Al and Robins 20x30 1 1/2 near Lake Eufaula, OK

Started by ajbremer, May 09, 2011, 04:01:01 AM

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CjAl

al i dont think it needs to sit on the top plate. i would just cut your rafter tails flat and nail up a 2x8 or 10 to the end of your rafters and the top plate and hang the rafyers from it. you could use simpson brackets or cut blocks to go between the rafters that you can nail them to. i forget the name they have for those blocks. its the old school way

ajbremer

Good to hear from you again Mount.Don.

Yes, that sounds good about the exposed surfaces. That will make the job easier and faster, plus, we love the look of rustic framing.
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MountainDon

We get out of internet range a lot in the summer.  :)  Mostly intentional.   Hard to keep track of much of the goings on here.
Just because something has been done and has not failed, doesn't mean it is good design.

ajbremer

Quote from: CjAl on June 22, 2012, 04:13:05 PM
al i dont think it needs to sit on the top plate. i would just cut your rafter tails flat and nail up a 2x8 or 10 to the end of your rafters and the top plate and hang the rafyers from it. you could use simpson brackets or cut blocks to go between the rafters that you can nail them to. i forget the name they have for those blocks. its the old school way

Hey, that sounds pretty good CjAl. So what your saying is for me to cut the main rafter tails flush/plumb with the wall. Then nail a 2x8 to not only the rafter ends but also to the edge of the top plate or plates. Keep in mind my osb goes all the way up to the top of the walls top plate, on its edge. Now that I think about it, what about also nailing that 2x8 to the face of the blockings? That blocking is not nailed to the top plate but they are nailed to the rafters. Then, I could use joist hangers just like I did at the very top of my rafters at the beam. Sounds good to me, I'd like more input from others though too.
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CjAl

something like that ya. but your better off getting the exact procedure from one of these guys with more experience. i grew up around builders and i have seen alot but lack some practical knowledge. i am not sure if you would want to cut back the sheething to put your nailer on top of it or if you would get some scrap sheething and go over the rafter ends then nail up your board so you have a fluse surface. these are the parts i am not sure of but it is how i would probably do it.



Don_P

I don't think I'd try to carry a roof on a ledger attached to the end grain of heavily notched rafter tails and small blocking. You can drop under and use ledgerlock type screws to attach a ledger to the wall and hanger the rafters from that. Or you can lay a ledger on the sheathed roof and attach the porch rafters to that. Or you can modify your blocking and set the rafters on the wall.

Personally, I would want the porch carry beam's bottom at least 90" off the porch floor. I like a 10 or 12' porch. If you go that route, and I haven't sketched it, I think you'll be better off sitting the porch rafters on the main roof. I prefer level porch ceilings on these to keep from having an oddly tall wall on the porch, but it's personal preference.

CjAl

see, told ya i'm a dummy.

although i did say to attach it to the top plates

ajbremer

CjAl, Thanks for the post once again. We're all learning here...I know I am for sure! You are at least suggesting some thoughts to people on what to do. I haven't been able to do that because I'm such a beginner at all this I wouldn't want to mess something up. In time I hope to be able to help a few people out with some ideas though.

Thanks again Don. I had thought that the strongest way to hold the porches rafters were to set them on the top plate and nail them to the main rafters - like what I've seen here on countryplans. I'm not sure what you mean by 'level porch ceiling'. You mean creating a level ceiling instead of viewing the raw underside of the porch roof?

Also, a 10 or even a 12' porch would be awesome - would my porch pitch be ok with a 12 footer?
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CjAl

 like what don said. with a 10' porch or more you would probably end up running the porch rafters off the roof to get it high enough, not the wall.  that is a look i dont prefer but for a big porch its about the only way to do it without the front edge getting too low.

adirondac dans roof isnt like that on his ten foot porch but it looks like he has 12' walls not 10'


ajbremer

Laying a ledger on the sheathed roof sounds easier than the other methods and it'll make the 12 foot porch have a higher ending. I'm trying to imagine how the ledger on the roof will look with the porch rafters connected to it. Will the roof ledger be vertical or laying on the roof flat. My first impression is that it would lay flat and then the rafters would have some kind of angle cut on their bottoms. Nailing the porch rafters to the ledger wouldn't be sufficient in that kind of situation...it seems. Is there some kind of StrongTie thingy for that?
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CjAl

i am not sure you use a ledger for that but i am not positive exactly how its done. i am looking through threads looking for examples but i am in northern wi tonight  and my internet sucks.

