I’m looking at a 24×17 additon that will have a ridge running the 24′ length, north to south. The west wall is approx. 14’6″ with a 3/12 roof and the east wall partially lays on another roof but the total height is 12’9 or so with a 9/12. The 12’9″ section of wall is only 13’4″. The ridge is approx. 11’4″ from the west wall. These tall walls are not getting any ceiling joist or rafter ties, fully cathedral. There are no drawings that I’ve seen but the HO has a permit so I am only looking to build this from a lumber take-off from a yard I don’t often deal with. I’m worried about this roof sagging and the walls spreading. The ridge is 11 7/8 LVL and the rafters will be 2×10 on 16″ centers, I’m sure that the rafters aren’t undersized, but what keeps everything tight, certainly not the OSB that the shingles are nailed to..??
Dustin
Replies
hire a pro.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Are you busting my balls? I'm asking a freaking question about something I've never dealt with before!!
yes I am.
there is so much wrong with that entire first post.
U are clearly over your head here.
I'm against anyone charging money to start a job which they have no knowledge to perform ... sorry.
why do U need drawings ? what do U need a lumberyard takeoff for ?
what's the worry about walls spreading with a chathedral ?
ridge what ? ... board or beam ?
etc ...
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
I've done many foyers with tall walls that have had ceiling joists. My problem is with an offset ridge pushing on an almost 15' high wall.
And to answer your question about drawings. I don't wan't any liability. That's why we deal with engineers isn't it?
If you don't have any drawings, which implies no engineering, how did you arrive at the point where an LVL was spec'd for the ridge?
Do you know that the LVL is correctly sized for the spans and is properly supported as a STRUCTURAL ridge?
If you don't know the difference betwen a ridge board and a structural ridge, which is apparent when you are concerned with wall spread because there are no rafter ties or ceiling joists, then Jeff, in his blunt way, is justified in suggesting you hire a pro.
That's my point exactly Ralph, without anyone else other than some lumber desk guy, who the hell knows if the LVL is sized properly. I'm trying to get some simple feedback from people that I have corresponded with many times before, I'm not looking to be shot at. This design is not something I've come across before and without an engineers stamp, I'm a little leery. I don't know how the HO even got a permit. If I could sketch this for you I would and maybe it would come out clearer than my description.
Not appreciating being made to feel stupid,
Dustin
sarison, You questions are valid. Is it even possible to get a permit without approved drawings where you are located ? (Here it definitely is not !) Is there a building code used in your area? I would ask what the lumber yard used to arrive at their takeoff. Seems more than likely there had to be something on paper for them to look at.
They can't get your Goat if you don't tell them where it is hidden.
Ralph, The OP never mention ridge "Board " or "beam ". He simply said that a lumber yard take off lists a 11 7/78 LVL. He may well know the difference , but from what information he has at hand he may not know which is intended and planned on . My take is the OP has yet to actually see any drawings on this thing.
I may be wrong , but that was what I got out of his post.
They can't get your Goat if you don't tell them where it is hidden.
" I don't wan't any liability. That's why we deal with engineers isn't it?"That is why he said to hire a pro
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"why do U need drawings ?" Don't most builders use them ? That way they know what and how to build the project. "what do U need a lumberyard takeoff for ?"" My understanding is that is the only information he has to look at.
I think he knows what a take off is used for.
They can't get your Goat if you don't tell them where it is hidden.
Don't most builders use them ? That way they know what and how to build the project.
Not most remodelers ... not me ... not drawn by some stranger.
Me ... I already know how to build what I'm trying to sell ... I check the site ... take measurements ... then I make my own drawings. U know ... cause I'm the one that knows to to build it.
I'd never walk into a project and ask the customer where the drawings are ...
isn't that why I'm there?
to be the guy that knows what he's selling?
"My understanding is that is the only information he has to look at.I think he knows what a take off is used for."
Mine too. and again ... U think it's a good idea to have a lumberyard desk clerk tell U how to build something and what to build it with?
