typical wood roof trusses

[bb29510]

I,m in the middle of thinking about floor plan for my new house. I am trying to decide on a great room design, I need to span 30 feet without a support wall. I know everybody going to tell me to go to a truss mfg, and I will when the time comes i just need ideas now. It going to be a typical buildup roof. singles, plywood, a/c ductwork, insulations, drywall, no crawl space or storage. can it be done and how, what size wood.

 

[Ron]

A 30ft. span for a wood truss is not that tough, but will require some engineering based on the configuration of your vaulted ceiling.&nbsp;&nbsp;Size of wood will depend on local code design requirements for live load, dead load, wind load, seismic, etc., but you are probably looking at 2x6 top and bottom chords and 2x4 diagonals.<br><br>You mentioned a typical built-up roof.&nbsp;&nbsp;Does this mean you will have a flat section?&nbsp;&nbsp;You also mentioned shingles and plywood sheathing.&nbsp;&nbsp;Will these trusses support a flat roof section as well as a steep roof section?&nbsp;&nbsp;If so, this will throw a few curves into the truss design.&nbsp;&nbsp;If just typical steep roof (shingles, underlayment, plywood) then pretty straightforward.

 

[Imagineer]

I know a couple of the truss manf. have trusses designed for ductwork, etc.&nbsp;&nbsp;Unfortunately, can't remember their names, right now.&nbsp;&nbsp;An electrician friend built his house using these.&nbsp;&nbsp;His trusses are about 12-18&quot; deep. Basically, enough for a vent duct and 2x6's for the cords. He clear spans about 30' in his basement.&nbsp;&nbsp;<br><br>He went by close to the maximum spacing (~24&quot to save a couple of trusses.&nbsp;&nbsp;Cost him in the long run.&nbsp;&nbsp;He now has cracks in the first floor dry wall.&nbsp;&nbsp;If he had bought the couple of extra trusses and put them on 18&quot; or 16&quot; spacing, he would have been fine.&nbsp;&nbsp;He's happy with the trusses, realizing that the spacing was his fault.<br><br>I'd also suggest that you not let the truss bear (even via deflection) on any walls as this tends to crack the wallboard.&nbsp;&nbsp;Put a 1/2&quot; sponge between the top of the wall framing and the bottom of the truss.&nbsp;&nbsp;This will let the truss deflect without imposing any loads on the wall.&nbsp;&nbsp;This lets non-load bearing walls remain non-load bearing.&nbsp;&nbsp;The sponge gives you something to &quot;mud&quot; and paint.<br><br>Good Luck, <p> Imagineer<br><a href=mailto: > </a><br><a href= > </a><br>

 

[DavidA]

You should connect your interior non-bearing partitions to the bottom chord with a slotted angle clip (Simpson's STC clips are available at local lumber yards). Allow about an inch between the top plate and the bottom chord. Verify the deflection with whoever does the truss calcs<br><br>There are companies in Southern California that specialize in wood truss calculations, for a fee.&nbsp;&nbsp;Usually the truss manufacturer will provide these for free if you purchase your trusses from them.<br><br> <p>David Allee, Architect<br><a href=mailto:darct@tfb.com>darct@tfb.com</a><br><a href= > </a><br>Professional affiliations include International Conference of Building Officials and Light Gauge Steel Engineers Association.