Building A Stawbale Cabin (Pier Foundation, Timber Frame, Stawbale In-Fill)

Last week I started my Summer/Fall project of building a 18 x 15 (exterior dimensions) strawbale cabin about 30 minutes from Ithaca, NY. It's on 40 acres of land that my family (2 brothers and parents) bought so that we could all live close together. There is one house on the land currently, another being built by my brother. The cabin will give my girlfriend and I a place to live while we're saving up money to build a larger (hopefully strawbale) home. The cabin, which I call "The Study" is meant to give us a place to be 80% of the time 80% of the year (so it doesn't have to fit all of our needs, all of the time) and also to give us a chance to experiment with different ways of doing things to find out what works before building our larger home. Here are my current thoughts on what we'll do:

TimberFrame

StrawbaleInfill

Concrete Piers

Earthen plaster (interior and exterior)

Earthen Floors

Rocket Mass Heater

Composting Toilet

Outdoor Showert

I'm hoping to use this post to 1) Document the process to help others doing similar things and 2) Get help along the way when I run into unexpected issues or to hear from those who have gone before. I hope I'm putting this topic in the right place.

My first update is that last week I dug holes for my piers. I went down 48" making a 12" diameter hole and belling out the bottom to 18". I rented a mechanical auger and thought it would take a day for my brother and I to dig the 12 holes. Instead if took 4 days of almost constant work. By the time we got down to about 30" the auger (a 1-man auger) seemed to constantly bind up on rocks and it was easier to just go the rest of the way by hand and chop through the rocks with a post-hole digging iron and then excavate the holes with clamshell diggers. Issues that have come up so far:

1. At about 24" water started slowly seeping into the holes. Some of the holes are filled up to the 24" line if left overnight. I'm worried about that weakening the concrete mix but I'm going to use garbage bags for my belled out footers anyway so I guess this will be ok? I wonder if that fact that I hit water so quickly means that digging a shallow well might be possible later on in the project. Anybody have any thoughts? It did rain a few days before I was digging, not sure if that my influence what I'm experiencing.
2. I hit a huge rock on one of my piers. The thing goes down about 8 inches and bisects the hole. The bottom is at least 3'10" below grade so I'm thinking that I'll just pour around it since I can't seem to get through it. I'd be very interested in thoughts and advice about this.

I'll write a bit later about the process I had laying out my grid. I'll attach pictures of the site, the hole with the huge rock, and of my plans for my piers. I wonder if I'm overbuilding with the number of piers that I have but when I did the weight calculation for the building, + snow load + live loads it seemed like I will need every pier I've got (assuming 1,500 psf since the soil seems like it's silt, clay, or silty clay).

Thanks for any comments, thoughts, or suggestions.
Jesse

Just wanted to add a couple more pictures.

Sounds like a great project and you are thinking well ahead.
I just had one question. You mention a pier foundation and you also would like earthen floors. Will you infill with earth to bring up the starting dirt floor level to the top of the piers?...and how will you get stability for the earthen floor?...tie-ins, rebar, have a floating floor not tied to the house footer/piers, tamped adequately...? I guess, I'm worried about the amount of moisture you are seeing in the dug holes already. Keep up the good work.

If you that close to the water table I'd pack some 2-3 inch rocks at bottom. Trash bags will just tear.

Jesse Boring wrote:
1. At about 24" water started slowly seeping into the holes. Some of the holes are filled up to the 24" line if left overnight. I'm worried about that weakening the concrete mix but I'm going to use garbage bags for my belled out footers anyway so I guess this will be ok? I wonder if that fact that I hit water so quickly means that digging a shallow well might be possible later on in the project. Anybody have any thoughts? It did rain a few days before I was digging, not sure if that my influence what I'm experiencing.

Hi Jesse, this is a cool project, but this line makes me worry. Drainage is your #1 priority at this point. You will need to excavate the entire site if you don't want issues down the road.

Jesse Boring wrote:2. I hit a huge rock on one of my piers. The thing goes down about 8 inches and bisects the hole. The bottom is at least 3'10" below grade so I'm thinking that I'll just pour around it since I can't seem to get through it. I'd be very interested in thoughts and advice about this.

That rock is a great foundational support mechanism, I don't see any reason to remove it.

