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Author Topic: Roof valley connections  (Read 1829 times)

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Offline Algorythm

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Roof valley connections
« on: February 22, 2019, 08:22:13 PM »
Hi,
 
I am a forest engineer from eastern Canada with knowledge in ecological housing. I was raised on a tree farm. I have a wood mill and what it takes to harvest my lumber. Me and my wife have the project of building our own ecological house.
 
I am currently making plans for a timber frame structure 24'x48' with 45deg angle roof. The main frame consists in 2 similar 24x24 high posted cape frames (3 bents each) but oriented differently. I wanted to optimize solar energy and also wanted to eventually later have a good spot to build a greenhouse next to the south wall (we live in the north so the having access to a greenhouse in winter would be nice).
 
I am starting to work on the roof valley connections and I have a few questions:
 
1. Is it best to keep both frames at the same roof elevation (for the central king post) or is it better to join both frames at a different roof elevation (for later works on the envelope and metal sheeting)?
 
2. I have opted for horizontal rafters to close both 24x24 frames. Then when I started working on the roof valley junction, I was wondering if I could keep using horizontal rafters or if I had to change the design for vertical rafters? Do both work and if yes which is best?
 
3. I could not find any joinery designs for the bottom and top roof valley connections (to main post and king post). What is the best way to make those connections? Bolts/nuts are used for reinforcement somewhere?
 
Any general comments, suggestions or help would be appreciated.
Frank

Offline Algorythm

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Re: Roof valley connections
« Reply #1 on: February 22, 2019, 08:46:05 PM »
Here is a picture of the framing

Offsite photo link deleted by ADMIN, linking to offsite photo hosting sites not permitted. Refer to rules posted at bottom of every page.
Frank

Offline Mike W

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Re: Roof valley connections
« Reply #2 on: February 22, 2019, 09:11:04 PM »
Algorythm,

Welcome to the FF, you'll find great info and great people here lurking around.  I am unable to provide solid advise to you on your questions, however I am sure Don P or Jim R will chime in when they are available and would be the ones to get you on the right track.  IMHO - they are guru's on the topic on this forum from everything I have been able to glean from all the various projects others have sought out advice on "how" to make their timber frame project become reality.  I as well am in the design stages of my first timberframe project, been a conventional framer my entire life and this is the next step in the saga of life.  I am just at this point reading all info I can and incorporate everyone's questions being resolved here into the initial design before  I fully engage with those mentioned to help with problematic connection points and loading I am unable to resolve myself.

again, welcome aboard, grab a seat and start browsing all the threads relative, sure you'll gain as much insight as I have thus far, just looking forward to learning so much more here as well.

I look forward to their responses and will be following this thread, looks like a good build in the making

Mike

Offline Don P

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Re: Roof valley connections
« Reply #3 on: February 22, 2019, 10:31:13 PM »
Hi Algorythm,
Welcome to the forum. First just a point of forum order, please put your pics in the forum gallery, at the bottom of the posting frame there is a tab "Click here to add photos to post". If you can post the sketchup file it might be easier to navigate it. Until I can replace my old computer I'm limited to the 2016 version myself.

I think Jim can be of more help, his design services are listed here;
http://forestryforum.com/board/index.php?board=23.0
Do count on design and engineering for something this ambitious. I'll throw in some general comments. As you develop the joints start with thinking about the mortises, keep them with the grain and bring the tenons into them. You can use either common rafters in the valley as drawn or purlins as in the rest of the drawing. In my mind the load on the valley is increasing towards the foot as drawn or towards the peak if purlined. The red design book on the TF Guild website does have a series of articles on hip and valley design.

Try drawing the kingpost supporting the head of the valley wider and bringing the valleys into the wide faces to see if you can get more joinery room.
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Offline Algorythm

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Re: Roof valley connections
« Reply #4 on: February 23, 2019, 12:08:21 AM »
Hi guys,

Mike, thanks a lot for the information and the warm greeting. I have a great deal to learn and also some stuff to share so I will make sure to look around the posts and see where I can be useful. Being part of the community was the next step and I am glad I made it.

