Offsetting joist from studs? 4

[JMAN124]

I have a storage unit and I built a loft above with 2x6 walls and 2x12 joist that span 8 Ft. when I put the joist in I put them on 16'' on center, the only problem was they were offset from the 2x6 studs.... Is this structurally sound?

 

[msquared48]

Not normal, but with a double 2X6 top plate, only an 8 foot span, and wall sheathing, it should be OK.

Mike McCann
MMC Engineering

 

[MiketheEngineer]

With a double plate - should be just fine

 

[JMAN124]

Thanks guys, i know this is a tough question to answer but how much weight do you think I can get away with? there is a total of 104 sqft ( 15ftx8ft)

 

[csd72]

I have used a similar detail which was designed for floor joists to be placed at any location and it worked fine.

 

[AHaddad1]

The shear stress in the 2x6 top plate is what usually controls how much load you can deliver to it from the 2x12.

If you have a single top plate (double top plate is a standard code requirement in almost all codes), with an 85 psi allowable shear stress in the 2x6, the 2x6 will have an allowable load from the 2x12 of about 234 pounds, the further the 2x12 moves to the center between the 2x6 studs the higher the load can be, if the 2x12 is exactly in the center between the two studs, the allowable load can go up to about 468 pounds (2x234)

If you have a double top plate the allowable load will be 468 pounds (2x12 close to the studs) and 935 pounds (2x12 close to the center between the two studs)

Using the worst case scenerio of single top plate and 2x12 close to the stud, the allowable uniform load on the 2x12 joist with an 8 foot span 234 pounds times 2 (shear on 2x12 is half the total uniform load) = 468 pounds divided by 8 feet = 58 pounds per linear foot of joist, with 16 inch spacing would be ~ 45 pounds per square foot total allowable dead plus live load on the 8 foot joist.

If the top plate is doubled, this translates to 90 pounds per sqaure foot allowable dead plus live load on the 8 foot span.

I hope this helps.

A

 

[JMAN124]

I have a 2x6 double top plate with the joists 8 inches of set from the studs.( instead of sitting directly above the studs)

so are u saying that i can hold more weight if the joist are sitting right about each 2x6 or if they are sitting between the 2x6?

i have 90 pounds per sqft limit with a total of 120 sqft which gives me a total of 10, 800 lbs capacity??

 

[csd72]

JMAN124,

We are not going to design it for you.

 

[AHaddad1]

JMAN,

The 90 psf is based on certain assumptions on my calculations and specifically related to your question, there could be other parameters that are not addressed that can bring the 10,800 pound capacity down. For example, the allowable shear on the 2x12 joists could limit the floor total load capacity to 80 psf for an 8 foot span, it all depends on the species of wood you have used.

If you have concentrated loads you should use wood blocking at midspan of the 2x12 joists even if the 8 foot span is within the limits for requiring any floor bridging. Do not park your truck on it, lol.

Please double check my numbers before making your final decision on how much your floor can handle considering other issues that are not addressed in my response.