Don_P

Normally a wide horizontal ledger is nailed through the sheathing to the rafters below (we just changed the rafter loading). This is another case where supporting the heel of the porch rafter top cut to prevent splitting of the bottom edge is important. The angle will be major roof pitch ~45* + porch roof pitch 18*(4/12, what I normally shoot for)=~63*, it is a long cut.

This is a doodle from last night, it is a 10' porch with a 4/12 roof. It meets the main pitch about 4' measured along the main rafter inside the wall line. The main pitch I've extended below the transition is just for pretty, I have a pic of one where we just turned the overhang there as well, easier, either way works.



Do sheath the main roof down to the blocking area, do toenail the blocks to the plates (roof shear transfer to the wall, hence to the floors and walls below, and then to the foundation and ultimately the ground, always trying to distribute the loads across the entire box, 3-8d's per) the sheathing and tails can run on over the wall for now if you do a leavel ceiling, just leave it hidden up there and enjoy the protection now. A level ceiling also forms another triangle... strength.

ajbremer

#687
Saturday Morning - June 23rd, 2012 Mid-Oklahoma

Thanks for that sketch and info Don_P. I've played with google sketchup before and I also have that chief architect $500 software but I still can't whip out the sketches like you can, your stuff is big time helpful!

I love the huge porch idea and concept but the looks of how high it is up there on the roof seems just a touch unnatural to me. I did some experimenting this morning and went out on the build just to play around with some ideas. I thought to myself, "What if I just laid the porch rafters right on top of the blocking and then nailed them to the main rafters."

I thought I was onto something good until I realized that if I did that I would also have to re-block that extra height area - but maybe that's ok?

Here's what I did this morning: I initially checked out the difference between a 10 foot porch and a 12 foot porch...wow...12 foot is a lot of space! I thought I would stick with the 10 foot width and marked that off. Then I took a ladder and clamped a vertical 12 foot board to it so that it can hold a test rafter for measurement purposes. I stuck with the suggested 90" from the bottom of the end porch beam to the porch floor, added my 50" from my ground to floor and that's why I chose the 12 foot board.

(Ok, I've got pictures that follow but let me explain them here first)

Then I took another 12 foot 2x4 and simply laid it on top of the vertical 12' board and on top of one of the blocks and against a rafter. Now I know this is using a 2x4 for a porch rafter but in reality I'll use a 2x6. In doing all of this I measured and found that in this scenario the porch roof pitch would be ~3:12. It wouldn't be as steep as I would like it to be but I think it would be ok. We don't have very much snow here in Oklahoma but there are ice storms.

It seems to me that this connection would work because of the rafters being nailed to one another and also resting on the blocking. I could actually cut a very small angled flat on the underside of each porch rafter where it would sit on the blocks, that would create more surface area there.

My main concern in all of this is that if I did it this way I would have to install higher blocks between each rafter once again. BUT, I feel better about doing that than destroying the blocks that I have now in order to rest porch rafters on the top plate. I also feel better about doing it that way than putting a ledger on the finished roof up top side.

Let me know what y'all think about me resting my porch rafters on my installed blocks, nailing them to the main rafters, and installing higher blocks to cover the space. Here's the pictures but keep in mind that the 2x4 your looking at would really be a 2x6:





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CjAl

your makingbit harder then it needs to be agian Al. are you an engineer of some sort by chance? how will you sheeth it? how will you do the roof vents?

remember the KISS pronciple. your coming in above the roof so just sheeth the roof as it is now and when you do the porch just nail your ledgeracross the sheething right at the edge. same principle and end result but easier


Don_P

#689
There's that, but that will also work fine, I've scabbed porch rafters alongside the main rafters like that and put "kickers" in where your blocking is. It's pretty common for that height to get to a few feet so instead of blocking there it's a kneewall  with the wall sheathing extending up. I don't see a need for higher blocking here, you'll need to notch the insulation baffles a bit when the time comes but that's easy. The soffit vents are out at the porch overhang. Figure out the 2x6 intersection point on the rafters and run the main roof sheathing from there up. Some scrap sheathing screwed on from there down past the wall line and you can dry it in for now. Do not drop below a 3:12 if you're doing shingles.

