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| Not the greatest picture. I will update when I have a minute. Alternating 2x4 and 2x6 horizontals with 24" spacing. |
I continue to go over to Mom's for loads of lumber. Correction, I made trips until I ran out of places to put it.
Dad had much of it stored in racks that hung from the floor joists of his two-story garage.
Figuring my dad was pretty smart, I decided I needed a similar rack.
$100 later I am pretty close to done. I did some calculations after the first-go-around and decided that I did not want to be beneath it if I loaded 1200 pounds of wood into the 60" wide by 16" high by 12' long space.
I doubled up on the horizontal supports and used 2X6s for the added horizontals. I should have used 2x6s for all of the horizontals.
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| Maximum load. Dead load at exact center of 60" span |
No wonder the big guys can break a chord on a standard truss when they walk in attics. The engineering design limit suggests that 190 pounds is the limit for a 60" span of Douglas Fir and I know that a lot of guys weigh more than that.
I used the center loading instead of the more precise distributed loading because it is more conservative and because the math is much easier.
In a perfect world, four 2X4 beams and three 2X6 beams could support a bit over 1600 pounds of center load in simple bending.
I would appreciate it if any of the engineers out there wanted to double-check my math. I have not done these kinds of calcs since 1994.
"When in doubt
Make it stout
Of stuff you know
A lot about."
I'd worry about the roof trusses as well.
ReplyDelete1200 pounds with half going to posts and stringers on the side of the building. The remaining 600 pounds (more or less) will be shared by seven trusses or a bit less than 100 pounds each.
DeleteThe floating end (non-wall end) is suspended from droppers. Four of the droppers are suspended from a longitudinal that the builders used to position the trusses. THe other three are deck-screwed into a horizontal chord and a diagonal brace. I tied in very close to a vertical element (and press-plate) so I am not loading a horizontal mid-span with a bending load.
The droppers to the 2x4s are attached to the truss with 3 #9 deck-screws. The droppers attached to the 2x6s are attached with (2+2) #9 deck-screws.
It may sound weird but "It looks right".
I am curious about the metal nails - screws that are securing your horizontal supports to vertical wood members. They are taking the real load, holding the bottom chords up..
ReplyDeleteWhere I used to work, there was a wood catalog rack which had shelves of 1 x 12s and vertical corners and intermediates of 1 x 3s. A single nail held the front vertical / horizontal shelf together, and these were about 5' apart. The books / catalogs in them (I thought) would have collapsed it, but as long as I was there, not an issue.
While I haven't run the numbers, I agree with you - I wouldn't put a large load on single 2x4 or 2x6 supports.
ReplyDeleteI know that when doing unsupported spans for the floor of a living area, the beam requirements get big fast - steel beams are often used instead of 5 to 8 2x12s.
Unless it's changed, as far as clear span for 2x12 SYP, at 16" o/c, you can span 16'. For 2x10's you can span the same 16' if the joist framing is 12" o/c. That's what I remember from building an addition to my Dad's house about 35 years ago.
DeleteAs a carpenter foreman, We built a bunch of homes using 2x8's for floor joists on 2x12 PT x 3 girders at 8' o/c. on support columns, either poured block or poured concrete also at 8' o/c. Made a really solid floor.
Looks okay to me. And yes, over rather than underbuild!
ReplyDeleteCopy what your dad did.
ReplyDeletesam
Big difference between a static load hung and a floor supporting overweight riverdancers with clodhoppers.
ReplyDeleteyou'll be fine with what you got.
Any advantage to making the "storage frame" a secondary truss and making it long enough to transfer the load to the roof trusses at a point adjacent to the side walls? 24 feet of 1 foot space equals 12 feet of 2 foot space for storage capacity. There is still a shear value consideration when loading the trusses close to their support point.
ReplyDelete