Porch verandah type roof. Central KY snow loads. 2/12 max pitch, 12′ SPAN 2×8″ with 2×6 jacks and commons. commons span 10′ Final roofing TBD.
Should I double the 2×8 hip?
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I would as its not that much extra cost and with that low slope I can't help but think it would help stiffen things up a bit. That low slope is almost a flat deck so I would say doubling couldn't hurt.
Just my .02 of course.
I'm leaning that way anyway, just wondered what I may be missing.I keep hearing we can get dumpers of snow here, I've been here 6 or 7 winters, and yet to see what I am used to from growing up in Pa.
Prolly best to at least buy two, so if I butcher one, I have a spare..LOL
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I would
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works for me.
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Guess I should elaborate.I am finding more and more over the last few years, that I am less happy with typical framing lumber.I don't know if my standards of performance and expectations have gone UP, or if the industry has downgraded theirs, or if trees are just more limber lumber from being fast plantation grown, but I have come to the conclusion that anything that is even close to max allowed spans should be upgrade when framing in solid lumber.
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yeah, I'm of that mind too. commons and such are local sawn pine, full 2x6, but he didnt saw any 8" so Lowes it is. someday it'll have a ceiling so it'll all be hidden anyway.
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Why not go w/ a 2X10? Wouldn't that be stiffer in the vertical plane than a pair of sistered 2X8's?DonDon Reinhard
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It's been a few decades since I was a Framer, but I seem to recall a R.O.T. that ridges and hips were one nominal size UP from the rafters.Now that may be bunk, but for some reason, in my mind's eye, a twin 8 is more appealing?Not discounting that, but so far it's 2.5 votes for double 8's, me being the .5
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Sphere: I have to defer to the guys who are a bit more recent on their engineering, but Making something thicker doesn't gain you as much as it does to make it deeper. I've had to deal w/ some pretty badly sagging hips on a son's house in Urbana, IL. We jacked them as straight as we could (which wasn't much), stopping just before we would start lifting them from their bearing points, then stuck a vertical under them somehow bearing on a something or other that went to the foundation.DonDon Reinhard
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Don,
That is a good point that a 2 x 10 would be an upgrade. I guess it just depends what the underside ceiling is to look like as then you would have to boxwrap the bottom of the 2 x 10 as it will protrude moreso than a 2 x 8 relative to the rafters. This is of course me guessing it will be openvaulted underneath. If ceiling joists are to be used, my line of thought is moot.
And honestly with a 2/12 pitch there isn't much of a vault there.
May not be an issue really just something to think about ahead of time...
Mike
IIRC, 2x the w =2x the single member, where 2x the D = 4x the single member,so my thinking is that I'd need a 2x16! , but yes, I see yer point.
I'm doing this solo, my house, so I am leaning for the 2@2x8. I MAY even get fancy and bevel the tops..wooo-hoo.
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Double it up. Switching to a deeper piece of stock, as suggested, often looks good on paper. But then you go to cut the roof and realize that huge birdsmouth you have to cut into the oversized hip just rained on your upsizing parade. Now you're into fiddling with plate heights to maintain the integrity of the 2x10 yet still tie into your 2x6 commons. I see this goofy junk constantly even in otherwise well designed new homes. The architect draws a pretty picture and then the engineer gets ahold of it and calles out doubled 16" LVL hips with 2x10 commons and then it's all supposed to flush out with crisp plaster lines for the cathedral ceiling.View Image
'Zactly.
And it's staying exposed for quite some time. eventually a 3 season room, for now Porch.10" diam. cedar trees are the posts, double 2x8 beam to carry rafters, and hung off the log wall at the house w/hangers. Will be stone floor.
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What's the span between posts for your double 2x8 beam?View Image
10' . We st them a few weeks ago, the hip corner is closer to 11 actually so that I could miss the septic tank..yikes. And the actual hip length "Post to House corner" is 12' abouts.
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Doubled 2x8 spanning 10' sounds a hair light to me... but then I'm used to New England snow loads. I'm sure it'll be bomber. Those posts sound like a nice detail.
