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Unregistered
Registered Users
Posts:2321
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| 12/14/2001 3:39 PM |
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I'm wondering if there are specs as to what the typical floor loads are for "Method 1" in the Floor Deck section of this website. We're using two 1/2" anchor bolts placed 12"OC with a cutout in the ICF for concrete pad exposure against the PT ledger board. I think the building inspector is concerned about the shear strength of the anchor bolts and their ability to hold the ledger board with no support(foundation wall)below it. The joists attached to the ledger are 2x10s covering a 14 ft span.
Should the shear strength of the anchor bolts be a concern? This is the first residence in town using ICF so it's all new to him. |
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Ian ICF Builders
Registered Users
Posts:612
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| 12/15/2001 6:59 AM |
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I would guess that the Building inspector should be concerned about the 2x10 ledger failing rather than the bolt. There is a thread under accessories about Simpson's ledger connector. You might want to investigate these connectors since they are very easy to use and Simpson provides engineering backup. Look at them at Simpson's website: www.strongtie.com The nomenclature of the connectors are ICFLC-W or ICFLC-CW. If you are using 2x10, then you are interested in the first one.
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louper
Registered Users
Posts:2
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| 12/15/2001 8:15 AM |
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Thanks for the reply.
One correction I need to make is that we used 2x12s (not 2x10s) as I previously mis-stated. Also thanks for the Simpson Strong Tie info however all our flooring is already installed with the anchor bolt method.
I'm trying to gather info ahead of his potential question. When we first met he was initially suprised (concerned?) that the floor didn't actually sit on the wall as in conventional framing but was "hung" with these anchor bolts/ledger boards. (This may have just been a "not what I'm used to" reaction but I don't know)
All of the ICF info I've seen suggests this is a proper way to secure a floor. What I can't find info on is what floor load this is expected to support using this method or if any particular grade anchor bolt should have been used.
Any suggestions in this area?
Thanks! |
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panelbuilt
Registered Users
Posts:52
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| 12/15/2001 1:35 PM |
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You're building inpsector needs to go back to school and finish the class on ledger connections 101.
It's surprising that he has never seen a ledger attachment situation before.
Your engineer should be able to provide the back up data for your building inspector. If you do not require an engineer for you plan approval there are sources giving sheer values for the type of bolt you used. Contact the manufacturer of the bolt you used and get that information for your inspector |
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markross
Registered Users
Posts:1035
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| 12/15/2001 6:48 PM |
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The mainstay of the ledger board is not the shear of the anchorbolts, but the friction connection between the ledger and the concrete developed by tightening the nuts to a pre-determined torque. This allows the ledger to effectively generate enough friction between itself and the concrete to prevent movement. Otherwise, the only true measurement of the strength of the bolt is the strength of the concrete under the bolt in shear, effectively 3000 psi, or 375 pounds prior to compressive failure, or spalling of the concrete on which the anchor bolt rests. Assuming 1/2" anchorbolts that is.
Mark Ross
"Le Canuck" |
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James Eggert
Registered Users
Posts:1001
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| 12/16/2001 5:29 PM |
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louper
I believe anyone dealing with any of the building inspectors should provide backup as you are preparing to do.
One of the easiest books to use, and possibly provide to the inspector, is "The Prescriptive Method" book as developed and published by NAHB for HUD, PCA and NAHB. This book provides many answers to general conditions and should allay the fears of the sometimes uninformed official. This is not the pancea to cover all circumstances, but many conditions are noted with back-up in the rear appendices.
For example, your span of 14' calls for one 1/2" bolt staggered every 12". Your providing two every 12" should provide a confort level for your inspector so you can develop a relationship concentrating on the ICF benefits so they tell others, or at least are more comfortable with those who follow!!
Take Care
Jim |
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Take Care
Jim
Design/Build/Consulting
"Not So Big" Design Proponent |
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jdcoombs
Registered Users
Posts:57
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| 12/17/2001 10:32 AM |
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It's surprising that this guy hasn't seen ledgers. They are used almost exclusively in CMU and tilt-up construction; and are very common in ICFs. Sounds like he's pretty well limited in residential construction.
