View Full Version : Engineered Roof Trusses...is this an overkill?


gto65goat
06-01-2007, 07:49 AM
Hope to have pictures soon.
Building a 25' wide X 28' deep X 17' tall garage. (6/12 roof pitch)
The footer pour and block build got a lot more costly then originally planned.
County requirements are: in order to pour the footers we have to first find 'virgin' soil. This is where it got costly. Instead of (5) tiers down, we had to go 10 tiers deep. There also was a lot more backfill required. If I'm not mistaken, the final count of the blocks were something like 750 total. Close to 370 of the blocks were 12" X 8" X 16"...the others 8" X 8" X 16".
Now that the floor, and apron is poured (10 yards), and $9400 later...I have contacted several framers for quotes.

I plan to go with the Engineered Roof Trusses, so as to be able to use at least 12' wide X 28' long of the upstairs as a light storage area. Some auto parts, and the rest household items. I was thinking of placing the trusses on 16" O.C. versus 24" O.C.. (with 3/4" T & G flooring)
One contractor mentioned that for what I was wanting to do with the upstairs...he thought this was an overkill...16" O.C.. since I plan to use 3/4" flooring.

Anyone build a garage near this size?
What roof pitch did you use and how much head room do you have upstairs?
My reasoning for wanting 16 O.C. for the trusses, is I don't want any wavering of the floor boards.:lol_hitti

I would appreciate your thought and comments.
Thank you,
John

twostory
06-01-2007, 09:15 AM
John,

Talk to a truss design company. They can design whatever you need, based on the weight you will place on the truss floor.

My garage is 26ft wide, with a 8/12 pitch. I have an attic storage area that is 10 ft wide. You desire a 12ft wide attic, that will be tough to do with your 6/12 pitch. (i.e. the ceiling height will be low).

As for the truss spacing, my trusses were designed for 24 O.C. with a 40psf total rating, 20 lpf live, 10 psf dead. The bottom cord is 2x6 material. If you want a higher load factor, you will probably need a 2x8 bottom cord.

If I were building my garage again, I would have the 2x8 bottom cord truss. I have alot of heavy wood stored in my attic now. I would like to store more heavy stuff up there. I used 5/8 plywood for the floor boards, it does flex between the rafters, but saves weight. I think you 3/4 may be more than you really need.

goodluck....

http://www.gtcreations.com/workshop/24%20Garage%20Sep%2016%20.jpg

Zen
06-01-2007, 10:11 AM
I would go with a spread web storage truss with a 25' 6/12 truss. The type twostory has are attic trusses and won't really work well with a 6/12 pitch (no headroom). The storage type truss will be a lot cheaper also. Oh yea, 24" oc should be fine, 16" oc is overkill and costly.

Zen (truss designer)

kbs2244
06-01-2007, 11:01 AM
Check out this site

http://www.public.iastate.edu/~mwps_dis/mwps_web/tr_plans.html

cw_racefan
06-01-2007, 12:08 PM
Man, you just can't seem to catch a break with good ole AA County! My trusses are 32', but only 4/12 pitch. We did attic trusses so that we could store light household stuff. We only have 3' 6" of headroom, but it's enough to get stuff up there and move it around. They were designed for a 20psf live load in the center, with the trusses at 24" oc, and a 2x8 bottom chord, 2x6 top. Talk to the truss people, but it does sound like 16oc is a little overkill. I also didn't use 3/4, I forget what I actually used, but it doesn't seem to flex much if at all. My last set of trusses is 36" on center with the second one in being a double truss with laddering in between the top chords. We design it that way so we could get boxes and stuff wider than 2' up there.

Good luck!

Craig

Dave88LX
06-01-2007, 12:22 PM
AA Reppin'! ;)

gto65goat
06-01-2007, 01:53 PM
Two Story - I appreciate the picture. Looks real nice.

Zen - Thanks for the knowledge.

KBS2244 - Thanks for the download.

CW Racefan - I could use a few breaks. AA County as you well know can be tough

Dave88LK - Sounds like you've been there too?

I'm now wondering how much a "knee wall" would help me, but that would require me to get away from the roof trusses, and place some LVL Beams across the 25' width. The Rafters attach perpendicular to the Beam (14' long) on each side of the Beam, 24" O.C.. I'd like to get at least 5 1/2' to 6' of clearance for storage area. I know the collar ties will get in the way.
Damn, if it aint one thing its another...but that's what makes it fun.:)

Thanks to all,
John

Dave88LX
06-01-2007, 02:05 PM
Sorry to get off-topic, I just moved to Pasadena last month.

clmrhayden
06-03-2007, 04:40 AM
I just finished my 24x26 garage in annapolis and I can give you a few tips. If you want more room inside go with a higher pitch and canterleave the over hang that will raise the peak of the roof for more room.

I went with a 12/12 with a 1" over hang on both sides.
http://www.garagejournal.com/forum/showthread.php?t=5965

Where are you getting your trusses from?

Chris

z28toz06
06-03-2007, 09:49 AM
I'm 24X32 here.I did a half vault for lift room. The other half is trusses with 2x6 bottom joists. I have a 40 psf rating I believe also. they are 2 feet oc.

http://i26.photobucket.com/albums/c142/z282z06/garage1127006.jpg
http://i26.photobucket.com/albums/c142/z282z06/garage1127005.jpg
http://i26.photobucket.com/albums/c142/z282z06/garage1123007.jpg
http://i26.photobucket.com/albums/c142/z282z06/garage1123004.jpg
http://i26.photobucket.com/albums/c142/z282z06/garage1123006.jpg

mleichtle
06-03-2007, 10:39 AM
3/4" will span 24" spacing just fine, thats what most is rated for. There won't be enough deflection for you to notice. So yea I think the 16" spacing is overkill, save that money for some other garage goodies. If you ever plan on making the attic a living space, then the 16" spacing will help you. When I was designing trusses, my boss had us design for 80 psf. You can stack alot of stuff up there. My dad has a V8 block up in his rafters.

Steve in Mi
06-03-2007, 01:00 PM
I'm now wondering how much a "knee wall" would help me, but that would require me to get away from the roof trusses, and place some LVL Beams across the 25' width. The Rafters attach perpendicular to the Beam (14' long) on each side of the Beam, 24" O.C.. I'd like to get at least 5 1/2' to 6' of clearance for storage area. I know the collar ties will get in the way.


I did it like this to maximize space above in my 28' X 48' build. 16" on center, 7' tall at the knee wall.

http://img.photobucket.com/albums/v19/ceethese/Shop%20Photos/Trusses37inall.jpg

chaingang
06-03-2007, 06:31 PM
Here are a couple of pics of my build. The main portion of the building is exactly the width you are doing 25w x 32d. My spacing is 24oc with the 3/4tg plywood floor. I have a 17ft 6in wide room upstairs with a 9ft ceiling. The knee walls are 4ft 9in and I have an 8/12 pitch. The knee wall really is not a concern because the ceiling climbs rather quickly with the 8/12 pitch. My trusses have been calculated for living space because this is what is required in my county for any attic truss. The bottom chords are 2x10 and I blocked between them with 2x8's at the 8ft 6in mark from each side. Once the floor went down it stiffened it up greatly. You can jump up and down in mine and it barely moves. I did screw and glue the floor also. I think the 24oc will be fine for you as I plan on using my area for heavy storage.
PS. There is no LVL or center posts in my lower level.