Don, thanks a lot for the tips, I will work on my model considering those (I joined my actual Sketchup model). I have some joinery built in Sketchup already (from Steve Chappell book) and I am good at drawing in Sketchup (I have some computer design skills). Everything is not polished in my model yet since I am still moving things around but I am comfortable with design, engineering and I want to build shop drawings myself using Sketchup. I need some general word of advice and tips concerning design mostly.


Frank B. (Algorythm)
Frank

Offline Don P

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Re: Roof valley connections
« Reply #5 on: February 23, 2019, 07:50:33 AM »
Hi Frank, I tried to open it but it was a newer version that I don't have enough graphics card to support. In sketchup if you hit file>save as> then in that popup under "save as file type" click, dropdown appears in mine, see if your version will allow saving as 2016, mine will allow all the way down to version 3 but I'm not sure if newer versions still have that option.

One thing I can say with valleys is think through raising order very carefully, it may take many hands or a couple of pieces of equipment, or both. There is not much worse than having to take everything already assembled back down because the raising order isn't right.
And watching the crane operator reading a novel at full wages while you get it together  :-X :D
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Offline Algorythm

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Re: Roof valley connections
« Reply #6 on: February 23, 2019, 11:39:29 AM »
Hi Don,

Here is the model saved as a 2016 version. Let me know if you can't open it, I will try something else.

I worked for a wind farm construction contractor for the past 8 years so I could saw crane operators read the newspaper a lot thanks for remembering me :D. When you can't call it a wind day and you have to look hopelessly at 700T cranes doing nothing it makes you want to cry :'(. I will not forget about it and make sure to think about everything twice. I hope everything goes well when it comes down to it (fingers crossed).

Frank
Frank

Offline Cosmo52

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Re: Roof valley connections
« Reply #7 on: February 23, 2019, 12:39:55 PM »
 

 I am currently erecting this one - roof levels at different elevations


The connection to the king post is similar to this joint.  It is a wedged tenon.  The mortise is cut through the king post and tenon extends beyond the post.  Bottom part of the mortise matches the profile on the tenon

Offline Don P

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Re: Roof valley connections
« Reply #8 on: February 23, 2019, 05:31:05 PM »
Thanks Frank, got it and have taken a quick look around. It looks like the top of the valleys are well supported. I'd be tempted to notch the top, compression side of the ridge, maybe making it deeper, rather than notching the bottom tension side of the valley. The bottom tenon should run with the axis of the timber, I'm thinking just remove that corner of the post, looks like about 2-1/2" wide and running the tenon through clipping it at the intersection with the other post, so unhoused just sitting on a notched corner but trapped by the other post, if there is enough bearing.

I kind of like the common rafters there and the dropped ridge, it makes less clutter at the king and is not weakening the principle rafters. I wonder about that everywhere vs the purlins. It does concentrate the load on the kings though. You've doubtless looked at this for a lot more than 10 minutes :)

One other thing I noticed, on winder treads we cannot be less than 6" at the narrow side. Codes do vary there.
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Offline Algorythm

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Re: Roof valley connections
« Reply #9 on: February 23, 2019, 07:15:49 PM »
Don,

Thanks a lot for your time I really do appreciate it. I was wondering if the design (purlins vs common rafters and the dropped ridge) was viable and I would stick to it or if there would have been a better way to do it. I definitely like the look that the common rafters provide (looks like a leaf!). If you like it also that is a very good reason to keep it like that. Would you consider adding bolts/nuts to hold the 2 valleys together at the top? I was thinking about holding both principal posts at the bottom with bolts/nuts also.

The design keeps me awake at night, I keep thinking about it all the time :D. I really like to draft but I am still a rookie and sometimes I need to have someone with more experience telling me if I am wrong or right. I still need to figure loads out and do some tweaking here and there. I believe I understand what you are saying concerning the king post. I need to redirect some of the weight away from it towards the central post. I also need to think about adding additional support to the roof valleys as well. I need to build some additional support involving the central post in order to make sure everything is solid!