So, it looks like you have a good grade and the only thing missing here is the foundational drainage system. Gravity is used to remove the excess water by draining it to daylight in your biome or in my desert climate, I usually french drain this sort of thing. Water will defy gravity if it has no other choice and ascend into your earthen floor, creating a disaster. Once you have excavated and backfilled using the techniques described in this thread https://permies.com/t/36478/natural-building/Raised-Earth-Foundations, then you will have a nice drainage layer on which you can install your earthen floor. You will also see in this thread, that you don't need concrete, just the abundant stones already on your land.

Please post any additional photos and questions as these threads are highly educational for others in similar situations.

All Blessings,
Bill

Hi Jesse,

I had a big posting started to send you the other day but got side tracked....sorry for that.

I had included some of the posts I have started here but Bill beat me to the most important one.

At this point, I now have some pretty serious "red flags" about your project, that made my other post inappropriate. There is too much about this project "I don't know" to give any good advice. I can share the following and let you decide what you would like to do, questions you may wish to ask, or you may choose to just do it the way you plan and I will be silent.

Pier foundations (especially concrete which I only do as a last resort) are not as "easy" as DIY directions often make them out to be. There is much more to them than the "average" builder suspects. Soil types (i.e. clays), drainage design applicability, local geology, water table location, just to name the primary concerns that need to "always" be addressed.

You can not pour OPC of any type currently in the DIY market that will cure properly if the water table is that high in excavated holes.

I agree with Bill that a rock in a hole is not an issue...per se...yet there are some basic rules of this type of foundation that "rocks" need to either be "placed" in the excavation to function under specific tasks or if "native" to the excavation, must be confirmed as actual "bedrock" and not just a loose erratic, or other geologic artifact. Native stones/erratics can shift, split, roll, or dislodge otherwise and compromise the foundational support they become part of.

Stone is good, yet must be solidly placed or part of the natural bedrock and of sound condition.

Pier foundations are much more than just...digging holes and pouring some type of concrete in them. I can not stress that enough...

Sorry for the hard news, and perhaps tone of this post, but the potential for later issues is way too high from what has been shared thus far.

Regards,

j

There are 2-3 maps I use when considering a building site. The first is my local zoning map we have a portal, if not call them and make sure I can build what is allowed, it has set backs, easements, right aways, roads, etc. You can battle zoning codes, check for cost and time locally. Second, USDA has a "Web Soil Survey" map below that describes the soils types and some basic properties, approximately where the water table is (this could be the second "red flag") ...If the water table is high or I'm doing earth construction with site soil that tells me to get a Geo-Tech Engineer involved and allow for that expense. Mistakes with foundations are rarely easy to repair. Third, FEMA has a flood plane map portal, they are updating it now so get with them. Some homes are going in the plane and insurance rates are going to cost if there are lenders, some are going out.

I've never had this issue of being so close to a water table. It can be good for well water, bad for foundations. You can find cases of piers being successfully poured. Below is one from an Engineer that makes generalities about the soil strength. Others using underwater concrete, but my guess is these guys know what they are doing. I wonder about frost line and heaving. I guess is water if moving it won't freeze but if it is not under concrete it will heave. Might be able to just add some lateral lines at each hole. If you use quickcrete I doubt you need to add water

http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

http://www.concretenetwork.com/concrete/footing_fundamentals/water_in_the_excavation.htm

Thanks for the responses everyone!! I really appreciate the ideas, feedback, and encouragement! =) Sorry it took so long to respond. Claire and I were at a Rocket Mass Heater workshop with Ernie and Erica Wisner over the weekend (which was super helpful and informative!) and I got sick with a stomach bug on Sunday so I've been struggling to catch up again.

Just to give you a quick update on the project, I finished belling out all of the holes except the one with the big rock in it (I want to be able to spend time with that when my arms and mind are "fresh"). As long as the weather holds I'm planning on pouring my piers next weekend (I'm hoping to do it over a 3-day period but I may be over or under-estimating the time it will take).

Let's see, I guess I'll respond to all the replies more or less in order:

Dean: Thanks! I guess I should clarify that I'm planning on putting an earthen floor on top of a wooden subfloor. The base of The Study will be 12" to 36" off the ground, which I'm doing to control moisture for the strawbale/earthern plaster walls. Some of my friends/family have thought it was silly to put an earthen floor over a wooden sub-floor but I like the idea of the additional thermal mass, the feel and look of them, and I'm just curious and want to see if it's something I'd want to do for my "real" house later on.

