truss spacing...?

[OIIIIIIIO]

Hi,

I'm pretty sure I know what the answer will be from the guys on this board...I did search a little bit, but just want to confirm...

What are your thoughts on having trusses set 24" on center with 7/16" OSB sheathing an H-clips vs 16" OC...one side of the garage with have nearly 7/12 pitch (scissors trusses)...the other will be 4/12 (storage/spreadweb trusses)...I'm in south central Wisconsin...

My father-in-law (licensed contractor in IL) and I (no construction knowledge of any kind) am concerned about a potential wavy-roof with the extra span of 24 OC (sagging of the sheathing between the trusses)...but everyone else (truss designers, local building inpsector, etc...) seems to think it shouldn't be a problem with good sheathing....both say 90-95% of houses going up are going up 24" OC...but those same people say it's tough to find quality building supplies...things like sheets of OSB with not enough glue that they fall and flake apart and stuff...

Thoughts?

Thanks!
Patrick

 

[flat350]

I'm no expert,but you do see a lot of homes with the wavy roof syndrome with the trusses on 24" centers,new and old ones.

 

[FRANKIEWHIPIT]

When I built my Garage, the engineer spec'd 24" oc, for the extra $104.00 I went for the 2 extra trusses I needed to put them 16" oc i makes for a much nicer finished job!

 

[Addrock]

I just built mine with a 10/12 roof 24 OC in southern WI. A steep pitch cures a lot of ills. It has had no more than 6" of snow all winter. The other thing taller pitch gives you is a room upstairs. When I ran the numbers it cost nearly nothing for the extra room. Because I built it myself I payed $17.33 per square ft. Good luck.

 

[Zeke]

When I built my Garage, the engineer spec'd 24" oc, for the extra $104.00 I went for the 2 extra trusses I needed to put them 16" oc i makes for a much nicer finished job!

Put that way, I would too. But, 7/16ths or what ever you call it, is not enough for 24 OC. So, if the 5/8ths you need is more than the extra trusses, you found your answer.

 

[OIIIIIIIO]

According to my calculations for my garage (one run is 36'...the other is 20')...24 OC vs 16 OC results in 28 trusses vs 42...

 

[framer]

2ft. centers is standard with 7/16 osd. Have seen allot of roofs with asphalt roofing look wavy when frost is on top. Most of time problem is caused by lack
of good roof and soffit ventilation. Condensation on underside of osb causes
swelling of panels. Framer

 

[Doug B]

If it is an option,you should upgrade to 5/8 sheathing with clips , or better yet, 5/8 t&g sheathing.

 

[aar0s]

Most homes around here (southern Illinois) put trusses on 24's with 5/8 osb roof deck, if you have your heart set on using 7/16 then plan on buying a few extra trusses and put them on 16's dead over the studs. If your worried about snow load or any extra weight on the roof system 16 inch centers is a good idea anyway.
That said i have seen some use 3/4 plywood and trusses on 16's before, talk about a solid roof!

 

[327-365hp]

I used 1/2" ZIP Roof which doesn't require clips at 24" OC. That stuff is heavy, it's OSB with a laminate on top. It's weatherproof for 30 days.

 

[Wanna Ride]

I too, live in Illinois. Back about 13 years ago, I personally built my garage. It's a 40' x 30' with 6-12 pitch trusses on 24" centers, with 7/16"OSB and H-clips. Mine shows no signs of dipping between trusses.

 

[NUTTSGT]

I used 1/2" OSB with clips on mine, along with 4/12 pitch.

 

[rwhite692]

My 24x36 is built with scissor trusses on 24" centers...The trusses were engineered for a tile roof, as well.

 

[kb2tha]

If it is an option,you should upgrade to 5/8 sheathing with clips , or better yet, 5/8 t&g sheathing.

I agree. I will use 5/8" ply with h-clips when using 24" centers. With 16" oc spacing I will use 1/2" CDX. If you do use the OSB for sheathing, just be sure you put the rough side up, or you may be looking at your roof on your back, from the ground.
Ken

 

[Skyking1992]

I have mine on 24" spacing with 7/12 pitch. Used 1/2" plywood with clips. No waviness yet. Located in Northern Illinois.

