Maximum pullout weight attached to plywood

[pdave]

Does anybody know what kind of load can be placed on a shelf that is screwed to 3/4" plywood. There are no studs in the center of the plywood where the shelf would be attached. What kind of screws would resist pull out the best?

 

[theoldwizard1]

Toggle Bolt

 

[rlitman]

Does anybody know what kind of load can be placed on a shelf that is screwed to 3/4" plywood. There are no studs in the center of the plywood where the shelf would be attached. What kind of screws would resist pull out the best?

There's not enough information to answer the strength question. How much load a shelf can support depends on the shelf brackets as much as the wall attachment.

Also, how well the plywood is attached to the studs, and what the stud spacing is will make a difference.

Do you access to the rear of the plywood? If so, t-nuts behind the sheet will give you the best grip for a bolt. If not, a toggle bolt is probably your best bet.

 

[pdave]

This is a 12' tall pole barn with 8' on center poles. There are horizontal 2x4's between the poles. The plywood is placed longways between the poles. The sheets are screwed top and bottom to the 2x4's. I want to mount shelving around the top 3'. The brackets will be screws into the middle of the plywood where there is no additional support. Trying to find out what kind of weight it will hold just screwed to the plywood. I would prefer not to have the expense and time on removing the plywood to install studs if I don't have to.

 

[ard]

Another option..

Two verticals of unistrut, would be able to attach at several points AND hit a stud or too. And mount what you want where you want....

 

[lakeroadster]

The sheets are screwed top and bottom to the 2x4's..

Plywood:
What kind of screws? Structural screws? Size and length? Spacing, screw to screw? What type and thickness of plywood.

2x4's:
What is the spacing of the 2x4's? 2x4's are attached to what and how? Do they attach to the girts? What grade are the 2x4's

Girts:
Standard or bookshelf girts? How are the Girts attached to the columns? nailed, screwed, to the face of the column or toe nailed into the side of the column?

Columns:
What type of columns, dimensions? Solid lumber or built up from 2x6's?

Photo's would help.... lots of different pole barn configurations.

Headers:
Does the barn have headers going from column to column at the top? If so, what's the dimension of the header? Double header? How do the headers attach to the columns? Screwed, Nailed? What type, size, quan. spacing? Does the plywood attach to the header?

 

[Muzzy]

The strut isn't a bad idea.
You could also use those vertical shelf rails, ensuring that the rail (or strut) catches the top 2x4. How much weight you're planning to place on the shelves factors in here too. The 'how much can it hold' is pretty open ended.

 

[pdave]

Plywood:
What kind of screws? Structural screws? Size and length? Spacing, screw to screw? What type and thickness of plywood.
The plywood is screwed to the 2x4 with what appears to be 2" coated exterior screws. 5 screws along each long edge into the 2x4. I didn't install this
2x4's:
What is the spacing of the 2x4's? 2x4's are attached to what and how? Do they attach to the girts? What grade are the 2x4's
The 2x4's are horizontal 4' on center. They are screwed to the posts with what appears to be 2 - 3 1/2" coated exterior screws. They are probably standard Lowes 2x4's
Girts:
Standard or bookshelf girts? How are the Girts attached to the columns? nailed, screwed, to the face of the column or toe nailed into the side of the column?
They are screwed to the face of the poles with 3 1/2" exterior screws
Columns:
What type of columns, dimensions? Solid lumber or built up from 2x6's?
Columns are 2x6 buildup.
Photo's would help.... lots of different pole barn configurations.

Headers:
Does the barn have headers going from column to column at the top? If so, what's the dimension of the header? Double header? How do the headers attach to the columns? Screwed, Nailed? What type, size, quan. spacing? Does the plywood attach to the header?

I'm just looking for storage. I can't imagine I would get more that 30-40 lbs sq. ft. but You know how that goes. I'm just trying to get a general idea of how much a 18-24" shelf with supports make out of 2x4's in a triangular configuration will hold if screwed into the plywood only.

 

[lakeroadster]

pdave,

You keep using the term "Exterior Coated Screws"? Are those structural screws... or deck screws?

Regardless... 40-psf? Trust nothing that you yourself didn't install.

Here's what I would do for a 24" wide shelf...

Build a shelf ladder frame out of No. 2 grade 2 x 8's, with 2 x 6 joists, 24" on center.

Then use struts to apply the loading back up to the header. Space the struts 24" on center (See photo below for visual of struts).

Use 1/2" plywood for the shelf top.

The shelf photo below comes from the following GJ thread: https://www.garagejournal.com/forum/showthread.php?t=39367&page=2

 

[Lelandwelds]

You can always add additional screws to the plywood. You can brace the front shelf edge with a vertical 2 x 4 column.

The shelf width needs to be considered also. ( 8 inch shelfs support more weight than 24 inch.)

 

[matt_i]

I think you could put 50 lbs on it.

As usual the problem goes back to how the loading is done, being a cantilevered setup. If it was a 1" steel plate more or less affixed to the back wall, it could probably hold 500 lbs if you put enough screws into it to take up the shear loading.

If you want to eke heavy stuff just over the edge its a different problem.

Directionally making the triangular brace larger & vertically longer will assist.

The toggle bolt mentioned above is probably the strongest solution as far as resisting pullout, most other solutions will involve threads holding in the wood itself, which are usually lesser in strength.

I don't know if its possible but if you can extend the shelf wider so it can be attached to the posts themselves.

Eventually the 3/4" ply is going to bow in the center, not sure where you are in relation to the centerline of the 8' span.