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Author Topic: How stable/strong is this type of corner joinery for pavilion?  (Read 2020 times)

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Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #20 on: September 09, 2021, 07:31:05 PM »
See if this makes sense. The ridge is supporting half of the building width, less overhangs so 7' width x the unsupported span, 9' =63 sf x 42 psf= 2646 lbs.

Now when you get to the point load on the tie beam that overhang load is bearing on the ridge support post and then onto the tie beam, so half of 12' x 7' coming down on each ridge support post onto the tie.

In my work I don't get to say "It's only a 3/4" notch on the tension face". It crosses over the limitations published in the code reference, engineer country. I would avoid that cost by marking the reference point with a pencil and leave it full dimension.

There is a lot to be said for post frame, less "damage" to the timbers and if you buy something like Simpson connectors they come with published strength ratings and connection details. Pricing the correct steel for this might sway that too. If you can weld it might open up more possibilities if the inspector is agreeable. 
The future is a foreign country, they will do things differently there - Simon Winchester

Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #21 on: September 09, 2021, 08:26:07 PM »
This is what I've been playing with. The plate is passing through the post on the way to the cantilever. The tie beam is notched into the post and butts square to the plate. A bed bolt or cross bolt or there is a timberlinx connector to hold it all together. The bolt could pass through an outside decorative corbel in the bed bolt connection with a strap across the top to the tie. You've picked up the uplift connection of beams to post in that as well. Just one way that was bumping around.



 
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Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #22 on: September 10, 2021, 12:51:13 PM »
Quote
Size Factor (what does this mean?): 4x12
The base design values in the strength tables are multiplied by various adjustment factors, that is what those inputs are asking for in the calc.

Size factor in dimensional (2-4" thick lumber) came about after full scale testing of many samples. It recognizes that smaller dimensions are stronger in bending, tension and compression parallel to grain. The base design value for 12" wide material is multiplied by 1.0, no change. The size factor is multiplied by 1.1 for 10" wide up to 1.5 for 4" wide material.

For heavy timber the size factor is 1.0 up to 12" deep members and then derates the base design value when deeper. For round logs up to 13.5" 1.0, for larger round or diamond oriented square beams inscribe a rectangle within the section and use that size for calculations. We had an engineer on one log home job that said he inscribes that rectangle 1" inside the log just to be sure... and he did have some healthy logs in the design, rambling.

Incised, for dougfir mainly. To get treatment chemicals to penetrate refractory species it is incised with a knifed or spiked roller of specified penetration, cut size and incision density, good for treatment but it damages fiber, a 20% derate of bending, tension, compression parallel to grain, shear, 5% derate of stiffness.

Wet service, wet wood is weaker. On a treated deck, wet location, of incised timber... these factors become major. Dougfir would take a 35% strength hit.

Repetitive member, many members sharing the load distribute stress amongst themselves, a 1.15 increase in base design values.

Gotta roll, more later.
Thank you for the explanation Don!

Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #23 on: September 10, 2021, 12:54:30 PM »
See if this makes sense. The ridge is supporting half of the building width, less overhangs so 7' width x the unsupported span, 9' =63 sf x 42 psf= 2646 lbs.

Now when you get to the point load on the tie beam that overhang load is bearing on the ridge support post and then onto the tie beam, so half of 12' x 7' coming down on each ridge support post onto the tie.

In my work I don't get to say "It's only a 3/4" notch on the tension face". It crosses over the limitations published in the code reference, engineer country. I would avoid that cost by marking the reference point with a pencil and leave it full dimension.

There is a lot to be said for post frame, less "damage" to the timbers and if you buy something like Simpson connectors they come with published strength ratings and connection details. Pricing the correct steel for this might sway that too. If you can weld it might open up more possibilities if the inspector is agreeable.

Thanks Don. I did some research on the forum about Post vs Timber frame. One cons of Post frame people said is that you need special engineering to figure out metal connector position, spacing of bolts and etc.

If we use Simpsons product, as you described with published connection detail, does this eliminate some of the engineering issues?

Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #24 on: September 10, 2021, 01:11:10 PM »
This is what I've been playing with. The plate is passing through the post on the way to the cantilever. The tie beam is notched into the post and butts square to the plate. A bed bolt or cross bolt or there is a timberlinx connector to hold it all together. The bolt could pass through an outside decorative corbel in the bed bolt connection with a strap across the top to the tie. You've picked up the uplift connection of beams to post in that as well. Just one way that was bumping around.


(Image hidden from quote, click to view.)
 
