Here is a roof shape I am thinking of. I attached a wireframe sketch. House footprint is 36 x 44, roof pitch is 10/12, the tall continuous ridge goes the 36-foot way, and from the little mini-plan I have, there is no way to post-support the ridges at any intermediate points. Looks like I might be dealing with some large heavy ridge members and valleys. Likely need the crane again.
Can’t truss it, because there’s a lot of living space under the roof, with vaults.
In my neck of the woods, we design for a 50psf snowload.
Can any of you structural or framing specialists rough-guess the sizes of those key roof frame members? Just a guess, now. I’ll engineer this booger if I get into it, but for now, I am looking for something off the cuff.
Replies
Somewtimes, I forget the attachment too.
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I thought for sure I popped it in there! Here it is.
here's something off the cuff..
you're talking about a 36' structural ridge witha 50 LB. snowload ?
hah, hah, hahMike Smith Rhode Island : Design / Build / Repair / Restore
no, wait... it's also got to carry the two intersecting gables....
c'mon... you're killin me.. ( rough guess.... hah, hah, hah )
sorry, micro... devil made me do it ...
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 12/28/2003 12:11:17 AM ET by Mike Smith
What do you mean you can't truss it.
I vote Boss Hog can get it.
I am tired and going to bed. Tomorrow I will scan the little mini floor plans that are in this mag I was looking at where I saw the plan. I'll post the scans here. I cannot for the life of me see where the walls below this roof can pick up any decent bearing, where needed. There are walls under the valleys that have potential, but no straight paths down under the ridges, headed for the solid ground below.
If I spring for the plans, all will be revealed, I'm sure.
I know, it looked nuts to me, too. All I could think of was WF steel.
"If I spring for the plans, all will be revealed, I'm sure."
Now I'm laughing too!.
Excellence is its own reward!
What's wrong with scissor trusses for living areas below?
CAUTION: above comment made by tired skier who didn't even look at attachmentsLignum est bonum.
It might be a scissors truss for the main and a thru run ridge for the cross dormers lower. That way the whole interior ceiling could be same..
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I gotta agree. It ain't one for rough guesses. Gotta sleep on it.
Log truss and purloins?.
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Should be atleast five hah's, according to my calculations.
I fooled around with Adobe, and resized the plans to something more friendly. Here they are.
I can see a structure in my mind, now let's see if I can draw it.
Excellence is its own reward!
Here's one thought. let it keep your engineer up late at night.
;)
Wireframe showing only the major timbering.
Two main continuous ridge beams sharing loads with a post and transfering some load to the valleys. The center of the longer ridge for the lower dormers acts in compression to spread the two 'wings' apart.
The lower one takes up some load from the upper and it's span is shortened by the valleys.
There are a lot of dynamics going on here that I haven't even begun to thoroughly analyse. It's just a vision to start with is all..
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You can post down from the Main Ridge from the Upper Floor Office/Closet wall down through the Main Floor Greatroom/Foyer Wall down to a I-Beam that sits on top of the foundation and the basement Storage Room/ Mechanical Room wall, with a lally column and footing at the end. That can cantilever out a couple feet until it's under the Main Ridge above that can be posted down because according to your basement, main floor and upper floor plan they all line up.
This way you can eliminate a column in the garage.
Edit; I just looked again at the Main floor and realized that the opening from the Foyer to the Great Room looks like a pocket door so there would have to be a structural header there also that goes to the closet wall so therefor the I-Beam in the basement has cantilevered a little more.
I'm not an Engineer but I'm sure you can cantilever an I-Beam. How much I don't know. If not then put a Lally Column in.
Joe Carola
Edited 12/28/2003 8:37:09 PM ET by Framer
Edited 12/29/2003 7:11:36 AM ET by Framer
While you and Pifin were doing some analysis and writing posts, I was busy with my digital calipers, the magazine page that shows the plans and pic, and my trusty CAD program.
I picked up as you did on the closet walls at the upper floor that stack over the mainfloor walls, right above a line that goes from midway between the leftmost garage door and the adjacent one to the right. Then I saw the telltale little dotted lines in the basement/garage plan indicating a pier footing. Look at the wall separating house from garage, just to the right of the door. Aha! says I, that's how he did it!
