Foundation planning for off grid ICF Home

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Old 12-11-13, 12:14 PM
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Foundation planning for off grid ICF Home

Hello we are building a small off grid ICF home on our ranch in north Dallas. We are almost ready to pour the foundation but I wanted some feedback and opinions on the design. I am building this house for the long run and I'm willing to spend some extra now in hopes of it outlasting my wife and I. I have met with several concrete guys and so far have this design as the plan. I am extra interested in my footings and piers sizes and making sure they are more than enough.

The house is about 800 sq. foot. Perfect rectangle, 35'x24'. The land where it is going to set will be flat after we bulldoze it. I am planing on having select fill brought in after that and we will build a pad and compact it along the way. I am currently thinking about a ten inch or twelve inch pad for drainage around the house. Do you guys think this is an OK height? I want to be able to walk out of my house with only one step if possible but don't want any drainage problems.

The perimeter footing are 12"wx12"d and there will beams going through the middle of the slab both lengthwise and widthwise. (I will upload a pic later to be more clear about the channels and dimensions of everything) Do my footings need to be any deeper or wider? The concrete walls will be 6" wide. I was planning on a 4 inch slab on top. It will be monolithic slab. This will be a single story ICF home. I have been told to do anywhere from 3 inch to 6 inch.

Also I'm doing concrete piers underneath. The current thought is 8 peirs around the perimeter. They will be 15 foot deep minimum...... On the corners and at the middle points of the walls where the beams running through the middle connect. I'm not sure what diameter to do these? I thought one contractor said to do 24 inch piers but those seem huge. I see alot of 12 inch is that the standard? The piers are pretty cheap to do so I want to make sure they are sufficient now, I don't want to have to jack up the house or anything later. We have very shifty soil here which is why I have added piers.

Also for the ICF blocks I need to have rebar coming up out of the foundation to connect. Do I just wet set these? How far up should these stick out of the concrete and at what spacing? Do I need any extra around the corners or anything? I can't find much reading about this, I guess I could call a maker of ICF but I haven't 100% decided what brand I'm going to use, I will figure that out next.

The slab will have #4 rebar and the footings #6. Should the piers be the bigger #6 rebar also I assume?

Any and all thoughts and opinions are appreciated especially about the footing and piers as I have been told a couple different things. This is my start and I will adjust the design if needed. I'm hoping to have the dirt brought out at the beginning of the year and then I will let it weather for a couple weeks before digging my footings and drilling my piers.

I'm sure I have forgot some info. that is needed and will ad more. I have also drawn the foundation on CAD but can't get a pic on here till my wife gets home.

Thanks!
Ryan
 
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Old 12-11-13, 08:35 PM
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You have to get a local architect. The main reason is that he will know the local codes. You don't want to build a structure & have the building dept. tell you that it's not right. Show him what you have on your CAD.
 
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Old 12-12-13, 06:20 AM
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Thanks for the reply,

We are in the boonies on our ranch on unrestricted land. We have no codes to adhere to. We aren't even in a technical city. Sorry I meant to ad that bit of info.

I do have to send in an application for my septic tank to the county but that is it.
 
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Old 12-12-13, 08:07 AM
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i'd scrape the footprint w/o ' building a mat ' UNLESS you need more elevation - ' cuts ' are always more stable than ' fills ',,, unless you have a padfoot roller handy, plan on compacted lifts,,, finished floor elevation is personal but, as a caution, get a pe soils engineer advice - eg, expansive soils, loam, etc

at the end of the day, you're still bound by a bldg code,,, it would seem prudent to build to any mortgaging agency or other organization's qualifications, restrictions, &/or addl rqmts under which your dwelling may become subject - eg, hud - just a thought !

your walls should be 8" thick according to the structures i'd built using icf's - most w/reward systems altho no financial interest,,, your icf supplier should have avail plans showing rebar placement & size.

why piers AND a perimeter foundation ?

btw, congrats on picking icf's ! imo, GREAT choice !
 
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Old 12-12-13, 11:49 AM
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Thanks for the reply.....

I would prefer to not have any elevation to it, but based on where it is going to be I think a little would be a good idea. Maybe a little less like 6 or 8 inch that way the footings are deeper. We will be using a roller on the select fill mat. I understand it would be more stable to dig it all out but I need to think about water also.

I'm not sure of a building code I'm bound by I have talked to the county. I have no lenders or mortgage agencys we are building it all cash, the whole ranch is. I am concerned with what insurance will want in order to cover the house and I have talked to them already.

I'm not trying to skip corners with code or anything I want to build a house that will outlast me.

I know ICF comes in all different thicknesses and I had originally planned on 6 inch but I'm willing to go bigger if it's worth it. I have done some reading and talking but will do more, and expanded insight on this is appreciated.

The piers are to help because of our shifting soil and I thought perimeter footings are needed to distribute the weight of the walls. If it is overkill that's OK that's what I want.

And I'm very excited about the ICFs I'm an off grid person and also a prepper, so I love the thought of concrete walls.
 
