Attic Flooring question

[texascrane]

I have an attached 32x20 garage. It's finished with ladder access to the attic upstairs. A few sheets of OSB were placed around the ladder opening to act as a floor but otherwise the trusses (rafters?) were left exposed from the attic side.

I'd like to add some additional flooring. I ripped some OSB into 2'x4' sections and hauled them up. However when I started really thinking about it, I realized the issue I'm going to have are these "big" trusses that stick up several inches higher than the others. I need a way to support the edge of the board up against those large trusses.

I'm out of my element here so before I do something unsafe, I thought I would check in here. Do I just cut some 2x4's and screw them to the side of the big trusses to create a lip that I can attach the OSB to? If so, is there a standard for how many screws I should run into that 2x4? 2 2.5" screws every 12 inches? Should I use lag bolts instead?

Nothing too heavy is going to be stored up here. It's a 10 ft ceiling and I'm not going to haul anything that heavy up the damn ladder. But it would be nice to have some storage space for old toys, christmas ornaments etc.

Thanks for the help and here's a pic of the space. In it you can see one of the "big" trusses that sticks up a couple of inches or so higher than the others:

 

[Bondo]

Ayuh,.... You could rip shims to put on top of the lower joists,....
Or,....
Screw cleats to the taller beams, but then you'll be steppin' over the bumps,...

 

[danho]

I wouldn't over think it too much. As long as your not cutting chunks out of the support members or are really going to be overloading the floor/ceiling system, I would go either way with you plan. A few 2.5" screws aren't going to hurt anything if you want to go the 2x4 route and that should allow you to get the OSB sheets you cut in place with just enough screws in them to keep them locked down. I would consider insulation beneath this floor if appropriate as well prior to covering it up.

 

[St-rider]

Do I just cut some 2x4's and screw them to the side of the big trusses to create a lip that I can attach the OSB to?

Yes. Some would say nails would be better because of the shear load but screws would work fine for what you're doing. Don't use drywall screws though. Every 16" should be a good spacing.
Nail gun would be easier and faster than screws, IMO.

+1 on the insulation

 

[Scsmith42]

Osb is usually a poor choice for flooring. It is not made to support a lot of concentrated weight.

Plywood or pine boards would be a better choice.

Also, what you are referring to as "trusses", are not trusses. Those are joists.

You can sister some 2x6's onto the other hoists to bring them up to the same height as the LVL, or simply make do with the protrusion in the middle.


Scott

 

[CTyankee]

Attach the 2x4 as mentioned. Screws are fine, you don't need to lag bolt anything. Install the screws in pairs.. 16 on is plenty.

Can you tell me what those 2x4's are that are running on top of the joists and the ones rising up between the bays are for? I've never seen that done. Are they there to stiffen up the joists?

 

[wssix99]

I realized the issue I'm going to have are these "big" trusses that stick up several inches higher than the others. I need a way to support the edge of the board up against those large trusses.

Those aren't trusses - they are beams. You shouldn't have to worry about them here, but I'd be curious to know what they are supporting. Maybe the roof? I see what looks like a post on top of the one in your picture.

I'm out of my element here so before I do something unsafe, I thought I would check in here. Do I just cut some 2x4's and screw them to the side of the big trusses to create a lip that I can attach the OSB to?

Yes. You'll see that the builder did the same thing for some of the other 2X4's that stabilize your beams and joists. BTW - You won't want to remove that stabilization system unless you replace it with something else. Those 2X4's act to stiffen the beams and joists.

 

[CTyankee]

Yes. You'll see that the builder did the same thing for some of the other 2X4's that stabilize your beams and joists. BTW - You won't want to remove that stabilization system unless you replace it with something else. Those 2X4's act to stiffen the beams and joists.

As I mentioned, I've never seen joist bracing done like that. Why someone would do that instead of just blocking between the joists is beyond me. Before I'd consider doing any kind of flooring up there, I'd be eliminating that mess.

 

[finn]

Looks pretty functional from a structural engineering standpoint.

Simple blocking won't spread the load as well.

 

[texascrane]

Those aren't trusses - they are beams. You shouldn't have to worry about them here, but I'd be curious to know what they are supporting. Maybe the roof? I see what looks like a post on top of the one in your picture.

Yes, as I looked at it some more, it appears that the beams are in place to provide roof support. There's a post running from the top of each beam up to the roof.

 

[Frank Dukes]

based on that pic, i'd just build the floor to them and stop there but thats me.

 

[Falcon67]

I hope you picked the thicker OSB for ripping down. 7/16 cut into 2x4 strips is really, really weak. Busting a sheet into 2x8 is about as weak a piece as I'd want to stand on. Use lots of decking - not dry wall- screws to secure those little pieces to the joists.

 

[wssix99]

As I mentioned, I've never seen joist bracing done like that. Why someone would do that instead of just blocking between the joists is beyond me. Before I'd consider doing any kind of flooring up there, I'd be eliminating that mess.

Yea, on the surface it does look like a lot of work. (Less so, if one has a nailer.) Maybe there was a spec to have the 2X4 standing on end? Otherwise, I'd probably just lay the thing down flat and nail straight in to the top of the joists.