Skyking

 

[Mr.N]

2ft. centers is standard with 7/16 osd.

I take it you don't live in heavy snow country...

In MN many cities require 1/2 plywood as a minimum for code for snow.

 

[Vethead]

1/2" CDX 24" O.C. with a 5/12 pitch. No real snow load worries to speak of.

 

[little d]

O, 36'(12")= 432" divided by 24"= 18+1=19. 20'(12")=240" divided by 24"=10+1=11.
36'(12")= 432" divided by 16"= 27+1=28. 20'(12")=240" divided by 16"=15+1=16.
So, at 24" on center you will use 30 and with 16" centers you will use 44.
My figures are not including any extra truses if needed.
Ok, now let me explain how i learned constrution. My Dad tought me, we tore down houses for the materal to fix up other houses. In doing so, I learned what worked and what didn't (time tested). The one thing that always stood out was carring the "load" from the peak to the foundation. This is something that I try to pass on to everyone that I can.
Can you set them on 24's, ya. Would I, for 14 extra trusses, no. I tend to over build but, I can walk away from a job knowing it is there to stay and not having to worry about comming back to fix something. This is just MHO, so take it or leave it, your shop, not mine.
I hope i gave ya something to think about, little d.

 

[5lima30]

Another consideration is what type roofing material (metal or shingles) are you using? If shingles I would go with 16" OC. If metal I would be fine with 24" OC IMHO.

 

[MP&C]

When we installed the metal roof on our house and my shop, the metal roofing manufacturer specified 5/8 plywood on 2' centers. These used hidden clips to hold the standing seam roofing, held in by screws. I'm quite sure the plywood thickness was to increase the screw engagement and thus wind removal resistance. I'm also quite sure the Dewalt drills we used to screw in the clips would have stripped out holes in OSB. As usual, I went with overkill, the 5/8 plywood on 16" centers. Never have been a fan of OSB on a roof, or 2' centers.

 

[Falcon67]

The 20x24 I built uses hand built rafters at 24" OC. I used 7/16 OSB decking and IIRC it is 6/12 pitch. No waves that I can see, but there's no snow load here either. Well, until THIS winter anyway.

If you do use the OSB for sheathing, just be sure you put the rough side up, or you may be looking at your roof on your back, from the ground.
Ken

Been there, fallen off that.

 

[darkk]

I did a full two story addition 30 X 30 with 24" on center trusses per the building plans 7/12 pitch with 5/8" T&G glued advantage board with 11 foot vaulted ceiling on the second floor and I defy anyone to find any waves in my roof. It is two years old this month. We just had over 6 foot of snow in the last month and a half.

 

[dipper]

My 20x22 is 24" o.c., but i used real plywood with h-clips for the roof instead of OSB.

 

[slickgt1]

It doesn't really cost that much extra to go 16 OC. Would be a no brainer for me.

 

[mobetta]

umm- the real no brainer is to use 1/2 CDX, not OSB. OSB is for walls.... maybe...

"...but everyone else (truss designers, local building inpsector, etc...) seems to think it shouldn't be a problem with good sheathing...."


exactly- GOOD sheathing.

avoid the wave, go 2' OC and use 1/2 plywood w/ clips.

 

[OIIIIIIIO]

sorry...i'm a total newb...not familiar with what CDX is...

i asked the local building inspector about plywood vs OSB...maybe plywood being stiffer...he said he's seen some really crappy plywood lately and had more confidence in finding good OSB...

planned on asphalt shingles...

 

[6768rogues]

We have a 50 lb. per square foot ground snow load and standard construction methods used here are 24" centers for trusses, 7/16 osb and clips between trusses. I own roofs that are built that way and they are straight as an arrow. The trusses must be designed for the spacing used.

 

[mobetta]

CDX is C/D grade plywood w/ eXterior rated glue- IE, sheathing plywood. do not buy the chineeese **** at home depot...look for COO, made in USA is what you want.