Alternate pier foundation for frost heave/expansive clay situations

[poppy]

I have been following this forum for some time and now seems like a good time to chime in.

I followed with great interest the thread by "prohomesteader" on his "1.5 Story In Kentucky" build.
As far as I can determine, they and I have similar building sites and geology, that is freeze/thaw & dry/wet cycles in expansive clay.

I had already placed reinforced concrete piers for my foundation before finding this site, but after seeing the problems that our KY friend had, I started to second guess my own design.

The bottom line is that I have determined to move the cabin site for this (and a variety of other reasons) and have been researching pier designs suitable for a sloped site with expansive clay that would account for frost heave and not require an elaborate drainage system and have low impact. (it's a wooded site)

I have spent hours reading on this forum and have not found what I just ran across this week.    It's a pin foundation by Diamond Pier. http://www.pinfoundations.com/   I found it using "frost free foundation pier" as a search.  It would also show up using "green foundation" as a search.

Unless I'm missing something, this pier system appears to be the perfect solution for my criteria.  It's basically a concrete block sitting in a shallow hole with 4 pipes driven thru holes in the block at an angle & long enough to get below the frost line and provide the necessary bearing capacity as well as uplift resistance.

I am surprised that no one here (at least that I can find) has used this system.  Are any of you familiar with it or have any experience with it?

If this is the right pier system for my cabin (16' x 16'), it would surely benefit others as well.

[hnash53]

Cool website.  I insulated my footings using wood chips over a tarp to keep the ground from getting wet and it also keeps them from freezing.

You can get an idea at http://countryplans.com/nash.html





ED: repaired hal's link - MD

[MountainDon]

Somebody here did discover that pin foundation a year or more ago. I don't recall anything happening with it as far as a project though.

[firefox]

I think the idea is good. The only pronblems I see is the steel rods rusting away and the concrete blocks breaking. If I were going to do it, I would get or fabricate a steel block with holes in it. Wouldn't have to be solid
all the way thru but enough to where the rods would go thru two steel plates. Actually you could prbably use a short length of square tubing
3/8" or 1/2"  walls maybe 6"x6" inside dimension or something that would accomodate a 6x6 post.

The other thing I would do is encapsulate the steel rods in epoxy. This is what the highway department does when they make freeways. They encapsulate the rebar in epoxy.

Drive the holes initially with a plain steel rod, then extract it and drive in the coated rod.

Ok, I know it is probably overkill, but I don't like to do things twice.

Bruce

[Redoverfarm]

I am like you Don I remember reading about it.  Some discussion but no one came back actually using if my memory serves me correct.

[MountainDon]

Previous mentions of these...

http://countryplans.com/smf/index.php?topic=190.0

http://countryplans.com/smf/index.php?topic=4313.0

http://countryplans.com/smf/index.php?topic=341.0

http://countryplans.com/smf/index.php?topic=341.0

[Bobmarlon]

On there website they say that there galvanized so they wont rust out.  It looks like an awesome product but I just don't trust it.

[poppy]

Thanks for the responses, especially to Don for the links to previous discussions.  I guess I need to figure out the search function better.

I am going to continue to pursue this system.  I like the idea of a homemade solution.

I too was concerned with cost, but am confident that the theory is sound for my situation.

I plan to get a piece of pipe and drive a test pin with a sledge.  If that works, I will work on a design to pour a concrete cap.

I've had my property for 2 1/2 years and don't have a rigid schedule for construction, and I actually like the idea of being unconventional.

Will keep you posted.  Dale

[MountainDon]

poppy, for searches I use the search tab, left side near the top, under all the header stuff

Home  Help Search   Profile   My Messages  Members   Logout      

All I did on that one was search for the pin foundations website you gave as I was pretty sure it had been listed before. Actually I surprised myself as it found other references I had forgotten about or didn't know of.

My experiences with driving pipe have required a lot of pounding, except for one case. I can see how having a power driver would be an asset.

[Woodswalker]

I've been doing volunteer work with the local Habitat for Humanity affiliate here for several years now.  They are over half done building a cluster development of 15 homes, the first three of which used pin foundations.  Soil is expansive clay, like yours.  Those homes were built using insulated concrete forms (ICF's), on grade, two stories high.  Some of the forms had slanted holes for driving the pins.  Think the pins were much larger than those presented on the web site link you provided.  They were not driven using "simple hand tools," as mentioned on that site.  A contractor came out and drove the pins, using, I think, compressed air in some fashion.  I didn't see the installation process.  The approach was approved by City of Olympia officials, and the homes have been occupied for a couple of years now, with no problems that I'm aware of.  Subsequent homes in the project did not use ICF's or pinned foundations for cost and volunteer compatability reasons.  Volunteers prefer working with nails and wood, rather than concrete.

