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MJW
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# Posted: 16 Jun 2012 09:43 - Edited by: MJW
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Question on foundations...
Other than rotting over time, what are the advantages of building on a concrete pier with a wooden post at the top over just coming straight from the ground with the post?
It just seems to be so much more expensive (and labor intensive) to use the concrete and add the post at the top rather than digging the holes and using the posts.
There have to be other advantages that I don't know about.
Thanks for your input.
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OwenChristensen
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# Posted: 16 Jun 2012 10:01
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I confess although I've built at least a hundered cabins, I havn't seen an advantage to concrete. Larger treated posts are rated for forty year ground contact. Lately I'm willing to use wood. The one big advatage to wood is lack of the extra joint and another is the ability to bolt or screw directly to them.
Frankly though I would prefer setting a cabin of 10' to 16' wide on two treated skids set in about a foot from each side. With this type of build there is never a rogue post and can always be releveled if necessary.
Owen
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MJW
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# Posted: 16 Jun 2012 10:08 - Edited by: MJW
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Thanks, Owen.
We are in the planning stages of our 20 x 32 and in working out the final details (well, final for now - subject to a million changes, of course) I am looking for someone to convince me why I need to spend the extra time, labor and expense for that concrete.
We travel and love history and I gotta tell ya, we look at alot of 100 - 200 year old houses and yes, some of them aren't exactly square or level but they are, well, 100 - 200 years old. I am fairly healthy but I don't think I will have to worry about it quite that long.
Forty years will work for me.
In your experience, what is the best way to set those posts regarding the footings, materials, etc.?
Thanks again.
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OwenChristensen
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# Posted: 16 Jun 2012 10:36
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Use a big hole. I have two augers for my JD. The small one won't allow me to pack fill back against the post. Gravel or sand against the post will keep it dry arround it and frost won't be as bad. Laminated beams, like 2x10 three wide will allow you to extend to the length you want and stagger the joints. Treated beams bend easy because they're wet, so short spans are good, 6 to 8'. No foot should be required in most soils.
Owen
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fpw
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# Posted: 16 Jun 2012 10:48 - Edited by: fpw
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I like concrete. My cabin will be standing long after I am gone. However, it was great deal of work. In particular because I had to dig down below the frost-line by hand and mix the sac-crete in a wheel barrow. With a bobcat and auger and a cement truck it would be quick work.
We are working on a timber frame cabin from my brother in the same location. For this we decided to use wood post piers. We will obtain either railroad ties or phone poles to set in the ground. This will save us a great deal of time.
And, if one of the stumps does rot. A little jack, a chainsaw, and a couple of hours, you can have it replaced. If the wood posts rot off (at ground level) replacement is more difficult.
Either way, make sure your design and grading keeps the water away from the posts.
Concrete footing
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Stumps ready to cut level
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MJW
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# Posted: 16 Jun 2012 11:33 - Edited by: MJW
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@ Owen: So are you are saying a 12" hole for a 6 x 6 would work or something larger?
Say I plant this post 4 feet deep, just backfill with gravel or sand or do I hear you recommending a mixture of both? No footing is needed at all?
How many posts would you recommend for the planned 20 x 32?
@ fpw: I understand what you are saying about the difference in repair with concrete as opposed to just the post. I am just weighing the benefit/cost factor of the two methods.
Of course I am assuming either would be done correctly and no problems would result in the short term. Maybe I am being too optimistic. 
I just visited with a guy that built his own place (and did concrete) and he told me when he builds again he will never bother with that again. He feels it was a waste of time and money.
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OwenChristensen
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# Posted: 16 Jun 2012 16:00
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Gravel or sand same diff. Good drainage is key. Most frost damage is from a squeeze just below ground level , not from undernieth the post.
Any one can overbuild. In my lifetime that would have cost me my retirement. The absolute best foundation is a concrete trench footing below frost and keyed in posts to the beams. It just isn't required.
Probably threee rows of five posts. You can hold them all in a foot from the full measurement. I'd see how firm the ground is down at the bottom of the post hole. You can always use a few more.
Owen
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larryh
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# Posted: 17 Jun 2012 15:49
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The one advantage I did see in the two with post is that if one should happen to be unlucky enough to get hit by a severe wind the strain that the wood can endure is much larger than the bolted on wood can. With all the odd weather and storms its something to consider. I do differ a bit on the need for the foot under the post. Where I am the soil is heavy clay most places and tends to allow for post to sink rather easily. In a small out building where I added some flooring I used a concrete patio block under each foot of wood and they stayed much better than just the wood alone. If your soil is such that its doesn't tend to allow for sinking then you probably don't need it.
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MJW
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# Posted: 17 Jun 2012 16:49
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Quoting: larryh I used a concrete patio block under each foot
This is what I was thinking. At least dig the hole and drop a small square or round down in it for the end to sit on.
One thing about cabin construction. There are as many opinions as there are builders. 
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fpw
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# Posted: 17 Jun 2012 21:01
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The opinion that matters is yours. Understand why people say what they say, then decided for yourself based.
I too, think a footing is needed. Either big rocks, or some concrete under the post.
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Retired
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# Posted: 29 Jun 2012 17:33
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I am a retired concrete contractor, use a concrete foundation or monolithic slab. 30 yrs passes pretty quickly it happens before you know it. Someday your going to want to sell this property and building. Think resale value, and fear owning this building on piers in 30 to 40 yrs as it will likely need expensive repairs.