Terry: I appreciate your advice, especially considering your qualifications. I was able to locate some interesting soil characteristics that seem to fit with my building site using the USDA website you linked me to:

Ap - 0 to 10 inches: channery silt loam
Bw - 10 to 17 inches: channery silt loam
E - 17 to 20 inches: channery silt loam
Bx1 - 20 to 49 inches: very flaggy silt loam

Depth to restrictive feature: 14 to 26 inches to fragipan
Natural drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately high (0.00 to 0.20 in/hr)
Depth to water table: About 12 to 19 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low (about 3.5 inches)


I'm going to take your advice of compacting large gravel into the holes though I think I'll still use the garbage bag idea for my footing. The idea is to tape them to the bottom of my sonotube this way (so they'll be supported on the bottom and won't ever have take the weight of the concrete): http://www.finehomebuilding.com/how-to/video/build-a-deck-footings-piers.aspx

Bill: I think you're probably right about the best course being to excavate the site but unfortunately I don't think it's a possibility at this point. This is a little "guerrilla" structure that I'm hoping not to draw too much attention too. It doesn't need to last forever or be perfect. I'll pretty much be happy if Claire and I can live there safely and happily for 3-5 years without having to pay rent someplace else. It's mostly just a practice run for the larger project (which I will build to code). My current thinking is that I'll move ahead this year and plan to place a french drain around the site for drainage next year. Thanks for the input on the rock! It's good to get confirmation that it should help, not hurt, that pier.

Jay: I certainly appreciate your concerns and I'm sure you know a lot more about pouring piers than I do. That said, as I think you may have intuited already, I'm going to go ahead with the project largely as planned (with tweaks to prevent issues whenever possible). You certainly may be right about your concerns. I think my fallback, if things start to go horribly wrong down the line, will be to create a dry stacked stone foundation underneath the piers and then cut the piers out from the process completely. Hopefully if issues come up it will be 5+ years down the line after The Study has served it's primary purpose. I hope you don't feel your post was wasted. I really appreciate the input and will be more vigilant now to issues that may come up with the piers. If you have a moment I'd be curious if the idea of putting in a french drain relieves your concerns at all? Or if your basic message is more "Pouring piers is not a DIY project for the uninitiated." By the way, I will commit now to making sure that if things do go horribly wrong with the piers, even years later, I'll post the results to this thread so that others can learn from my mistakes.

Thanks everyone! I'll write another update after the pour. If anyone has experience pouring piers and has pieces of advice I'd be all ears. I'm planning on using a cement mixer to mix the cement and I'm imagining it will take about 120 80lbs bags of cement to pour all of them (12 piers the tallest of which will have a total height of about 84 inches and the lowest of which will be about 60 inches). A couple of quick questions I have if anyone is of the mind to answer:

1. My sono tubes are 48" long and my tallest pier will be 84". I'm planning on keeping the tubes 12" of the bottom of the pier so I'm missing about 24" of height for my tallest piers. Can I tape the tubes together and/or splint them in some way? I worry about them not staying in a straight line if I do that. Some of my tubes nest within each other even though they're all nominally 12" diameter. Maybe I should nest them to make a longer tube? Just curious if this is a normal issue or if I just need to source longer tubes somewhere.

2. How much do I need to worry about wet weather? I'm assuming rain is fine for the curing concrete (though probably not so good for the concrete still in bags) but will the sonotubes hold up to rain for 48 hours or so?

3. Does 3 days seem like a reasonable time frame for pouring 12 piers. I'm going to have to relevel my batter boards and redo my grid since I put those too close to my piers and wound up knocking them around as I was digging.

4. Darn it... I know there was another basic question I wanted to ask the community. I'll probably think of it the moment I submit this. ....grrrrr.


Thanks everyone!
Jesse

Hey Jesse,

I will do my best to keep in mind this is a "guerrilla project" as well as a "living experiment" that is not intended to last very long, or be perfect...

You certainly may be right about your concerns. I think my fallback, if things start to go horribly wrong down the line, will be to create a dry stacked stone foundation underneath the piers and then cut the piers out from the process completely.