So my sketch here shows a wireframe of the structure down to the foundation top, and you can now see the structural ridge having some intermediate support by a post at A.
The post goes down to a beam B, embedded right up against the top plates in the closet wall below, which transmits its end reactions down through posts in walls, straight to the steel beam C, which runs across the ceiling of the garage. Beam C's end reactions move down through walls to the foundation below.
Both king valley members will come to the ridge very close to the ridge's post support, which will help in keeping the ridge's size down, as the point loads will create much more shear stress in the ridge there, than flexural stress. I figure the longest span of the structural ridge now to be 23 feet. Not too bad.
Out on each gable elevation, I am showing with wireframe members how the ridges are picked up by posts that need to go down and bear on "spreader headers" due to windows being centered in each gable.
Look at my post and pic which came after yours. You will see the steel beam running across the garage ceiling, that picks up the roof load coming down from above.
Beam C will also be doing a lot of work picking up floor loadings from the main and upper floors. I will probably need floor trusses or deep I-joists, given that 23-foot span.
OK, here are some pics. Plans of basement/garage, main floor, and upper floor, plus a rendering.
As can be seen from the rendering, they are packing living space up under the roof, and the underside of the valleys are used as ceiling features in a couple places.
The problem for me in trying to view this structurally, is that I cannot see any straight-down support paths via bearing walls, to post either the main ridge or secondary ridges down to the foundation level. It must be done with a sequence of floor beams.
The little room-size notes on the plans say that the master bedroom, the "couples" room, on the upper floor, has a vaulted ceiling. No other second floor rooms say "vaulted."
I am a great believer in the creative solutions that good truss engineers can provide in complex roof frames, but I cannot see the bearing points here, inside the outer walls. It must be that the garage has some lally columns going down to piers, between the car bays.
The plans are available, but they cost about $1500, and I don't want to spring for that yet. This thing will site perfectly on a nearby lot, but I am not sure if or when the owners will sell it to me.
Are you talking about supports under the main 36' ridge in the center of the house somewhere and also on the gable ends?
Do you want to put supports down to a wall so that you can reduce the size of the 36' ridge?
The four gable ends all have windows so all you need to do is put a header above the windows with a flitch plate in it that will carry the posts under the end of your ridge. Then just run 2x's under your king studs and jacks all the way down to the foundation because the load is spread away from the center of the ridge and windows.
There's really no need to put supports on the 36' ridge if it's engineered big enough to span 36' holding up the two Supporting Valleys on each side.
Those two smaller gable ridges at the end can be supported by a header in the same manner as I mentioned above.
These posts that support the ridges don't have to go down to the foundation if you put a header in above the windows that can handle the load wether you use a flitch plate or just a billet beam or paralam.
In this situation you should drop your main ridge down and set all the commons and Valleys on top of whatever size ridge it will be.
Joe Carola
You are right, "IF" it is engineered big enough for the clear span, but done normally it would also add a proportion of the load from the dormers onto the high ridge, I think. That makes that ridge beam a real steel sky hook/boxbeam/trusswall/bastard barjoist??????.
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Not quite what you had in mind, but here you go:
PAHS Designer/Builder- Bury it!
since everybody giving you a bad time, I'll actually give a 'rough estimate' -
since the span is 36 feet, my 'rough guess' would be a 36 I 155 beam, I'll bet that will hold.
BTW, I've got one in the back, it's yours for twice the shippiing charges <G>
Can't tell a lot from those little plans. And I don't want to download the big ones on my dialup account.
But it doesn't look to me like there's any way to truss the thing.
I think you're gonna have to pick up some more bearing in the basement somehow and suport the ridge somewhere along the way. A 36' long clear span beam that long would have an ENORMOUS reaction on each end.
Maybe Piffin will come up with some creative ideas.
Uncle Sam wants you...to bend over.
Thanks for the vote of confidence, but I took a quick look at trusses too. I've seen some monstrosities in those log honchos out in Colorado but can't quite remember any to handle this double winged open space without some head knockers in the rooms upstairs.
Excellence is its own reward!