How to calculate Joist span table for 3x8's

WillSTX

Found the answer, or rather the AWC sent it to me. Go to: http://www.awc.org/Standards/wsdd.html and download the Span Tables - Quick Finder

You will have to lookup the Fb for the type of wood you're using but then it's just following the table.

kwikfishron

The guy is sitting on a pile of 3x8’s and wants a little storage space in the barn. What’s the big deal? It’s not like he’s building a apartment to store the in-laws up there or something. What ever happened to common sense? If the thing's sagging throw in another beam , add a post or something. It’s just storage in a barn.

I’m new here and see a lot of good information coming out of this site but also see a lot of very simple things get turned into complicated ones.
Why couldn’t the “Engineer” ask another question or two and help the guy out with his “Storage Space”.

I would think the purpose of a DIY site would be novices along with the pro’s helping each other getting through their projects and not “you must give your local Engineer a $100 per hr. before you can put your Xmas boxes up there”.

Daniel Holzman

Since you ask, I will tell you why the Engineer does not design the job for someone on this site. I have a license as a professional engineer in multiple states. As a licensed professional, I have obligations and am subject to laws and regulations that do not apply to unlicensed individuals. Additionally, I am subject to penalties for errors and omissions that do not apply to unlicensed individuals offering their opinions on chat groups such as this.

So I avoid designing projects for individuals on this site, since I would be potentially liable for the consequences of my actions, even if it were as simple as the individual misunderstood the instructions and improperly installed the beam. I only design projects when I have a contract with the person for whom I am doing the design, and I only take on a contract when I can personally visit the site.

So occasionally I will offer what I believe to be factually accurate information that could be used by an individual to help with their design or installation. I don't design jobs over the internet. I leave that to the unlicensed folks who have no professional license at stake.

Scuba_Dave

The big deal is when it becomes overloaded & collapses
40 live load is more then what a bedroom floor is usually designed to carry (30?)
My last house is over 100 years old
Many other people on here have houses that are just as old or older
Very few people live in their house for the lifespan of the house
Building to code means building it to last

Going to an engineer may not be needed
Having the beams sized for the span is

I have 6 sets of LVL beams in my house
All were sized by a lumber yard for free & my plans were sent out to be stamped - for FREE
I did buy all my LVL's from them & 2 major lumber orders
So a simple trip to a local lumber yard could answer the question & gice proper sizing & spacing

WillSTX did find a span table that lists a 3x8

kwikfishron

Well since it’s clear that you guys will always give the best information you can on a subject to ensure that the DIY’R competes his or her’s project up to industry standards and code, that’s great, I completely agree. The last thing anyone wants is for a project to fail in any way that could result a failed inspection when trying to sell, creating more problems in the end than you started with or even worse, getting hurt. That’s why we have codes in the first place and that’s exactly why we have the “Permit Process”. You (or someone else) draws up a plan for a proposed project submits that plan to their local building department and they will either approve the plan, reject the plan or say the 3x8’s won’t do, revise to a 3x10 and we’ll approve.

I see time and time again a post with pictures of a project in process with a question like “Is this wall load bearing, can I take it out?” or any other structural or mechanical question for that matter that would not have had to been asked if they didn’t skip one little step, “The Permit Process”.

So my question is this. Is the purpose of this site to help the DIY’R to properly complete a project from idea to end or how to successfully outlaw in your little remodel without hurting someone or something?
　
　

Scuba_Dave

I'm not sure what the part I put in bold means ?
As much as possible I try to help people with everythig I can
But when they want to remove a wall & puit a beam in I will always say get the beam sized
I guess I'm lucky to have lumber yards that will do this without cost
Others have reported lumber yards in their area do not offer this

IMO things should be built to code or above
As many say...Code is the Min that you can build to & pass
I went oversize on my roof rafters & floor joists
Just for that one heavy snow/ice storm, that big party when there is a 100 people in the house, maybe that slate pool table, or the large saltwater aquarium I want to put in
I've put enough electric in that I could put a space heater in every room if the heat failed
...and as luck would have it my heat did go out & I heated with wood & 3 space heaters for 3 1/2 days
Or in case of a lot of people here each person could use a hair dryer in each bathroom

In some cases even with pictures its hard to reach a definite conclusion on if something will work or not
And in some cases people here have outlined the proper way to meet code & build/wire something
...only to have the person go & build/wire it with in such a way that it does not meet code

There'a lot of very talented people on here who offer their assistance
Usually if the answer is not provided there is a good reason

forresth

what is the differnce between three 2x8s and two 3x8s? common sense says there is no difference apart from the load caried by the decking spanning the larger gaps when a load is aplied between the spans, but we are talking beams here, not decking. That is common sense not a wild guess. just because you cant find a table that has all the exact variables you are looking for doesn't make it unsafe. you are acting like a computer that recieved an invalid input and not a thinking human being.

as far as comparing 3x8s to 2x9s:
all other thing being identicale, all that is left is the formula based on cross sectional shape. I remember that formula to be 1/3 x base x hieght^3. all other factors will cancel out. If my memory serves on that formula (and I'm pretty sure it does), 3x8 is slightly stronger than 2x9 bending along the thick dimension. I don't know were my textbooks are stored, so I cant go and look up the complete formulas, but that should be easy enough for someone to verify if they are overly concerned. but it is irelevent because a 3x8 table is easier to find than a 2x9 table.

Scuba_Dave

2x8 = 1.5" thick x 3 = 4.5"

3x8 = 2.5" thick (unless true 3x8) x 2 = 5"

You don't guess with beams, joists, rafters & spans