False Rafter Tails & SIP's

[e.myers]

First post.

Currently detailing out my first hybrid "SIP" (Structural Insulated Panel) design that is a result of wanting exposed rafters & trusses in interior.
I'm not a builder but do architectural detailing and design for a living (mostly commercial) and I'm considering having this house become my first design build project and at a minimum, attempting to "play" general contractor on it.

The owner wants exposed rafter tails and "lookouts" at the rake and I'm attempting to come up with a solution that makes sense architecturally.
It seems to me that I could for all practical purposes cut off the rafter tails and leave the rafter/truss ends flush with the exterior face of the studs.

this would allow me to sheathe completely up the sides of the wall without fidgeting with notching around rafter tails. It would also allow for a tighter exterior wall and get rid of that extra thickness of roof at the edges potentially so that the house will look more traditional. It also would help with future designs in that the exposed tails could be placed on different centers than the rafters and allow for some flexibility as to visual spacing that could determined on site or by window placement etc that did not adhere to a rigid grid of 24" or 16" OC. It also would allow for a different more weather resistant species of wood (ie cedar) to be selected for the tails.

My thinking goes along the lines of, don't "they" really do this with porches anyway? What would be the difference in creating a ledger that some false rafter tails were screwed to, then lag bolting it to studs or a top plate etc, then, effectively extending the roof sheathing down over the tops of the tails.

I typically don't like ANYTHING fake/artificial/applied, and that's what drove me to the rigid insulation on top of the rafters in the first place. Can't really put my finger on why this is different (not fake somehow). It just somehow makes sense to me and in my thinking opens up some possibilities for detailing. Am I rationalizing?

Interested in where you would see problems with this "technique".
I haven't located a framing crew for this yet so I'm curious if I'm asking for the world here or if I should keep looking until I find a contractor who finds this interesting, or at least doable and want try to talk my clients out of the idea.

I haven't been able to find much info about this technique and it's viability.
I did however, see a house the other day (very old house) not far from here that was falling down unfortunately (concerns me) that looks like this was done to it. The frieze board was still there, but no rafter tails at the overhang. You could see however where "applied" rafter tails had been painted around.

Lots more questions about this and other items but figured I'd start here.

Thanks,
Eddie

[Dragon]

Yeah, there is a reason why you could see where they had been.

Because they came loose and fell off.

If it isn't cantilevered it will not stand the test of time.

Gravity rules.

[e.myers]

Dragon-
Thanks for the prompt reply.
While I agree that "gravity rules" (har har), are all your porches cantilevered? I'm really having a battle with this one and I think the reason is because at least some of the porches I see are basically shed roofs attached to the side of a house with a ledger board. Granted, the end of the porch rafters would be supported but... well maybe I'm answering my own question.
Is there any way in your mind that you could rationalize/justify or detail a method of doing what I am considering?
Man, I'm having some BIG issues making this cathedral make sense.
Eddie

[e.myers]

Anyone know of any good details for getting exposed rafter tails with rigid insualtion on top of the deck?
Anyone done exposed rafter tails and just carried the 3" or so of polyiso sheeting down to the edge of the roof and ended up with a "thick" roof with exposed rafter tails below? I could use some ideas....
Eddie

[dhill]

e.,
If you're going to expose the lookouts, why can't you tie the faux rafters into the near rafter in the same manner the lookout is attached? It would require establishing the angle and notching out the last rafter, but it would tie the rafters solid and they could be exposed. I'm not sure how the seams of the notches would look, but I doubt it would look much different than butting those fake rafter extensions right into the last rafter. The roof sheathing is going to give the rafter extensions some support but not enough for those extensions to stand alone if they are simply butted and tied into the last rafter. Gravity, as Dragon said, would cause the roof to sag.

[e.myers]

dhill-
If I'm understanding you correctly, you're describing some sort of splice, more or less some sort of tongue that would be "inserted" into the "real" rafter.

