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cspot
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# Posted: 23 Apr 2016 19:06 - Edited by: cspot
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Ok. Been on here for a while looking, but now have a serious question since we just closed on some property in Ohio. We are going to use the camper that came with the property for this year, but plan on building something next year.
We are looking at doing a 24'x24' single story building with no loft. Will get 24' residential trusses on 4/12 pitch. I have read alot of posts on here for the foundation suggestions, but was wondering what everyone recommends for a pier foundation for this size for both the beams and the floor joists. The walls I am planning on going with 2x4. I realize that a smaller footprint with a loft would be cheaper and more efficient per sf, but for ease of building and the wife's desire to not have a loft we are looking at going single floor.
Here is a couple pics of the site and a couple random property pics. Plan on putting it behind where camper is sitting.
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MtnDon
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# Posted: 23 Apr 2016 19:30
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Quoting: cspot was wondering what everyone recommends for a pier foundation for this size for both the beams and the floor joists.
A 24 x 24 deserves a real foundation; something like perimeter block wall on a poured concrete footing. Your frost depth is probably about 2 feet; not too bad.
I don't like lofts either, often too warm no matter the time of year. Not to mention floor space lost to stairs because I really also don't like loft ladders.
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cspot
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# Posted: 23 Apr 2016 19:51
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Really wasn't wanting to go the "real foundation" route on this. Would staying 16' wide help this? Maybe going 16x32? The 24x24 isn't set in stone yet, just looking at something about that floor space. Even thought about going 16x24 and then if needed adding on more later. Still in the rough development now and just starting to figure costs.
Thanks for any insight!
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beachman
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# Posted: 23 Apr 2016 20:09
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What type of soil are you putting this on?. If it is clay, go for the full foundation. If it is sandy, the piers should work but every 30 to 40 years, you''ll have to level it a bit.
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Don_P
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# Posted: 23 Apr 2016 22:56
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Quoting: cspot Really wasn't wanting to go the "real foundation" route on this
Pier and beam advice will take someone effusively optimistic. I'm sure something will bubble up directly 
Better methods than piers would be to look into permanent wood foundations or post frame construction.
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cspot
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# Posted: 23 Apr 2016 23:02
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By pier and beam, I was meaning using 6x6 in the ground (sitting on concrete) with 2x12's or something for the beams and then 2x10 or 2x8 for the floor joists. Not sure if I was using the correct terminology or not. Seems like alot do it on here, but there is alot of variations.
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Don_P
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# Posted: 23 Apr 2016 23:55 - Edited by: Don_P
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Over the past several years I think I've seen 5 fail and one required to be taken down. I've dug under several in this area and replaced them with full foundations, generally in old work piers need work.
If the posts run from the concrete footing on up to the top of the wall they are braced by the walls against tipping. There are hangers with inturned ears that fasten to the posts and are heavy enough to carry the beams between posts. This is post frame that I mentioned above, you will probably know it as "pole barn" construction. That method of construction has grown up over the past several decades. It might be worth investigating having a post frame construction company set and brace the posts and get it under roof, then turn it over to you. Your local truss plants will know the crews.
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beachman
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# Posted: 24 Apr 2016 10:49
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What about screw piles. I used them on a raised deck last year and I have seen them used on cabins with good success. The deck was on clay type soil and the piles never budged.
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Don_P
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# Posted: 24 Apr 2016 15:18
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As long as they engineer and warrant the work its worth considering. It's simply another form of pier and beam, it is relying on the soil (seasonally, read mud) exclusively for the lateral bracing of the foundation. If the posts run full height they rely on the soil for vertical load only, the lateral loads are resisted by the walls.
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rockies
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# Posted: 24 Apr 2016 19:13
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I like Techno Metal Posts. They are engineered by the company and when they are installed the torque on the drilling machine tells them when they have reached the proper depth and load bearing capacity for the column. They give you an engineering certificate stating what the post will support and it can be a lot. You can order them with a "frost sleeve" and should you ever have to move the structure you can unscrew them from the ground and take them with you.
I don't know why everyone assumes that piers are a weak foundation or that they will have to hand mix hundreds of bags of concrete and pour the piers themselves.
http://www.technometalpost.com/en-CA/
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Don_P
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# Posted: 24 Apr 2016 21:57 - Edited by: Don_P
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Piers are an engineered foundation, and for good reason, just about every DIY one I've seen does qualify as a very weak foundation. One engineer described what we typically see on these forums as a collapse mechanism. These metal posts are slightly better but theoretically someone is minding the store designwise.
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MtnDon
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# Posted: 24 Apr 2016 22:18
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Quoting: rockies I don't know why everyone assumes that piers are a weak foundation...
Not assuming... speak with a state licensed professional engineer.
