HI, I'm in the process of building an earth home that will have a 56x29ft 6" core ICF wall attached. Attached to the wall will be a free support pent style roof attached to the side of the wall above the 2nd floor. The roof will be 7ft deep and have a 12/12 pitch in the center and 10/12 pitch at either end (please see https://1drv.ms/i/s!Ah_EyvMgDnpxik7jKDRs6KieK1u2 ). My question is on the ledger boards, which are indicated in blue on the drawing and the required anchor bolts(J-bolts) needed. The truss manufacture is telling me 2 bolts every 3-4 inches. Does this seem excessive? Any advice is greatly appreciated.

Sorry your attachment didn't take. Putting images in this forum can be difficult. IMO it is easier to put the images somewhere else like Photo bucket and put a link to it in your post. Sites like photo bucket have tools that create the link for you and copy it to your clipboard. You then simply paste it into your post.

Not really visualizing what you are trying to do from your description, so need to see the picture/drawing.

In clarify your question about J-bolts, what does your engineer say? Usually the engineer of record specifies the wall to roof attachments to meet the local design criteria. This design criteria is used to calculate the roof/truss load, to which the truss manufacturer designs and builds the trusses...

2 bolts every 3-4 inches might not be out of line if you have a large span or roof load, or have seismic considerations to design for... Where are you building at?

Thanks for the lik advice please let me know if this link works. https://1drv.ms/i/s!Ah_EyvMgDnpxik7jKDRs6KieK1u2
I'm building in Northern Minnesota, so seismic disturbances shouldn't be a concern. The overall span will be about 45ft.

That link worked, now I understand. A complete awning roof structure hung in shear off of the top half of a 6" ICF wall. That in an area with a fair bit of snow?

Since that entire structure is supported by the wall, the bottom in shear and the top in tension and shear I can see the desire to avoid concentrated loads especially on that shorter ledger along the top. The high connector count to disperse the load is probably correct in this case.

Did they spec anything special with the rebar in the wall across this area? You might be able to reduce the connector count by tying the connectors into the rebar cage in the wall which would spread the load via the rebar structure inside the wall. That is one for the engineer though...

Interesting structure, What is the arched roof structure made of, and how is It tied into the wall?

It's constructed of 13 steel beams with 3-4 layers of vert/horizontal rebar around it. It will then be shot with 4-5" shotcrete. The back 25' of the the structure is actually a dome shape with the front 18' being a barrel shape. The wall is tied in with plenty of rebar. To get a better idea you can check out www.earthshelter.com.

Don't listen to any stress analysis BS out here. The truss mfg/designer is probably using FEM (Finite Element Modeling) software like Miteck, meeting various roofs allowables w/positive margins. The Engineer stamps the drawing knowing the software is correct. If you deviate, Engineer is not responsible for personal injury, that usually happens when people act as Engineers they are not qualified for. You have to realize ppl giving internet advice they are not qualified to give, which is 9 x 10s, are protected legally from the site disclaimers or they would not give it so freely.

3-4" fastener pitch based on diameter is per international design standards in just about every industry a qualified stress analyst know right off the batt. 2-4" (2-4 D) metals, 6-8 D composite. 2(D) min edge distance metal, 3 (D) composite. Has nothing to do with the reasons stated above. Excessive pitch causes buckling/bending between fasteners, low concentrated stress or unnecessary dead weight. Short ED low static bearing area tear out, large buckling, failures.

Truss load transfer and design is complex, especially with concrete, anyone trying to do that out here just proved how little they know. Beware! Not the kind of question to ask anyone on the internet. Find a pro and pay them well before you end up hurt.

So, Shaggy how can we trust your analysis, your on this site. More of your BS

Posted By smartwall on 24 May 2017 02:53 PM
So, Shaggy how can we trust your analysis, your on this site. More of your BS

<!--[if gte mso 9]> I didn’t provide an “analysis” I’m not that dumb, not nearly enough info, and, if I did it would be to a standard or FEM, not “mine” or “BS”, dah! And you call yourself “smartwall”?

Inter-rivet buckling dates back to the 19^th century when the Wright Brothers first noticed it well over 100 years ago. The term is generically used now for any fastener any industry, so is the corresponding edge margin term ED and, associated class of holes (Interference being strongest) as noted in MMPDS (MIL-Hand-Book 5) various structures ICCs, ISO, ASTM, ANSI Y14.5, standards, any basic FEM algorithm. The primary failure stress an Engineer shows good is static compression & dynamic moment arm bending, not shear or tension that’s at the fastener itself, or rebar, where the bulk of load is. The fastener allowables & design guides prevent permanent deformation by sizable safety margin 1-2xs), however, in cases like this complex roof full-up FEM is recommended and s/b strictly enforced by drawing’s & inspections.

https://www.google.com/?gws_rd=ssl#...5640360784

I’m done playing dumb with the peanut gallery. Bad advice here can cause serious injury and it wouldn’t be the first time.

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I am sorry, what part of consult your engineer was bad advice?

Posted By ronmar on 24 May 2017 08:17 PM
I am sorry, what part of consult your engineer was bad advice?

Since that entire structure is supported by the wall, the bottom in shear and the top in tension and shear I can see the desire to avoid concentrated loads especially on that shorter ledger along the top. The high connector count to disperse the load is probably correct in this case.

Did they spec anything special with the rebar in the wall across this area? You might be able to reduce the connector count by tying the connectors into the rebar cage in the wall which would spread the load via the rebar structure inside the wall. That is one for the engineer though...

The specs are on the noted site you did not read. In cases like this, just point to the Engineer leave the rest of the BS thats so far off it's not worth the cost of discussing with one out.

Otherwise, I read your advice and for the most part it's to a proven standard and code which is good, better than most, like what youre doing on the cantilever thread I see now is derailed I posted on. Sometimes IRC structures code can be confusing like braced walls earth/shotcrete & Atteberg limit walls don't follow especially domed. If it gets to the point you don't know code point to a licensed architect that probably has a PE co-worker or, there is plenty of proven earth code in SW sunshine states, especially NM..

Now you know more about fasteners stresses.

Looks like a great design for the most part.

Parahomes, thanks for your feedback. Being the vertical #5 rebar is 10" oc, I will tie the anchors where able though it doesn't specifically note this. To play it safe I will follow guidance they gave me and with connecting some with the rebar I will be that much better off.

Posted By Oients on 26 May 2017 12:23 AM
Parahomes, thanks for your feedback. Being the vertical #5 rebar is 10" oc, I will tie the anchors where able though it doesn't specifically note this. To play it safe I will follow guidance they gave me and with connecting some with the rebar I will be that much better off.

I recommend you follow the engineers design to a tee and not act as one and redesign. You could be putting too much load on the anchors. As I said above, you alter the engineers design you take full responsibility for the consequences so you better know what your doing and I can tell by the nature of your inquires you don't. Better to be safe than sorry. At least run it by the engineer or ask the designer(s) if they can add the tie to the model to see what happens to the stresses on the bolts that are rated for a max stress (ie: tensile, shear, compression, bending) Fatigue is calculated. Or, they may be a pre-determined low impact failure path if it occurs like extreme weather, you are ruining or creating, the better engineers design like crack propagation/growth the better softwares model accurately. If they can get a stamped print to pass inspection.

I can tell you my answer would be absolutely not, I'd want even distributed load to all fasteners or none, not some taking more than others. Thats just basic stress analysis, thats a function of pitch, ED, bearing area, I described in this thread. I charge my clients for these silly questions and if the answer is no they still pay for my time to do the analysis and educate them. Bring your wallet.