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Solar Dave 07-25-2008 10:52 PM

Truss attachment
 
Good evening.
I am building a 2000 sq. ft. home, one level, 5" radiant slab floor, 2 x 6 const. The trusses will make the roof slope 4 in 12 with a single peak running east to west not quite centered from north to south.

The south wall and north wall are 46 feet apart. The two interior bearing walls are at 24' and 36' from the south wall measuring south to north.

My big question is whether or not to attach the trusses to the interior bearing walls by nailing directly to the top plates, or to use steel simpson brackets that hold the trusses laterally but allow them to float vertically for thermal expansion and contraction.

This is my first building using trusses and I really need to know the pros and cons of the two different attachment methods.

Thank you very much for your time.

Solar Dave

joasis 07-26-2008 08:56 PM

You didn't indicate a location, which will affect the answer. In Oklahoma, truss "lift" is pretty rare, and we attach the bottom chords to the interior walls, to secure the walls, not to provide "bearing support" for trusses. In extreme climates, temperature changes can actually cause the top rafters of a truss to "shrink" or humidity to expand the length...causing lift.

Solar Dave 07-27-2008 09:50 AM

Thanks for your response
 
Quote:

Originally Posted by joasis (Post 143331)
You didn't indicate a location, which will affect the answer. In Oklahoma, truss "lift" is pretty rare, and we attach the bottom chords to the interior walls, to secure the walls, not to provide "bearing support" for trusses. In extreme climates, temperature changes can actually cause the top rafters of a truss to "shrink" or humidity to expand the length...causing lift.


The home I am building is in Ferndale WA about 13 miles south of the Canadian border, about 5 miles North of Bellingham WA. and about 5 miles West of I-5.

I am really at a loss about this. The people who work for the construction company who built my shop building for me said they just attach the trusses to the top plates. They also build houses so I value their opinion.

But another friend who is a builder said to worry about truss lift.

I like the idea of using the truss system to help anchor the tops of the walls. I would like to directly attach them if I thought it was not going to cause problems in the future.

Thanks again for your response.
Sincerely,
David Culver

Termite 07-27-2008 01:47 PM

I've inspected thousands of homes, apartments, and commercial buildings with trusses and have never witnessed this phenomenon called truss uplift, but all the truss guys around here say that it does happen. Based on that, I would personally use the Simpson STC's. They'll hold the walls laterally but will allow the trusses to creep if they need to.

http://www.strongtie.com/graphics/ca...TC-t_clips.gif

jerryh3 07-27-2008 05:01 PM

Quote:

Originally Posted by thekctermite (Post 143461)
I've inspected thousands of homes, apartments, and commercial buildings with trusses and have never witnessed this phenomenon called truss uplift, but all the truss guys around here say that it does happen. Based on that, I would personally use the Simpson STC's. They'll hold the walls laterally but will allow the trusses to creep if they need to.

http://www.strongtie.com/graphics/ca...TC-t_clips.gif

Come to the coast. I've seen a lot of new construction houses have 3/4"-1" gaps on the interior walls from truss uplift. There are some drywall techniques to minimize it, but it can be a big problem.

Termite 07-27-2008 05:49 PM

All the more reason to use those clips then! :thumbsup:

joasis 07-27-2008 10:45 PM

Humidity and temperature are the factors. I have seen it twice here....not very common. The "uplift" was less then 1/2 an inch. Use the Simpson clips.


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