The problem here (and maybe I'm missing something) is that the top of the fake rafter tail is actually going to be above the top of the real rafter... or maybe that's what you are getting at- I could leave a tongue on top of the fake rafter tail whatever the thickness of the insulation is and bolt it into the top of the real rafter (or maybe the tongue and groove decking that will be on top of the real rafter).
That way I would be providing a cantilever situation (as Dragon describes).

Something else I was considering (after thinking about cantilevering) is taken a metal strap (ie simpson) and strapping the top of the fake rafter to some sort of sheathing AND lag bolting the false rafter tails to the ledger board AND lag bolting the ledger/frieze boards to the framing.

This is getting complicated and I need to weigh whether it makes sense anymore. I hate it when I research something for weeks/months, think I have it figured out, then have to back up and do something conventionally. I'm even starting to get paranoid about the foam and ants, and termites and condensation and cold vs warm roof blah blah blah. Man, I don't want to go backwards after all this.

Another thing. Aren't Brackets that you see holding up eaves applied? The down and dirty way to do this is to just have the panels extend and box in the underside with T&G. Then, at various centers along the sides of the house attach brackets to the framing through the siding. This would give the appearance of traditional framing (thick roof looks like rafters extending and covered with brackets supporting rafters).... only I'm supporting the roof with the brackets.
But then I think, what's the difference here and what I'm thinking about doing anyway?

[e.myers]

I found this video and it's similar to what I'm thinking. I'd be interested in everyones thoughts.
Eddie

[e.myers]

C:\Documents and Settings\Eddie & Holly\Desktop\Video Roof Insulation and Jet Blocks.htm

Try this...

[e.myers]

Double oops.
Hopefully this will do it...
http://www.hvac.bobvila.com/Video/633.html

[dhill]

Sorry, Eddie, that I was unclear. That's the problem with trying to describe what I see without being able to point and show. What I was describing was something like what I did on my house where I broke the rafter ends to create a mansard effect at the eaves of my house. The difference I think is that I went a little below my original rafter line. All I had to do was block it out. I wasn't concerned about making it pretty because I'm covering it all anyway. I didn't realize you were talking about being above your original rafters. I sure understand the dilemma of over-thinking everything, but it's worth the time to think it through and get it right. Hope you get this figured out.
Dusty

By the way, my mansard effect was a lot of extra time and trouble, but I like the effect, and I'm glad I did it. Go with your vision.

[e.myers]

Dusty-
I can kinda gather what you're describing with your "mansard" application and it certainly has potential relevance here. It's always difficult to talk through this stuff rather than as you say "point" at the real thing or at least a drawing.
I guess I knew when I posted that this is just one of those things that I've got to work through myself. That being said, I do appreciate the encouragement to "go for it" by someone who has apparently taken up something unconventional and then in the end been happy with the results.
Thanks.
Eddie

[Rich]

I think the method used by the video above would be more than acceptable. But - what they've done in the video is use an applied piece that's tall than it is deep which makes it pretty easy to withstand pressure and uplift. If you're wanting exposed rafter tails that attach to the exterior of the home I would suggest against it. Unless you're only going to have an overhang less than 1' is the only time I would consider it. More than that and you're asking for trouble.

[Cole]

That damn Bob Villa he knows everything :lol: :lol:

[Rich]

That guy doesn't know SH*T about building. He's got a lacky that tells him what to say.
I saw one time they were setting footing forms - Bob walks over to them and steps right on it - it drops 1-2". Bob doesn't say a word - you just see Riley walk over, shake his head, and fix them form.. LMAO

[Cole]

:lol: :lol:

[Dragon]

And I hate how 'This Old House' found the one guy on the planet dumber than Bob Vila to replace him with.

Poor Norm...

[Rich]

Is that the younger guy with glasses - looks like he could be Norms son?

[Cole]

Yeah it is, what is his name.

[Rich]

Wingnut.. it's gotta be Wingnut.

[Rich]

I thought it was Steve or something..