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OSB Attic Subfloor???

| Posted in General Discussion on December 19, 2000 10:15am

*
I’m getting ready to “create” some attic space in my garage (28 x 40). The trusses are the standard 2×4 style spaced 24″ on center. I’ve added 2×3 (attached vertically) across the tops of the trusses spaced 16″ on center to raise the subfloor over multiple runs of wiring that my builder simply laid across the trusses. I figured it was easier than moving all the wires plus it allows me more space for insulation. This space will be used only for LIGHT storage. My builder has warned me that an unsupported 28′ span is not designed to carry large loads and I understand this. In an effort to cut costs, I’d like to use 5/8″ OSB as a subfloor however I’m not sure if I’d be better off with plywood. Any thoughts would be greatly appreciated. I’m a rookie so go easy on me!!!

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  1. Jeff_Clarke_ | Dec 15, 2000 08:50pm | #1

    *
    Sorry Keith, my opinion is don't do it. The trusses weren't designed for it.

    Jeff

    1. Steve_G | Dec 16, 2000 01:50am | #2

      *keith, I'm with Jeff. You could contact the truss mfg. if you know who built them, and seek their advise an any modifications that might make storage possible.

      1. Jim_Nation | Dec 16, 2000 04:58am | #3

        *Let me add my admonishments to the two previous comments don't do it without having an engineer or the truss manufacturer analyze the loads. The tendency is for most attic storage to concentrate near the center which is the worst place for it. Relatively light items can cause problems. I once paid for putting an HVAC unit in a truss space without checking.

        1. Keith_Jarboe | Dec 16, 2000 04:59pm | #4

          *I guess I should add some more info to possibly help clear things up. My builder didn't say not put anything up there, he just said be careful. Any items I store will be placed as close to the outside walls as possible, not down the center. It's a 28x40 floor so I can really spread things out. Additionally, anything I store in this space will not be close to the weight of the open garage doors that are hanging from these trusses all day long. One final note, my builder roughed in for, and offered to install, a pull down staircase. Why would he do that if I'm not supposed to be up there???? (No mechanicals in the garage)Please help!!! There's got to be a way to do this.Thanks Everyone!!!!!

          1. Keith_C | Dec 16, 2000 08:05pm | #5

            *Light loads mean empty cardboard boxes(from the computer and such) and Christmas lights. The access steps may have been to get up there for those extra wire runs for cable and TV that people put in there garage. If you wanted actic trusses, they would have cost a lot more. I have had my customers ask me after the fact the same question. I respond that" it is now your house and you can do what you want, but it is not designed to hold it. I will note that in your file, and the fact that I warned against it in case it results in any damage" Once they know you have shoved the liability on them, and noted it, they will find other storage places more suited for the situation. For the record, I repaired one of these situations this summer to the tune of $30,000. Homeowners insurance paid it, but went after the builders(not me)insurance. They lost, homeowner learned a lesson.Keith C

          2. Boss_Hog | Dec 17, 2000 12:33am | #6

            *Keith - Trusses are typically designed for a 10# per square foot load on the bottom chord. That includes the weight of the trusses, drywall on the ceiling, insulation, and about 2 PSF for miscellaneous loading. That doesn't leave a lot left over for storage. Everyone here has basically advised you to proceed cautiously, and/or talk to the truss manufacturer, but you seem to be resisting doing that for some reason. You may be able to do some minor modifications to the truss to beef it up for some storage loads. But the truss manufacturer is the one you need to talk to. They know what plate sizes and brand they used, what lumber species and grades, and your local codes. No one here has those answers, so we can't give you specific advice. I'm not trying to give you a hard time, Keith - That's just the real answer about where you need to start.

          3. Mad_Dog | Dec 17, 2000 12:46am | #7

            *Ron,You forgot to tell him what you do for a living...

