Build your own roof trusses -advice ?

[nickel plate]

I spent ten years selling roof and floor trusses for a living and one of the first things we had to do as a new salesman was to go to the fabrication area and be handed a claw hammer and a wood pressed truss plate then attempt to remove the plate from the wood. When completed, the once flat plate was a wadded up ball of metal. That excercise was to demonstrate the plate's adherent properties when pressed.

 

[MikeD74T]

I spent ten years selling roof and floor trusses for a living and one of the first things we had to do as a new salesman was to go to the fabrication area and be handed a claw hammer and a wood pressed truss plate then attempt to remove the plate from the wood. When completed, the once flat plate was a wadded up ball of metal. That excercise was to demonstrate the plate's adherent properties when pressed.

And had you removed a plywood gusset plate with glued ring nails you'd end up with a pile of splinters & bent nails. Metal plates are a great product but must be pressed with proper equipment, cannot be hammered into place. They eliminated the aspect of needing honest ambitious employees that always used enough properly spaced nails as well as cut and aligned the plywood grain on the gusset plates. Metal plates are cheaper to buy (than plywood), quick to install in a factory setting, and make thinner trusses which allow for easier bundling & transport. However none of this means that plywood gusseted trusses are less than adequate for the intended job. MikeD74T

 

[flusher]

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?

Yah, I understand --sheds are different from living space. But do yourself a favor and have those trusses fabricated by someone who's done it before--preferably a certified fabricator who has the experience to do the job right the first time. Factory-built trusses are not that expensive.

 

[Little_Grizzly]

Very interesting thread! I have one question. I looked at the two truss drawings and I wonder if the splice of the bottom chord is positioned correctly. I've always understood that splicing in the middle of any support member is the absolute worst place you can do it. It's where the tension (the bottom chord is in tension right?) is the highest. A while back I asked an engineer about a foot bridge I was building. He said two splices out towards the edge (let's say 1/3 in from each end) was stronger than one splice in the middle.

Comments?

Edit: Looking at the second drawing closer it seems the splice was moved a bit to one edge.

 

[MikeD74T]

Very interesting thread! I have one question. I looked at the two truss drawings and I wonder if the splice of the bottom chord is positioned correctly. I've always understood that splicing in the middle of any support member is the absolute worst place you can do it. It's where the tension (the bottom chord is in tension right?) is the highest. A while back I asked an engineer about a foot bridge I was building. He said two splices out towards the edge (let's say 1/3 in from each end) was stronger than one splice in the middle.

Comments?

Edit: Looking at the second drawing closer it seems the splice was moved a bit to one edge.

Not sure in what context the engineer answered your question. If you're talking about a laminated beam his answer would be correct. If the botom member of a truss is in pure tension, which it should be, it wouldn't matter where the joint(s) was. Would it make a difference in a rope where the knots were? Miked74T

 

[massey990]

Very interesting thread! I have one question. I looked at the two truss drawings and I wonder if the splice of the bottom chord is positioned correctly. I've always understood that splicing in the middle of any support member is the absolute worst place you can do it. It's where the tension (the bottom chord is in tension right?) is the highest. A while back I asked an engineer about a foot bridge I was building. He said two splices out towards the edge (let's say 1/3 in from each end) was stronger than one splice in the middle.

Comments?

Edit: Looking at the second drawing closer it seems the splice was moved a bit to one edge.

"engineered" trusses are different from beams etc., the rule of thumb for butt joints is no further than 25% of the overall span away from a bearing point.

 

[gabeancounter]

Well, I have been calling around to the local truss manufacturers. Some good info. Long and the short is that I can not build them for what I can buy them. The numbers from earlier was from a craigslist guy.

Based on 2' centers. Picking up - delivery extra.

24' - $35
28' - $37
30' - $43

#1 top and bottom- #2 braces #30 live load 7# deadload

Weight of a 28' truss 120#'s.
Week and a half leadtime.:thumbsup:

How do these guys stay in business at these prices?

 

[Little_Grizzly]

"engineered" trusses are different from beams etc., the rule of thumb for butt joints is no further than 25% of the overall span away from a bearing point.

Exactly my concern with the first drawing. Isn't the splice at exactly 50% of the overall span away from a bearing point? Namely the ends where it sits on the wall.

 

[SandburRanch]

How do these guys stay in business at these prices?

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I'll give ya a hint.

If you want to converse with the delivery people you will need an interpreter.

 

[schmism]

How do these guys stay in business at these prices?

working in the industry for 5+ years (for the second largest maker of steel plates and truss fab equipment)

a large facility that is makeing stock trusses (like the ones you wanted) buys lumber by the train car load. Significant saveings over what you pay for a 2x4 at lowes/HD

autosaws, automated lumber bunks and feeders mean you can cut every stick of lumber on a stock truss simultaneously. litterly able to cut out an entire truss worth of material in seconds.

autoset tables with laser layout mean you can assemble them with near 100% precision even with the most uneducated/unskilled labor.

Theres no question thats its impossible for a home owner to build a stock truss as cheeply, quickly, and maintain better quality than that of profesionaly fabricated trusses.