All your help really gives me a second breath, back at the drawing board. Thanks for the winder treads tip also I will check that out. ;D


Frank
Frank

Offline Don P

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Re: Roof valley connections
« Reply #10 on: February 23, 2019, 10:21:24 PM »
Yup, I was thinking bolting the 2 posts together to form that notch/pocket. Bolting the valleys together is a good idea as well. I don't mind running Simpson strapping up the valley and over the ridge, over the ridge and rafters at any of those points up top, its cheap insurance if a big wind hits and storms are not going to get friendlier.

We lost your pic in post 1, hope you don't mind me reposting it for those who aren't downloading the sketchup file. One thing I was just thinking about. A valley is a beam with load increasing uniformly towards one end. With the common rafters the load is increasing towards the lower end. As snow accumulates in the valley it also loads toward the lower end. If you use purlins instead of common rafters in the valley area the purlins load the valley towards the upper end and the snow loads towards the bottom, a more even load distribution. The appearance of either ceiling is going to be dendritic, leaflike. I'm not pushing one way or the other, just an observation.  





Zooming in on your joinery I see you have Cosmo's wedged half dovetail through mortise and tenon in there.
Cosmo, do you have a sketch of your roof?
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Offline Cosmo52

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Re: Roof valley connections
« Reply #11 on: February 24, 2019, 01:40:47 AM »
Some roof sketches - 

 

 
 

 

Offline Algorythm

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Re: Roof valley connections
« Reply #12 on: February 24, 2019, 04:00:39 PM »
Thanks for the sketches Cosmo, I like them. Did you use AutoCAD to make these?

With the help you guys provided, I will try to do a bit more drawing and see if I can keep the common rafter idea and put some more effort into bracing and supporting the valleys using the central post.
Frank

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Re: Roof valley connections
« Reply #13 on: February 24, 2019, 04:25:33 PM »
Do you need to have the section going from the main frame to the side frame open to walk through?
The part where the valleys are holding up the jack rafters from the dormer roof.

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Offline Algorythm

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Re: Roof valley connections
« Reply #14 on: February 24, 2019, 09:38:46 PM »
Hi guys,

I have polished a few things so I attached the updated version of the Sketchup file (version 2016).

- I added braces under the king post
- I added tie beams under the valleys
- Modified the king post a bit to support the ridge beam
- Adjusted secondary layers to the timber frame model

I have more than the timber frame layer in the file so you can toggle other layer's and see the floors, annex, divisions, etc.

Jim, I think the answer to your question would be yes for the first floor and only on one side for the 2nd floor. You can have a look at the division and floor layers in the model and see where the openings need to be from what I figured so far. I have been wondering if I would not be better off making the interior bent of the side frame differently.

For those wondering about the house plan:

The main frame's 1st floor would be dinning room&kitchen oriented south with pantry, locker and storage in the back. The 2nd floor of the main frame would be opened with living room in the back. The side frame's 1st floor would have bathroom south with master's bedroom north and the second floor would have a small bathroom with 2 secondary bedroom. Since I have 4 kids I would probably use the 3rd floor to place a few beds and some storage.


Frank
Frank

Offline Cosmo52

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Re: Roof valley connections
« Reply #15 on: February 25, 2019, 12:18:24 PM »
Thanks for the sketches Cosmo, I like them. Did you use AutoCAD to make these?

With the help you guys provided, I will try to do a bit more drawing and see if I can keep the common rafter idea and put some more effort into bracing and supporting the valleys using the central post.
Frank - I had these drawings supplied to me, I would think they were generated with autocad though.  I trying to become more proficient with sketchup.

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Re: Roof valley connections
« Reply #16 on: February 25, 2019, 08:59:55 PM »
Cosmo,

If you want to have a better understanding of Sketchup, I suggest:

.

This video really shows what Sketchup can do and is about creating timber frames. Also, if you want to draw with Sketchup, Clark Bremer's videos on YouTube are very instructive and give essential tricks to build joinery and speed up the process of making a frame.

Offline TimFromNB

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Re: Roof valley connections
« Reply #17 on: February 26, 2019, 11:41:43 AM »
Hi Frank,

Interesting project. What part of Eastern Canada are you in?