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Old 12-12-13, 01:51 PM
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On or off the grid is meaningless.

Since you unfortunately don't have a code to protect you from yourself, at least research some good codes in your general area. The code is not the ideal way to do things, but it is a minimum and a good "crutch" to use to not make the same mistakes by trying to be unique, but end up with similar problems in the end. Unfortunately, too many "antis" and well meaning individuals try to avoid the feeling of being told what must be done and don't appreciate a proven resource.

Manufacturers instructions and recommendations are the proven way to use a product based on testing, history and performance and not redo some old problems, plus they are based on code minimums or better. Bigger and stronger is not always good and can create problems.

Being in Texas, the two things needed are a soils engineer that makes recommendations for your site and a structural engineer to provide a structural continuity considering the soils and extreme wind/storms probable during the time you expect it to last. When it comes to layout and usability, that is up to you to make the mistakes that come with any new structure. Your piers could be a mistake unless you have a few cheap borings to tell you what they may really be bearing on and under.

There are many different techniques and methods of rolling, if the is what is needed considering the underlying soils.

Dick
 
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Old 12-12-13, 03:03 PM
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I'm not interested in being cheap or going less than code per say. I understand what code is I have been in construction a number of years. I just didn't think I needed to go hire someone to build it exactly for code, but I will look up some general codes in my area good idea it can't hurt. I know what codes place I just don't have any inspectors or applications to wait on or pay for. Im really interested in a long lasting home period and I would like to think it will be better than a city code would call for. Nothing I have tried to do is less than code to my knowledge.

I'm not trying to be unique Ive tried to design a very simple house. I'm no "anti", everything going into this house has come from outside knowledge including concrete "pros" that have met me at the site. I feel like you jumped to a conclusion about me that I take offense too. I have spent years building my ranch without a single penny of debt. I would have never gotten to this point without help and I don't claim to have. I will listen to any and all advise and change designs where needed no problem. In my few posts if I have come off in another way I apologize.

I appreciate all your thoughts.
 

Last edited by ryan3316; 12-12-13 at 04:27 PM.
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Old 12-12-13, 03:36 PM
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And the piers are in the design because of a concrete guys advice that knows the soil. I met with him and he gave me a quote to do it. He poured a foundation for my neighbor which is how I got in contact with him. His words were he wouldn't feel comfortable pouring my pad without piers based on the soil. I will ask her more about her foundation specs, I have used hers as an model. They did a great job with her house, it is an engineering marvel. Her pad is very similar in size to mine. I can learn more from hers.
 
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Old 12-12-13, 05:04 PM
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Thinking long-term, there will come a day that the property will be sold. If you are building this place without building permits and without documented code compliance, it could make all future buyers' lenders reluctant to provide mortgage $$$ for it. Not to mention scaring off potential buyers. I suspect you wouldn't want your widow sitting in it for 20 years, waiting for the right cash buyer to come along. If I was in your shoes, I'd at least have some appropriate documentation to furnish when that time comes (such as having a licensed Texas P.E. perform a few construction inspections, and verifying on his stamped letterhead that the property at least meets minimum IRC requirements). Costs for same would be minimal, in the big picture.

Make sure you have a safe room for the tornadoes known to frequent Texas. Being a prepper, you'll probably have a huge basement for food and water storage already, which would work as a storm shelter. And shop carefully for your ICFs--I've worked with one brand that had performance problems (allowing forms to kick out at multiple locations when the placement went too fast, and they were just 3' tall stemwalls).
 
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Old 12-12-13, 05:36 PM
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Quote-bridgeman45
"
Thinking long-term, there will come a day that the property will be sold. If you are building this place without building permits and without documented code compliance, it could make all future buyers' lenders reluctant to provide mortgage $$$ for it. Not to mention scaring off potential buyers. I suspect you wouldn't want your widow sitting in it for 20 years, waiting for the right cash buyer to come along. If I was in your shoes, I'd at least have some appropriate documentation to furnish when that time comes (such as having a licensed Texas P.E. perform a few construction inspections, and verifying on his stamped letterhead that the property at least meets minimum IRC requirements). Costs for same would be minimal, in the big picture."

This makes some great points. I need to have some documentation after you worded it like this to me. We plan to live there forever but your right there are some scenarios where the ranch could end up having to be sold by someone else besides meyself. Making sure that they can sell it easy would make sense even if the chance is small which I hope it is at least in my life time. I will look more into this....I can talk to the guy bringing my dirt and doing the dozing, he is also a concrete guy and has been helping me along with another concrete guy that did my neighbors.

And yes I agree we have a plan for an underground bunker. Although this won't be happening this year it will in the next few I hope. We are pretty self sufficient out here and if we can't grow it or make it we don't need it.
 
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Old 12-12-13, 05:42 PM
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Oh and about the ICF brand I have yet to make up my mind 100%. I have been reading for awhile and talking to a couple brands but still haven't decided, I hear so many conflicting stories lol.
 
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