I'm trying to build things that won't collapse, such as pic related trusses to use for a roof. Literally all I want to know is "can this support X load without failing" and all internet resources seem to tell me it's black magic only an engineer would know. If the mexicans can build things that don't collapse, so can I.
What formula can I plug numbers into to find a max load for a beam/truss/floor system so I don't have to build it twice?
>pic related trusses for use on a roof
Those are floor trusses, so I wouldn't recommend it (yes, even for a flat roof). If you're talking pre-built trusses, every manufacturer will provide span charts for various loadings (top dead, top live, bottom dead, etc). If you talking about actually making the trusses yourself, yeah you need an engineer. And a lot more information than you probably have available, down to the specific species of tree the wood you're using came from.
>floor trusses, so I wouldn't recommend it (yes, even for a flat roof)
What's the difference between an interior storage load on a floor and snow load on a roof? Also I should specify that this truss would be used as a beam on a sloped roof, as shown in this professional engineering sketch.
>yeah you need an engineer
>down to the specific species of tree the wood you're using came from
I'm building a shed that will cost less than his consultation fee. This shouldn't have to be rocket science or shaving every penny of cost, if I overbuild then I overbuild.
>What's the difference between an interior storage load on a floor and snow load on a roof
Depending on the area, the correct top load will vary significantly. For most residential floor trusses, they will be designed for 30-40 lbs. Roof trusses in Minnesota and other states with meaningful snowload will be 60 lbs+. And you don't want to use a floor/flat roof truss in a slope configuration. Sloping flat trusses trusses are subject to different forces due to the difference in angle.
You misunderstand. The slope will be regular rafters, just straight 2x8s. The truss will hold up the high end of the slope, see
, across a longer span than regular boards would allow. In other words, the truss isn't holding the snow load directly but transferring load from rafters to posts, i.e. bearing half the total snow load. I want to be sure I design a truss that doesn't snap under half the total. The truss doesn't slope.
NTA but I spent a few years building trusses in my youth, I feel confident doing my own for something simple like a shed/garage like picrelated in the 20 foot wide range.
If you're actually building a roof, it's probably easier to look up specifications for a stick built roof using rafters. It'll tell you what size 2by material to use for what length and you can go bigger if you want.
Framing isn't like doing one-off plumbing. "I have x and y in a bathroom, what pipe size do I need?" is easy stuff. Framing has to take into account wind loading, snowfall and rain and has to be able to hold its own weight.
You can get an engineer to calculate your requirements or you can spend a few months learning the basics so you can do it yourself. Visit your local library.
>You can get an engineer to calculate your requirements or you can spend a few months learning the basics so you can do it yourself.
or you could just use a pre-engineered, prescriptive solution such as those provided in the WFCM or the IRC
just save yourself a lawsuit and contact the manufacturer, or just talk to a salesman at your local lumber yard. also just see if you can get a span chart from your local building inspector, or hell you can even just ask him about what he'll let pass.
I'm building this shed in my own yard for myself and building codes are not enforced here. Worst case scenario is it collapses on the lawnmower tier shit I'm gonna store and I have my own incentives to prevent that.
>truss and joist spacing
I have reviewed some of this information. For a *loaded area* e.g. a floor or roof, the information in here is straightforward and I did use this to calculate size and spacing for the roof joists on this project. The truss I am asking about will hold up *one end of all the joists*, i.e. it's *in place of a wall* and will function as a beam. I keep having to explain this. Is there a way to apply the IRC charts to a single beam, or a separate section in the IRC referring to load bearing beams?
I'll let you in on a little secret. You tell the lumber supplier to quote you the truss load on the blueprint so you can get a bid, then you become a white collar Black person if they give you the engineering report and then you say that the project's financing fell through or something equally dastardly.
Never done that myself, but did have a few projects fall through after they did the groundwork.
there's no need to lie you're not obligated to by lumber from someone just because they gave you a bid.
Well, if you're planning on buying from them in the future it's probably not a good idea. Like getting a diagnosis from a mechanic and then taking it to the lowest bidder. They'll probably eventually tell you to frick off.
not really they give bids all the time on jobs they don't get. it's just part of it. builder's bid on jobs that they don't get, and most. lumber companies understand this, it's just part of the business.
I suppose it depends on the scale of their operations. If they're one of two suppliers in a 3 hour regional area and you're Joe Blow doing random renovation projects, they'd probably tell you to pound sand if you start coming to them multiple times.
Worked for a few residential homebuilders, and even the Porta Potty guys will tell you to frick off if you're a rinky dink operation and don't pay the monthly because the funds didn't come in just yet.
right, you're not wrong about that. if you're just a home owner doing an addition you're gonna be treated way different from a g.c. whose building 110 spec houses a year.
Just review the international building code. There's a table of required truss and joist spacing including species. It's not that hard.