Don't worry about "wasting" my time, I had a feeling that this project was an "experiment for learning." Now for the ideas around future "mods", this could be possible in a warmer climate where there is not freezing of the ground. In Ithaca, NY which I know well, there is all kinds of challenges. I am always dispelling the "myths" around "frost heave," yet that doesn't mean that the "clay soils" don't freeze and cause havoc with foundations...It is actually the clay soils that are the issue and if they are not removed or mitigated properly they can tip over a mountain...literally.

Now...with the "doom and gloom" stated...I can see ways around this in the future as you are planning of a timber frame for this project. With a wee bit of "tweaking" (I can go into that when I see a frame model plan/CAD) we can "strengthen" this to facilitate future adjustments and alterations should the need arise...Hoping for the best for you both on that front...

If you have a moment I'd be curious if the idea of putting in a french drain relieves your concerns at all?

Only if the dig holes clear themselves of ground water after a 24 our period...if not that means you have some type of stratified ground flowing water from perhaps an artisan or some other source. It would actually be better if this does flow year round as it..."may"...carry enough ground heat with it to never freeze. Big gamble there. A "after though" french drain...might...mitigate this or do nothing at all. It is really hard to get a read on such things remotely and only with limited photos... I am more worried about there being a stratum of bentonite clays there trapping the water. Bentonite and water are a hideous combination. Simply put...bentonite clays can stop most projects in there tracks till there understood, mitigated and/or removed. Think of expanding ice...then give that a "steroid boost" and you have just the beginning of what Bentonite clays can do...again...literal split a mountain in have...that is their force multiplier. It is an ancient way to split and quarry granite...

Piers on decks (like in video) not critical and something "some" DIYers pull off just fine...in domicile architecture...things get a whole lot trickier as I think you are figuring out...

1. My sono tubes are 48" long and my tallest pier will be 84". I'm planning on keeping the tubes 12" off the bottom of the pier so I'm missing about 24" of height for my tallest piers. Can I tape the tubes together and/or splint them in some way? I worry about them not staying in a straight line if I do that. Some of my tubes nest within each other even though they're all nominally 12" diameter. Maybe I should nest them to make a longer tube? Just curious if this is a normal issue or if I just need to source longer tubes somewhere.

Oh Boy...big red flags have just come down for me...sorry!!

First, I see more "bad info" on the net than I do good...that includes "Fine Home Building." Even a lot of there stuff is more "I think" and "experimentation" than "good practice. With that said, the first thing I heard him say of note was about not having a "wet mix" Well...??...guess what...his mix was WAY to wet!! It should "ball" and be virtually dry to the touch. If you don't understand "angle of repose" in soil/gravel types and have a good handle of "slump characteristics" then mixing concrete is "Russian Roulette" to whether the concrete is noting more than sand and stone stuck together with mud...

I am not a big fan of OPC to begin with and know some of the major players in the RD side of it here in the states. All one has to do is look at our crumbling infrastructure to get a handle on what we actually "don't know" about OPC and how to use it properly. Actually the Egyptians 7000 years ago new more than we do...and I see most of what the OPC industry does is more about making money than making "good product" and material methods of application.

My PE that I work with would do back flips if I had a 12" pier sticking higher than 2 feet out of the ground!! Even to put a very small house on...let alone one that is going to have the weight and lateral load characteristics yours probably will. If I go higher than 24" I am looking a 18" and it goes up in diameter the higher I go...Past 48" and I would be required to have tensioning cable or related tectonic resistant elements designed in the piers themselves.

2. How much do I need to worry about wet weather? I'm assuming rain is fine for the curing concrete (though probably not so good for the concrete still in bags) but will the sonotubes hold up to rain for 48 hours or so?

I am not into this "bag" experiment at all. It is nifty in concept, but as Terry has pointed out...not a good idea in practice. I don't use concrete much unless spec'd by project parameters I am brought in on. With that said, now supper dry whether and no supper wet whether on pour days...ESPECIALLY...if ground water is present...this stops pours period...

OPC needs to dry slow and be kept "moist" not wet...

3. Does 3 days seem like a reasonable time frame for pouring 12 piers. I'm going to have to relevel my batter boards and redo my grid since I put those too close to my piers and wound up knocking them around as I was digging.