EDIT: The doubled 2x8's spanning 10' that I refer to as sounding 'light' in this post is referring to the main carrying beam of the porch and NOT the doubled 2x8 hip rafter that this thread is all about. Taxes and service fees may apply. $1000 down due at lease signing. Check with your doctor before taking or using my advice.
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Edited 12/5/2009 9:43 am ET by dieselpig
Oh I know I'm on the edge, but this is rustic, I need the head room. Limited to the house wall with windows at FLOOR level upstairs.House drops 4" on 42' side to side that kinda stuff. You seen the pics. I think.I also don't want to skimp on the views/and light from first floor windows and 3 doors.
It is, what it is. LOL
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Wasn't passing judgement brother... I don't see a problem with the plan. View Image
I gotcha.Man you should see all we got done, just this summer. I had Grants boom here for a few weeks and some $$$ to throw at the house. I got a real chimney! Wire brushed and coated the roof ( from 1905) and some siding and soffit ( all the high stuff) knocked out.getting there.
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Offhand I can't see any reason to double the hip rafter. In my experience, if rafters fail it's always been because of poor connections - Never because of being undersized. So my suggestion is to make sure the rafters and hip rafter are secured very well at the high end and don't worry about it.
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Your vote is counted.I think when I get the rafters in a bit ( they were sawn a few months ago) I may look for a 2" by 8" and then keep it single, but if I'm goin w/planed SYP from Lowes, I'd like to see more mass, being a longer member and the hip jacks tieing in.More visual at that juncture, verses a structural stand point.
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Duane,How about a real lumber yard and get a 3x8 or 4x8 hem/fir.Chuck SThe sky is falling.live, work, build, ...better with wood
It don't get more real than Jim and his band mill. Hell, I could use 4" quarter sawn cherry ( I have no idea why he 1/4rd Cherry) or flat sawn Sycamore.
But I'm buying the Pine from the landowner who had it sawn ( 75 cents for a 2x6x10) and I think he bucked all the pine at 10', thats the issue.Now ya got me thinking, I should check the sawyer's stash in his barn, he may have some fat and long poplar or hackberry. My sycamore upstairs flooring is still in that barn, I'll go poke around before I hit the Lowes.
Good Idea.
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"In my experience, if rafters fail it's always been because of poor connections - Never because of being undersized."I guess I have more experience than you.;)
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Use a oak 6x8 from a sawmill. It'll look beefy and good, and hold up to a F5 tornado.
You got it right!
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If the commons are 2x6, then the seat cut will eat away half the depth of a 2x10
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Correct me if I'm wrong, but the only thing left after a seat cut is the rafter tail, which is not structural. If it needs to be stiffened that's easy. The stength of the 2x10 would still bare down on the beam. I would hate to add a fur strip to a doubled hip, or bevel it in order to attach my sheathing, then again I'm a little lazy.
I'm not gonna do it, but I believe you can rip the bottom at bevel and take that strip and add it at the top. Just two rips for two hips.If that was desired for cathedral. Which a 10" hip w. 6" rafters would be a tuff nut to crack.
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I do not have my SP key to draw this out and explain it with pictures, but consider yourself corrected.A full 2x6 when cut for min. seat cut has 5-1/2" of solid HAP with his 2/12 pitchSo the hip rafter 2x10 gets half it's depth cut out to match that HAP, effectively lowering its rating to that of the 2x6. Under load, it can split from seat cut back up into center.
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If the pitch were increased, the 2x10 then at some point would become effective?
no, the iissue is not the pitch, it is the HAP ( height above plate. The full 2x10 cut to a HAP of 5-1/2" has 4-1/2" cut out of it.for comparison, go to a 12/12 pitch. Now the 2x6 has a HAP of 3", so to match that, the 2x10 gets 7" cut out of it
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So the fact that you are landing on a 90deg corner, increasing your plate depth does not compensate?
I find rafter framing very interesting, however I'm sure you can tell I have limited know;edge of the subject.
