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-   -   Attic flooring on 2X4 trusses for light-medium storage (http://www.diychatroom.com/f19/attic-flooring-2x4-trusses-light-medium-storage-62885/)

Ehollenbaugh 01-26-2010 07:04 PM

Attic flooring on 2X4 trusses for light-medium storage
 
I'm going to put down some OSB in a small 4X8, (spanning three bottom chords), section of the Warren-style 2X4-trussed, (24" OC), attic in my townhome. From what I've been reading, the trusses are not designed to support storage and I need to get a structural engineer's on-site opinion as to what all needs done. However, I've spoken with several people who have identical attic layouts and have just layed down 2X's perpendicular to the bottom chord and called it a day... one of the people I'm referencing has over 20 years of construction experience, owns and runs a construction company and built the house he currently lives in.

Despite these experienced opinions, I'm looking for a way to reinforce the trusses while at the same time raising the floor for the insulation. Sistering seems to be my easiest option, but is it viable? Would stacking another 2X4 on the bottom chord & gusseting on both sides with plywood be an option? Are there other options? Am I overthinking it since it's such a small area?

All input appreciated. :thumbsup:

Just Bill 01-27-2010 05:56 AM

They will generally support LIGHT storage, but there is usually so much insulation, 8-12" required, that there is no logical way to lay a floor. Sistering supports for the floor may upset the design of the trusses.

Ehollenbaugh 01-28-2010 07:32 PM

What about screwing 2X4's to bridge a few of the V sections, then OSB on them? Better idea, worse idea, or the same as the others?

TANC 01-29-2010 11:30 AM

I would also be interested in this answer, I have a similar situation. I am looking at an attic ladder to get up there and I have a 8 x 12 area that would be perfect for storage.

wnabcptrNH 01-29-2010 11:52 AM

if you are putting xmas decorations, and other light material up there just make sure you are above the insulation level so you dont compact it down and affect the R value. Just dont put a lot up there and you will be fine. Those trusses are built to withstand snowload etc so they can handle it. I have a degree is stuctural engineering an I have installed trusses many times.

Ehollenbaugh 01-31-2010 03:57 PM

Quote:

Originally Posted by wnabcptrNH (Post 391175)
just make sure you are above the insulation level so you dont compact it down and affect the R value.

This is a large part of the problem. The blown insulation up there is 13". The bottom chord of the each truss is only 4". So I need to raise the floor. But should I sister... say, a 2X10 to the bottom chord, going past at least one joint for added strength, or maybe just stack a 2X6or8 on top of the bottom chord & gussett the lengths and joints, with plywood?

Scuba_Dave 01-31-2010 06:21 PM

Quote:

Originally Posted by wnabcptrNH (Post 391175)
Those trusses are built to withstand snowload etc so they can handle it. I have a degree is stuctural engineering an I have installed trusses many times.

Even when they are installed in Georgia which does not get much snow (if any) ?

Trusses are built to meet the span & specific load (range)
To modify this means getting an engineer to sign off OR finding out what your specific trusses can carry as far as load

One reason you are not getting much feedback on this
In addition no-one wants to guess without a picture or more information
You may build it for light storage & use it for light storage
Then the next person moves in & loads heavier items up there causing problems
My understanding is trusses are stamped & you may be able to find out what they are rated for

Ehollenbaugh 01-31-2010 07:34 PM

Thanks for the replies so far guys. :thumbsup:

IIRC, the only markings on the trusses were an I.D. code of some sort that would likely mean something only to the manufacturer, whose name I could not locate anywhere.

I'm not afraid to take and post pics. If anyone would be able to better help with pics, I'll post as many as requested of whatever is requested.

I'm not afraid to do a little math. If I knew what the calculations were, I could plug in my numbers and see exactly where I am. The biggest problem with this is that I'm the center townhome of a five-unit structure. I'd imagine that might make the math a little different, but if anyone knows the calculations or where I could find them, please let me know - they sure wouldn't hurt. My searches have been fruitless thus far.

Ron6519 01-31-2010 07:47 PM

Quote:

Originally Posted by Ehollenbaugh (Post 392446)
Thanks for the replies so far guys. :thumbsup:

IIRC, the only markings on the trusses were an I.D. code of some sort that would likely mean something only to the manufacturer, whose name I could not locate anywhere.

