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Discussion Starter · #1 · (Edited)
Been away for awhile and this place seems to have taken off.What's with the massive increase in viewers all of a sudden.:eek:

Anyways,I've got an addition that I will be doing some work on this summer and was a little surprised at the requirements for shear on this three season room.

The HO wanted as much glass as possible but it seems,without strongtie connections,we need 4' of sheathing at each corner.

The addition will be 16'x20' with the 20' running parallel to the main house,Gable roof abuts the existing house on its gabled end.

Windows will be about 5' tall,leaving a 2' knee wall that will be tied into band joist and corners.

It seems to me that by tying the gabled end into the header with plywood sheathing would give enough lateral support to prevent any shear forces from racking this wall.Since the roof gets tied into an existing wall,and can't move laterally(once sheathed)wouldn't this also protect the 20' wall from any shear forces?

I've seen dozens of additions and enclosed porches framed
without a 4' corner,mostly on older homes,and their still standing.

Funny part about the plans for this addition is the engineer that drew it up,didn't have the shear requirements,building inspector passed the plans,and then the truss manufacturer said we need the 4' corners.


Also,if the 4' is needed for shear on the 20' wall,why would it be needed on the shorter walls which are tied directly to the house?

So,who's right?


Couple pics:
 

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I'm The BOSS
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I think what you'll find that needs to be done.

LVL headers all three walls corner to corner,
Both outside corner vertical plywood w/ blocking mid-height.
any horizontal sheets will need blocking at seams.

I'm in Massachusetts, Check local code requirements.
View attachment 111865
 

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Joseph A. Capece
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If the ceiling isn't cathedral you can glue & nail plywood to ceiling joists. Here's one I did a few years ago where the engineer approved the shear strength of this design.



 

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Got me, post & beam structures work until you use glass. The glass creates a resistance that doesn't count for shear. Did you scan the code book for language that states the minimum percentage of bracing? Do you have a cathedral ceiling that losses the shear benefits of a flat diaphragm?

The engineer stamp will override, must be outside of his day to day work.
 

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Discussion Starter · #5 · (Edited)
Good point on the cathedral ceiling,it could be part of the consideration here.

I've have seen a lot of similar structures, that were built as screened rooms,
closed in with windows without any consideration for needing added shear.
Good to know what's needed ahead of time for bidding and code purposes.

I sent the Simson wall bracing calculator http://www.strongtie.com/webapps/BracedWall/
to the original engineer so he can redraw to code.
I'm anxious to see how he responds to this.
At the very least,I'm hoping to gain added glass area in the two end walls.
If not,maybe having a flat ceiling sheathed will do the job.
As it sits,the plans call for a raised ceiling area:
 

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You need to swap those silly concrete footings out for some awesome helical piers.

There are definitely ways of eating up the lateral loads without the 4' shear walls.

I looked at a project that we were able to satisfy the loads by framing in 2x6 and then insetting 2x4 with 3/4" ply on both sides inside a 14.5" bay along with a little metal and zip sheathing on the outside.
 

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Discussion Starter · #8 ·
You need to swap those silly concrete footings out for some awesome helical piers.
The HO started as a mason and works for the biggest concrete supplier in the state,I don't think he'd be an easy sell.

I looked at a project that we were able to satisfy the loads by framing in 2x6 and then insetting 2x4 with 3/4" ply on both sides inside a 14.5" bay along with a little metal and zip sheathing on the outside.
I was wondering about adding the ply to the inside bays.Seemed like a viable solution to me anyways.
What exactly did you use for metal on the outside?
HO was informed that the simpson solution would run upwards of 1K.
 

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The HO started as a mason and works for the biggest concrete supplier in the state,I don't think he'd be an easy sell.



I was wondering about adding the ply to the inside bays.Seemed like a viable solution to me anyways.
What exactly did you use for metal on the outside?
HO was informed that the simpson solution would run upwards of 1K.
The Simpson Strongwalls are $$.

I so not have the details handy but I remember A35 or A50's, MST straps and Post to beam connectors...Maybe HH not post to cap...It was a lot of metal.

The hold downs were something along the lines of HD12 or 19.
 

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Talk to the Engineer about providing a detail with flush shear panels on the ends. As Dan says the Simpsons are spendy but solve many issues.

You do not appear to have any difficult shear issues and may be able to simplify the solution by speaking with the Engineer.
 

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Eater of sins.
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I am confused here, the engineered certified his design and the truss company is over-riding that somehow?

How does that work?

If I was the engineer I would re-look at the design and calcs. and if there where no mistakes or omissions I would tell the truss company to mind their own ****ing business and design the end truss to the proper lateral loads for wind and whatnot.

The 4' requirement is generally for prescriptive design, called braced design using a min. of 4' braced panels.

What is referred to as "shear" is an engineered design value, as long as the engineer of record can support his design and calcs he can make the shear panel whatever size he thinks is correct for the situation.

Andy.
 

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Discussion Starter · #16 ·
OK,so I try and find code requirements to support the original engineer's design and find these charts at the APA-The Engineered Wood Association;

From what I can figure,with max window height of 5',we'll need closer to a total of 4' to 4'6" of bracing,allowing corners to be close to 1/2 of the 4' the truss manufacturer was suggesting.

The only other required consideration is the nailing schedule.

The building inspector directed me to the Simpson site for reference.They seem to suggest a min of 8' total bracing without their fasteners.
I tried the code requirements,and they are hard to read without referencing ten other sections in the code for clarification,
so it'll probably subject to interpretation by local BI.

All I want to do is get this thing built and make HO happy.They want a more open feel to the room,so we may have a bit of a challenge getting there.

Thanks for the replies guys,I'll let you know how this all pans out.
 

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I am confused here, the engineered certified his design and the truss company is over-riding that somehow?

How does that work?
.... I would tell the truss company to mind their own ****ing business and design the end truss to the proper lateral loads for wind and whatnot.
If the engineer approved it and the city approved it then I would find another truss company.
 

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Discussion Starter · #19 ·
If the engineer approved it and the city approved it then I would find another truss company.
Not an option at this point, on this project because,once I asked the BI about the truss manufacturers opinion,he changed his stance on the design he accepted, and referred me to the Simpson site.
That site leans towards a min of 4' at each corner,without their fasteners,prompting me to believe the BI will hold this as Gospel when it comes to final approval upon inspection.
 

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Not an option at this point, on this project because,once I asked the BI about the truss manufacturers opinion,he changed his stance on the design he accepted, and referred me to the Simpson site.
That site leans towards a min of 4' at each corner,without their fasteners,prompting me to believe the BI will hold this as Gospel when it comes to final approval upon inspection.
A BI overriding an engineer's stamp based on structural concerns? Around here that would be inconceivable.
 
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