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pash
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# Posted: 24 Apr 2016 23:34
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As someone who has built a 24x24 with a pier foundation, I would tell you, if you have the money use the block. I don't regret not using it, I didn't want to spend the money and the piers work and function fine. But for perfection and ease of build, block would be much better. If I build another one, I will probably save for the block.
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deercula
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# Posted: 25 Apr 2016 01:21
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Does the build location make a difference? I've been in a bunch of cabins on piers and never heard of any problems, as long as they were deep enough. My builder says he has used them for years without problems. We don't have earthquakes, tornadoes, or hurricanes, and winds are rarely over 50 mph.
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Don_P
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# Posted: 25 Apr 2016 09:28
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Sure it does, an engineer designing an alternative foundation takes those things into account.
Another way to think about our anecdotal experience.
I've been in a bunch of cars but have never witnessed or been involved in a drunk driving accident. I think it means I don't get out much vs it doesn't happen.
Within the limits given in the building code, that is to say, following accepted engineering methods, we know that the foundations they detail prescriptively work pretty well. We also know that using those limits and building a pier foundation results in much higher failure rates. It is tougher to get it right, this is why they call for engineered design. I seriously doubt that the specs will come back looking like what we've seen here though.
What we've typically seen is a footing, then a poured pier, then a wood post pinned (read free to rotate) at it's bottom and top, then an unbraced girder on top of that, then joists on top of that. Finally a 20' tall x 20' wide sail rigidly braced and solidly sitting on top of that assembly of hinged parts. No qualified engineer working within his area of expertise is going to draw that.
Your builder has used them for years... well, if he has designed and installed them then the liability is his. This falls outside of code, his limit, so his insurance won't cover that, he's betting the farm that he is right. When a builder steps outside of prescriptive code the engineer, who's insurance does cover this, does the design work. On your own y'all have lightened up and eliminated or misunderstood key structural parts, he isn't going to make that mistake and that does take time and money. Often it is cheaper and stronger to spend the money on materials to do it prescriptively than to call in someone to design a way to properly do it lighter.
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rockies
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# Posted: 25 Apr 2016 20:19
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The problem I have with block foundations (and I'm just using block as an example of a foundation that runs around the entire perimeter of the cabin and closes it in underneath) is that it essentially creates a crawlspace under the cabin. From what I've read on sites like "Greenbuildingadvisor" properly venting this "crawlspace" can become a nightmare. Is it a cold zone, a warm zone, how will the moisture get out, etc?
One description I've read is that most enclosed crawlspace foundations are more like rooms to grow mushrooms in and cause a lot of mold and rot to occur on the underside of the cabin floor. Wouldn't putting the cabin on piers eliminate the drawbacks of having an enclosed crawlspace?
As to the type of piers, I would rather have a company come out and install a metal post that is engineered for the size of the structure and it's location in the plans than try digging holes, placing forms and pouring concrete myself (and hoping I got the mix right).
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Don_P
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# Posted: 25 Apr 2016 21:10
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If that is your bent... pardon the pun, you could also post frame it with either a raised floor or slab. Generally easier to source and a stronger building. The metal posts aren't available here, they are not suitable for many soils.
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KinAlberta
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# Posted: 25 Apr 2016 22:50 - Edited by: KinAlberta
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Both of our cabins sit on concrete blocks dug into the ground. One is 24'x30' built in the 1950s and the other is 24'x24' built in 1945 and moved onto the property as a 16x24 then an 8x24 addition was put on it in the late 1950s or early 1960s. Frost depth is generally about 6' around here and I'm near certain that the blocks don't go down very far. Both are 2x4 construction with pine board interiors.
Both have survived very well probably due to the drainage and the equal freezing everywhere. Everything moves in unison.
Now though both require a bit of levelling and my only wish is that I could crawl under them everywhere. So I'm thinking of sliding some stronger beams under them and adding reinforcing boards to really beef of the strength of the beams. (If only they'd been grossly 'over-built' with laminated 2x12 beams. I could lift, level, insulate, plumb, etc. the entire cabins myself.)
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cscmtp
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# Posted: 28 Apr 2016 09:04 - Edited by: cscmtp
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Any other cheaper alternatives than using block for a tiny cabin foundation? I'm looking at building a 20x24 small cabin and using this website-(http://www.homewyse.com/services/cost_to_install_concrete_block_wall.html) to calculate the cost of the foundation in our area its showing a range between $3700-$5k! Would a pier foundation be cheaper?? Any other options?? We are building in Western North Carolina and will be using the cabin for all four seasons...
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Lawdog
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# Posted: 30 Apr 2016 17:44 - Edited by: Lawdog
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I purchased land in Southern Illinois and going to build a 24x28 cabin/camp on it. I was thinking about putting the camp on concrete piers using sono tubes with 24" footings. Attaching 4x6 beams to the top of the concrete pier with either bolts placed in the concrete or Simpson strong tie galvanized post base/cap placed in the concrete. I don't like or can afford blocking all away around the camp. Any advise or issues with me building it this way ? Thanks
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Lawdog
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# Posted: 30 Apr 2016 17:47 - Edited by: Lawdog
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I don't have experience in building in Southern Illinois. Where I'm from we have no frost line and can build on top of the ground. I would appreciate any advise.Thanks.
