Another ridge beam and rafter question

[MontanaJared]

Hello! New to the forum, been lurking for 2 years! I was hoping for some help now that we are finally started, although I've already gotten a ton of advise from just reading all of your projects and posts!


16x24 1.5 story, balloon framed, ledgers let in to 2x6 exterior framing w/structural (LVL) ridge beam. At the front end, probably a horizontal shelf beam to give lateral stability to front wall per advise on this site.


I've read on this forum from Don and others that its better to place the structural ridge below the rafters to provide a better bearing surface.

I have also read the ridge sticky, but I still have some related questions...

My original plan was to frame the gable walls with pockets for the ridge, get them stood up, then hoist the ridge into place and attach the rafters to the ridge face with Simpson connectors as shown below in Figure J3.

lpi%20detail by JaredCuneo, on Flickr


Is this acceptable for a structural ridge?

Here are some views of my current framing (please note that I have not drawn in the proper "yoke" to support the ridge yet and that the ledgers for loft are not let in. These details will be added as I close in on the final plan. Also not shown is the center piers and beam to support the interior walls and mid beam vertical log support/detail.

Thanks for any and all comments.

I'm pretty new here, so I've also attached a couple pics of our current status....

Jared

Rafters above Ridge (not desired for construction ease, but as I understand it, better for insulation and venting?)




Fly Rafter removed




Overall




Found this on web, but I don't see top plates.



The gable end detail is eluding me here. I guess my question(s) are, should I put rafters above beam or attach to beam face. Then, can I frame a pocket for the beam to make it easier to hoist into place. And finally, should I double top plate just like walls, or is my gable rafter on edge the top plate?

Thanks for taking time to answer my stupid questions.....





Our outhouse, I even chainsaw milled all the siding (ship lap) from our beetle kill trees.

My wife was opposed to the Dutch door at first, but she's since come around..... Maybe just because I made it from scratch....





Our view of the continental divide

[Don_P]

Attaching the rafters to the face of the ridgebeam is fine.

That is one way of framing the gable and is ok for light wind and snow loads. The better way to frame it is to have lookouts up on edge supported by the wall with no rafter at the wall, just blocking between lookouts.

[MontanaJared]

Attaching the rafters to the face of the ridgebeam is fine.

That is one way of framing the gable and is ok for light wind and snow loads.

Thanks Don! That's what I was afraid of. We have moderate to heavy snow load (40-60psf). I take it then, that I should plan for resting my rafters on top of the beam then and standing lookouts on end.

I will use J1 or J2 method.

If someone had a CAD detail (or photo) of the gable end pocket, that would be fantastic.

[Don_P]

You can hang the rafters from the side of the ridgebeam and still have lookouts on edge. What is the size of and load on your ridgebeam?

[MontanaJared]

Load info follows.

Turns out that putting the rafters on top is not so bad in my application, had to do some manual drafting, but the more I read, the more I get the impression that it really is the better approach if you have the option to do either.

I have the beam pocket, which (until I get loads sorted, is 2 plys of 1.75" x 11.75" LVL, for a total beam size of 3.5" x 11.75") is supported by a sandwich of two 2x6 + .5" plywood = 5.5" x 3.5" bearing surface.


Here is an update to my drawing


Also, I have a log post mid way (14' is the longest unsupported span) on the ridge which has direct support all the way to foundation as shown below. Can I safely use 14' as my span or do I still need to do the calcs with the full 24'? Seems obvious that I can use 14' but I'm no engineer (which I plan to have look at all this once I do as much as I can)




Finally, for the below loads, does anyone know if the Simpson VPA or USP TMPH connectors are good for these type of lateral loads? I am wanting to avoid birdsmouths as I don't like the idea of cutting into those I Joists.

Anyone know what these numbers mean? Click to enlarge, this one is hard to read.



Roof Calcs:

8'x24' Total Span (I have a post at 14', I will calc that separately below)
8'x24' = 192 sq ft
192 sq Ft x 81psf (66psf + 15 dead) = 15,552lbs
15,552 / 24' = 648 plf


Post Calcs
8'x14'
8'x14'= 112 sq Ft
112 sq Ft x 81psf = 9,072lbs
9,072 / 14' = 648 plf

[Don_P]

Why are you thinking of using I joists for rafters... or, can I talk you out of it?

[MontanaJared]

Sure, I can be talked out of it. The only reason thus far is that they are easier to transport for my situation, but not so much so that I won't listen to the voice of experience 

[Don_P]

The detailing on them while up in the air takes more time than I enjoy, and the hardware begins to add up.

For the drawing, raise the gable end top plate up to the underside of the lookouts, that rafter becomes blocking in between the lookouts. Take a look at the drawing at the bottom of pg3 in this pdf;
http://www.strongtie.com/ftp/bulletins/t-01wfcm08.pdf

A dropped ridgebeam needs to have either a sloped top or a bevel strip to give full bearing for the rafter that rests on it.

[MontanaJared]

Sold! I will make those changes, and switch to 2x10 SS rafters, and I see that rake overhang framing needs to be connected to the gable wall.

From the drawing, it looks like there is no gable rafter, just pieces of blocking in between lookouts.... that sound correct?

Since I'm saving money here, I was thinking about using connectors to hang the loft floor. It would seem from the specs that, depending on the hanger, I can get a stronger and more compact connection by doing so, plus I don't have to weaken wall framing with the let in. Negative seems to be that I don't get the collar tie effect that nailing joists to opposing walls give me and that could break the deal.


Thanks so much for all the help!

J

[MontanaJared]

Here is a revision with the facing side of roof modified. I also made the lookouts 9.5 to match framing.... bad idea? Roof could start to look heavy, but I can always cut them to 5.5 or so at the blocking to lighten the look if needed.



The rafter tails as generated look strange. Any ideas as to what to do here? I was going to use VPA's on those before, and I suppose I could still do that to avoid the birdsmouths. I just can't see this as a good bearing surface.

[Don_P]

Rant warning, I've been having a discussion with the AWC engineers over the new notching provisions regarding birdsmouths in the building code... they are... stupid. The current codebook drawing and description was written and drawn by someone with very little actual experience  . These are fine in my book but probably would not pass. Do not use the VPA's. The lookouts and blocking should probably be 2x6, just lift the bottoms of the lookouts and blocking till they plane in with the fly, then bring the top plates up to meet that height. Can you post or email the skp file, it might be easier if I doodle on it.

[MontanaJared]

Birdsmouth it is but could you elaborate on the rationale? I would think that by not cutting the bm that you would have full rafter strength and less chance of the rafter splitting. I would love to send an .skp but this model is in Chief Architect. I can only export to AutoCAD....

If I lift the plates up to that level, won't that force the ridge beam out of plane with the undersides of the rafters?

Also, with our snow load and this small bearing surface, I think I will switch to 16" oc rafters.


Thanks!

[MontanaJared]

Here is the alternate with rafters on face, but I don't know how I would get the ridge in place with a 2 or 3 person crew without a pocket......

[Don_P]

Gettin late, see if this is enough for you to see where I'm going.

[MontanaJared]

How would I do that config with rafters on top?

J

[Don_P]

See if this is along the right track.