Using two 1/2" dia anchor bolts at 12" o.c., the bolts will not be the weak link. They're rated for about 2500 to 3000 lb each. Neither is the concrete in bearing (not shear) likely to be the concern if they are anchored properly. Depth of anchor needs attention; it should be at least 4" and can be a problem in 4" walls. Nor are they held on by friction. That type of design is only allowed in steel. Wood dries and shrinks and loses it's friction carrying capacity. The capacity of the ledger is what usually governs and needs to be checked for shear, bearing, and tension parallel to the grain. Then some other things in long walls and high seismic zones. All of those values will vary depending on the grade of lumber. Engineered lumber will often reduce the required number of bolts, but they're not treated. These are some of the reasons why ICF manufacturers don't go very deep into this topic. Some lumber guides address prescriptive uses for ledgers. With long spans, a good prescriptive table or an engineer should be consulted, but for these spans (in residential loading) it shouldn't be a problem.
Jerry D. Coombs, PE
Director of Engineering
American Polysteel, LLC
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steve rutherford
Registered Users
Posts:13
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| 12/17/2001 3:45 PM |
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quote:
Engineered lumber will often reduce the required number of bolts, but they're not treated.
Isn't Parallel-strand lumber (PSL) available in pressure-treated.. Wonder if it would make good Bucks ??
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Greg Swob
Registered Users
Posts:8
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| 12/19/2001 6:51 PM |
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| I feel the inspector has a very valid concern. Thinking of bolts 'hanging' out from the foundation wall the thickness of the EPS, if it is not removed behind ledger. By these bolts not being supported for 2 - 2&1/2 inches, bending due to shear could result if not properly spaced and of adequate size, strength. Simpson (as stated earlier) and others make brackets and hanger for ledger configurations. An engineer should be easily able to calc the bolt size and spacing needed. Greg |
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James Eggert
Registered Users
Posts:1001
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| 12/20/2001 8:49 AM |
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Greg
I only partly agree with you, mainly because you bring up one of two points.
1. The inspector should have been asked to visit the site as erection proceeded so he(she) could have seen and learned more about the installation procedures. Perhaps someone took pictures or saved the foam cut-outs to show what was done. In any event I find the inspectors leave you alone after reviewing the amount of work necessary to get to the first pour. Some like to come and visit during a pour. Why not?
2. The inspectors do not and cannot know everything. Most pick up on items that don't seem right COMPARED to prior situations. Many things we do with ICFs are new fangled ideas to the uninitiated. I have yet to have any problem with inspectors, probably due to up-front discussions and questions with them so I can provide all info they want to see in the begining, not after the fact!
Take Care
Jim |
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Take Care
Jim
Design/Build/Consulting
"Not So Big" Design Proponent |
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markross
Registered Users
Posts:1035
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| 12/20/2001 12:39 PM |
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Jerry:
Good point about the steel vrs wood connection, I quess the american vrs. canadian design methods may be slightly different, our mainstay is to design using one of three methods, this approach is the one I use, but steel friction connections as you put it, would probably not apply here, my apologies. I have a better question directed at you Jerry, which is, if we are bolting a wood ledger on a wall, in america, what is the best design approach, from an engineering requirement, to use. This information would help me greatly, as I believe I may be using approaches which are not good engineering practice in the US.
Email is fine if you dont want to post, I appreaciate you assistance in this.
Thanking you in advance.
Mark Ross
"Le Canuck" |
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louper
Registered Users
Posts:2
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| 12/20/2001 5:07 PM |
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Jim,
You nailed my situation right on the head!
All,
First I'd like to come to my inspectors defense a bit(especially in case someday he reads this thread  ) by saying that he has been VERY cooperative and interested in learning more about ICF construction.
As Jim points out the inspector can't know everything. This is the first residential ICF construction he has seen. It is for this reason that I am gathering the data ahead of the potential questions.
Upon his first inspection (prior to backfilling) the flooring was already in place and no one was on site. My contractor and I setup a meeting with him to go over the methods used. He inquired about the method used to hold the floor and we showed him an example on the exterior wall where a ledger will be hung for a deck. The concrete pad was visible and flush with the outside of the EPS with the two anchor bolts firmly in place. The whole meeting took about an hour answering various ICF building methods. He left saying he was much more comfortable after that discussion. Since that time he has dropped by to ask more questions (since other houses are now slated to be built in the area as well).
I beleive that in this situation, any knowledge I can have in anticipation of his questions will go a long way in making this project go smooth. This forum, the manufacturer/distributor and other references have helped me quite a bit. (I've been in lurk mode for about 9-12 months researching ICFs myself)
I was told to be prepared to re-train every sub-contractor who works on this house since EPS will be new to most of them. I guess he'll be just one more person to train.
Thank you all for your replies/discussion,
Lou
P.S. Jim, Thanks also for the pointer to "The Prescriptive Guide". It is a very good reference. |
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