This is a great idea.
I recreated your idea using Timberlinx A475 with threadbolt and nuts. I'm thinking of recessing the nut into the post.
The last issue is how to attach the decorative corel to the post. Do you mean adding a metal strap tie on top of the corel to hold it like this? Since it at the top, I reckon it is barely visible and wouldn't take away the "timber frame" look?










Lastly, is it worth my investment to get a Makita chain mortiser? After this built, I will want to build a 16' x 30' pavillion with similar method. Since the design doesn't use a lot of mortise, I wonder if it is a good investment?
 

 

 
Timberlinx A475 with threadbolt

 


Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #25 on: September 10, 2021, 07:32:57 PM »
Take a look at the A155 further down in those Timberlinx drawings. I think that would work for the corbel and tie connection.

A heavy duty router would do a good job making housings for the braces, if you want to house them. I don't see a need for a mortiser if you go with these connectors.

On the engineering required. Timberframe joinery needs to be checked as well so I don't see a difference. With these proprietary connectors whether Simpson or Timberlinx, or whatever, if it has code approval there is a document with very good engineering for the connector and applications. Which, I'm not seeing US approval, if you have a building inspector involved. They are showing Canadian approval which most would probably be fine with but get the ok first.

And then I take issue with their installation manual ::). I would rather see the connector lower than midline, at most 4" or so off the post bearing surface. I would rather have the beam sitting on the seat rather than hanging from the connector when fully dry. If going with 2 connectors which isn't a bad idea, I'd space them no more than 5" between to avoid splitting during seasoning.
The future is a foreign country, they will do things differently there - Simon Winchester

Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #26 on: September 12, 2021, 09:34:49 PM »
Thank you Don.

Here is the new design based on your inputs:

a. One Timberlinx A155 to connect tie beam, Plate, post and corbel
b. Two Simpson 15" Strong-Drive« SDWS TIMBER Screw (Interior Grade) to reinforce the above joint

Strong-Drive« SDWS TIMBER Screw (Interior Grade) | Simpson Strong-Tie

c. Four 15" SDWS on top of plate to secure plate to post. This should be ok for uplift?


Question:

1. Can interior grade screw used in this application when my pavilion will have roof and the screw will be protected from rain? There is no 15" screw for exterior grade...

2. at what stage do you stain the wood? After cutting all the joints?

3. When designing roof pitch, does the pitch has to be exact such as 6/12, 7/12 etc?  Do I start with a desired roof pitch such as 8/12 then derive king post length based on that?




 

 

 


Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #27 on: September 12, 2021, 11:30:46 PM »
The A155 is taking care of uplift with the shear connection at the post. I think I'd omit the other screws, they look like just more wood damage to the cantilever beam to me.

OK, check the tie beam. That will be the center point load calc, use the design values from previously. 7' trib width x (include the overhang this time) 6' x 42 psf

I usually draw it in sketchup and take the measures for kingpost, and everything else, directly from the sketch. The pitch can be anything. Usually it is called out in whole numbers but when there are intersecting roofs then pitches can be whatever makes it all work.
The future is a foreign country, they will do things differently there - Simon Winchester

Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #28 on: September 13, 2021, 01:53:16 PM »
The A155 is taking care of uplift with the shear connection at the post. I think I'd omit the other screws, they look like just more wood damage to the cantilever beam to me.

OK, check the tie beam. That will be the center point load calc, use the design values from previously. 7' trib width x (include the overhang this time) 6' x 42 psf

I usually draw it in sketchup and take the measures for kingpost, and everything else, directly from the sketch. The pitch can be anything. Usually it is called out in whole numbers but when there are intersecting roofs then pitches can be whatever makes it all work.
Thanks Don. I will take out the screws.


In rafter and ridge beam design, ridge beam always carries more load than tie beam and plate and should use heavier timber than tie and plate beam, correct?

Load:
Ridge Bean > Tie Beam > Plate , correct?


If I ever need to upsize the timber, it is always more economical to increase vertical depth of timber instead of lateral thickness, correct?

4x14 better than 6x12 when factoring wood cost, correct?



Tie Beam Calculation:

Two tie beams to transfer load from ridge beam, am I correct?

7' x 6' x 42 psf = 1764.

Passed.



 



For plates calculation, please correct if I'm wrong:

1. Each plate carries 1/4 of roof load : 12' x 16' x 1/4 x 42psf = 2016lbs



 



While we are here, I want to ask you about joining two plates for larger timber frame design (two bays).
Does something like this work? The red beam is another set of plate that will be supported by another post. This will be for a two bay design (6 posts total).
Red plate and non-red plate are seated at Post and connected by something like A155.
Tie beam and the non-red plate, and corbel are connected to the post via A155.