          4. Luka_ | Dec 17, 2000 01:05am | #8

            *Kieth,Don't do it.Do you realize that you aren't talking about just some boxes stuck back near the walls... You have already added the weight of the 2x3's. Then you're talking about the weight of extra insulation, and then the weight of whatever sheating you decide on, for the floor, and finaly, the weight (dead weight) of whatever you end up putting up there to 'store'. Once you have invested all that money, time and effort into putting some semblance of a real floor up there, you are not going to want to take it easy on what you put up there. Given time, you may even start looking at it as an extra living space.Bottom line, it's easy to say "oh we're only going to put boxes of fluff up there, and we'll go to the extra trouble, every time, of making sure it is distributed evenly and as far to the outside as possible", etc... when you don't have what looks like a real floor up there. You are going to already have more weight than the trusses are designed for, on the trusses, just in the weight of the floor you put up there. Then you are going to be sorely tempted to start hauling every little piece of junk that you just can't bear to part with, up there. And you are not going to continue to be careful to distribute the load, etc...If you want a floor up there, have someone design a real, working solution, and have it done right. Otherwise, quit wishing, and realize that it's just empty space over your garage.

          5. Keith_Jarboe | Dec 17, 2000 04:16pm | #9

            *Thanks everyone for the advice. It doesn't look too promising. I did talk to the local suppliers and they said "everyone does it even though it's not suggested". That doesn't sound like good advice to me. I talked with my neighbors and they all store things in their attics. So far no problems, but....time will tell.Anyone ever heard of somebody building beefier "sister trusses" next to the existing ones? Probably a pipe dream from my novice mind but I had to ask.Anyway, I have to respect everyone's opinion. Y'all know wayyyy more than I do. It's a real shame my builder didn't ask me about this before it was built. I mentioned it during our planning, but only briefly. Sure wish someone had some real world examples of how I could somehow use this space without putting support beams through the roof and trunk of my car and truck. Thanks Everyone!!!

          6. Boss_Hog | Dec 17, 2000 04:49pm | #10

            *Mad Dog - I thought the phrase "I stand behind my trusses.........Not under 'em" would give it away.

          7. Brad_in_Wshington | Dec 19, 2000 10:15am | #11

            *Why don't builders routinely ask the owners if they want light storage or attic trusses? They really don't cost that much more for the storage space that you get. Specially when you consider that most homes these days are built without basements. I'm building my own house and asked the truss manufacturer about these trusses before I ordered. Once you put non load bearing trusses in your pretty much stuck. I have attic trusses over my garage that added a 13 X 20 room that can eventually be used as finished living space. I just want to get the main part of the house done now. I also put light storage trusses over the main part of the house. They have a 2X6 bottom cord and are rated at 40 and 10. I'm going to put four rows of I joists perpindicular to the trusses so I have room for insulation and put up eight 4X8 tounge and grove 3/4 inch osb subfloor sheets down the center of the trusses on top of the tjis. When I found out how little extra this all cost it was a no brainer. I know this doesn't help Keith this time but if he ever builds or has a house built for him in the future he will know about this option. And all you builders should ask your clients if they want this option if your codes allow it. You guys are a great bunch and have helped me out while I learn to build this house so just take this suggestion for what it is and not criticism. Thanks for the help.

  2. Keith_Jarboe | Dec 19, 2000 10:15am | #12

    *
    I'm getting ready to "create" some attic space in my garage (28 x 40). The trusses are the standard 2x4 style spaced 24" on center. I've added 2x3 (attached vertically) across the tops of the trusses spaced 16" on center to raise the subfloor over multiple runs of wiring that my builder simply laid across the trusses. I figured it was easier than moving all the wires plus it allows me more space for insulation. This space will be used only for LIGHT storage. My builder has warned me that an unsupported 28' span is not designed to carry large loads and I understand this. In an effort to cut costs, I'd like to use 5/8" OSB as a subfloor however I'm not sure if I'd be better off with plywood. Any thoughts would be greatly appreciated. I'm a rookie so go easy on me!!!

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