Gambrel roof trusses

[bkrahmer]

I know that I said I was going to run these by and engineer, but I just wanted to get a couple of thoughts here first. I was hoping that somebody would have an opinion about my truss design. Is it way overbuilt? Under? Am I missing anything major? Thanks.

http://www.krahmer.com/house/images/gambrel_rafter.gif

[bkrahmer]

Oops. Wrong forum category. On to cross-posting...

[grumpydasmurf]

I think typically gambrel sides (mansards) are steeper. But it may just be a matter of visual opinion. That's just my two cents.

Will there be any overhang?

[mjpliv]

I was involved with another member in a discussion about self-designed roof trusses. There may be some relevant information there -

http://www.construction-resource.com/forum/ftopic740.html

[grumpydasmurf]

One other thing typically I have found the exterior wall usually supports, or at least lines up with, the joint from collar tie(joist) to mansard.

This is obviously a truss system and I am not an engineer but I'm just speaking on my own experiences.

[bkrahmer]

I started out with a design from this webpage: http://www.taunton.com/finehomebuilding/pages/h00130.asp I wanted even more space on the second floor, so I added the second floor knee wall. With dormers and closets all along the north and south sides of the house, I have 100% usable sq footage. However, by adding the additional height, I had to drop the collar ties. Dropping them brings their span up to 26 feet. That was obviously too long for a single piece of lumber, so I added the vertical brace. After talking to a couple people that are experienced in building, they suggested adding the 'W' detail in the truss.

I think I'm definitely going to have to get an engineer to verify my design, or start from scratch.

My plan is to have an overhang, but to do it similar to the article I quoted earlier. The roof proper will be entirely enclosed with sheathing and tar paper. On top of that, there would be sleepers, and another layer of sheathing, then the shingles.

[grumpydasmurf]

Ya might be able to get a truss designer to do it for free at a lumber yard... ofcoarse if your going to buy the trusses from them.

[bkrahmer]

This is the first house I will have built. I thought that site-built trusses would be easier for me to deal with. I figured that I could cut and assemble them all on the second floor, and then have someone help me set them in place. I was planning on building a tool like a ginpole with pulleys to hoist them up by hand onto the second floor top plate. I have a few questions about using manufactured trusses. 1. Would they be more expensive? Cheaper? 2. Do truss prices typically include delivery? 3. Would I also have to pay time for a crane to set them in place? I also wasn't sure if most of the truss companies were set up to do gambrels.

thanks

[Rich]

If you include your labor of building them they would be more expensive. What you can't put a price on is if a site-built truss fails. There is noone to blame except yourself.
Truss price typically includes delivery.
Depends on how big they are on whether you'll need a crane. I've set some pretty good sized trusses on a second floor with 3 people. Although - they weren't gambrel trusses which will be a little heavier. I would suggest renting a crane server. Most cranes, with a spreader bar, should have no trouble with gambrel trusses.

[grumpydasmurf]

If I were building your house, I'd have them factory made and craned into place.

[Anonymous]

I would have to agree with what Rich and grumpydasmurf are telling you. Let the pro's handle the gambrel trusses. Those are not the trusses to "cut your teeth" on.

Best of luck!

[bkrahmer]

Thanks guys!

[mreynolds]

I was in the same boat you were, we had a room in our new house that we really wanted to get rid of the walls and expand it. My concern was if the trusses could span that distance. I was going to go to an archetict, but when I decided on a lumber supplier they designed the trusses for me (through their truss shop). What you need to know is the spans, over- hangs and the pitches you are looking for. They can take care of the rest. The really cool part is that they could send me truss drawings via email or faxes. It made it very easy to make revisions. To go along with what everybody else has said. trusses make roof framing so much faster. Building them would add at least a day to your roofing project depending on the help you have and how skilled you are at cutting. With 4 people, we will be able to set our trusses and sheath my roof in a day. :D