I'm not afraid to take and post pics. If anyone would be able to better help with pics, I'll post as many as requested of whatever is requested.

I'm not afraid to do a little math. If I knew what the calculations were, I could plug in my numbers and see exactly where I am. The biggest problem with this is that I'm the center townhome of a five-unit structure. I'd imagine that might make the math a little different, but if anyone knows the calculations or where I could find them, please let me know - they sure wouldn't hurt. My searches have been fruitless thus far.

You should consult a professional before you do anything. Which is what you mentioned in your initial post. I don't understand why you are constantly suggesting solutions beyond your scope of understanding and seeking confirmation.
Ron

Ehollenbaugh 02-01-2010 12:26 PM

Quote:

Originally Posted by Ron6519 (Post 392454)
You should consult a professional before you do anything. Which is what you mentioned in your initial post. I don't understand why you are constantly suggesting solutions beyond your scope of understanding and seeking confirmation.
Ron

Your concern is noted, but this is not nearly complex enough of an issue to be beyond my scope of understanding.

The reason I am suggesting possible solutions is to try and pull opinions out of people. Despite what must have been a less than helpful post from you earlier, your opinion as stated in this reply, will be logged with the others, and is very much appreciated. :thumbsup:

Ron6519 02-01-2010 01:04 PM

Quote:

Originally Posted by Ehollenbaugh (Post 392803)
Your concern is noted, but this is not nearly complex enough of an issue to be beyond my scope of understanding.

The reason I am suggesting possible solutions is to try and pull opinions out of people. Despite what must have been a less than helpful post from you earlier, your opinion as stated in this reply, will be logged with the others, and is very much appreciated. :thumbsup:

There is nobody on any forum in the world that can give you pertinient advice as, one, no one has seen the situation and two, most do not have experience dealing with truss assemblies and added loads. Myself included.
If you have this understanding, then the question that begs to be asked is, "Why are you asking people who have never seen your construction for an opinion?
To play the devils advocate, what happens when you sell the house and you have this storage space. Will the next owner and every owner after that know to, "only keep light things up there", or will some owner sometime load that puppy up with more crap then you can shake a stick at. That's why, when you build something, you build it to carry the prescribed loads of the rest of the house. Room specific caveats can be dangerous.
Ron

Ehollenbaugh 02-01-2010 06:34 PM

Quote:

Originally Posted by Ron6519 (Post 392831)
no one has seen the situation

That is why I stated that I can take pics for anyone who might be able to help.

Quote:

Originally Posted by Ron6519 (Post 392831)
most do not have experience dealing with truss assemblies and added loads. Myself included.
If you have this understanding, then the question that begs to be asked is, "Why are you asking people who have never seen your construction for an opinion?

This is a matter of knowledge, not understanding. I think it's well understood by everyone that these trusses were not designed for storage. The knowledge of the necessary calculations to properly assess my situation, is what I do not have, and am consequently seeking.

Quote:

Originally Posted by Ron6519 (Post 392831)
what happens when you sell the house and you have this storage space. Will the next owner and every owner after that know to, "only keep light things up there", or will some owner sometime load that puppy up with more crap then you can shake a stick at.

Possible solutions for your propsed problem include, but are not limited to;
- Removing the flooring when I move out. (screws come out as easy as they go in)
- Creating a permanent notification of the load capacities if the work is left in place.

Quote:

Originally Posted by Ron6519 (Post 392831)
That's why, when you build something, you build it to carry the prescribed loads of the rest of the house.

Which is why I have not blindly followed the advice of most of the people I have talked to about it. :wink:

Scuba_Dave 02-01-2010 06:45 PM

No one can do these calcluations for you by looking at some pictures
Trusses are not standard
You need someone to come out & look at your trusses, roof, walls, etc & do a load calculation
OR
Find out who made your trusses & the loads they were designed to carry

Doing a load calculation is not DIY
Putting the floor in & what is recommended by that Pro (possibly) is
Modification of a truss REQUIRES an engineer/design Pro to sign off on it
Stop back in after you have the Load calc


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