ok, here is my question: I’m new to actually dealing with the city RE: permits and such. Im building a garage that is 24×20 with a gable roof.
The city told me that 2×6 for the rafters, AND for the joists is fine. But it’s not written down anywhere. this is a homowners permit (my dads GAR. I’ve mentioned it in an earlier post) and im just sort of learning as i go.. anyway.. 2×6 joists on 24″ centers spanning 20′ doesent sound right.. By the way.. there will be nothing on the joists(no sheetrock below, or storage above).
I’m just looking for a second opinion..
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It may indeed be code. But in the end it is not a very sound roof. DOes it snow near you?
not often. but yes somtimes it does.-->
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What's the roof pitch and the psf snowload in your area?
5:12 pitch and i dont know what the psf snow load is, nor how to find it-->
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You"re talking about a 10' span for the rafters, correct?
And a 20' span for the simple collar tie joists, right?
Sounds ok to me.
Somebody who know more than I will check in before too long.
Samt
good, i hope youre right.. and yes youre assumtions were correct. 10' run on the rafters and the joists span the full 20'-->
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As SamT said you're really talking about rafter ties rather than ceiling joists. The span is fine for a 2x6, just don't plan on storing old yearbooks up there.
Jon Blakemore
No problem with rafter size or ceiling joist ties.Two foot centers mean H clips with your sheathing, or better yet 2x4 blocking.Blocking takes more time ,I still do it even though younger carpenters think I'm nuts.Strongback the ceiling joists also.
mike
great thanks, yeah i wasnt really worried about the rafters. I just was looking at a couple sources that said that 2x6 joists wouldnt 20'. but these were joist calsulators for residential house const. where there is ad addick space.. Anyway thanks for taking the time'-->
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Skyecore, those aren't really ceiling joist in a garage. They are actually wall ties. You only need maybe three of them to keep the walls from spreading. We used to use 2x4's in the good olden days.
I wouldn't hesitate to use 2x6 rafters 2' oc with ply clips. I'd want a decent osb manufacturer and I'd use 1/2" on the roof. That would all be fine here in Michigan where huge snowloads only come once in a while. everything that I've seen just like I mentioned has stood the test of time.
blueWarning! Be cautious when taking any framing advice from me. Although I have a lifetime of framing experience, all of it is considered bottom of the barrel by Gabe. I am not to be counted amongst the worst of the worst. If you want real framing information...don't listen to me..just ask Gabe!
thanks blue, thats what i was hoping to hear.on the roof i'll use 1/2" CDX, OSB is fine as far as code goes, but ive allways used CDX for roof sheathing and as a result it feels wrong to use OSB.-->
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Strongback the ceiling joist? Where? Just a tack board perpendicular down the middle?
I nail a 2x6 vertical to a 2x4 on the flat, nail thru 2x4 into top of joists. This pulls the joists into an even plane, strengthens midspan .
mike
Edited 12/11/2004 8:56 am ET by MIKEK4244
thanks for the idea, we might do that-->
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Sounds good to me. Snow load in portland is 25#.
Since you are in an area of only occasionall snows, that sounds fine to me. Where the subject of snow loads comnes up, it is really "live loads" that you would look for in a code book. Live loads include the pressure placed on a structure by any temporary condition such as wind, snow, people, etc. Typical minimum load ratings would be fifteen pounds/sq ft dead load(materials) and 15# live load.
Then the code book will not tell you 2x6 or two by 8. It will just state the emnd result needed anda study of materials and span tables is the next step in the process.
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Hey thats cool, thanks for explaining it to me, let me see if i understand correctly:
Live loads are applicable to situations that are rapidly chainging (like wether, snow)and dead loads, are loads that are in effect for a sustained amount of time (like storage)did i get that right?So do you add the two together to calculate what what is needed? For example, Diamond(thank you diamond) pointed out that snow loads here in portland are 25#, do i add that to what the maximum dead load might be to calculate what I need to use? did i get that right?-->
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almost right.Dead loads are part of the structure - always there, always dead and unmoving.I know, some of the boxes of stuff in my attic will never move again either until I die, but they are still live loads because they can be moved.Live loads for snow and wind can range from 15# to 120# in places I have lived and worked. That is on the roof.
If you will be making a storage space on the cieling, you have additionall live loads of flooring, normally at about 40#/sq ft.So, if this were a storage truss, it would be designed for dead loads of 15# for the structural system tuypically, and then at least 55# combined live load.
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Did you consider that it is only 12 more 12' rafters to go 16" OC. Then you can dispense with the ply clips and have a straighter roof with no sags in the shathing between rafters. Even though you say now that there will be no storage think long term. 2 x 6 are fine, use them every rafeter with 24 OC or with 16 OC rafters you could do every other joist. Run a flat 2 x 4 stiffener down the middle to keep them straight and you can leave off the strongback and tie each joist with a 2 x 4 to a rafter near the ridge. I would either screw or bolt these ties in to keep twisting to a min. Nails will pulll out and loosen over time. Keep a 4' section in the middle of the garage with no joist and you have easy access to either side for storage. A few sheets of plywood or not. Keep in mind this is for light storage.
good idea but the lumbar has been bought allready and today I laid out the plates for 24"-->
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I just caught up with the fact that you are the same person posting several Qs about this roof system on your garage, insulation, venting and all.
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you caught me.This is the first time that i havent had a boss to ask questions. I'm just really interested in building and im at a place in my learning curve where its starting to get REALLY fun(as well as satisfying) to learn. I could go on for pages and pages about this, not to mention pages and pages of questions. So.. I hope i dont get too overbearing with questions, and questions about answers etc..-->
measure once
scribble several lines
spend some time figuring out wich scribble
cut the wrong line
get mad
It's fun to teach someone interested in learning.
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