Me ... I like to go in with a materials list ...
kinda helps me get the stuff I actually need to build with.
hell ... why not just have the HO's fax their napkin drawing to the lumberyard ...
they'll deliver then I'll ask the driver what goes where?
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
What type of remodeling are you talking about?? Kitchen or bath upgrade? Im trying to think of the last remodel that Ive worked on that didnt have plans. Wondering if we are the norm of the deviantes. How is a remodeler different from a builder in that a builder would need the plans but the remodeler doesnt?Live by the sword, die by the sword....choose your sword wisely.
I'll try to type slowly.
I make the plans.
I decide which lumber ... in which sizes ... goes where.
that's why I said maybe remodeling is different than building.
I've never built a new home.
I have however ... built additions. And framed roofs. And removed walls.
and never ... have I expected the customer to provide the instructions.
I measure ... I design ... I draw ... I take it to the permit office ...
and if need be ... I call my engineer.
and even then ... I don't ask him "how to" ...
I tell him "this is what I'd like to do".
and he provides those last little specs the building inspector is looking for.
I don't need the customer to have the plans ...
as I make provide them.
even when I work with a designer ...
she does layout ... draws elevations ...
but I decide what lumber goes where.
maybe I expect too much from the rest of the world?
but I expect people that walk on to a prospective job to actually know how to do what they're there selling.
walls don't spread when the ridge don't sink.
and the ridge don't sink when that beam is sized right.
and I know it's right ... 'cause I figured out what size it should be.
and if I can't ... one call to my engineer can.
and the building inspector passes the prints ... that I drew.
I'm done fighting about the fact someone should know how to do their job.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
That's how I do it too.
I have built new houses.
Drew and designed them too. It's kind of like remodelling - just a whole lot easier.
Other than the mud.
Like I said, something here just don't add up.
Somewhere there's information missing, like - " I have watched all of the TV shows and decided to be a remodeling contractor last night. "Remodeling Contractor just on the other side of the Glass City
I'll try to type slowly.
Could you use big font too!!???
You seem to be tired of this so I wont post on this after this but........ahhh forget it, have a good holiday too.
Live by the sword, die by the sword....choose your sword wisely.
In all your years of experience you have never had a prospective customer hand you a set of drawings and say : "This is what I want you to build"? You do your own engineering to go along with those drawings? I wasn't saying "walk into the job" at all if you read what I posted. I told the OP to get a set of approved drawings and look at them before determining what to do next. Building an addition as the OP described is slightly different than your kitchen /bath remodels. I wouldn't dream of having a lumber yard clerk do my design, although many do have training in using the engineering programs for the engineered lumber and I would let them tell me what I needed for a beam to carry a stated load over a given span. But only AFTER I had a full set of drawings . Seems I recommended against using the lumber yard clerk's take off and recommended getting the drawings the building dept had.
They can't get your Goat if you don't tell them where it is hidden.
"In all your years of experience you have never had a prospective customer hand you a set of drawings and say :
"This is what I want you to build"?
You do your own engineering to go along with those drawings?"
Yes. I'm missing your point.
"Building an addition as the OP described is slightly different than your kitchen /bath remodels."
Uhh ... those kitchens and baths have to go somewhere.
sometimes inside shiny new additions.
weird how that works.
anyways ... again ... I'm done.
Hugs and Kisses.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Same to you. Enjoy your holiday .
They can't get your Goat if you don't tell them where it is hidden.
""what's the worry about walls spreading with a chathedral ?"" ""ridge what ? ... board or beam ?"" Valid question if one doesn't have a drawing that show what the ridge is spec'd to be , "Beam or "Board" . He stated he had no drawing to look at .
The OP didn't use those terms in his post. You assumed he didn't know the difference and introduced those terms.
They can't get your Goat if you don't tell them where it is hidden.
I think you misunderstood JeffBuck. I think he ment a pro as in a professional, as in a hooker. Now how a hooker would help I dont know, maybe you'd get lucky and she'd have a mech. engineering degree?