Tim

Offline Algorythm

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Re: Roof valley connections
« Reply #18 on: February 26, 2019, 06:01:15 PM »
Hi Tim,

Quebec, between Rimouski and Matane near the peninsula. I am 15 minutes from Metis Beach. I am 37 years old by the way. I have a nice and quiet spot for the house.

I am seeking new opportunities right now while preparing myself for the right moment to build a house. Our 4th child was born last summer and my wife has been interviewed for a job just now. If she finds a job before I get called or find another job myself, I might get stuck with the 4 kids at home. If so, I should have some spare time to start working on a frame for myself.

My dad has one of those old barns full of old school tools. You never know what you can find in there. He can pull something from an old pine cabinet
that has been totally forgotten to my generation :D. To see all those old wood crafting tools line up in the barn is magic. You only want to give the old tools a second life. I really like traditional crafting.

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Re: Roof valley connections
« Reply #19 on: February 26, 2019, 09:37:26 PM »
Frank - no kids yet, but I can only imagine you'll be busy with four!

Offline Algorythm

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Re: Roof valley connections
« Reply #20 on: February 27, 2019, 12:18:37 PM »
Hi everyone,

I spent some time reviewing joinery and making sure everything is clean. Still a long way to go before I can call it done. Here is a picture that shows the joinery connections between the roof valley and the two main posts. That valley might be hard to cut perfectly given all these angles :-[. Not sure the tenon is worth it but it seemed to fit with the rest. The valley can rest on a 3 inch wide support provided by enlarging one main post from 7x10 to 10x10. Any ideas on how to improve the model? Am I doing it wrong?



 




 



 
Frank

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Re: Roof valley connections
« Reply #21 on: February 28, 2019, 10:23:01 AM »
I feel like that tenon on the hip rafter is going to have no strength, since the grain will run out. I would probably set the hip rafter into notches in the adjoining timbers, and secure it with a heavy peg or big lag screws.
However disclaimer: I'm not used to working with this sort of roof support system, so all I have to give is general impressions

Offline Algorythm

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Re: Roof valley connections
« Reply #22 on: February 28, 2019, 02:40:23 PM »
Hi M. Bahler,

Thanks for your input, I appreciate. I agree whit you that the tenon on the hip rafter is definitely not for strength (if anything some stability) since the tenon is not made parallel to the grain. It is most likely more effort than it's worth to do it that way especially if it breaks so I will look for another option. :-\

Ideally I want to avoid cutting into the other members to fit the hip rafter. I will focus on making a steel bracket that holds everything together with bolts and see how it pans out before trying anything else. The valley already seems pretty solid resting upon the corner post. Adding a good steel bracket would most likely be sufficient. I will try to sketch something out for the bracket and post it.
Frank

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Re: Roof valley connections
« Reply #23 on: February 28, 2019, 04:02:13 PM »
Im certainly tempted to try to help you come up with a solution, but like I said this is way outside of my comfort zone. There are other people far more qualified than me to work with you on this, hopefully they'll come along and give you some suggestions. 

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Re: Roof valley connections
« Reply #24 on: March 01, 2019, 12:01:43 AM »
I made the steel bracket for the rift valley tonight (i made it 3/8" thick). Seems like this could do the job what do you guys think of it?



 

 

 
Frank

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Re: Roof valley connections
« Reply #25 on: March 01, 2019, 07:01:07 AM »
Will the bearing area support the load?
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Re: Roof valley connections
« Reply #26 on: March 01, 2019, 08:58:20 AM »
Hi Don,

Yeah, that's what I was hoping to do here. The roof valley would rest on top of the post (3"x10" bearing surface). The steel bracket would maintain the roof valley in place and give it a larger foot print over the bearing surface of the post. Let me know if you think something is wrong or if I am missing something ???.

Here is a picture of bearing surface for the roof valley for info:



 

Also had a message for Beenthere: "Regards your bracket, offset the bolt holes so they don't align with the same grain in the wood."

Thanks a lot, I will make sure to correct this.
Frank

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Re: Roof valley connections
« Reply #27 on: March 01, 2019, 04:45:45 PM »
To pile on to beenthere's comment, the hole should be at least 7 diameters down from the end of the notch.