Found a pic of a 6' and 10' porch, 4/12, the overhangs just turn at the transition rather than carrying thru like I drew above.

CjAl

Don.  at the risk of hijacking Al's thread, what do you think about running perlins on top of roof sheething to mount metal roofing on while.leaving more air gap? is running perlins horizontal across the roofing felt not a good idea because of traping water? its very hot where i live and i am trying to lower roof temps as much as possible

ajbremer

Saturday Afternoon - 6/23/2012 Mid-Oklahoma

Thanks CjAl for your input and yes, I do over think things some times but I've always been a very inquisitive type of person. If I wasn't super inquisitive like I am, I don't think I would have been able to build this house. And yes, it's super hot where I live too, it's over 96 degrees here now. Last year there was more than 100 days over 100 degrees here!

As far as how I would sheath the roof and do the roof vent thing - I would do it like I planned. The sheathing would just transition from one angle to another and the venting would happen through the rafter bays and out into the open porch area or if I was to have a porch ceiling, I guess it would vent out the porch eaves BUT I don't want the porch ceiling, I prefer the rustic look of the framing up there.

And thanks again Don_P for that. So what your saying is that the method that I described of laying the rafters on the blocking and nailing my porch rafters to the main rafters would be ok? Sounds good to me. Now, about that kicker you mentioned. Do you mean a short angled board that goes against the porch rafter to stabilize it on one side and angles down to touch the adjacent rafter and top plate on the other side?

Also, you mention the wall sheathing extending up to the point of touching the porch rafters. That would create the so called 'knee wall' correct? That would also mean that I would need to cut the protruding main rafter tails where they extend beyond the walls edge? I understand everything else you mentioned.
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CjAl

i learn more from a group of people throwing out ideas and discussing them then.i do by someone dictating its done this way and that way. if we had all the answers we wouldnt be here.

Don_P

CJ, in my climate and I think most of the US if you encourage airflow on the underside of the metal roof you are going to get condensation dripping off the underside of the metal many mornings. I put the metal on the felt and block the ends to prevent airflow there. Then if it is a vented roof ventilate the underside of the roof sheathing as normal. I don't love purlins, they usually show through the metal. But, I can certainly appreciate your idea, if you park a trailer under a carport it's going to be cooler in the trailer on a sunny day. If you do it there will be water running on that under roof that you want to keep outside.

Al I think your idea is fine without any kickers or other framing. You will need to bob the tails plumb above the wall framing below and sheath the ends of the rafters up to the porch rafters to continue a smooth wall. You can vent across that zone with a strip vent mounted horizontally or individual vents in each bay. I think I remember a few hurricane ties turned basswards in one picture, you may have a few in your way. If you don't own a sawzall and some long blades I'd declare it a late father's day present.

ajbremer

Don, You saw those backwards hurricane ties?, man...I thought I got away with it!

I'llput hurricane clips/ties on the inside and then remove the improperly placed ones.
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ajbremer

I've been laying out on graph paper how I'll be laying my sheets on the roof. My lower starting point will be, as Don_P mentioned, the 2x6 porch rafter intersection point on the main rafters and I'll go up from there. But I'm now questioning my stop point at the top. I know I have to stay away from the very top so that they'll be a gap on both sides of the beam so air can go up and out the ridge vent at the top.

I'm trying to figure out what kind of ridge vent to buy and where to buy it. My closest place is Lowe's but I'm not sure if they carry the ridge vent that y'all would suggest. Once again, how far back from the very peak should I leave my sheathing? I'm thinking about 2" each side...maybe a little more? Has anyone here had experience with a ridge vent?
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Don_P


CjAl

how are you going to attach the joists for the porch to the house Al,







btw, i'm stalking ya



ajbremer

Hey, your right around here! Ya need to stop by...except in that picture, your heading away from me.
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CjAl

i am through here quite regularily. almost every week but i usually stay on the turnpike. if ya ever need help with the heavy stuff.just give me a few days notice