If 15' is to the outside, your actual span is probably about 14' when you figure in the foundation wall, and the width of the beam. I think your floor would be ok with that span. I would go with a fir or pine joist and not spruce. If you have an island or a big tub you could add a few doublers.

 

Frame 12" on center with the 2x10's. Agree with above. Doug Fir, no SPF

 

I've done 16' with douglas fir, no problem, and that was without any solid blocking or even bridging.

 

Bridging or blocking is required over 12' per per the IRC.

 

So do we just ignore span tables now, or what?:blink:

 

He said he checked the tables. A 2x10 for a 10# dead and 40# live load @ 16" O.C. is good for 15'5" for SPF #2. Want to span that for bedrooms? You can now go to 17'2".

His issue is a concern for bouncing which is why I recommended framing 12" O.C.

 

Is the $$$ of 30' @ 11 7/8" I-Joists prohibitive?

A solid structure is the most important thing. Put $$$ into the important things.

But hey, I'm an over-builder (framer) so what do I know? :blink:

 

Yes,

I'm having a hard time springing for the 9 1/2" I-joist. I've never used 11 7/8", I'll check to make sure.

 

PS

I've never done ANY floor system with anything less than a 2x12. No load ceilings.....diff story. But floors.....you just never know what people will load on their floors.


When I remodeled homes with less, I always thought (cheap).

Again...........just my opinion.:whistling

 

The span tables used to be 16' for 2x10, 16" oc and 12' for a 2x8, 16" oc.

That was pretty standard. If you wanted to maximize, you built a 32' wide structure and used 16' 2x10's, or a 24' wide and used 12' 2x8's.

All of the homes in my neighborhood (1960's through the early 80's) are 24' wide and have 2x8 floor joists.

Why did the span tables change? Does anyone know?

Quality of lumber, fatter people, heavier live loads? Refrigerators are sure getting bigger, and people are sure getting heavier.

 

The span tables used to be 16' for 2x10, 16" oc and 12' for a 2x8, 16" oc.

That was pretty standard. If you wanted to maximize, you built a 32' wide structure and used 16' 2x10's, or a 24' wide and used 12' 2x8's.

All of the homes in my neighborhood (1960's through the early 80's) are 24' wide and have 2x8 floor joists.

Why did the span tables change? Does anyone know?

Quality of lumber, fatter people, heavier live loads? Refrigerators are sure getting bigger, and people are sure getting heavier.

They have not changed in years except for recently SYP was reduced in span this year. I am finding the same numbers going back to the 2001 NDS for DF & SPF.

 

Why did the span tables change? Does anyone know?

Quality of lumber, fatter people, heavier live loads? Refrigerators are sure getting bigger, and people are sure getting heavier.

Fast-grown, overly-fertilized, mono-crop plantation-grown trees is the main reason. Most of the good quality timber was cut and sold overseas at rock-bottom prices as fast as they could cut it. :wallbash:

 

It's Western Washington, we only use Doug-Fir.

 

The issue with TJI's is that some areas require that the bottom be sheet rocked for fire protection due to how fast TJI's burn. It is to protect firefighters where there are no sprinklers in a residence.

 

Bounce and deflection are different things. Span tables are for deflection. Bounce in an otherwise structurally good floor usually becomes a problem with larger floor areas / support areas. The resonant frequency becomes close to footfalls when people walk. Think of the head of a drum. Big drum, head a little slack, and you get low frequencies. Small drum with head stretched tight gives high resonance frequencies.

I don't think I'd worry about it too much for the spans you're dealing with, but if you have a room getting up much above 15'X15', consider putting extra solid blocking in.

 

Span tables are mainly influenced by strength and to some degree on an arbitrary deflection ratio is some how representative of an engineering approach.

Feel and vibration is a factor that is "people-oriented" and no group would attempt put that kind of factor in a table, because it cannot be measured by any standard.

There is no question that bracing and blocking improves the "feel" because it spreads the load out somewhat to more joists or a slightly larger area.

Not that the reduced stresses have finally trickled down through the politics, the next question is how much difference is there in the real elasticity of the new growth lumber compared to decades of testing based on old growth wood. My guess is that it will take a couple of decades to get by the politics (associations and lumber producers with deep pockets) of standards and finally into a real code.

 

TGI & 1" sub floor.

 

Glued and screwed of course

 

You can go 15' with a 2x10 and be OK with it without having a bouncy floor. If you plan to use tiled flooring or there is a bathroom above, you can double every other joist in that area.

 

I heard a speaker at JLC live bring up the point of the feeling of a floor. If you have two sections of a floor, one with a longer span than the other, the feel of the floor will be different. The one with the longer span will have more bounce. He suggested adjusting the size or spacing of different length joists so they have the same deflection.

 

PD.... GOOD LOOKING PUP....

Yes... If you have two floors near each other, you really do want them similar.... you'll really notice bounce/deflection if you are not consistant

 

When you design a floor to code minimum, yes the floor bounces. I know from experience having to retrofit about a dozen floors my company framed. They were all designed to code but people kept complaining about their china cabinet rattling every time they walked across the living room. The fix for the future houses was to switch from 1 3/4" wide TJI's to 2 1/4" TJI's I think.

 

New lumber dimensions are smaller per size than old day lumber and ****ty wood.

 

New lumber dimensions are smaller per size than old day lumber and ****ty wood.

That isn't it.

 

I'd price upgrading to 1.25 deck and 2x12 or 2x3 or 2x4 wood i beams or even trusses on 24 or 19.2 centers.

Far better for MEP subs.. and far cleaner basement. Less labor / fasteners/ even glue.