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KinAlberta
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# Posted: 2 May 2016 18:08 - Edited by: KinAlberta
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Just something I came across a couple years ago.
May or may not applied here:
Footings for small cabin re:frost heave http://www.eng-tips.com/viewthread.cfm?qid=146654Excerpts: looksatstars (Civil/Environmental)(OP)7 Feb 06 16:21 I am looking to build a small 600 sq ft cabin on a lake lot. ... The lot is in alberta, canada where the winters can be severely cold. It will not be a heated space throughout the winter so I worry about frost heaving. ...I first thought of concrete piles with a grade beam. The timber posts could rest on the concrete piles. Then I read that piles should be a minimum of 10 feet. I don't feel this method would be economical. Then I looked into a slab on grade. .. Rochplayer "For frost heave to occur, three things are needed - 1. Freezing temperatures, 2. Water source, 3. Frost susceptible soil.**Take away any one of the three, no frost heave occurs." ..."Remember, frost heave can only occur if freezing temperatures occur within a frost-susceptible soil.**If you make the frost penetration (e.g. the 4-ft depth) occur in the NFS soil, then frost heave will NOT occur in the soil beneath, because that deeper soil will remain thawed." "Frost heave is a thermodynamics problem that is dependent upon the moisture content of the soil and the latent heat of fussion of soil water." "I recommend anyone practicing geotechnical engineering in the northern tier states in the U.S. and in Canada (or other countries with significant freezing temperatures) take a frozen ground engineering university course or short course."
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Don_P
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# Posted: 2 May 2016 22:57
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Quoting: KinAlberta "I recommend anyone practicing geotechnical engineering in the northern tier states in the U.S. and in Canada (or other countries with significant freezing temperatures) take a frozen ground engineering university course or short course."
Couldn't have said it better. Be careful when practicing on your home.
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bldginsp
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# Posted: 2 May 2016 23:02
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You mean, 'Don't do this at home'?
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Don_P
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# Posted: 2 May 2016 23:06
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I mean if you don't know how, practicing engineering can be a ... crash course
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bldginsp
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# Posted: 2 May 2016 23:15
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Of course you'll crash if your engineering practice has no know how, mean I.
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Lawdog
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# Posted: 3 May 2016 18:27
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OK. I'm still confused. So will the concrete piers work as long as I start them below the frost line ? If so, how far apart should I space the concrete piers on the 28' camp ? Also, would you use 4x6 or 6x6 beams on top of the concrete piers ? the camp is 24' wide x 28' long. Thanks.
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bldginsp
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# Posted: 3 May 2016 18:54 - Edited by: bldginsp
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Concrete piers will work, but they have problems. First of all if you are getting a permit, you won't be able to show structural calculations with piers for lateral loads such as wind or earthquake. It just doesn't work for that. Second, since the piers are all independent, they will eventually move in relation to each other and then your building is out of whack. But many people building vacation cabins choose piers because they are the least expensive way to get the wood off the ground with concrete. If you want the building to pass code and be passed down to your grandkids, do a full perimeter footing.
How far you space them is a matter of calcs and choice. You can space them wider, in which case there are fewer, so each one needs to be larger to take the weight, and the beams between need to be larger for the increased span. Or, you can space them closer, in which case there are more, but they can be smaller because the weight is distributed among more. And the beams between them can be smaller because of the lesser span.
Unless you just guess, you need to figure the weight of the building on each pier, figure out how large each must be based on the load bearing capacity of the soil, and go from there.
For 24' wide you could run 4 or 5 lines of piers, either spaced at 8' or 6'. At 6' spacing of girders, you could use 2x6 floor joists, but at 8' spacing you would need 2x8. 2x8 is a good idea in very cold climates cause you can get R30 into it.
Along the 28 foot linesof piers, you could space piers every 7 feet with 5 piers or every 9 feet with 4 piers. Load and span calcs will tell you if the girders need to be 4x8 or if you can get away with 4x6.
So this is the kind of design process you go thru to design a building based on the numbers. There are basic design books that would fill in the details.
I would NEVER build a 24x28 habitable structure on piers alone, unless I didn't care if it was still there in 30 years. That's just me.
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MtnDon
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# Posted: 3 May 2016 19:34
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Lawdog
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# Posted: 4 May 2016 06:57
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Thanks for the advice. I read that if you build a full perimeter footing with blocks, you will have problems with moisture. Is that true ? I hate to sound stupid asking all these questions, but like I said I have never built anything dealing with a frost line. I want to build it to last.
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