[poppy]

Here is an update to my idea for "poppy's pin pier plan." (based on the Diamond Pier concept)

I bought a 20' 1.5" sch. 40 galv. pipe from Home Depot; had them cut it into 2 5' pieces; bought a pipe cap and headed to the farm.

Using 1.5" pipe is based on the DP-100 which has a bearing capacity up to 8,000 lbs. depending on the soil.  The DP-50 with a max. capacity of 4,000 lbs. does not suit my purpose.

I wanted to determine if I could drive a 5' pipe with only an 8# sledge.  My preliminary calc. show that the 5' pin driven so that it goes to 4' nominal depth making the spread 3' (3-4-5 rule), would get me well below the frost line (avg. 10", code 24") and would give me some where bet. 6,000 to 8,000 lbs. load bearing with 4 pins.

I had already done a preliminary foundation layout, pretty much fixing the location of the first pier on the NE corner (as any good Free Mason would).  I have not finalized the cabin orientation to the sun path, so I decided to let the site slope determine the pin pattern.

I threaded on the pipe cap and began the driving.  I had little confidence that the cast iron cap would survive the pounding, but it held together long enough to get the pin deep enough.  It was hard work, but doable.

Cost became my next concern, since each pipe cap cost about $3.00, and it would take a new cap for each pin, I needed an alternative.  I went to my local welding shop, and presented my case, and he found a piece of 2" pipe and welded a 1" thick plug into one end, and wa la, I have a re-usable driving cap all for 15 bucks.

That's as far as I got physically.  It looks like a 4 pin pattern can be easily capped with a 12" concrete pier using a 12" section of Sonatube.  The concrete pier will need to be cone or diamond shaped on the bottom to stay true to the Diamond Pier design.

Conclusion: I think "poppy's pin pier plan" will work and will not be cost prohibitive.  The 10' pipe cost about $38, so 4 pins will run $76 plus about 1.5 bags of concrete, 1/4 of a Sonatube, and an anchor bolt for a total pier cost of about $86.  That is more than I spent on my current foundation with 12" concrete piers to a 3.5' depth, but less work.

I read somewhere that the DP-50 cost about $100 each in material, so the DP-100 would be something above that, so I think I can justify my homemade design, and not have to worry about lack of drainage and future tilting.

It would be nice to find a cheaper source for the pipe, especially since I don't need the threaded end. I will check out the local plumbing supply store, but I expect it to be similar in cost to Home Depot.  My local Lowe's didn't have 1.5" galv. pipe at all.

So that's my story.  I will attempt to document my build with photos and start a construction thread at some point.  I have already had my property for 2 1/2 years, so this will not be a fast process.

Any thoughts and suggestions are welcome.

[MountainDon]

Look for somebody that sells used pipe. You might get lucky, although around here most of the used pipe is larger and not galvanized. I get lucky once about a decade ago and found a bunch of odd lengths of 3/5 galvanized iron pipe.

[bayview]

   I can see where this system would keep the pier from moving horizontal . . . 

   What would keep the pier from moving vertically if you are in a deep clay condition?  Wouldn't the whole thing move?  Pins and pier . . .

   I live near a deep clay area.  Foundations are generally piered to bedrock.  A couple of contractors have tried to stabilize the soil.  Didn't work well.  Home foundations still  cracked. 

[Alasdair]

I read your thread with interests as it sound as if we have similar soil conditions in much of Cape Breton. Many houses I have seen here have used a post and pier foundation with no evidence of frost heave. I have been told that the "trick" is to wrap the pier / sonotube with a double thickness of plastic (DPC or suchlike) as this stops the ice gripping it.

I will be interested to hear how your project goes.
Al

[firefox]

In the case of clay like soil where you are worried that the pipe will pull out, you might steal a trick from the linemen
The drill a hole at right angles to the pipe so that it intersects the pipe near the bottom end. Then they take a collar
and slip it over the pipe and secure it. Then fill in the extra hole. The pipe now has to pull out the collar at the end of the pipe as well as the pipe. The size of the collar will be dependent on how much resistance to pulling you want.

