Floor Joist 2 x 10 x 10' Times 2 vs 2 x 10 x 20'

[new land owner]

If I am going to build a 20' wide building with a full basement and a center beam is there any issue with using 10' Joist and Plywood gussets to create 20' long floor joist with the seam laying right on the center of the beam?

My thought is that it is much easier to find straight 10' Joist then it is to find 20' 2 x 10's?

Also working alone 10' pc's would be easier to work with?

[Squirl]

I don't see what the problem would be. Six one way half dozen the other.  Just be sure to size the center beam and posts right.  There are charts in almost every framing book.  The advantage is you can go with smaller lumber or greater spacing with the joists.  The cost works out close to the same.  Also make sure to make a proper footing for the basement posts.  These are the most common problems I have seen. I don't understand the need for the plywood gusset.  Proper blocking should hold everything in place.

Oh, and try and make sure the splices for the beam are over posts.

[MountainDon]

IRC
R502.6 Bearing. The ends of each joist, beam or girder shall have not less than 1.5 inches (38 mm) of bearing on wood or metal and not less than 3 inches (76 mm) on masonry or concrete except where supported on a 1-inch-by-4-inch (25.4 mm by 102 mm) ribbon strip and nailed to the adjacent stud or by the use of approved joist hangers.

R502.6.1 Floor systems. Joists framing from opposite sides over a bearing support shall lap a minimum of 3 inches (76 mm) and shall be nailed together with a minimum three 10d face nails. A wood or metal splice with strength equal to or greater than that provided by the nailed lap is permitted.

So the only question is whether or not the plywood meets the strength requirement mentioned in R502.6.1?

Buying 12 footers and overlapping over the center beam is one way to meet the rule. Buying more same depth 2x material and cutting one foot pieces and splicing the center joint. would be another.

[new land owner]

Don

   Thanks for the repy.  Does the line "splice with strength equal to or greater than the nail lap" mean that the "gusset" would have to be 2x 10 material?

[MountainDon]

That's a point that a picky inspector could pick on, so I'd say that next to having an engineer give a paid opinion the 2x10 would be best for a splice, or as I added above, just buy 12 footers. Or something longer and use the cut off for the blocking you will need to have anyways.

[Squirl]

I guess I'm just not understanding something.  Why wouldn't they lap 3 inches?  If you have an outside header joist of 1.5 inches on each side, it seems like a 10' board would lap 3 inches in the center? I thought that this was another advantage of a center beam, because you didn't have to cut 3 inches off ever 20' board.
My example was like this picture here.
http://www.tpub.com/content/construction/14044/css/14044_20.htm
It is also in most of my framing books.  That's why I didn't understand the need for plywood.  Also, I would be willing to bet a company like simpson or other bracket company makes a metal strap or similar rated for this exact application.  They are usually pretty cheap to if you were very worried about inspections, but I haven't researched it.

[new land owner]

It seems to me that if you have 1.5" on each end then you would only overlap by 1.5"?

My next question is if I do overlap does that cause an issue with the subfloor of Osb?  It would seem that the front of the cabin would line up but I would have to shift the back over by the width of a 2 x 10 as the floor joist no longer line up front to back?

[MountainDon]

Squirl's right. Take two rulers, butt the ends, then move each 1.5 inches to the center. They overlap 3 inches. So as long as the 10 footers really are 10 foot everything works out nicely. If you want to be cenrtain lay the foundation and all out to be a few inches short of 20 feet. That may also help with the width loss encountered because of the T&G joint in the sub floor sheathing.

I was thinking that since blocking is required along the beam anyways one way to get it was to buy some 12 footers.



As for the sub flooring sheets, there will be a spot where a sheet won't line up over the joist. That is remedied with  nailing in some scrap 2x4 for a nailing surface. As you move along further shift the sheets to center over joists. That suggestion came from Don_P a while back; it works him.