Architectural-Structural Questions

[SteveS]

My shop has 16' ceilings with standard 2x4 trusses for the roofing supports. I am planning a drop ceiling so that my shop has 10' celings with the balance of space above it used for storage.

The uprights are on 16' centers are are of 2x6 construction. The dimension are appx. 36x26.

What kinda construction would be required to make the upper level storage strong enough to walk on, etc.? I have NO experience in this type of thing but would like to tackle it myself.

Thanks for any tips or ideas!

[TDHofstetter]

Hi, Steve.

That'd depend on the design of the trusses. My guess is that they weren't designed to carry any more than the "dead load" of an ordinary ceiling (sheetrock is standard these days). Fear not, though; it's likely that we can add a partition wall at a strategic point or two to provide the support you need.

I presume the trusses span the smaller dimension of the shop - the 26' dimension. That seems most sensible - that the trusses count from one end toward the other end.

It'd be really helpful at this point for us to understand which design truss you have - be it kingpost, queenpost, "W", "Fink", et cetera. To get to that point, could you possibly take a digital picture of one truss, showing as much of the truss structure as possible? That'd help a bunch.

Also, what's the truss spacing - you said the studs were 16" o.c., are the trusses also 16" apart?

Next - what's the typical snow load in your area of the country? I didn't peek at your profile to see what state you live in, and I can't get there from here easily without losing what I've just typed.

Chances are very good that you can ALREADY walk on the trusses. Surprise! As part of my job, I regularly monkeybar around among trusses in peoples' houses with zero trouble. The trusses are very probably plenty strong enough to support you... as long as you're not immense (to put it indelicately), and as long as you don't already have a considerable amount of "stuff" among the trusses. The more stuff you've got up there, the less safety factor for your slouching around.

To keep that safety factor high, though, we'd best consider adding at least one partition wall... and for that we need to know the design of the trusses - hence the pictures. Can ya? Would ya?

Thanks.

-- Tim --

Argue for your limitations,
and sure enough - they're yours.
- Richard Bach -

[Frank]

If you have no experience in this type of thing, I recommend you befriend someone who has, or start hitting the books. With spans like you describe, this could be dangerous. Don't want to discourage you, just don't want you dead.

Food for thought: (Just my speculation) You'll be building a new floor for your storage space, that will require at least 2x6 joists, perhaps 2x8. So now you have your shop, 10 feet up to the drop ceiling, 7 inches from drop ceiling to the new ceiling, then the floor thickness 7 to 9 inches. This leaves about 4'8" to 4'10" actual storage, not taking lights into account. Don't quote me, I'm no pro.

Other things to consider: can the walls handle the extra load, will additional suport posts and beams be required that would be in the middle of your floor space? Have enough breaker space for the additional lighting? Got a building inspector you can pay off?

Do it right the first time, you'll make out in the long run. You can robably build it yourself, but get an engineer to look at what you have and design it properly**. Good luck Steve!

**Or have TD look at a photo! Thanks, TD.

Frank



Just another day in paradise.

[SteveS]

I am thinking about putting a dividing wall in across the smaller span (parallel to the trusses) to divide the shop a bit (air filtration, heating/ac issues etc. are easier to manage).

So, the beams/supports will need to span the 26' length. I do *NOT* want to put poles or uprights in the middle of the span since it would interfere with my workspace AND a 12' door on the other end. Even if it means BIG beam(s) to accomplish this. On a side note, the uprights on 16" centers are 2x8's.

I will make a detailed design and a few pix to help clarify my current shop and needs,

Thanks!

[kcW]

Steve

I'd consider using Wood I's or similar product. For a 26' clear span, you'd probably be looking at 14" to 16" joists on 12" centers.

Tim

[Danford C Jennings]

Steve,

First thing you need to check are your building code's allowable modulus of elasticity, if the span is to be limited by deflection or allowable fiber stress if span is determined by bending.

Minum floor joist live loading is 40lbs per square foot. Your local lumber yard should be able to help out on this. As mentioned, wood "I" joists might be the way to go. I checked my tables and 26' is about the max for 2 x 12s on 12" centers, where fiber stress is used (when ceilings are not drywalled and deflection does not pose a problem)...FWIW.

More than likely you have pitched trusses as these are most commonly used in light framing...a roof truss is engineered to carry the loading of the roof and not always the load of the ceiling material to be fastened to the bottom chord....

Dano

[SteveS]

Here are a few pix of my task at hand the first pix shows a corner of my shop. The upright 2x6's are on 16" centers. The truss design is a W-shape and looks to be on 24" centers (I did not get a ladder out and actually measure it).

http://www.in-motionphoto.com/shop/Shop0.jpg

The second pic shows the 12' high garage door. This is a bit of a dilemma also, since I want to have appx 10" high ceilings. The garage door would have to open up into my loft/storage area. Perhaps I need to replace it with a sliding door? A'la barn-style?

http://www.in-motionphoto.com/shop/Shop1.jpg

The third photo shows the exact center of the roof trusses. This will better detail the design/style of them.

http://www.in-motionphoto.com/shop/Shop2.jpg

Thanks for all the help...this is a GREAT place!:D

[Danford C Jennings]

Steve,

Thanks for the pics; 'pears to me these are pitched trusses. Is it my imaigination or are those bottom chords in the last pic really deflecting that much?

Any who, to add the "second" floor, you would follow the methods used in balloon framing. A 2 x 4 ribbon strip is let into the wall studs to act as a ledger for the floor joists, the joists are run to the sheathing, then nailed to the studs. If you are going to sheath the inside, fire stops need to be used.

See my previous post on determining what to use for your floor joists.

As to the "retracting" into the "loft", I suppose that could be done.

Dano

[SteveS]

Danford,

Can you elaborate on all of this with more detail? I am not a constuction guy so as much detail as possible will help. Does this building's structure/spec lend itself well torward my goals?

Also, can I span the entire 26' length with this technique?

One last thing...I think that third photo's deflection is actually just an optical illusion from the use of a wide lens. I am going right out there to double-check though.

Thanks a million.

[Lou_williams]

I added a second story over one part of my house. It required s long span of about 20 ft. I could have used normal timbers as jousts but went with Engineered I beam floor joists. They can be made to meet almost any span with in reason, you should be able to get them to span 26 ft. You would need to support them by stud's that are set to the 10 ft hight you want on the inside of your existing wall studs, I don't know what the spacing would be since the joist manufacture will tell you that bases on the span and size. What I did on my job was to build a second stud wall to support my joists. It cost me 4 inches of room size but it made the framming easy.

What I would worry about is if you set the celling at 10 ft your floor will be at about 11 ft. That gives you only 5 ft to the bottom of the roof trusts. could be a real pain. I think that if you really want to do this and have a real useable space above you need to see a structureal engineer to determine how to change the roof trusses to get the head room needed.