up? Maybe time to fix?
« Reply #1 on: August 06, 2017, 04:18:43 PM »
My napkin is saying it would be a good idea to call a local engineer.

Offline akwoodchuck

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Re: Trusses....did we mess up? Maybe time to fix?
« Reply #2 on: August 06, 2017, 04:34:27 PM »
Purty light, purty light.....'twas me, I'd go ahead and throw in those struts on each truss, plus another rafter pair @ 24" on center between the trusses....better safe than sorry.

Offline JRR

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Re: Trusses....did we mess up? Maybe time to fix?
« Reply #3 on: August 08, 2017, 03:58:15 PM »
In the area of the loft, will there be loft floor joists?

(I have a hard time getting my head around the king post being in tension, rather than compression.  ??)

Offline brandywine

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Re: Trusses....did we mess up? Maybe time to fix?
« Reply #4 on: August 08, 2017, 04:22:12 PM »
Under the loft area is all rooms on the 1st floor. bedroom, bathroom and pantry. Joists,,, and knee wall out 9 ft from the side of house on both sides.


Offline Don_P

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Re: Trusses....did we mess up? Maybe time to fix?
« Reply #5 on: August 08, 2017, 06:04:06 PM »
In the area of the loft, will there be loft floor joists?

(I have a hard time getting my head around the king post being in tension, rather than compression.  ??)

I don't think you are alone. The brits sometimes call it a king rod truss which might help because that is really more descriptive of what that member is doing. imagine pushing down on the ridge, the rafter feet want to splay outward but are restrained by the bottom chord, which is in tension. As the bottom chord gets longer it wants to sag. Drop a rod, or even a rope down from the ridge and tie it to the middle of the bottom chord to keep it from sagging, the kingpost is in tension. You can notch the web members into the corner formed by the king and bottom chord and run them up to the middle of the top chord to break that span in half, those web members are in compression. The webs can also spring from the kingpost itself and run up to the rafters

Offline JRR

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Re: Trusses....did we mess up? Maybe time to fix?
« Reply #6 on: August 10, 2017, 05:16:44 PM »
That video shows much.  Now I understand better.  (Wish I knew how to post videos.)

You've done a lot of good work.  I agree with checking with engineer.  As someone has suggested, you may want to add the king post, and perhaps branches/webs, to all trusses and give up the loft.

Don P, I see what you mean about the king post correcting strain; not stress.  Probably the correct reasoning.

 

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