Stick framed roof without ridge beams, Non Trusses

[DoubleStud]

Someone shared this in facebook.

https://www.facebook.com/1400992839...uQJ29eSHTAeBRGTGqziuqcDd4Lgl/?mibextid=cr9u03

If I see projects like this, I would specify trusses. People still engineer roofs like this? Seems weak?

 

[StrucPatholgst]

Seems legit to me. Had there been cathedral ceilings in there, none of that would have worked.

 

[TheDW]

I see a few valleys without direct support which don't work on paper but seem to stand the test of time

Whats up with this ridge connection at the curved wall...I would assume theres something going on there that I'm not seeing

Looks pretty typical besides that, I'd probably stick frame it without much issue

 

[phamENG]

I believe those rafters form what is known as a "fan column". (Just don't try to google it...)

EDIT: This is a joke in case anyone missed that.

 

[DoubleStud]

So the rafters are only toe nailed to the ridge board and valley board? some of these rafters are quite long and look very flimsy.

 

[TheDW]

Sure. Its the alternate rafters stopping 2' short of the ridge with no blocking that looks odd to me...maybe its normal and just isn't done much in my area edit: whoosh

Usually, yes

 

[phamENG]

Doublestud - I'm guessing they look flimsy since you're accustomed to some snow. But for a low/no snow area, you can stretch rafters a really long way. If you spec good lumber (say, No.1 or better) you can stick frame a gable roof with lightweight shingles on a house 30' wide with 2x6's in my area.

 

[DoubleStud]

More than anything I am just a bit confused how the structural drawing look. You think the engineer specify all of these mid support braces? Do they go to a load bearing wall? Just design it as a triangle and the ceiling takes the tension? No collar ties?

phamENG, I saw the FB post and the framer is somewhere in NY. Should get plenty of snow?

 

[KootK]

People still engineer roofs like this? Seems weak?

It is becoming increasingly rare in many markets. One of the more interesting books on my shelf is shown below. It's dedicated to how one frames complex roofs with stick framing. It's pretty cool, especially for me given that I come from a prefabricated truss background.

Quietly, I wish for some kind of apocalypse to come along and thin the herd of humanity to point that I, and this book, have some genuine utility. Want a bay windo turret roof on your thatch survival shack? Hike two settlements down the big lake, find KootK if he's not yet been infected, and offer him two goats and a blade.

 

[DoubleStud]

Oh man KootK, I would love to see the structural roof framing plan for framing like this. When I lived in Houston, our house roof was framed like this. I was always worried especially because only part of the attic had plywood on the floor. They put the HVAC and water heater up there. Scary if it leaks.

 

[KootK]

Oh man KootK, I would love to see the structural roof framing plan for framing like this.

Of such a plan exists at all, I suspect that you would be underwhelmed. A few beams, some extents called out joist runs, and much left to the imagination.

In my own home, I don't think that there's a single piece of connection hardware on any of the floor levels. Just bearing and toe-nails.

 

[Eng16080]

The framing is impressive. It would be interesting to dissect the structural plans if there are any.

At the turret it looks like there is a floor/ceiling at the bottom of the rafters. If so, that should keep the roof from spreading assuming the rafters are well connected to it. The roof looks really steep, so I would imagine the snow load is small there. Of course it’s hard to tell how long the rafters are.

I’m not sure how I would justify the valley working, but perhaps there’s a way.

I would try to analyze a roof like this by looking at it like trusses in locations where the bottom of the rafters are restrained against thrust.

We had a cool project with a turret roof like this except it was totally cathedral. We used a steel tension ring at the base to resist the outward thrust.

 

[KootK]

I feel as though the floor might be a little lower than the rafter bearings but it's difficult tell from the photo without staring at it for 30 min.

Were this mine to have done, I'd probably handle it as shown below.

 

[SWComposites]

Fine Homebuilding mag/site has lots of articles on complicated framing techniques.

 

[KootK]

The thing might also benefit from some nifty, semi-circular hoop stress action to help prop the ridge board. Drag it back to the adjacent shear walls. That said:

1) I don't think for a second that this would have been an intentional aspect of the design.

2) The strategy would be riddled with potential, and likely, detailing fails. Starting with tension continuity in the curved top plate.

 

[phamENG]

NY might change things, but that's a pretty good slope and is likely to shed pretty well. That said, unbalanced loads might get interesting.

Collar ties could be straps over the sheathing which is not yet in place, so not too concerned there. And those braces are just as likely to be props used by the framers to keep things stable until everything is in place and fastened.

Prescriptively, SP No2 2x12 can still go 14' with a ground snow load of 70psf. So this still seems quite plausible as those are easily 2x10 or 2x12 in most places on the roof. Higher grade lumber or a lower snow area and it works. The valleys are certainly suspect, but good luck convincing the framer of that.