Yes, it compensates somewhat. I am simplifying the variables, since I can't draw it out and have a harder time explaining textually
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There are many ways of shoring up that hip, if it necessary. The variable are dictated by the overall structure and finished product. The "heel" is the weakest point on the hip but the his is also supported by the framing and sheathing. That hip isn't going anywhere once it's framed and sheathed. He probably could frame that hip with a 2x4 and it wouldn't sag. Valleys are a different subject.http://thewoodshedtavern.com. = no peer mods!
I definitely see your logic.... but you still feel that way about 2/12 pitch? When I see a pitch that low I tend to look at it like a floor system. In fact that's exactly what went through my head when I read the original post. If I were framing a porch floor that wrapped around an outside corner and the floor framing was to remain perp to the house (resulting in a corner to corner beam) I'd expect to see at least a doubled 2x8 for that member. IIRC we're talking about commons spanning 10' resulting in a diagonal of +/- 14'.
Not trying to argue, just trying to learn something.
(Gonna go back and read the original post now and make sure I've got the details right)
EDIT: I just reread the OP and he states that it's a 2 in 12 pitch where the commons span 10' and the hip spans 12'.... I'm either missing something or something's not adding up. That hip should be around a 14' span and, given the low pitch, around a 14' actual length.
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Edited 12/5/2009 9:26 am ET by dieselpig
Ok, it's actually more like 9' commons , I bought 12's for OH and end trimming , just called it 10' for math .And yeah, I measuerd the diag for the hip in PLAN ( on the ground) and that was a bit over 12', so I may be at 13' on plane of 2/12 or whatever it works out to.This is all round taper posts and crooked log house wall type building, sorta like a big tree fort LOL. String line EVERYTHING. And every hunk is cut diff. no gang cutting here.
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Step aside with your facts and logic Duane. I'm trying to micro-analyze this (now) hypothetical to death. ;)View Image
LOL.
I'll just call you when I get to the next hurdle. This place is hell to work on. I got the OTHER roof up on the west side, and it's higher than the south so I'll still have a jump up along that side.I hadda make that about a 4/12 and this will have the same plate , but lower wall height, due to them stupid windows out front in the dormers.
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OK, now qwitcher bellyachin and get out there in the snow and frame it!;)
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Lumber in the truck, that was fun, no wipers this morning.But I'm feeling like Lith-ion today, I don't work well in the cold. Its still below freezeing out there.I had to go way back to an old farm stead where the lumber is stacked, here is the house, built in 1774...17 rooms beleive it or not. Abandoned since 1974...
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deserted you say?
That's a shame - still straight lines
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Yeah, it had another chimney on the left, and it's huge out back.
It was hard to get good pics with my phone. It was snowing still and damm cold.It's log under that siding, chestnut and W.oak like my place, but older.A good mile or so off the paved road, back in the hollers...we got some neat old stuff back here in the sticks.
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Okay...lets analzye it a bit. If you didn't put ANY hip in there and just leaned the rafters against each other...where would they go? Without sheathing, they would fall away from the corner. With sheathing, they would have to suck the sheathing down with them selves. http://thewoodshedtavern.com. = no peer mods!
I see where you are going, but it is an over simplification don't you think? For instance, I recall a spec house we were framing a few years ago. We had just finished framing the roof when it sold. New HO wanted a more open floor plan so a beam was specified to take the place of a good sized chunk of the interior bearing wall between the kitchen and living room. Seeing as the floor was already sheathed above, I proceeded in simply tearing out the wall (with a little surgical skill) without bothering to temp brace the floor joists it was carrying. (For the safety police, I put a 2x4 across the staircase and made sure nobody was working anywhere in the house above me.) You and I both know what happened. Nothing. I cut in the new beam and then used a 2x4 kicker to get the joists back flush with the beam.
So it didn't fall down. The plywood held it all together while I worked. But had it been left that way it obviously would have failed eventually. And that's the argument I have about the hypothetically undersized hip rafter in question. I think you're making the argument that the hip serves the same purpose as a non-structural ridge board.... where it's basically just a nailer with little structural value. You could just butt the opposing rafters to each other and achieve the same structural integrity as you would with a ridge board in place. But I don't see that to be a parallel situation in the case of the hip rafter. Am I wrong?