Hard to say...I am still hoping that the holes are 60" deep and no pier is going to stick up higher than 24"....Even that has me concerned with the other elements we have discussed. It is all hard to get a read on from a distance. Sorry to be back seat driving on this...

For now, in closing, my main concern is that water and getting rid of it and understanding the source, plus above grade pier height...Also, if this is going to carry the weight I think the building has it is going to need a center pier and really big log floor joists as well as connecting girts/beams.


Hope you feel better soon...Regards,

j

Ap - 0 to 10 inches: channery silt loam
Bw - 10 to 17 inches: channery silt loam
E - 17 to 20 inches: channery silt loam
Bx1 - 20 to 49 inches: very flaggy silt loam

Depth to restrictive feature: 14 to 26 inches to fragipan
Natural drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately high (0.00 to 0.20 in/hr)
Depth to water table: About 12 to 19 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low (about 3.5 inches)

Looks like it got your water table depth fairly accurate. Soils drains decent. Here is what I found for channery,

A soil that is, by volume, more than 15 percent thin, flat fragments of sandstone, shale, slate, limestone, or schist as much as 6 inches along the longest axis. A single piece is called a channer.

Some decent plate strength to support those rocks that will also help to distribute some load out to soil so the concentrated loads are not so high per pier. If there is a concern you could always add more peers to take the vertical/lateral side loads down, or increase the compression strength of the mix by adding more OPC. You could make your own mix out of MGO, contact Preimier for "light burnt MGO" use it instead of OPC or an admix and you will have no issues..look at their site for more info. Rather than plastic bags since you have a mixer already why not some perlite (it drains well) and lime or other rock aggregate like vermiculite and binder, lime, local pozzolan, casted in around the piers after poor as a WRB and better more even load transfer to soil if you create a larger distribution area surround, it will also help cold condensation and manage drainage. Bill, Jay? There is no stopping our NY friend might as well water down the fire

Also, there are "water reducing" ad-mixes cheap at the local big box stores or concrete supply: http://www.cement.org/cement-concrete-basics/concrete-materials/chemical-admixtures

Siloxane has some great properties as a WRB too seen on this breathable wall thread, if you want the fast chem solution: https://permies.com/t/43637/natural-building/Breathable-Walls

It or a limecrete are far better WRB than plastics/foams.

As far as combining tubes create a doubler with another, use a strong gorilla glue, you could also fiberglass and duct tape the seams or all the above to make sure. If just has to be as strong or stronger than the area outside of the join.

Hi everyone, I'm moving up the timeline for the project a bit to take advantage of the good weather this week so hopefully the piers will all be poured by the end of the day Saturday (fingers crossed!). Was excited today when I ran at a nearby state park and found trout lilies, ramps, and may apples in abundance. Time for some foraging fun soon!

Jay: Thanks again for your thoughtful comments. For what it's worth, I was referring to the total height (minus the footer) of the piers when I was referring to 84". The highest piers will be 36" above grade, with the middle piers being about 24" above grade. Do you think it will help at all to put extra pieces of rebar in the piers on the high side? I was thinking about putting two pieces in but maybe I should put in 4 instead? In terms of the weight going to the piers, and the weight on the joists, girts, and beams, I think I should be alright. The design is based on the Sobon woodshed. I did expand it a bit but made the alterations in lumber dimensions that he suggested each time I made an alteration. Once I get the piers done I'll be in full timber-framing mode and will post my plans (I'd do it now but I don't have them available in an easily shareable form at the moment).

Terry Thanks very much for your help despite the imperfect nature of plans (or my imperfect execution... you can really take your pick). The soil description certainly fits what I've seen as I've dug down into the earth. I will go ahead and add an admixture (I had no idea such a thing existed) to improve the strength of the concrete. I'm also interested in using perlite and lime as you suggested to encase the piers. Any tips on where to look at a procedure for mixing it up? Good point that I should make sure the joint is as strong or stronger than the area outside of the joint. Make perfect sense to think of it that way. I should be able to accomplish that by using the tube within a tube idea + gorilla glue + duct tape. ...or at least I think I should. I'll report back on that. If all else fails I suppose I could always use 3 tubes with the ends fitting around the outside of the inner tube that is slightly smaller. That should be 100% stable.

