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Tarmetto
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# Posted: 27 Aug 2014 18:12
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Is there a significant cost difference between poured footings and perimeter block VS round concrete pilings VS stacked block pilings?
My land doesn't create an issue that would hinder any choice, and either way I'd like to be about 30" off the ground (which would be about 54" on the low side of the slope).
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bldginsp
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# Posted: 27 Aug 2014 18:24
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Any full perimeter fooing is going to cost a lot more than constructing piers of one sort or another. One big question is if you can get a concrete truck on your site. If not, hand mixing a whole perimeter footing is a lot of work, and you would have to haul hundreds of bags.
I would guess that your list constitutes the most expensive decending to the least.
Make sure you get below the frost line to avoid heave.
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Tarmetto
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# Posted: 27 Aug 2014 18:35
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Quoting: bldginsp I would guess that your list constitutes the most expensive decending to the least. Make sure you get below the frost line to avoid heave.
Exactly what I wanted to know. Thanks!
Yep, know about the frost line thing, only other concern might be the water table. I should be roughly 15' in elevation above the lake level, and OK, but I remember when a family member built near another lake (lower elevation) his foundation cost a fortune due to the water table at his elevation.
I "think" a concrete truck would be able to drive right to the sight. Kinda iffy the way the drive comes off of the main road, but the build site is within 150'.
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bldginsp
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# Posted: 27 Aug 2014 19:47
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The concrete supplier will probably be willing to send someone out to your site to scope it out and tell you if it is feasible. If you need to get a pumper along with the truck, its about another $500
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Tarmetto
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# Posted: 27 Aug 2014 19:54
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Quoting: bldginsp The concrete supplier will probably be willing to send someone out to your site to scope it out and tell you if it is feasible. If you need to get a pumper along with the truck, its about another $500
Thanks for the info!
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toyota_mdt_tech
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# Posted: 27 Aug 2014 20:43
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Tarmetto, the full footing/stemwall keeps varmints out. But do not install an outside crawlspace, make a trap door inside. This also makes for mass secure storage too. Its exactly what I did and never a varmint in there yet.
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Tarmetto
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# Posted: 27 Aug 2014 21:06
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Quoting: toyota_mdt_tech Tarmetto, the full footing/stemwall keeps varmints out. But do not install an outside crawlspace, make a trap door inside. This also makes for mass secure storage too. Its exactly what I did and never a varmint in there yet.
Thanks! Great ideas. I would likely underpin even with pilings, but I really like the trap door idea.
I'm a closet survivalist, firearms dealer and enthusiast. My plans include a closet mounted safe as well.
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Don_P
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# Posted: 27 Aug 2014 21:59
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Prescriptively, code requires a full perimeter foundation. The reason for this is mainly to provide lateral bracing for the braced walls above, bracing against racking, sliding, or overturning. Typical piers do a lousy job of that which is why they should be designed by an engineer if you need to use them. It is very easy to overlook lateral loads on a house but even on a small building it is not hard to get a couple of tons of horizontal force in a design wind.
Carrying loads down to the foundation is much easier if there is a full perimeter foundation, point loads from headers, or posts supporting things like a ridgebeam are much easier if there is foundation under the entire perimeter. This is part of the "continuous load path" required for habitable structures.
A floor system performs better over a continuous perimeter foundation as well. Deflection and vibration are not only caused by the joists but by the girders under them. If the entire floor is on girders then there is a higher likelihood of annoying floor vibration.
Drive around and pay attention to how many professional builders you see using piers to support a house or cabin. If it were an economy they would be on it like ants on a cookie. In my area no builders use them. It's not because we don't know how to use them, they have a track record of failure which is why we have laws that require competent design. Also notice the size of piers supporting light poles in parking lots, then look at what owner builders support a house on.
A thin "rat slab" in a crawlspace creates a drier, much more useable space.
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bldginsp
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# Posted: 27 Aug 2014 23:04
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Don_P is correct as usual, but at the same time I personally believe a little perspective on this is in order. First of all a lot of these little cabins get located where its impossible to bring in a concrete truck. But secondly for very small buildings the forces involved in lateral shear are, in most cases, small enough that the risks are lesser, though still present. If a person has any expectation of longevity for the building, or if you are in a high wind zone, or very high snow zone, a full perimeter footing is the obvious choice. But a 200 sq ft bunkie that is not expected to last forever and not in an area with unusual forces on it may be just fine on simple piers for years, and if not, the owner may not care or may be willing to do repairs in 15 years.
I built my 300 sq ft foundation with full perimeter spread footing partly because I was required to do so but also because I wanted it to last, I could afford it, and a concrete truck could squeeze in. Not everyone is in the same situation.
But you should know going into it that if you choose piers you are definitely getting an impermanent structure that probably won't outlast you, so you won't have anything to pass on to others, if that's a priority.