The steel should cover the entire contact area between post and valley, just reiterating that you should develop full bearing no matter how you do it.

What I was driving at with my last comment was that you should quantify the load on the bearing surface and compare it to the allowable stress*
This is a pic showing the tributary area supported by the valley (both shade colors). Half of each jack rafter is bearing on the ridge, half on the valley. Then in yellow shading is the halfway point between your new mid valley support and the post, so that is the area to quantify load on the valley heel bearing. It will take some judgment to fudge the load of sliding consolidated snow laying in the valley on the worst day, that is the design day.





Using this as a teaching moment for others following this, notice the valley is a beam with the load uniformly increasing towards the lower end. If you visualize a purlin rather than a rafter arrangement that "kite" of tributary area flips end for end, the load uniformly increases towards the top.

*The post in parallel grain end bearing is probably not the control, the valley heel bearing on something between parallel and perp to grain is the member to check for crushing. The Hankinson formula gives the interpolation between perp to grain and parallel to grain design values in compression to use. You run into this with rafter and truss heels as well.

Sorry for the aside, back to the discussion in progress.
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Re: Roof valley connections
« Reply #28 on: March 01, 2019, 10:46:46 PM »
Alright I will be working to improve the design considering placement of holes and full bearing of the valley.

Also, I looked online for a Hankinson formula calculator. I ended up on the American Wood Concil website. They had a calculator but I am not certain of all the values I need to put into this ???. I played with values to get a feeling of how it affected the capacity. What surprised me most are the variations of the fastener's diameter but I am still not sure how to interpret all of this and what to compute for my design :-\. Here is a picture to the calculator:



 


Don, I was also wondering how the tie beams placed below the Valley would affect the tributary area. They would likely help support some of the extra weight and also prevent flexion up to a certain point.



Frank

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Re: Roof valley connections
« Reply #29 on: March 02, 2019, 07:57:13 AM »
Let me sketch a little more and show it in a different view. The shaded areas are the entire tributary area supported by the valley. Now look down the valley the inside corner of the yellow area is halfway between the supporting tie and the post, that is the area of concern right now, the load the post and valley heel are carrying. The green area is loading the tie, the blue is carried by the peak. Can you see how the load is being divided by halves, halfway up each jack rafter, halfway between truss and first jack, halfway between points of support? Just remember snow is going to slide down into the bottom of the valley and lay there, this will substantially increase the load beyond ground snow load values.




Hankinson... first see if we need him. Quantify the load in the yellow area and the area of the valley heel bearing area. Multiply the bearing area by the allowable compression perp to grain. If that allowable is higher than load then you check without going further.

The actual grain angle is heading towards compression parallel to grain which is stronger than perp to grain, we are somewhere in between the two. That is what Hankinson does, it adjusts the allowable compression for the angle to grain. Hmm, it would take longer to figure out how to write the equation here legibly than to google it, here we go;
https://en.wikipedia.org/wiki/Hankinson%27s_equation
I'll start trying to put that into a calc for the toolbox, that might take a bit.

Now, what is the steel doing? You aren't using it to increase bearing area, the heel controls there either way. You are really using it to hold the valley in place, against what? Uplift?, drift? I'm just exploring that. Would a strap running in the valley topside and down the post outside do the same thing but hidden? Just thinking not directing.
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Offline Don P

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Re: Roof valley connections
« Reply #30 on: March 03, 2019, 08:38:44 PM »
Hankinson calc is ready for a test drive;
http://forestryforum.com/members/donp/hankinson.htm
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Offline Algorythm

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Re: Roof valley connections
« Reply #31 on: March 07, 2019, 11:58:05 AM »
Hi Don (and everyone following the post),

I was away from home in the past few days and just got back. I have carefully read everything you said and got back to work today. I am not ready yet for Hankinson but I will be gathering and putting together in a spread sheet the values I need to calculate the roof load. Once I got things sorted out, we can try the formula.

