storage shed foundation

Discussion in 'Off-Topic' started by strantor, Dec 22, 2015.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I know this is a weird question for an electronics forum, but I think there's at least a handful of people here who know something about this.

    I want to build a large lean-to shed, an extension to the back side of my detached garage.

    Details/assumptions:
    • I live outside city limits and as far as I know (I could be wrong) I don't need the blessing of any building inspector to build my shed.
    • As far as I know (I could be wrong) as long as I don't attach the lean-to to my garage, it won't affect my homeowner's insurance.
    • Where I live, it doesn't even freeze every winter, and if it does freeze, you can count the freezing days on two hands. As far as I know (I could be wrong) the term "frost line" has no meaning here, and I don't need to design the roof to hold snow.
    • No snow, but this is hurricane country.
    • The footprint of the shed will be about 12'X36'
    • I will be storing some pretty heavy things in there (engine blocks, a large lathe, steel boxes of scrap iron, etc.)
    • This is flat country and water doesn't drain well. Soil is black dirt that turns into black mud. Things tend to sink in it.
    • I am building this on a tight budget.
    I haven't gotten any quotes for a concrete slab foundation because what I've read so far seems to indicate that a concrete foundation of this size will cost a fortune. Like $10,000+. So I'm looking at pier and beam structure. The information I'm finding online is all over the place. I've seen people who sink a grid of (9) 8"X8" piers six feet below grade and encase them in 8" thick concrete all the way around, to support a 10'X12' prefab tool shed to house their rakes and leaf blower. I've seen people sink 6"X6" piers 2' in the ground and set in place with tamped dirt, sunk 16' apart, and they park a giant iron tractor on it.

    I'm trying to evaluate #1 if pier & beam will even work for me, in my sometimes-soupy soil, and #2 if so, what size beams and how far apart should be they be.

    I can't seem to find anything resembling an official guide, so in absence of that, all I have to go on is my gut. my gut says:
    • 8X8 piers are bonkers. No way I need that.
    • 6X6 piers are probably closer to what I need.
    • I might be able to get away with 4X4 piers if I place them close together (like 4' between piers) and use a wide bottom in my holes to get a lot of surface area. This might be better than using bigger piers, farther apart, because:
      • given my soil conditions. it will give me more points of load distribution, maybe preventing soup-related problems (ex: one corner sinking into the ground)
      • Given my hurricane prone area, there will be more anchor points to the ground, making it harder to blow away.
      • The piers will be much cheaper and It will allow me to use smaller, cheaper beams (ex: 2"X6" instead of 2"X12"). although this will probably be offset by the cost of all the extra concrete
      • This will make the whole project a lot more manageable for one dude to do by himself with no assistance from heavy machinery
    So what do you weekend warrior craftsmen have to say about what I propose here (using copious amounts of 4x4 piers heavily cemented in mud soup)?
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    I have been an owner builder on two of the houses I have lived in. From what I hear from you, you are not ready to build yet. You are going on too much hear-say. Just because you are outside of the city limits does not mean that you will not have to satisfy a building department somewhere. A building dept. can actually help you. Find the Building dept. closest to you and go down and talk to them. You will walk out of there with tons of papers describing how to do it and what they want. The building dept. likes owner-builders because they normally want to do a better job than contractors.

    My advise to you is talk to people in your area about what you want to do, especially the building dept. You are not the first person to do what you are doing.
     
    wayneh, #12 and strantor like this.
  3. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Good, you're the kind of people I was hoping to hear from
    definitely not. I'm not even done with preliminary research; that's part of what this thread is. If I thought I was ready to build, I'd be out there building, not asking for architecture tips on an electronics forum.
    Point well taken. If they can provide guidelines for how to build in my specific locale then I will consult my local building permit/Engineering dept. I looked them up and got the address.

    While I was on the county building permit website, I found this curious blurb (full quote, no deletion):
    So considering this project couldn't come even close to half the appraised value of my house, not sure if that means I need a permit or not. Whatever, doesn't matter right now. I'm going there and talking to them regardless; I'm sure they will be able to clear it up.
     