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MtnDon
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# Posted: 28 Aug 2014 00:25 - Edited by: MtnDon
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I agree with Don_P. I view a structure that is intentionally made to some lower standard as a potential waste of materials. If it is worth the effort to build at all it should be built to last more than a decade or two without needing major reinvestment. Remedial work is always more work and expense than doing it right in the first place. It will be worth more down the road, it'll be insurable if the owner-builder is so inclined.
One does not have to use concrete to build a code compliant foundation. Do a search for permanent wood foundation. It uses a special foundation grade pressure treated lumber and plywood. A full basement can be done or just a crawl space. They can be constructed with a perimeter concrete footing or with gravel. Detailed instructions can be found that meet all code requirements. I would build on one if I was building a new cabin today. I have a road the concrete company declined to use.
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Tarmetto
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# Posted: 28 Aug 2014 17:39
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Well, maybe a full perimeter is the way to go, especially since this will likely be near 900 sq ft VS a tiny cabin.
I can dig the footers myself, have a compact Kubota with a BH, and I'm reasonably sure that a cement truck could get to the site.
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MtnDon
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# Posted: 28 Aug 2014 17:44
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For that size of a structure you will never be sorry to have a proper foundation. 
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bldginsp
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# Posted: 28 Aug 2014 18:20 - Edited by: bldginsp
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If the concrete trucks can't make it into the site, cement mixers are made that mount to a Cat 1 three point on the back of a tractor, powered off the PTO. You still gotta haul a lot of bags, though. But you can mix your own- buy gravel and sand delivered by truck, then the only bags you need to haul are cement. But hopefully the truck can make it. How far is the closest ready mix batch plant? Trucks can only go so far from the batch plant before the concrete hardens in the truck
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Tarmetto
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# Posted: 28 Aug 2014 18:38
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bldginsp,
Looks like the closest plant is 20 miles away.
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bldginsp
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# Posted: 28 Aug 2014 19:55
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That's plenty close. Make sure you tell the guy who scopes your road that you have a tractor. He might have you grade the road a bit to accommodate the concrete truck. Those things have such a high center of gravity a slight slope can topple them. Good luck and post pics along the way
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Don_P
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# Posted: 28 Aug 2014 20:41
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I've actually never failed to get the concrete truck to the address. From there we've had to be creative at times. The footing pour on mine the truck couldn't make the grade. A 4wd, a drum and trash can and 5 gallon buckets and I was one tired puppy that night. For the slabs we had a dozer here and pulled the truck up. On the current job I'll probably get a line pump to come in and pump from the drive around the house. The last job we set up my mixer underneath, brought in gravel sand and portland and mixed there. I did the same with my shop solo, slipforming as I went, I would do sessions of about 4' x 10' x 1' thick at a time leaving rebar sticking out for each successive pour, basically casting large interconnected reinforced blocks.
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Tarmetto
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# Posted: 28 Aug 2014 20:52
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Quoting: bldginsp That's plenty close. Make sure you tell the guy who scopes your road that you have a tractor. He might have you grade the road a bit to accommodate the concrete truck. Those things have such a high center of gravity a slight slope can topple them. Good luck and post pics along the way
The only issue at our lot is that the entrance from the main road is steep....only fro about 30', but that's the steepest part of the property, and it's a 90 degree turn off of the main road. There's another drive directly across the street, so he could pull up it and back down ours for a straight shot.
The wife's Camry can do it without bottoming out.
My F-250 can go in with ease and the mirrors don't clip any trees, but it is heavily wooded.
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Tarmetto
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# Posted: 28 Aug 2014 21:00
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What scares me is what happened when we built our current house. We discovered that "we" are responsible for the cement truck once it leaves the main road! The driver came up our 650' driveway and OBVIOUSLY drove off the driveway and got stuck (I have pics of the truck tracks proving this)....we had to pay for the huge wrecker to come pull him out! The driveway was 100% accessible, we'd had larger trucks delivering materials with no problem, the driver just screwed up.
He came in at 11:30 PM! to pour the footings.
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bldginsp
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# Posted: 29 Aug 2014 07:33
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I was surprised when the concrete supplier was willing to back their trucks up an old timber skid trail to my site, but it had been graded a bit. When the truck got to the top, the driver wanted to pull it a bit closer to the up side of the hill, he did, and the whole thing sort of tilted to the left, toward the downhill slope.... a scary moment..., but it didn't tip. Whew!
Now Don_P is the the real thing- he mixes his own gravel sand and cement- but he's probably younger than me.
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Don_P
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# Posted: 29 Aug 2014 19:40
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but he's probably younger than me.
Only in my dreams 
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MtnDon
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# Posted: 1 Sep 2014 23:37 - Edited by: MtnDon
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FWIW, in 2008 we built a 16 x 30 cabin on 6x6 piers with individual poured concrete footings, 5 per side, 44 - 48 " deep, well below frost depth.
A year or so after the build my education increased to the point where I realized I had made a mistake in choosing the pier and beam foundation. With the aid of a structural engineer I had met I made modifications that can help with one of the shortcomings of piers, that of lateral instability.