Two quick questions for anyone who has a moment and some insight/experience:

1. My current landlord (who is a contractor who has done numerous project with pier foundations) suggested that I build up the middle of the footer a bit with gravel or cobbles so that the foot has slightly concave shape. He said that this was done on the footers for sky-scrapers and that it would give extra stability. On the face of if this seems to make a lot of sense, especially when I think about it in terms of what it would mean to have a convex footer, but I'm wary of doing something like that when only hearing about it from a single source. Once concern would be if the footer would get too weak since it will be thinner in some places if it has a concave shape. I'd be interested in any thoughts.

2. I had been planning on putting the bottom of my sonotubes 12" above the bottom of my holes because that's generally been suggested in the things I've read about it. However, it would be a lot easier for me if I could bring them up a bit higher, say 24 or 30 inches above the bottom, to cut down on the number of times I'll have to splint two sonotubes together to get to my final height. Anybody have thoughts and/or experience with that?

Thanks again everyone!

We always put the tube 6-12 inches from the TOP of the hole. Just enough to prevent blow outs. Cardboard in the hole just makes for termite bait.

Thanks R Scott, that's helpful! I didn't realize that's how it is typically done (good ol' fashioned lack of experience!). It certainly will simplify things. I guess with the piers that will be 3 feet from grade I'll just need to make sure I pile enough dirt around them to make sure they're completely stable during the curing process.

Hey Jesse...

(First, please don't take my musing and rambling as too negative....I am rather conservative when I don't know someone's true building abilities. I have just seen too many calamities that could have been avoided...especially in elements of modernity of means, methods and materials as they are often applied to traditional/natural building.)

I was referring to the total height (minus the footer) of the piers when I was referring to 84". The highest piers will be 36" above grade, with the middle piers being about 24" above grade. Do you think it will help at all to put extra pieces of rebar in the piers on the high side?

Oh boy...I feel much better now...!!...

I think you said they are 12" tubes, that is good, yet 18" would be better in my view because of the other less desirable elements this site has to offer. Rebar is actually more of a negative than a positive in OPC work...especially for most contractors and DIYers. I haven't seen any go it that hasn't already started to rust. This oxidation doesn't stop and one of the reasons so much of our "concrete infrastructure" like highways and bridges are starting to fail after only 30 to 50 years. The rebar continues to degrade and as it goes through oxidation exfoliation the concrete spalls, cracks and begins exfoliating itself...

3 coat epoxy metal rebar can work though I don't like it, and my first choice is either fiber reinforced OPC (mandated in most builds today by PE spec) and/or carbon/nylon fiber rebar with NO metal. I have even used retired spectra and nylon rappel/climbing lines to "strengthen" the core of OPC work I have "had to do." I would leave you with a bit of history...the Parthenon is still the largest free standing concrete (geopolymer?) dome in the world and oldest at 2000 plus years...it has no rebar, and modern OPC can't achieve even half the loads it is exposed to...

Short answer: no rebar unless none metal...and make sure there is glass fiber in the mix...

Jack is colleague and good acquaintance, and I think I have some CAD models of his shed (and many more) rattling around my hard drive. I just had another person send me a copy as well. When you wish to go into that I would be glad to help.

...build up the middle of the footer a bit with gravel or cobbles so that the foot has slightly concave shape. He said that this was done on the footers for sky-scrapers and that it would give extra stability...

The entire bottom 1 foot minimum (3 feet is better) of the excavation the piers go into should be 2" to 7" stone hand packed in a vertical orientation with a substantial "mounding" to facilitate a concavity in the bottom of the pier for stability. Your contractor landlord friend is most correct...

This concavity is in the "bell" of the flare and should be well centered. This now reflects the detail that actually is supposed to go into such foundations types. There are even PE standards and formulas for the flare in the bell to load projected they must take, as well as many other issues that "are suppose to be" considered on such foundations. This isn't a skyscraper, and I do tend to build things so they last a very long time....

I had been planning on putting the bottom of my sonotubes 12" above the bottom of my holes because that's generally been suggested in the things I've read about it. However, it would be a lot easier for me if I could bring them up a bit higher, say 24 or 30 inches above the bottom, to cut down on the number of times I'll have to splint two sonotubes together to get to my final height. Anybody have thoughts and/or experience with that?