As for the metal bracket, I first needed to rework my model a bit in order to answer your question. The bearing of the roof valley was suboptimal. By cutting the bottom of the valley by 1 inch I was able to improve the bearing surface by a significant margin (approximately 28% without the steel bracket and 35% with the steel bracket. The first image below shows the modification on the roof valley (cutting 1 at the bottom). The second image shows the bearing surfaces of the roof valley before and after modification and with or without the steel bracket.



 


 

Without the modification, I have approximately 10% gain on the bearing surface value by adding the steel bracket. After modification I have approximately 20% gain on the bearing surface value by adding the steel bracket. I believe that the steel bracket could be interesting but it has downsides and requires more work. It needs to be aesthetic and carefully calculated. What do you think?
Frank

Offline Don P

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Re: Roof valley connections
« Reply #32 on: March 07, 2019, 08:10:32 PM »
The calc is pretty simple so I'll walk through it real quick with what I think I remember. If the roof pitches are 45 (12/12 pitches) then the valley would be around a 35 angle from horizontal. The calc is asking for the angle between load direction, vertical in this case, and direction of grain. I plugged in 55 and #2 EWP which has an allowable compression parallel to grain of 400 psi and perpendicular to grain of 350 psi. The resulting allowable compression would then be 365 psi. Multiply that by your bearing area, I'll try 13.35 square inches=4872 lbs allowable load. I'm coming up with roughly 35 square feet bearing on that area so 4872/35=~140 psf total load allowable on the heel (that was not a check of the valley size itself only of the compressive capacity of the heel).
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline Algorythm

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Re: Roof valley connections
« Reply #33 on: March 07, 2019, 11:32:30 PM »
Alright Don I think I got it. I tried calculating the dead and live load of the roof for the 35m surface. I approximated at 910 lbs the dead load. For the live load, I considered that the snow was very wet and icy (55lbs/ft) and that there was 1 foot all over the 35m area. The sum of dead+live load gave me 2835lbs for that 35m section of the roof so approximately 81 psf total load. If there was 2 feet of snow it goes up to 126 psf total load. I am not expecting to have that much snow on the roof with a metal sheeting and a 45deg roof pitch but better be safe than sorry.
Frank

Offline Don P

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Re: Roof valley connections
« Reply #34 on: March 08, 2019, 07:02:30 AM »
I was using 35 sf, I think you just typo'd but check.
Moving up the valley, I'm getting around 50sf in the green section center point loading the tie which has about ~11' span. The sketch now has the valley just touching a corner there... next detail to think about, that might be the bracket ???.
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An artist uses his brain, his hands, and his heart

Offline Algorythm

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Re: Roof valley connections
« Reply #35 on: March 08, 2019, 04:36:59 PM »
With 50 ft:

4872 lbs / 50 ft = 97,5 psf. Withstands a bit more than a foot of wet snow including the dead weight.

I think at that point I might need to improve something else and adjust some values to make up for uncertainty. I don't want to monitor the roof on a daily basis. I see a few options I could explore ???.

1. Using the bracket

16.7 inch x 365 psi = 6095,5 lbs allowable
6095,5 lbs / 50 ft = 121,91 psf.

2. Improving support of the tie beams under the valleys by adding braces, spline joinery for the tie beam to central post joints. Also going to see if I can improve bearing area of the roof valleys over those tie beams. I might need to adjust the central post.

3. Reviewing my roof weight calculations to improve accuracy of the results.

I will be making adjustment on the model shortly to improve its strength. Here is an image of the improved version of the bracket considering recommendations I had. I feel like It is slowly getting better.



 

Frank

Offline Algorythm

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Re: Roof valley connections
« Reply #36 on: March 20, 2019, 11:00:56 AM »
Hello all,

I have been trying a lot of different things in order to support the valley's. Here is what I came up with (see pictures below or skp file attached). I still think that it is not perfect but I believe I am making progress. I decided to change the staircase a bit and use the staircase post to support one of the valley. As for the other, I went for the spline joinery at the center post. As for the other end, I did not want a post in the middle of the dinning room so I used a shouldered mortise&tenon with a bigger brace to support the tie beam. Also posted an exploded view of the junction of the valley with the king post.



 

 
Frank


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