JeffBuck does have a lot of good info, but can come off rough when he wants to.
O.k, Ive helped you as much as JeffBuck has, so Ill let everyone get back to answering your question.Live by the sword, die by the sword....choose your sword wisely.
The pro would help relieve his frustration when the HO calls to complain that his ridge is sagging
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"The pro would help relieve his frustration when the HO calls to complain that his ridge is sagging"
Are you talking about the HO roof ridge or Sarison's ( OP) "ridge" sagging ??!! :) O.k., this could go down the gutter quick. Im done.Live by the sword, die by the sword....choose your sword wisely.
My apologies for snapping back at him
I dont think you need to apologize for anything. I think he was a little short with you, but oh well.......Live by the sword, die by the sword....choose your sword wisely.
I hope that "By Looking At" you mean trying to give someone a guesstimate about $ or simply considering if you are interested in it after a quick review of the project.
You don't have enough information to be seriously "looking" because you have nothing to really look at .
MY advice?
Tell the owner to get you a complete set of prints.
Tink youse got problems.....
13 ft wide loading on a 24 ft long beam is how your description reads. Really do need a sketch, the numbers above are what can be gleaned from the verbage?
Just doing numbers off the top of head, at 25 psf on the roof, 11-7/8 lvl would need to be 8.5 " wide for strength, deflection not calculated. took a look at your profile, you probably get lake effect snow where you are so the 25 psf may be too small, increase the needed LVL width by the same ratio as (snow load +dead load)/25.
If you LVL is not at least 8.5" wide for 25 psf snow+dead load, you got troubles.
The vertical posts and shear strength of the wallsections at the end of the LVL keeps stuff 'tight', also make sure that and the footings (at least 2 feet sq ) are not undersized!!!
edit PS: Joist hangers or sitting on top the LVL? You gotta tie the joists togheter structurally at the ridge (overlap/connectors/other/plywood gussets?)
Edited 11/18/2007 5:37 am ET by junkhound
Dustin,
I completely understand your question, I've built something like this before.
You're just curious what will keep the walls from bowing out if there are no collars tying things together, as you said this room will be a "full cathedral".
If your ridge is 24' long, then the top plates of the walls will also be 24", the best solution would be to use top plates that are also 24' long. This will create a rigid wall with virtually no "bow out".
A small problem would be that 2 x 4's and 2 x 6's don't really come that long, so you might have to order another LVL of the same length which will get ripped down to the wall thickness, then used as top plates.
24' long 2x6's resisting the outward thrust of the roof? I don't think so. No way no how.
He needs a structural ridge beam, which keeps the ridge from sagging, which keeps the walls from spreading. The one he has spec'd is too small.
The only way wall plates 24' long could resist that thrust is if they were much larger--somewhere near the size of what a structural ridge would be.
"The only way wall plates 24' long could resist that thrust is if they were much larger--somewhere near the size of what a structural ridge would be".
Then instead of using the typical double top plate, then beef it up to maybe 3 or even 4 top plates. But the goal is a rigid wall, one without splices in the top plate which might allow for the wall to bow out.
Also, keep in mind this roof pitch is only 3/12, so it's not very steep. A low pitch roof like that doesn't have as much outward thrust as say a 12/12 pitch roof.
Also, keep in mind this roof pitch is only 3/12, so it's not very steep. A low pitch roof like that doesn't have as much outward thrust as say a 12/12 pitch roof.
Hate to keep disagreeing with you Mike, but actually the outward thrust is the same regardless of roof pitch, from an engineering point of view anyway.
If this was a 10' long wall I'd be inclined to agree that a stiff top plate could do enough to prevent bowing. But this is a 24' long wall, and the way it's built every day around the country is to hang the roof system off a structural ridge.