 


Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #29 on: September 14, 2021, 09:36:21 PM »
You used the wrong calc to check the tie beam, this one is for a beam with a concentrated point load at midspan, it uses a different set of equations;
Midspan Point Loaded Simple Beam (forestryforum.com)

It depends on spans but I've usually ended up with the same sized tie beam as the ridge for those support conditions. Although the tie is only carrying half of the ridge load the ridge has a uniformly distributed load along its length, the tie is carrying half of the ridge load each but as a concentrated load at midspan... which, well let me show the equations for maximum bending moment for each beam condition.

Max moment for a simply supported uniformly loaded beam is
WL/8 (load W in lbs x span in feet/8 = bending force in the beam  foot-lbs)

Max bending moment for the same beam but with a concentrated load in the middle is;
PL/4 (point load P in lbs x span in ft/4= bending moment in ft-lbs)

A point load produces twice the bending force in a beam as a concentrated center point load.

That then quantifies the stress, the calc is comparing the allowable stresses in the beam size you plug in to see if it is below the allowable stress for that species and grade.

In factoring cost there is more going on than just the volume in the timber. Bending resistance is based on the shape of the beam. Depth is squared in that equation. Adding the same amount of volume to 2 beams, one of square cross section and the other being rectangular, the rectangular one with an equal number of board feet will be far stronger and stiffer.

That is referred to as the section modulus of the beam in the bending calculations, the equation is bd2/6 (breadth x depth squared/6)
Going deeper builds strength fastest. Deeper is usually cheaper. That said stepping to a 14" deep might be crossing an availability line that carries a heavier cost than going thicker.

Now for the plates, tributary width is half a rafter span + the overhang- 3.5'+1' x 42psf=189 lbs per foot of beam. We have another situation here. The plate is a beam that is overhanging the support at one end and there is a 200# load out on the end of that overhang. I'm going to cheat and check it the easy way first. It would be very conservative to check this as a beam overhanging one support with a uniform load of 189 lbs per foot. That is this calc;
Beam Overhanging One Support-Uniformly Distributed Load (forestryforum.com)

For the joinery question look through the timberlinx standard detail manual, They show several post and splice details. Near the end they show a 4 way connection to a post, in several places they show a stub tenon into a post. Your 4x12 inserted a bit into an 8x post is pretty much the same detail as the stub tenon in their drawings.

The future is a foreign country, they will do things differently there - Simon Winchester

Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #30 on: September 27, 2021, 11:49:03 PM »
Thank you Don for the detailed explanation.

I did the overhang cal and it seems to be ok.



 
My next question is related to how to secure King Post to tie beam and Ridge Beam.

I plan to use two 3/4 pegs as the connection. Would this work without tenon and mortise? Or I should add timberlinx?



 

 



Finally, for rafters, I was going to go with 30" OC for aesthetic reason but it looks like I can't use 1x6 T&G pine on 30" OC. 2x6 is going to be significantly more costly.

As result, I'm going with 24" OC with 1x6 T&G. I plan to add a sheathing on top of the T&G to avoid roofing nail from piercing. Should I use OSB or plywood? What thickness?

Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #31 on: September 28, 2021, 07:24:56 AM »
That brought back a memory. Everyone says the Amish are wonderful builders, and the workmanship is usually good. When we step outside and isolate ourselves it can cause some thinking problems. We stopped in to visit a log home they were building, the 1x6 T&G roof sheathing was spanning from purlin to purlin. I asked what the spacing was on the purlins, 7'.

Wander the sheet goods aisles looking at the APA stamp on the sheets. There will be a span rating stamped on each sheet, the shorter number is allowable floor span, the larger span rating is for roof sheathing. Check, but 19/32" osb or ply should be rated for the desired 30" span. then what is the T&G, wallpaper, the ply is the sheathing. Load goes to stiffness.

The unique inspector we had last wouldn't let someone use home milled, ungraded, walnut stair treads. Adjust riser height and put graded SPF lumber sub-treads down first, the walnut is carpet on the structural tread.

