rafters and what wood to use

[Randy88]

I'm in the planning stages of adding an addition to an existing shed, on my last barn/shop remodel we had to make my own rafters, it wasn't an option, no rafter company would build them for me due to liability reason's so we just did them ourselves.   

On this project, we're pricing new rafters but the question comes up on how the rafters are built, they use metal tie straps like most pole building rafters have been done for decades.    On my last project we used 2x6 top and bottom cord, 2x4 bracing, plywood, glue and screws to hold the joints together.      My first question is this, which way is better, lasts longer and stronger??

I have several buildings now with the metal tie strap design and we've been forced to strengthen them up with 2x's screwed on over the rafter, due to age and wood decay and also rusted metal tie straps.     

Since my shop made rafters are only a few years old, I have no data to back up them lasting longer without needing repair.    Anyone have any ideas as to which is better?

Next question is this, yellow pine or fir for rafters, which is more rot resistant or shall I say, which will last longer under a roof before rotting or decay sets in.      Basically what it gets down to is this, the metal tie strap rafters lasted roughly 30 plus years and needed a lot of help and repair, the job sucked to say the least.    If I do this addition, in all reality I'll be in my upper 70's or 80's and need to repair these rafters, not really something I look forward to doing or hiring done by then.    If it would help for longer lasting, I'd make them myself now with better materials and spend the money and time now upfront, rather than repair later on.     

Anyone want to shed light or ideas as to which is the best way to go?    I know its somewhat of an odd question, but the only answer I get is whoever is selling what now, their product will last four lifetimes and not worry about it, history and the past tells me differently.   

Its an addition on a pole building, for now housing machinery, livestock later on is possible as well.   

[Bruno of NH]

You are talking about a roof truss .
Rafters are cut single and nailed to a ridge pole .
Truss shops use plates because they are pressed in the wood .
Around NH an upgraded truss has syp top and bottom cords spruce as infill .
I have built a lot of my own trusses with plywood , glue , and good quality screws not drywall screws they are for drywall not building .
If code lets you build your own thats what i would do 
Bruno

[Randy88]

What I have now is a pole building, clear span of 50x100 and I'm wanting to add a lean on one side of 25 foot clear span as well, using a sloping flat roof truss tied onto the existing building.     

I've been told fir is better for the entire truss compared to southern yellow pine, no roof truss manufacturer around me will use fir, in order to use fir I'd have to make my own truss's. 

Its agricultural purpose and exempt from code, so I can do anything I'd like.   

I've used deck screws in the past, not drywall screws and how I'd do it again if it would add to the life of the rafter.   

I've never seen a rafter built with plywood, glue and screws before till I made my last one's so I have no idea how they'd hold up long term.     

I know the downfalls of the steel press plates they use in roof truss's, but would plywood, glue and screws be any better??

There are Amish in my area that build their own rafters, but instead of plywood they use home sawed 2x's and a few use boards, laid both ways to add to the strength of the joint, one board with the grain one against on each side, any idea's or thoughts on those for a joint lap then they glue and use deck screws.    I've never seen them only been told about them, and they haven't done either long term in my area so its a guess which is best scenario for long term durability. 

[Whitetail_Addict]

SYP is significantly stronger and heavier than the fir. I'm building my own trusses right now for a garage with a 30ft span. Using Hemlock and Ash I've sawn out of my woods. Plywood gussets. Glued screwed and nailed. I found an old study from Purdue University where they tested the strength of trusses built using various types of fasteners gussets and mending plates. The Glued and nailed Plywood was the strongest. Gave me a little more confidence in what I am constructing.

[Larry]

Check out Midwest Plan Service as they have free plans for trusses up to 60'.

I would guess the truss builders won't use fir because there engineering data is for machine graded SYP...just a guess.

[Bruno of NH]

I like framing with fir kd lumber from the west coast .
I find the lumber better quality

[bluthum]

I would use SYP with plywood gussets and nails. SYP is a great truss wood. If you research the load carrying capacity of nail vs. screws vs. cost you'll opt for nails. Screws have greater withdrawal loads but that's not the issue, it is load carrying capacity. I can't say about the need or effectiveness of glue, I have no experience there. For sure a lot of glue types do not have structural benefit, some do.

The last few times I priced making vs. building trusses the truss plant got  the jobs. Of course all that is locally variable. It is surprising to see how much the plywood gussets add to the cost but I don't think you can get around using them on owner builds.

What ever materials you wind up using the plan is the key, you cannot seat of the pants engineer some thing like a truss. Math and science.... 

[Randy88]

The rafter companies will build them for half the price of doing it myself in materials alone, so the big question is, will the plywood, glue, screws or nails outlast steel gusset plates over the decades of time??

Locally they told me to buy half of the rafters and build the other half, then in 30 plus years I'll know which way we should have gone with all of them??

[bluthum]

I finally understand your question. I think you are asking the unknown.

Around here you could expect SYP to last indefinitely under an open roof that didn't leak. The pressed in steel truss plates have been in use for decades. I've yet to see one fail that was right to start. But I haven't seen everything.

If it was me I'd opt for the factory trusses and plan to fix it if required. Who knows what innovations in fasteners and scaffolding might be around in 20 or 30 years?  For sure you can't plan for all eventualities, some times maybe it's best to just press on.........

[plowboyswr]

Dad and Grandpa built several pole barns in the mid to late seventies all of them used the pressed in steel plates on the trusses. Of the only failures we have had none of them resulted in the joints but the wood split in the few that have failed (twister uprooted a tree and fell on the building) I moved on a place that had an old layer barn on it built about in the same time period it had plywood joints nailed through (don't know about glue). The posts gave before the trusses did. My opinion go with the more cost effective route. ;D

[Jemclimber]

My opinion go with the more cost effective route. ;D

+1

More than likely glued and screwed using plywood would only make sense cost wise if you're sawing your own chords. Otherwise the truss company will be cheaper.

Hopefully not taken offensively, trusses are not rafters and rafters are not trusses.  It can be difficult to understand context when these words are interchanged.