Stiffness (of a wall, ridge, or any beam) is determined by the moment of inertia of the member, and it's modulus of elasticity. The moment of inertia changes greatly with depth (or width, in the case of a top plate.) The formula is 1/12 base x height^3. Unless the moment of inertia times the modulus of elasticity of the top plate is equal to that of the equivalent structural ridge, sagging of the ridge and bowing of the wall will occur.
but actually the outward thrust is the same regardless of roof pitch
Care to draw out a couple of vector diagrams with some trig to back up that statement?????
My math says a 12/12 has only 63.3% (neglecting structure weight, live load only) the thrust of a 6/12.
Take the Limiting case - near flat roof- outward thrust approaches infinity for given load.
I was thinking along the same lines. A 12/12 with the same run has a lot less weight than a 3/12. The outward thrust would have to be different but I'm willing to learn something. FKA Blue (eyeddevil)
You know, I had written out that the flatter pitch has more outward thrust, but I didn't feel like drawing out a vector diagram to double check myself. Guess I should have. Either way, flatter pitches certainly don't have less thrust than steeper ones.
I realized what you meant by re-reading the previous post in the thread, but the way it came out could have confused others.
The OP post (11" LVL, probably only 3.5 wide?) would be an interesting structural problem, one that I'd not be able to do min my head, would require a 3D dynamic vs. static analyis with the ridge beam sagging,wall spreading loads, edgewise 6x8s for top plates, etc.... Looking at some of the old cathedrals it sounds like someone should suggest the HO build some flying butresses <G>, then the top palets would only be 1/4 as strong. Maxwell 3D FEA program would do it up nicely.
Maines is right.The pitch has nothing to do with this. It is the load on the roof that becomes outward thrust when the ridge is unable to resist it, and the horizontal method you are suggesting is one that requir5es special engineering work not found in the tables, but that definitely would take something much wider than you suggest.It is all a perfect example of why Jeff was right - the OP needs a professional to design a solution that will work for his area and situation.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I would disagree about Jeff having it right. The OP needs to be given the plans that the OWNER has and have been submitted for permitting. Then if those plans approved plans do not carry engineering the OWNER has to provide it. The OP just has to be given what he needs to in terms of a complete set of plans so that he can assess the job with all the information. The only thing Jeff had right was his rudeness IMO. But that is his style. He made a number of unwarranted assumptions about the OP 's situation and the plans themselves. I found the OP's post to be very tough to make sense out of, but one thing that was made clear was that the OP had no plans to look at .
They can't get your Goat if you don't tell them where it is hidden.
Most of that is true and I don't want to get into a Jeff vs. X thing, but would point out that it is also an assumption that the HO has some plans that he is with-holding. it is probably a fairly good assumption, but an assumption nonetheless.
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Here.
http://www.ci.rochester.ny.us/dcd/Buildings_Zoning/Buildings_Zoning_PlanReviewInsp.cfm
Looks to me like there are two sets of prints out there somewhere.
Not sure if there is a question in your post.
Me, I'd have calced the loads by now, If that's too much for you, then either throw it back to the HO or hire an engineer.
A hammer and saw are not the only requirements for a remodelling contractor.
This just don't add up.
Remodeling Contractor just on the other side of the Glass City
Dustin,
I agree with jhole. The home owner got the permit with a e-stamped set of plans, gave the lumber yard another "owner edited set of plans".
I can tell you with first hand exp. to walk away. I had a home owner do this very same thing. When I did see the right set of plans, alot of e-stamped details had been eraseded! Including rafters moved to 36" oc instead of 16" oc.
So if you have other work lined up, go to that. This could be another thread later called "What I shouldn't have done!"
Nailer
"The home owner got the permit with a e-stamped set of plans, gave the lumber yard another "owner edited set of plans"."
How did you determine that from the postings? I must have missed that. Not disagreeing with you but around here a permit would probably not require such exotic things as engineered drawings.
I don't do the kind of work you describe. But whenever I find myself in the position you are I decline to quote the work. If they are unwilling to give you the information you need they either don't want you to quote or will be a nighmare to work for as the goal will be a moving target all the way through.