The pegged ridge post is fine, I would us a single peg about 3" from the inside pocket at each end. Think through shrinkage whan making connections. widely spaced cross grain pegs set up splitting potential. pegging closer to bearing seats keeps the shrinking beam bearing on the seat rather than lofting up and hanging on a more distant peg.
The future is a foreign country, they will do things differently there - Simon Winchester

Offline johnkim

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #32 on: September 29, 2021, 11:45:53 PM »
That brought back a memory. Everyone says the Amish are wonderful builders, and the workmanship is usually good. When we step outside and isolate ourselves it can cause some thinking problems. We stopped in to visit a log home they were building, the 1x6 T&G roof sheathing was spanning from purlin to purlin. I asked what the spacing was on the purlins, 7'.

Wander the sheet goods aisles looking at the APA stamp on the sheets. There will be a span rating stamped on each sheet, the shorter number is allowable floor span, the larger span rating is for roof sheathing. Check, but 19/32" osb or ply should be rated for the desired 30" span. then what is the T&G, wallpaper, the ply is the sheathing. Load goes to stiffness.

The unique inspector we had last wouldn't let someone use home milled, ungraded, walnut stair treads. Adjust riser height and put graded SPF lumber sub-treads down first, the walnut is carpet on the structural tread.

The pegged ridge post is fine, I would us a single peg about 3" from the inside pocket at each end. Think through shrinkage whan making connections. widely spaced cross grain pegs set up splitting potential. pegging closer to bearing seats keeps the shrinking beam bearing on the seat rather than lofting up and hanging on a more distant peg.
Thanks for the Amish story. I agree that a lot of the redtapes is due to local regulation...

Your inspector reminds me of a movie that was brought up on this forum called Still Mine: Still Mine (2012) - IMDb . The antagonist is building a retirement house using lumbers he milled without stamps. Inspector wants to torn it down despite it being engineered...


I will modify the peg based on your suggestion.

Thank you again DonP for your patience and taught me a lot about calculation. I just found out you are the one that created all those useful calculator as well. Great job!


If you don't mind, I want to confirm how to calculate load on another design I'm playing with.

This is a shed roof design. Outside post to post 14' x 12' . 12" roof overhang on all side except front which is 66" overhang.

Few questions:

1. On Shed roof design like this, is the only load-bearing beam the front and rear beam where the rafter will be resting on? What is the purpose of the side beam? Just to increase stiffness of the structure?

2. Total roof print dimension is approximately 16' x 19' = 304 sqft. Assume total load 41psf. Total roof load = 41 * 304 = 12464lbs .
If only the front and rear beams are carrying the load, the the uniform load on each beam is 12464/2 = 6232lbs . Is this correct? Given same dimension, we have to use beefier front and rear beam shed roof design compare to gable roof?

3. My biggest question is 66" of roof overhang. Is this possible? How do I go about calculating what rafter size to use with such a big overhang?


My idea:
a. Total Loads / # of rafters = uniform load per rafter
b. Find out load per ft and use your calculator here to test overhang : https://forestryforum.com/members/donp/oerhangbm.htm
Is this correct?

4. Can I omit the side beam or just use it for decorative purpose?

5. Since total load is 12464lbs with 4 posts, each foundation will need to carry 3116lbs of load. Assume 1500psf soil capacity , a 12" sonotube pier would not be sufficient for this structure (1178 lbs). Is it better to consider helical pier for this building? Maybe more economical than a 22" concrete footer? Is this calculation in the right direction?


 


Online Don P

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #33 on: October 02, 2021, 09:19:21 PM »
You really don't need the side tie on a shed roofed structure, bracing would be the main concern.

The outputs for R1 and R2 in the calc are giving the appropriate load at each rafter support, it is not evenly divided, the overhanging end has more beam and post load.

The future is a foreign country, they will do things differently there - Simon Winchester

Offline kantuckid

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Re: How stable/strong is this type of corner joinery for pavilion?
« Reply #34 on: October 03, 2021, 09:06:18 AM »
On the how to hide electrical wires-I got real good at long auger bits when I built my house. In my new timber frame great room I had the walls as hollow and covered with a skin of log siding in and out to play inside but for elevated wiring I made simple, homemade "U"-channel wooden strips that are hardly noticed unless you try to find them. Easily made on a tablesaw from same wood as the structure.
I find the Amish an interesting bunch. I've used them foir previous shingle roofs and more recently for home meat standing seam roof and screwdown shop metal roof. This last crew one kid smoked, one was a dipper and both were talking to GF's at breaks on flip phones.  ;D
Times a changing, huh? The general notion we see in many ads now days that all of them are a breed of master craftsmen is not true-if it ever was? Like the rest of us, I find them variable in skill sets and knowledge in construction. One constant theme is they DO! have a strong work ethic.
Kan=Kansas;tuck=Kentucky;kid=what I'm not


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