Trusses - 2x6 bottom chord?

[DMurray]

For my new garage, I was thinking about specifying a 2x6 bottom chord for my trusses. I thought it might be useful for hanging storage later on.

I've never ordered trusses before. Is this a common thing to ask for?

I guess one downside is that the trusses would be a fair bit heavier and harder to put in place.

Thoughts?

 

[Jlbc212]

You can ask to have the truss designed to carry additional loads. When I built my garage I specified attic trusses to carry a dead load of 10 pounds per square plus an additional 40 pounds per square foot of live loads. I also requested additional trusses so I could space them 16" on center. The bottom cords on my trusses are 2" x 8" and span 28 feet. I rented a crane service for four hours to lift the trusses in place. The crane charge was $650.

 

[The Cobbler]

being from Edmonton, your snow load calculation will be high. bigger isn't always stronger. discuss this with the truss company . it may be a case of adding more webs, but they are the folks to talk to.

 

[bigtater]

Just tell the truss company what you want to do and they will place a storage load on the bottom chord. It maybe a matter of changing the locations or number of the web members.

 

[duneslider]

Yep, just talk to the truss company and tell them what you want to do and they will design it to do that.

 

[gsmith22]

obviously have the trusses designed to do what you want. But as a base case, truss designs for an uninhabitable attic without storage are supposed to still include 10psf live load on the bottom chords, uninhabitable attics with storage 20psf live load, and inhabitable attics with sleeping areas 30 psf. Otherwise, 40psf live load is the largest live load specified for any location in a residential setting. That being said, if your plan is to store gold bullion next to piles of books floor to ceiling, make sure to give them an accurate number and not 20/30/40psf.

two ways to accommodate extra loading and it should probably include some of both - make the bottom chord taller and add more web members. Although individual members of a truss work together to span the entire distance between supports, you can idealize the bottom chord as being part beam (spanning between web member support points due to your storage load) and part tension member (induced load from overall truss action). Further apart the web members, the taller the bottom chord will need to be (keeping loading constant). I would point out that the more web members you have on each truss, the less likely the space will work well as a storage area because of the forest of members. I would suggest that you not only figure out what you are going to store (so you can get an accurate live load) but also come up with a truss configuration that helps define a storage area so the higher live load can be placed there and the web member locations can be adjusted to maximize this space.

 

[jbwilkins]

Your good designer should also ask what 'type' of load you plan on hanging from them.

A point load, a large load in one place, requires a different design than an 'attic storage' load where the weight is spread across a much larger place.

 

[ddurrett896]

Tell the truss manufacture what you might store up there and they will build to spec. Go ahead and get attic storage trusses while you're at it. YOU WILL USE THE SPACE EVENTUALLY!!!

 

[WisJim]

I .went with attic room trusses.which were designed for 40psf live load and have 2by6 bottom chords 24' span and 12' wide attic room.

 

[mobetta]

attic trusses are great even if you only get a 5-6' high space

How much is a 8x8 mini storage a month in your area?? doenst take long to recoup a few hundred dollar upcharge

 

[TurnipTruck]

I specified what I needed, and my truss builder used his program to fine tune lengths, chord sizes, and nail plate dimensions.

I asked for the top chord to be a multiple of 4 feet so I wouldn’t have to cut the sheathing.

My city specifies a LiveLoad of 50 lbs/sqft for snowload, and he rounded up to get 70 by just increasing a few key nail plate dimensions.

I needed a four foot gap in trusses for stairs, that was only a nail plate sizing upgrade.

I didn’t want too steep (for ease of roofing and appearance) yet steep enough to shed snow, so we got 4/12.

The shallow slope meant we had to drop the attic truss floor to get reasonable room size and headroom, which gave me a 4-1/2 foot energy heel for the back sixteen feet in order to match the common Watt trusses in the front.

And finally (back on topic), my common trusses only needed 2x4 bottom chords, but the attic trusses have 2x12 attic floor chords flanked by 2x8 outer bottom chords.

 

[DMurray]

Thanks for the great info folks.

Sounds like this is a common requirement - I'll go back to the truss company and have a discussion about storage loads and go from there.

 

[Milton Shaw]

Ask if there is a strong back in the design. That is a beam across multiple trusses to tie them together. That will support a lot more than just the single truss will support. The truss designer should be able to tell you what you need. The strong back was in some floor trusses I used and may not be in attic trusses. Mine was a 2/10 tied to every truss.

 

[kwb]

Tell them what you want to do, they will size the members accordingly. Maybe it is a 2x4 maybe it is a 2x10 that is what they are paid to do.

 

[DMurray]

Yes I'll go back and ask more questions. It's a big lumberyard that also has a truss plant. They sell "garage packages" which include all lumber and trusses and they will also build it for you for a price.

But they charge a lot of money to bundle everything up and sell you a package. I'm trying to save some money by just buying what I need and hiring a framer to put it up. But it seems like you get a very different level of service when you do it that way.

I'll check out some other truss companies - might get a better level of service which seems to be a lost art these days.

 

[MushCreek]

When I ordered my trusses, they said they design for the code-minimum 90 MPH wind load. I asked how much it would cost to up it to 120 MPH. I could hear the guy tapping away on his computer for a few seconds. "Hmmm. It comes out to the same price." OK then, that's what I want. It will likely cost you more to increase the storage load rating, but probably not very much. It's well worth the extra cost and effort.

That being said, I don't store anything in our house or garage attic. With 16" of cellulose up there, storage is out of the question anyway.

 

[astroracer]

I'm bubbling up a 24' x 36' addition to my shop. Pricing for attic trusses over normal "wasted space" trusses was about a grand. That works out to a little over 2 bucks a sq. ft. Cheap money for a lot of usable space.
Mark

 

[D45]

I am running 2x6 bottom chord boards

Well worth the, small, additional cost

 

[DMurray]

Yes I think so. I wasn't thinking of storing anything up in the attic because I live in climate zone 7 so it will be quite full of insulation.

But with nearly 10 foot ceilings, I would like the option of suspending some kind of shelving solution from underneath. Nothing too heavy really, but enough that I need to have that conversation with the truss people as many here have suggested.

 

[Mr_fixit]

You can ask to have the truss designed to carry additional loads. When I built my garage I specified attic trusses to carry a dead load of 10 pounds per square plus an additional 40 pounds per square foot of live loads. I also requested additional trusses so I could space them 16" on center. The bottom cords on my trusses are 2" x 8" and span 28 feet.

I did this also, plan was to put floor down between the larger spaces and use for light storage. Mine are 2x6 bottom chord for 30' span.

You might need to beef up the walls , too, depending on what max weight they might need to hold (truss + dead load + live load ).. .? and also consider the height of the walls...double up on some 2x4? 2x6? add blocking?