I think it's a common mistake that (hack remodelers in particular) make frequently. They assume that because it didn't fall down, before they left the property, then it must be just fine for the long haul. View Image
Lets add another variable.What if I decide on skip sheathing? double is mo' better for nailing that.
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"I would hate to add a fur strip to a doubled hip, or bevel it in order to attach my sheathing, then again I'm a little lazy."No need for any of that at all, especially on a 2/12.
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I wouldn't.
I might run out there in the spring if it took a 12" wet dumping and push a spring brace under it...if it was sagging....which I doubt it would.
The key for me is: 10' span. I'd agree that a 2x10 might be a better choice if you are worried. What species? I've always seen 2x8 to be fir or yp...that would be plenty for me.http://thewoodshedtavern.com. = no peer mods!
I'm an engineer, but not your engineer.
Consider hiring a local one.
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"A stripe is just as real as a dadgummed flower."
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You serious Gene?View Image
Our local AHJ would require it. I had to do it for a simple carport structure, not being licensed in NY.
View Image
"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
I'm Grandfathered in, this what it USED to have. See first pic.http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=37278.1
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This, from a regular over at CT, and it is the starter post in a "sticky." It stays right there in front to act as good advice and as a reminder.
I have been a framing contractor for 25 years and I have not yet seen it all. When I think I do, I drive by a jobsite where the framing contractor has neglected to read the truss specs carefully for piggy back trusses and are lacking proper bracing. It is my duty as someone who knows better to stop in and remind them to carefully read the truss specs on bracing and how their ignorance at erecting the system will fail and possibly kill someone.I've seen many threads here asking for structural advice and personally, it's not any of my business to give out structural advice. We owe it to the people who request this here to steer them in the right direction and that direction is straight to an engineer, architect, or lumber yard who has a qualified, in-house engineer who will have a stamp that can and will stamp a set of plans for you.I am a framer, not a structural engineer. I don't design structures. If you are a responsible structural engineer, you already realize that unless you are personally standing right there looking at the particular situation, you would know better than to respond with "you need this size" because YOU DON'T KNOW THE WHOLE SITUATION and will be liable for structural advice!When it comes to framing, I am responsible for putting the structural members in the place where the architect, engineer, or designer tells me to put them. Period. That is my liability. It is also my responsibility if I put something in that is sadly undersized. As a framing contractor, I must possess general knowledge of what is needed structurally for the building. This is not a business trade that you just pick up a hammer and say "I'm now going to frame homes for a living" If something is undersized, a call to the structural designer is needed.Floor joists? That is a gray area. You can easily find span charts in the code book and online. However, youstill need to know what your local codes are for your situation. Same with your wood species. Same with the modulus of elasticity. Same with the deflection. To someone who responds to a question, are you going to take full responsibility for someone's floor being bouncy? Are you going to place your signature on a piece of paper saying that it is right for the situation and if something fails or isn't satisfactory, then you will bear full responsibility?Rafters? No. Because you will have no idea what the snow loads are, or what the roof is really carrying, or what the local code says you need for live and dead loads or what is REALLY going on at the specific site and situation. These loads differ from community to community. Where I live, oceanside is lower than inland. Mountains, different even still. Ours is 40#, the next town over is 60#Beams? Not a chance. There is no possible way for anyone to be able to tell someone else online what their exact conditions are.Please stop giving advice on what you think "should be good enough". If you are not doing the calcs for the OP and giving them your state issued stamp of approval on a set of plans, stop giving this advice before you kill someone. This is not a game. This is structural design.
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"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
Okay...I surrender....lets just all agree that we should never offer any opinions, no matter how trivial the question and the standard answer should be: HIRE AN ENGINEER! If a guy asks about screws vs nail..."HIRE AN ENGINEER".http://thewoodshedtavern.com. = no peer mods!
That is pretty over the top to have as a sticky in Cook's Talk, don't you think?I principle, it is true, but to apply verbatim in every question is ridiculous.
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