Check out metal surplus yards. In some of the bigger cities you can find dealers that deal in industrial surplus. I have found things I beams large and small as well as stainless steel water pipe. At the time it was cheaper than the copper,
so I repaced all the rusted out pipe in my current house with stainless steel pipe. I think that is what is holding the house together now. The only reason this actually worked was because I found a bin with stainless steel pipe fittings the right size as the pipe in the same yard.   Oh, and it helps if you are a little crazy.

[Redoverfarm]

Not real sure if this is applicable but I would throw it in.  I had to make a cold pour joint on my bridge embutments to raise the heigth.  I could have used epoxy but at $5 a stick it would have broke the bank for two wingwalls & embutments.  My solution was to drill the holes at 45 degree angles and crisscross the rebar.  There was probably 18" into the old pour and then 18" into the new form pour.  With the crisscross there is no way it can pull apart once the top is poured.  They work against each other.  But I used 1-1&1/4 diam rebar.  Maybe driving three in at this approach would keep it from raising and provide a little better support.

[poppy]

bayview, I am not aware of any deep piers to bedrock in my area.  We really don't have a deep clay condition, but rather an expansive clay condition.  Go down about 3 1/2 feet and you get to hardpan clay which is very stable so long as it can't get wet.

Keeping the bottom of the foundation dry is the issue.  When basements are used around here the draining system is critical.  When a hole is made in expansive clay you either have to prevent the water from getting to the bottom or channel it away when it does.

For example, I started a hole for a fireplace foundation and after digging down about a foot, I decided to move the location for the fireplace.  I did not re-fill the old hole, just started another one.  After getting the second hole about 2 to 2 1/2 feet deep the rains started.  When I came back to the site, the first hole was as dry as the surface and the second hole was a bathtub.  The further down you go the harder and more dense the clay gets and harder for the water to penetrate.

The theory behind the pin system is that you are going deep enough without making a big hole.  It is a resistive pile concept.  For example for a bridge project close to the Ohio river, foundation piles were driven until the friction load was more than the design load; no need to go to bedrock.

[poppy]

Alasdair, frost heave is not really the issue here, although it has to be considered.  The conbination of freeze/thaw, wet/dry cycles over time in expansive clay is the issue.  Frost heave is easy to prevent in any pier design.

The problem with expansive clay is that it expands with moisture and shrinks when it drys creating large cracks that can fill with water, expand the clay, etc. If the surface is always wet or always dry, then the water can't get to the deeper clay and cause the expanding, shrinking cycles.

The other problem with clay when wet is that it gets softer and loses bearing capacity and then foundations tend to settle.

[poppy]

firefox, pulling out is not the issue.  This system is not designed to be an anchor, but to be a bearing load system.

Thanks to you and Don for the suggestions about used materials.  I will work or resources around here.

[poppy]

John, the criss-cross or triangle shape is exactly one reason that makes this system work.  The pins are driven at opposing angles to create the triangles and therefore obtain stability in all directions.  As a matter of fact, I would only use 3 pins if they provided enough capacity, or even 5 if I thought I could effectively encase them in concrete at the top.

[firefox]

Hey Poppy, come to think of it, the idea might work just as well for the load situation, so long as the collar was secured to the pipe solidly.
Be sure the collar is big enough in diameter and strong. Part of the key to this is not disturbing the soil along the path of the pipe, just where it intersects the collar.
Think about it.

Good luck on finding a surplus metals place, and be sure to post it for folks in your area.
Bruce

[poppy]

Bruce & Robbie, Thanks again for your response, but I guess I don't really understand the collar concept.  As you pointed out, a key is not to disturb the soil around the pipe, and so I believe I will stick with my current plan.  I want to keep it as simple as possible.

My next challenge is to determine if I can use the pin system as a foundation for a small fireplace.

[poppy]

Just a quick update on "poppy's pin pier plan."

The local plumbing supply store wanted to sell me 1 1/2" sch. 40 galv. pipe for over $7.00 a foot. 

I have not found a surplus source yet, so I will continue to buy from Home Depot to keep the project moving forward.

[glenn kangiser]

Check with a pump company for used pump drop pipe.

[John Raabe]

Interesting thread.

Good luck with your project Poppy. You've done your homework!

Let us know how it works out.