  4. #12

    Expert

    Nov 30, 2010
    16,252
    6,749
    This is a soil quality evaluation. Completely beyond my abilities, but Les got it right. The local building code enforcement office knows the limits. If you're paranoid, use the name and address of somebody a mile (or two) away from the actual site. I would, but I'm an old hippie. I wouldn't tell my government if the neighbor across the street concealed the pipes necessary for a second (un-taxed) bathroom under the concrete he had to get a permit to pour.
     
    strantor likes this.
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,771
    1,103
    The structure of the foundation of your existing house should give you an insight. Scale that to suit the anticipated loading of the lean-to foundation?
    I second the suggestion to consult with the local building regulations authority guys. When designing an extension to a previous home I found them helpful.
     
    strantor likes this.
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,674
    899
    I have built a few sheds in my life. The largest was 50X60 feet with an 18 foot eave. In Bakersfield, CA (high temps like Houston), used shipping containers are very popular. They done't even rust, 'cause there is no rain.

    In Cleveland, a similar wood-sided shed with treated plywood floor (<200 sq ft) is just built on 4x4 treated lumber "skids" about 3 ft o.c. I put up a 10X12 shed a few years ago. It was a pre-fab and the seller/builder built it on site for about $1200. I put down a couple of inches of #57 limestone and the shed was put on top. Code here requires that the beams be nailed or screwed to anchors that screw into the ground about 12 to 18". You have higher winds in TX and that may not be a bad idea. My cost was the $1200 + cost of stone.

    I have read stories about copperheads and rattlesnakes congregating under such sheds. That may not bother you. If it does, putting down a 4" concrete slab with wire mesh is really quite easy. I found a "finisher" to do a 17X20 slab in my barn for <$200. Basically, I prepared the area, put in the wire mesh and whatever rebar I wanted. He came the day of the pour and even did compacting for nothing. I helped on the pour with a wheel barrow. He did the finish (broom). In a shed like I think you are building, I would want a smooth finish. Look around fro the best concrete price. Small loads do not cost proportionately less. My concrete was about $400 with all the add-ons. My all-up cost was a less than half of the best bid I got. I would use conventional wire mesh and rebar. I would not use fiber reinforced concrete, if you want a nice smooth finish.

    John
     
    strantor likes this.
  7. wayneh

    Expert

    Sep 9, 2010
    12,089
    3,027
    I would add your insurance agent to the discussion as well. Some know nothing but others that have been in the business a while (or maybe a related trade) can have a wealth of good ideas. They've seen it all.
     
    strantor likes this.
  8. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I went to the county building and permit office today. They were very friendly, but less than helpful.
    • There are no local codes
    • They do not have any canned plans or examples.
    • They do not have any guidelines for anything (foundation specs, roof specs, anything)
    • I am free to build to whatever criteria I see fit, even if I choose to make my roof out of unprotected papier-mâché (literally, I asked that).
    • If I want any electricity or plumbing, it has to be done by a licensed electrician or plumber
    • If I want it to be insurable through my homeowner's insurance, it has to pass Texas Windstorm Insurance Association inspection. They do not have any guidelines for TWIA criteria.
    I did have them clear up that little blurb on their website; If I'm building an addition to my house or garage, and it's < 50% of the appraised value of the house, no matter the size, I do not need a permit. If I'm building a detached structure (shed) and it's > 200 sqft (no matter the cost), I need a permit, but there is no inspection or rules I have to meet; they just want $75 and a 1-page form filled out.

    I called my insurance agent. She doesn't have any info on TWIA guidelines. She recommended I have a contractor build the whole thing. She said there isn't a whole lot of info available, and she's of the understanding that it's pretty much at the whim of the inspector, who is accustomed to dealing with the local contractors, who already know the game. I scoured the TWIA website and could not find any guidelines or inspection criteria. All I could find on that website was Texas' amendments and modifications to International Residential Code, which leaves very large gaps in what the actual code says.

    I think I might just build a concrete bunker impervious to hurricanes and call it good.
     
  9. #12

    Expert

    Nov 30, 2010
    16,252
    6,749
    This is interesting. I live in a place where I have to be careful not to bolt a lawn chair to the back porch or my property taxes will be increased. Tcmtech lives in a place where you could weld (2) 55 gallon drums together, call it a Bar-b-cue restaurant, and nobody would notice. Strantor lives in a place where nobody even knows the rules for building a proper structure...and we are all in the same country!
     
    strantor likes this.
  10. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
    287
    The last lean-to I built ended up being a lean-from. :)
     
  11. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    Property rights is an unusual topic.
     
  12. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    What does that mean? Do you have some "don't do it like this...." advice?
     
    JoeJester likes this.
  13. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
    287
    Yeah....make sure you nail it to the wall it's leaning against. :)
     
Loading...