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Discussion Starter · #1 · (Edited)
First, I apologize if this isnt the forum this belongs in, but it was the most relevant one. I was wondering if someone can give me some pros and cons on building a house on a raised wood floor? This would be my own house, so not for a customer. Im building on a farm, and there are no codes or inspections required in this county. I have been doing exterior construction work my whole life, Ive been self employed now for about 6 years. While I've never done this exactly, Ive built a lot of pole barns, and am currently doing a lot of utility sheds for people that are portable (IE on skids), so between the two, I'll manage. I know the obvious cons would be termites and moisture. Im not real worried about moisture, since Ill be creating a crawl space underneath, and Ive researched a ton and found that the main termites that cause damage in my area (south central Iowa) are subterranean, so I guess Im not so worried about that either. Plus, Ive been building barns for quite a while and havent had any issues yet (atleast that I know of). The pros (atleast for me) are the fact that itll save me a ton of money, and that this way I can build the entire house myself. Im not a brick layer and I dont do concrete work, but I can definitely set posts and frame about anything. My plan is to dig a small basement for storm shelter, pour a pad in it and steel frame the walls/ceiling, then build the raised floor over it and have a hatch/crawlspace type door for access. The floor would be 2x12 framed, the boards around the exterior would be treated, 6x6 columns set below frost every 8 feet throughout. Does this sound like a fair idea? Are there any important points Im missing?

Here are a few questions I have for anyone thats done this before.

1. Would I be better to set my posts in crushed rock? In the past I have always liked to set my posts in concrete, but more and more counties around here are requiring rock instead so I doing more of that. Ive heard arguments for both, and dont really have a big issue with with either.

2. There will be a skirt around the exterior to keep weather, animals, cold wind, etc out, so am I right in thinking that I can get away with using untreated lumber everywhere except for around the exterior (and the posts obviously).?

3. What would be the best/proper way to insulate the floor?

4. The foundation will be framed with 2x12s and the floor will be 5/8 treated plywood, can I get away with the 2x12s being 2 foot on center or will the need to be 16" on center?

Thanks in advance, and I apologize for the ridiculously long first post!
 

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I know you don't want to hear this, but talk to a structural engineer about what size lumber you can or cannot get away with. There's too many variables. I've never seen floor joists or floor trusses for that matter that are more than 16" o.c.

As far as untreated lumber for your joists, it would depend on how high above grade you were going to install them.

As far as the posts and using crushed rock v.s. Concrete. My guess is the size of your footers will be dictated by the loads being distributed to the columns. Pole barns are only holding the roof load. Now you're asking those columns to hold the floor load as well. I don't live where you do, and our soil is very sandy. So a house build like a pole barn here would start to sink without footers.

Lastly, for the subterranean termites. Those things may live underground, but they still will come into your house provided you've given them moisture and tasty wood. They build little mud tunnels up the side of your house and will go to town on it.

Typically the soil would be treated here before the slab or crawl space was covered up.

Call and engineer and do it properly.
 

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Discussion Starter · #3 · (Edited)
Those are the answers I was looking for, thanks! Ill be atleast 16 inches above grade at the lowest point. I was kind of planning on 16 on center joists, but wasnt sure if it was necessary or not. Ive looked into having the ground treated for the termites and will definitely be having it done. I supposed I will talk to an engineer on the footings!
 

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There are code approved PT wood foundations (cellar walls and footings) - look around for more info.

If you're lucky enough to have a place that will screen it, you can prevent termites with the right size of sand. Basically it would have to be ~3 feet wide and 4' down all the way around the house. Since I don't remember what the size is, you'd have to research it.
 

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I know you don't want to hear this, but talk to a structural engineer about what size lumber you can or cannot get away with. There's too many variables. I've never seen floor joists or floor trusses for that matter that are more than 16" o.c.
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Call and engineer and do it properly.
I've seen everything between 12 and 36" on floor joists.

In the end, someone has to come up with the loads an what structural elements will be needed to handle them - in this case, that someone needs to be a structural engineer.

The other thing I'll mention is, even though areas don't have building permits, inspections, etc, it can be misleading and unfair to a potential buyer to sell them a building that isn't up to par from a performance perspective. Code is prescriptive - it tells you how to achieve the performance. You can still have a safe, comfortable, long lasting home without following codes, but only if you understand how to achieve the equivalent performance.
 

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hdavis said:
I've seen everything between 12 and 36" on floor joists. In the end, someone has to come up with the loads an what structural elements will be needed to handle them - in this case, that someone needs to be a structural engineer. The other thing I'll mention is, even though areas don't have building permits, inspections, etc, it can be misleading and unfair to a potential buyer to sell them a building that isn't up to par from a performance perspective. Code is prescriptive - it tells you how to achieve the performance. You can still have a safe, comfortable, long lasting home without following codes, but only if you understand how to achieve the equivalent performance.
I thought that's what I said?
 

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you start with the assumption that you will save a ton of money. That happens only if:
1 you consider your time to be free
2 you don't make many mistakes, wasting materials
3 you really do understand all the trades enough to fully understand their interactions.

It starts with proper design. You must design to not only handle all the loads but to properly deal with hvac ducting, vents, plumbing, and electric, all without negative interactions.

I've known several people who calculated out the cost of building their own home then decided that after building their own they would become a contractor and get rich. I've never known any of them to build a second home. Most gave up prior to completion and hired someone with real experience.

They say experience is the best teacher, well experience can be a very expensive education. I don't want to rain on your parade but, most contractors don't make a ton of money.
 
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I've known several people who calculated out the cost of building their own home then decided that after building their own they would become a contractor and get rich. I've never known any of them to build a second home. Most gave up prior to completion and hired someone with real experience.
I know one that acted as GC, and just contracted out framing and high (above 9') drywall ceilings, and did the rest themselves. They built 2 houses.
 

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Those are the answers I was looking for, thanks! Ill be atleast 16 inches above grade at the lowest point. I was kind of planning on 16 on center joists, but wasnt sure if it was necessary or not. Ive looked into having the ground treated for the termites and will definitely be having it done. I supposed I will talk to an engineer on the footings!

Code is 18" from top of dirt to bottom of floor joist minimum.
 
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