This morning Karen noticed a fine hairline crack in 9 floor tiles. The line extends through 9 ceramic tiles parallel to the exterior long walls. It is situated right about where the joint between the hardi cement fiber backerboard would be located. Other than the crack the building shows no other signs of distress. Well, other than the lightning damage. I'd like to blame this on the lightning, but that would be a stretch I think, Most likely something has shifted a slight amount. It wouldn't take much to crack ceramic tiles.
We don't think the crack was there a month or two ago. Maybe we just didn't see it. The past two years have been particularly dry and this July was the 4th wettest on record. August pretty wet too.
Just though I'd drop that info out there for pondering.
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bldginsp
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# Posted: 2 Sep 2014 09:07
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I wouldn't want to live in a building on piers, as a primary residence, for the reason you gave us, MtDon. But for a very small seasonal use bunkie sort of building, piers are a viable alternative, so long as you know what you are doing, and don't plan to convert to permanent housing later.
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toyota_mdt_tech
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# Posted: 2 Sep 2014 12:09
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I'd say if you can get a cement truck in to the site, use a full footing/stemwall type foundation.
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Mainiac
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# Posted: 2 Sep 2014 21:11
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Isnt a small cabin really not worth the huge expense of Concrete truck worthy driveways,full cellars,crawl spaces and etc?If you use an outhouse, will carry in water,build the cabin on the ledges.
I agree that sonotube foundations have lots of problems,They rarely have footings,go down far enuf,are plumb,too many rocks,not enuf concrete,and etc,
All this engineering stuff is too complicated ,BUT,
"FROst WIll tumble the cleverest wall." Robert FROST
"Right done is done once."
Any body ever build on a rubble bed?
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Don_P
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# Posted: 2 Sep 2014 22:15
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Well, when you build on piers, pilings, alternative foundations... you are engineering. Generally doing a poor job of it since we aren't engineers and don't understand the forces at work. This is why they have lots of problems.
When you build a prescriptive foundation following the tables and text of the codebook, the engineering has been done. They generally perform well.
I've built on gravel trenches, similar to a rubble footing, done rubble stone foundations per code with rocks from the site and from the neighborhood. Have slipformed, built on pier and curtain wall, worked on a house on a permanent wood foundation. By following the cookbook approach in the residential codebook these were designed to resist the vertical and horizontal forces that a foundation is supposed to resist.
I'll venture that a typical pier and beam foundation is not a viable alternative, as built they are incapable of performing the role of a foundation in resisting lateral loads.
I'm curious, is there a market for an engineered pier foundation "kit" that is capable of performing to the required standards and could be installed in sonotube type holes?
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bldginsp
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# Posted: 2 Sep 2014 22:41
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I'm sure there would be a market for such a thing, DonP, but I can't imagine how it would be done. A 'one size fits all' approach to foundation design can't work with buildings of various different designs, so an engineered pier foundation kit would have to stipulate the building design, I guess. Elaborate more on your idea.
I agree with Maniac that a small, temporary use, vacation type cabin is not worth the expense of a full spread footing. Or rather, it can be, but doesn't have to be, at the option of the builder. Some people just want a simple structure to use for a decade or two.
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Don_P
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# Posted: 2 Sep 2014 23:01
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Think more along the lines of most building components, each size fits a range. Several states do have camp exemptions. If you agree with that approach work to change the laws. I can see both sides of that but personally agree that if it is habitable it should be capable of providing shelter from the storm. That does not require a full continuous spread footing but does require more than what I've seen.
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MtnDon
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# Posted: 2 Sep 2014 23:11
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There are a couple of things I have noticed here. Owner builders who have expressed a desire to be able to live full time at their cabin property is one. A pride of ownership couple with a desire to share with family, as in passing the property along to younger family members. To me, these are not compatible with pier and beam construction. Yes, we have a pier and beam foundation, but in case someone has missed it, I do wish I had been better or more fully informed of pier and beam shortcomings before I built.
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Wilbour
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# Posted: 3 Sep 2014 09:29
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MtnDon has a point. Your small cabin will be one of two things, either a seasonal escape shelter strictly for recreation a few weeks of the year or its that great American camp that gets passed down from generation to generation. This will dictate how much to invest in the foundation. You have to know where you want to end up to know how where to start.
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Mainiac
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# Posted: 3 Sep 2014 20:04
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The forever camp wont be in the family forever.In Maine they were usually built by local guys that made sure they made a profit but stayed in the budget,The STD foundation for camps was cedar posts.Some used Locust I hear.They also used to form pyramids of concrete and rock,but they usually skimped on the conc. cause it was hand mixed,My barn was "REPAIRED" using these.They didnt last.Overturned and broke off.The original foundation was piled rocks that sank into the soil over time. That barn is still there after 163 years.Sounds forever to me.
Of course if U are Daddy WARBucks you can spend what U want,Judging by the size of the cabins on this forum,they might be more suited to Little ORPHAN ANNIE. ?? I know mine will be.
I think its the drainage that is crucial in any building,No wet,no frost,no heaving,
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