# Joist Question for second floor



## MattG (Feb 18, 2015)

Hello everybody I am going to be building a 2 story home that is 30x24. I have not built a 2 story home before so I do not know much about joist... I am thinking of using the 210 tji joist at 14" tall. or somewhere around there. The plan is to span that 24 feet across the depth of the house. 
My questions:
Has anyone used these types of beams at the size of a span I am wanting to use? 
Also, financially are the tji joist a smart choice or are there better more cost effective ideas for the size span I am hoping for? At 16 inches apart I would need 22-23 of the 24ft beams so I could only imagine that it would be pricey
Last question: Upstairs will the trusts be supported only by the walls? Is that 24ft to big of a span? The roofs going to be 6.12.
Please feel free to let me know what you think would be the best set up for the joist, I would love to read about it!


----------



## texican (Oct 4, 2003)

My current home is 24x30 with a second story.... instead of worrying about 24' joists (they don't come cheap, in any size), I put a beam in the dead center of the bottom floor and ran a 30' long beam (laminated 3 sets of 2x8's together), and then ran 12' joists from that center to the exterior walls. Unless you're going to have the entire bottom floor wide open, why bother with the expense..... plot out your lower partition walls, and readjust your joist sizes based on that. 

You can span any distance, depending on how much money you have. I'd build the same floor plan, but go with infinitely cheaper regular dimensional lumber, obtained at any lumber store...


----------



## TnAndy (Sep 15, 2005)

MattG said:


> I am thinking of using the 210 tji joist at 14" tall. or somewhere around there. The plan is to span that 24 feet across the depth of the house.
> My questions:
> Has anyone used these types of beams at the size of a span I am wanting to use?


Wrong question. Instead of asking if somebody else has disregarded what the manufacturer recommends:

Look up the span table (search engine "TJI span table). You'll find several conditions....such as DO YOU PLAN TO ATTACH A CEILING to the underside of them (I'm guessing you do). 

Then what load do you plan ? The least is 40 live and 10 dead. You'll see very quickly the 210 series is NOT rated for 24' span, even on 12" centers. You can also look up series IS rated for it, and on what center. Keep in mind 40/10 is a fairly light load upstairs load. Personally, I'd go with the heavier load rating of 40/30. Not much way to fix a bouncing floor once you've created it.




MattG said:


> Last question: Upstairs will the trusts be supported only by the walls? Is that 24ft to big of a span? The roofs going to be 6.12.
> Please feel free to let me know what you think would be the best set up for the joist, I would love to read about it!


First, make SURE you understand the difference in a RAFTER system, and a TRUSS system. A lot of folks use the word 'truss' for both, and they are not the same.

*Engineered trusses* can easily span 24'...heck they can span 100' if built to do so. By 'engineered' truss, that means one you generally buy from a truss manufacturer, not something built on site. A structural engineer worked out the loads, and the species of wood, and how the entire truss is required to be put together.

Can you site build trusses that will span 24' ?....sure.

Can you site build rafters that will span 24' ?....sure

In both cases of 'site built' above, it requires a lot more carpentry knowledge than the average person has.


----------



## moeh1 (Jan 6, 2012)

Pretty sure TJI will engineer for you free (or at least they did years ago). I did my own calcs instead and used their best series to span 28 feet - over engineered but rock solid. The skinny series can be doubled up also, but they are flimsy and hard to nail to without splitting and can snap in half if turned sideways unsupported while installing. Your roof trusses should be supported by the exterior walls. TJI has some recommended blocking to be nailed in at the ends of the I joists and a rim board as well to support second floor and roof load. 
Keep doing your research as others above have recommended.


----------



## simi-steading (Sep 27, 2012)

I'd plan and build so there was a supporting wall in the middle under most of the second floor.... A 24 foot floor span unsupported is not going to come cheap or easy...


----------



## MattG (Feb 18, 2015)

Thank you for the responds. After this reply I will be going to research some things that you all have said but a quick question on what simi steading said about just building a wall. Does the wall have to span the whole 30 feet? If not could I just use pillars instead? 
Is there someone I can go to with my plans and have them tell me what needs to be done, I hate bothering everyone with such simple questions.


----------



## simi-steading (Sep 27, 2012)

You can use just posts, but you would also have to have a beam running perpendicular between the posts and the bottom of the joists.

If you plan early, you can add a little height to the house so you can use floor trusses instead. Something like this would span the 24 feet... but as I said, wider open spans start costing more.. 

http://www.toolbase.org/Technology-Inventory/Whole-House-Systems/trimmable-open-web-floor-truss

I just talked to a supplier yesterday for a pole barn I'm about to build... I had to swap out trusses for the roof because I wanted a clear span for 24 feet, and not a typical fink truss... Getting either a scissor truss or a vaulted parallel was a fair bit more expensive.


----------



## Darren (May 10, 2002)

There was a seminar at the WV Fire Academy about three years ago that was informative and scary. Engineered I joists don't do well in fires. In the past when a floor started to move, firefighters had time to get out. If the second floor moves in a house with I joists it's too late. You're going down.


----------



## simi-steading (Sep 27, 2012)

Not because of fire, but simply because of failure, is the reason I pointed out parallel flat chord trusses. Much stronger, and less prone to failure.

I've heard of the I beams failing due to too much moisture... I guess what do you expect when they are made from particle board and glued wood?

OH, BTW Darren.. I'm a bonafide and certified FF now... Oh thrills.. more to be expected of me..


----------



## mreynolds (Jan 1, 2015)

MattG said:


> Thank you for the responds. After this reply I will be going to research some things that you all have said but a quick question on what simi steading said about just building a wall. Does the wall have to span the whole 30 feet? If not could I just use pillars instead?
> Is there someone I can go to with my plans and have them tell me what needs to be done, I hate bothering everyone with such simple questions.


The wall wouldn't have to span the whole thirty feet. If it spanned half or two thirds for instance you could put a beam from that inside wall to the outside wall and run the joists of that. You can go to a truss manufacturer with your plans and he will engineer your roof and floor for you. In my experience trusses end up being cheaper than rafters. They buy in large quantities their wood. I pay about sixty to a hundred a truss. This takes care of my rafters, joists and bracing. Not to mention its a labor saver. 

2x4 truss will span up to 40 feet with no walls underneath on a gable roof. 24' is easy.


----------



## mreynolds (Jan 1, 2015)

Just thought of something. If it's two story you will never to have at least a few walls down below. Where will your stairs go? You will need walls to hold them up after all. If your stairs are in the center of the room you could beam off those and run conventional lumber to those beams. Stairs @ four foot wide center of the room would leave 13' either side. You could then run a 6x12 beam to run your joists on. Or you could use two 2x12's with a piece of 1/4" steel plate and bolt the whole assembly together. It will essentially give you a 12" I-beam that can be nailed to. A lot stronger and better fire rating than a piece of OSB with two bys nailed on top and bottom. 


You should still check with local codes and truss companies.


----------



## mreynolds (Jan 1, 2015)

simi-steading said:


> Not because of fire, but simply because of failure, is the reason I pointed out parallel flat chord trusses. Much stronger, and less prone to failure.
> 
> I've heard of the I beams failing due to too much moisture... I guess what do you expect when they are made from particle board and glued wood?
> 
> OH, BTW Darren.. I'm a bonafide and certified FF now... Oh thrills.. more to be expected of me..


That's awesome. Been a FF now for many years. Love it.


----------