My latest to do this was my local newspaper. They called me, the editor walked me through the lobby with a bunch of generalized ideas and wanted a number. I asked for existing prints "don't have em". I asked for specific colors and finishes "haven't really made our minds up yet". What type of counter top are you thinking? "One the dimnesions that we told you but we don't really know what material or color yet". I said thanks but no thanks. DanT
I'm not real sure of what your situation and layout is. I think you are describing a gable roof with two different pitches and because there are no internal parts of the roof, the ridge will become the structural anchor for the entire assembly.
I'd beef up the ridge by doubling or tripling that micro and maybe upsizing it too. That's my off the cuff, seat of the pants engineering.
The other critical issues I'd be thinking about is the weight laying on the existing roof and the load transfer from the ridge ( the beam) down to the footing.
The spans are so small, I wouldn't lose any sleep about doing seat of the pants engineering because the fixes would also be easy if I was wrong. The fix would be adding extra beef in the form of additional beams below the ridge.
FKA Blue (eyeddevil)
Edited 11/18/2007 9:55 am ET by Jim_Allen
A quick calc shows that your ridge beam should be something like 3.5" x 16" or 5.25" x 14". The ends of that beam need to be well-supported.
Disclaimer: engineering advice provided on Breaktime is worth exactly what you paid for it.
I don't know what the local code requires there, but Rochester can get some hellacious snow loads. I was thinking 18" x 1-3.4" x 2 LVL
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I used 40#LL but rounded the answer down. Rounding up would give (2) 18" LVL's.
That's kinda what I was thinking. The call for engineers is the easy way out. At some point in time, every question will be anwered with "call the engineer". Maybe we could just create an acronym? CTE? Taunton could create a script and after every thread is started and automatic CTE answer could be generated. That will save all of us the trouble about thinking and discussing these types of situations.I'd like to see a sketch about this particular situation. FKA Blue (eyeddevil)
"I'd like to see a sketch about this particular situation."So would the OP.;)
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There are no drawings that I've seen but the HO has a permit
That's the first problem right there. Why aren't there any drawings, and how did the get a permit?
so I am only looking to build this from a lumber take-off from a yard I don't often deal with.
That's your second problem. How is a lumberyard doing a takeoff without a drawing? Is someone just making this up as they go?
I'm worried about this roof sagging and the walls spreading.
That's your third problem. Why is it up to you to figure this out? Your not an Architect or Engineer. Why is it your worries and not the HO's problem to have this designed the right way so that it is structurally sound?
So, you're supposed to design this for them? I don't get this whole thing. I've been framing over 20 years and if I walked into a job like your describing with a permit, no drawings and a material list, my first question would be, where are the drawings and if they did not provide them I would walk away, especially if I was concerned about the way this thing is supposed to be framed like your saying.
So now it's up to you to make this work???
The ridge is 11 7/8 LVL and the rafters will be 2x10 on 16" centers
Problem number four. You have a 24' single 11-7/8" lvl as a structural ridge. That's great!! Right there you should walk, or tell them you want it designed the right way from an Architect or Engineer before you go any further because you obviously know that it is not correct.
I'm sure that the rafters aren't undersized, but what keeps everything tight, certainly not the OSB that the shingles are nailed to..??
Your question marks tell me that your asking a question and think that the osb keeps it tight might be the answer when clearly that is not the answer. You are definitely in over your head here and this thing should be designed by an Architect or Engineer. I could tell you exactly what to put in there in your situation just by the same types of additions I've done , but these were all off a blueprints, not guess work.
I even question Architects when they draw something that I don't think will work. Sometimes I'm right and they made a mistake and change the drawing.
I understand your asking because you want to do the right thing as I would, but I wouldn't be asking here on the internet and use whatever answers beam wise you get. These are just options, the real answer is the HO or you getting a Architect or Engineer to size this job up.
Take what I say whatever way you want, I'm not trying to insult you here but this job isn't right from the start and now you have to design it and take the liability for this???
well stated, Joe.Expert since 10 am.