Steel and Timber Hybrid Building

[UND_Sioux]

Hello from a new member.  

I'm working on a new RV garage/workshop building.  I live in a neighborhood with HOA restrictions.  I'm required to face the building to match my house which is a combination of hardi siding and limestone.  The inside is an entire different matter.  I can do whatever I want.  

I've saved this picture for awhile.  I just really like the overall look.  The idea is going to be to you steel I-beam scissor trusses (mainly for looks) for the main columns and rafters spaced 16 feet apart and then the end walls will have steel and traditional framing. My big issue is the roof.  I want the purlins between the sections to be wood beams much like what is pictured.  Above the beams will be tongue and groove decking and insulation above, etc....

I used the calculators on this site and I think I'm going to need 6x8 or 4x10 purlins to support the 8:12 roof.  I live outside of Houston, so I'll need to take into account for 120 mph wind speeds.  Does this sound reasonable or even remotely in the ballpark?



 

[Don P]

Welcome to the forum.
That looks cool 8). I'm assuming you are looking at SYPine, what is the spacing on the purlins?

[UND_Sioux]

Welcome to the forum.
That looks cool 8). I'm assuming you are looking at SYPine, what is the spacing on the purlins?

Yes, SYP is the plan due to cost.  The spacing of the I-beams will be 16 feet, center to center.  I was hoping to get away with 48" oc for the purlins, but realistically it will probably have to be less.  Maybe 32" or 24".  

[Don P]

It isn't just cost, it is strong timber, be proud.
Unless the county requires more I would use 10psf dead load + 20 psf live load.
At 4' x 16' x 30 psf you have 1920 lbs uniformly loading on the purlin.
A 6x uses this calc;
https://forestryforum.com/members/donp/beamclc06b.htm
6x8 looks ducky to me in a #2

4x material uses this calc (higher design strength values!)
https://forestryforum.com/members/donp/ddsimplebeam.html
10 minute, no repetitive, 4x8 size factor, dry, non incised.
It says a 4x8 works but the deflection is 3/4", I'd still go with the 4x10.

[UND_Sioux]

Thank you.  I'd rather go a little larger than push my luck.

[Brad_bb]

Put something between the metal and wood so that they don't touch.  Some kind of contact barrier.  Use hot dipped galvanized or stainless hardware whenever going into frame members like that.