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adakseabee
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# Posted: 29 Jun 2012 22:20
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You may want to take a look at this option:
http://www.michianabuildingsupplies.com/post_protector/
See also:
http://www.postprotector.com/
They are relatively cheap and absolutely protect the post from rot/decay. The holes can be backfilled with concrete, gravel, sand, or soil, your choice. If I was building using posts, I'd use post protectors, no question.
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adakseabee
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# Posted: 29 Jun 2012 22:28
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Forgot to add that they are also available online at The Home Depot:
http://www.homedepot.com/Lumber-Composites-Fencing/Post-Protector/h_d1/N-brk7Z9prZ5yc 1v/h_d2/Navigation?langId=-1&storeId=10051&catalogId=10053&searchNav=true
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MtnDon
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# Posted: 29 Jun 2012 22:50 - Edited by: MtnDon
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If one must use piers then they should seek out and use foundation grade material. Virtually all the PT post materials found in a big box store are rated ground contact and are not meant for use as a foundation. Foundation grade can be ordered in. It may cost a little more but it has more preservative chemicals in it. It will also have no heart wood; maybe you've noticed that lots of 4x4 and 6x6 have heartwood. The chemicals don't soak into heartwood very well, so in true foundation grade there can be no heartwood.
Also if one must use piers for a foundation use nothing smaller than a 6x6.
Those sleeve like "protectors" are a waste of money IMO. If, or is it when, something goes awry and water does get in between the sleeve and the wood the water is trapped. That then becomes a good setup for rot. Spend the money on foundation grade PT instead.
One of the biggest failures with pier foundations is the failure of the builder to provide adequate bracing. I see very few pier foundations I would want to call my own. Many are disasters waiting for a trigger event. Piers are terrible in many soils that get wet much of the time. Most owner-builders hugely underestimate the ability of a pier foundation to resist lateral forces from high winds.
Concrete slabs and concrete perimeter foundations are vastly superior to virtually any pier foundation. One of the better systems for a pier foundation is to use the Bigfoot Foundation Forms in one of their larger sizes. If you read their information very closely you will find statements that make it sound like their forms are building code approved. However, if you talk to them and insist that you need proof that will be accepted by an on the ball permit department they will eventually admit that they can not provide an engineer stamped approval. That's because there are too many variables in the field that they can not control or influence.
Stability issues are no better with a concrete pier than a wood pier. In fact using concrete and then transitioning to a short wood post, as some do, is pronouncedly worse that a one piece wood pier.
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rayyy
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# Posted: 30 Jun 2012 08:06
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So many pros and cons.So many opinions.I have alway's just built with the standard pressure treated pole barn construction method used for decades for larger buildings.Pressure treated skids style for smaller buildings.Yes,best would be concrete but very expensive and labor intensive and time consuming.The first pole barn I built was back in 81 and it looks as good today as it did then.
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adakseabee
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# Posted: 2 Jul 2012 10:52
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Quoting: MtnDon Those sleeve like "protectors" are a waste of money IMO. If, or is it when, something goes awry and water does get in between the sleeve and the wood the water is trapped. That then becomes a good setup for rot. Spend the money on foundation grade PT instead.
Like any product used in construction, there are advantages and disadvantages. Post Protectors are made of landfill liner material. Consequently, not only do they protect posts from moisture, insect infestation, animal waste, and chemicals that may come into contact with the post, they also protect the environment from pressure treatment chemicals leaching into the soil and groundwater from the post. If the posts with post protectors are installed and are exposed to the weather, the optional drainage hole dimples on all four sides of the bottom "horizonatal" uplift ribs can be drilled to allow water to escape. The manufacturer suggests 4" to 6" of drainage stones as initial backfill material in this situation. Other options to seal the top include shrink wrap (if exposed to the weather temporaily during construction), sealants, or flashing. If not exposed to the weather and not subject to flooding, or splashing from rainwater then the posts will remain dry as the top of the post protector is above grade. Of course, improper installation or damage during construction would be factors that must be considered and action taken to prevent.
I have nothing against foundation grade posts. However, one must weigh the pros and cons of any construction material and balance them against good construction practices, building codes, environmental concerns, and the budget. Post Protectors when installed and used in appropriate applications will protect the posts from chemical and biologic attack while simultaneously protecting the environment from the chemicals used in pressure treated posts.
Quoting: MtnDon Concrete slabs and concrete perimeter foundations are vastly superior to virtually any pier foundation.
Agree.
Quoting: rayyy Yes,best would be concrete but very expensive and labor intensive and time consuming.
Agree. Another environmental concern is the amount of energy needed to produce cement used in making concrete.
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MJW
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# Posted: 10 Jul 2012 21:37 - Edited by: MJW
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I appreciate all the input from everyone on this topic. It looks like 6 x 6 posts will be the way we go.
Anyone know of a resource such as a map or anything else giving some kind of detail as to general soil types and frost depths over the US?
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MtnDon
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# Posted: 12 Jul 2012 14:28
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Web Soil Survey, for soil info. Not all locations have survey results listed..
Freeze depths are best obtained from local knowledge, local building departments. Some states or counties may have that info online.
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