Build your own roof trusses -advice ?

[EddieWalker]

I built my own trusses last year make a jig and save yourself a lot grief.If you make a fixture you won't have any difference in the size of your trusses,if you don't you will.
I built mine from 2/6/16 ft.It took about 10 days after work at night and they are about all 1 person can handle by themselves.
I went 2 ft on center Osb for the roof and I used shingles.Last winter it had over 2 ft of snow on and no problems,it was a 6/12 pitch.Good luck and enjoy!

While your trusses may or may not last, by attaching your chords to the sides like you did, you have lost a tremendous amount of strength. Nails are not load bearing fastnerns. They are to hold things in place. Relying on nails to hold the boards in place on the sides like you did puts all the weight of the roof on the nails instead of the lumber.

When the boards are cut and fitted together, the triangles created in the truss actually force it to stay in position. The downward preasure from the peak forces the boards into each other so that it cannot move.

The gussets are there to keep the boards where they need to be. They are not load bearing. The load is on the lumber. This is why the lumber used is so important.

Ripping lumber means that you migh be splitting the board right at the center of the rings. Ideally, you don't want this type of grain anyway, but by ripping it, you just make it worse.

I wasn't aware of the requirement for 3 inch nails, but it makes total sense. The strenght in the nail as a holding fastener is in the amount of shaft that goes through the wood. The point does not hold the nail in place and offers nothing of benifit other then starting the nail. Having the nails go all the way though the wood is critical in shingles, and it makes sense that it would do the same on wood gussets. Cutting off the tips after they go through the wood would be for apperances. The holding strength wont change any.

I like the second truss design A LOT better. That is what I make and use for myself.

Eddie

 

[grsthegreat]

Yeiks, in all the places i would scrimp and save.....it wouldnt be in the trusses. Not sure about where you live, but here the snow load engineering is something i wouldnt want to mess with. When my trusses were delivered and installed, a few had to have an onsite repair done. They used a hydraulic press to install a rather nasty looking plate...not the simple plate like lowes has. This thing took alot of power to install.

 

[Verticaltrx]

Your not suggesting he use trusses 8' on center for a roof that is going to get asphalt shingles are you?

MarkV

Went back and reread his original post, I forgot he was shingling it. Regardless, I still can't see making your own trusses as much of a money saving venture.

 

[MikeD74T]

Mike,
What type lumber are you using? (HD and Lowes #2?). The advantage to ripping in half was saving $4 per cut and the wood possibly being stronger than standard spruce. Would you use 7/16 osb and 19" spacing or 19/32 osb and 2' spacing?

GA, In NH KD spruce is available in box stores & real lumber yards . I go with whatever is the straightest. I use 1/2" fir plywood, never OSB, for gussets & sheathing. I wouldn't use southern yellow pine as it tends to be brittle/splits easily.
According to Beppington & Schism almost no one can do anything unless they have a title deposited on them by some bureaucracy, however many successfully complete this type of project following simple, standard, time proven designs. I use the W truss mostly for your length. 2" ring nails work at least as well as gangplates if enough are used. Nails are cheap, use enough.
Bearcreeks design has inherent weakness as described by Eddie, relying on shear strength with that few nails is risky. Cutting pieces to fit is really easy considering each cut makes two angles if you planned things correctly. It's rigid geometry that allows trusses to succeed. Talk to most professional firefighters & you'll hear that trusses should never be allowed. For 300UGUY to say that one cannot make two trusses the same must merely describe his carpentry skills. Measuring the triangles before nailing keeps things the same.
Good luck with your project. I wouldn't wish an HOA on anyone, hope you don't end up hating your neighbors. MikeD74T

 

[gabeancounter]

Mike,
I have to say you must be a mind reader! That is my exact thoughts. I was trying to be pc, but you put it on the line. :thumbsup:

I just can not understand a piece of metal pressed into a joint being stronger than a 1/2" sheet of plywood 4-5 times its size supporting a much larger area.
Seems it would distribute the weight better?

I do agree on dumping the idea of spliting the 2x8. I think I will use the 2x6 top chord as well suggested by Eddie. The second plan seems to be a better plan and the one suggested by Monte Burch - "Pole Barn Projects". Making these adjustments will probably but the cost closer to $40-50 per truss. I will let you know.

The other advantage is this is a weekend warrior project. Don't really have time to take off to meet and schedule truss delivery etc.

Do you normally use laminated post? If so, adhesive you use? I notcied Morton building and other large outfits change over from PT to standard spruce above ground. Is this purely a price savings - or is there an advantage?

 

[flusher]

To build anything over 600 square feet on my 10 acre place, I need a building permit. To pull the permit you need wet signed engineering drawings and if trusses are used, these have to be built by a certified fabricator. So around here it's a no brainer--no home-made trusses if you want to stay legal and build with a permit. And the county checks real close on any new construction they see in their periodic driveby inspections. If there's no building permit on file for your new shed or whatever, expect a letter in the mail followed by a visit from the building inspector.

 

[grsthegreat]

Mike,

I just can not understand a piece of metal pressed into a joint being stronger than a 1/2" sheet of plywood 4-5 times its size supporting a much larger area.
Seems it would distribute the weight better?

you wouldnt believe how easy it is to RIP plywood with shear force. Ive seen it first hand after working in Calif after the 1994 earthquake, and this was 1/2" cdx. The areas with metal straps faired much better than the plywood joined sections.

 

[gabeancounter]

I do plan to pull a permit and have spoken with the inspector. Ag buildings/ sheds etc are different than living space requirements.

grs, are you referring to plywood gussets and metal gusset plates? or sides of buildings etc?

 

[EddieWalker]

I just can not understand a piece of metal pressed into a joint being stronger than a 1/2" sheet of plywood 4-5 times its size supporting a much larger area.
Seems it would distribute the weight better?

You are not understanding the purpose of the plates or the plywood in a truss design.

Neither are there to support the load. They are there to keep the ends of the lumber in place.

When the truss is in poistion, the lumber pushes into itself to lock it into position. If you where really good, and lucky, you could assemble a working truss without any screws, nails or plates. The ends of the wood would wedge into each other like a keystone, and it would stay in place. Since that's not possible, you have to use fastners to hold them in place. Either metal plates of plywood will do this. It's not about the stregth of the plates as much as it is to make sure they wont let the wood move.

Trusses fail for a variety of reasons, but when tightly built and sized accordingly to their span, they are VERY strong with very little weight.

Eddie

 

[gabeancounter]

Eddie, you are right. I guess it is dispersing the stress of the connection more than the actual weight load.