As for the tube and lifting them off the bottom...here again...I don't like these tubes to begin with nor are they always the easiest damned things to use...!! For one thing they are "round" and that has its own set of issues in both building and later on cladding or incorporation into the finishing of the crawl space they create. It is a "quick" way...but in the long term not the best way to form piers...or...overall that quick. Many professional have now forgone these cardboard tubes and gone back to actual wood or cement board forms that are taped or stapled together. This includes the proper shaped and flared "foot" at the bottom. They are placed in the holes with great care and only stone and gravel is used for the backfill...NEVER dirt or materials from the building site unless they have been washed and graded...

All forms are place and checked for proper orientation and layout to the future frame above...Then...the pour begins...

Hope that is more helpful and less negative this time...Good luck and keep us up to speed on your progress...

j

In support of what Scott shared, IF...and only IF...the soils have the structural integrity to hold a basic form...including the flare...can "form works" be left to just below or at grade...

If this is not the case, then the formwork must go all the way to the bottom and this still does not address the stone packing nor drainage that needs to be there...

Right, so if you think in terms of F=P/A the larger A or compression area to the soil the lower the force at each pier distributed. The bottom "bell" works to do just that while at the same time reducing the dead weight. One could calculate the min cross sectional area at each pier, and combined compression allowables but lets keep it simple. The larger the fillet and corner radii of of the bell the better. If you think of water flow you don't want any kinks or sharp corners especially at the surface in tension that causes cracks. More portland cement helps compression or vertical loads but adds density/weight. Rebar nodes resist tension or lateral forces/bending. Helix fibers is stronger since it uses torsion, bassault just have higher mechanical and better chemical properties.

A limecrete-clay-cellulose mix of 30% binder (clay-lime) 70 cellulose would work to insulate or water manage. My test specimen did not freeze over the winter and sucks in water and evaporates it....clay petrifies wood. I used hemp and lime, but a rock aggregate would work too. SA type lime would be better but S will work.

Will write another update soon but was hoping to get a quick response. Does anyone know how I can tell if my concrete mix is right (using Quickcrete). I added the 3 quarts per 80lb bag, then about a pint more per bag, but it still seems to dry. It's not really hanging together. Wet, but a bit clumpy even after machine mixing for about 5 minutes.

One example of it seeming too dry is that if I poke rebar into it, the hole remains, the concrete doesn't flow back in to close up the hole.

Hmmm....that actually looks a bit wet to me...??

You are doing a proper "slump test" aren't you?

This will tell you all you need to know. In your case a very dry mix (yet still fully "wetted" and no dry patch) is the goal. "Tamping in is more than acceptable...

I will check in later...Good luck!

j

What I do with Quickcrete and my Rammed Earth mixes is form a ball in my hand...If I can not it is too wet, if it stains my hands alot it's still too wet. I drop it on the ground hard surface it should go back to looking like it did before I made the ball. As Jay said tamp it down with those 2xs or something and work some rebar in and out to get the air out. ...

Look at it this way. The binder in this case is Portland Cement. I think IIRR around 30%. All you want to do is add enough water to activate it enough so it holds onto the aggregate (sand, rock, etc)....Less is more since concrete is very slow to dry or dehydrate. When it is barley holding together with no dry powder that is perfect!

Thanks so much for your help Jay and Terry!

The mix I see on any video I can find of people working with concrete just looks wetter than the one I had. Particularly concerning was that when I put rebar in (to work out air bubbles), the holes didn't close back up, they just remained there until I tamped them in.

Jay, I haven't been doing a slump test, I'm hoping to go by the feel/sight (as well as the recommendations for the amount of water). Admittedly that has made things a bit dicey but the cones don't seem to be readily available to buy (for today) so I think I'll move forward without using the slump test. Just to double check, when you say "fully wetted" do you mean that the color of the concrete has all chanced from light gray to dark gray and is damp, with no discolored patches, or do you mean everything should be in a slightly liquid form?

Terry, thanks for your ideas, that's very helpful to get some ideas for how to mix should behave. I'll use that ball criteria to help guide me.

General updates:

1. The holes have dried up now. Once I remove the water from them 48 hours later they are just slightly damp or sometimes a very small amount of standing water is in them.

2. I'm putting cobbles at the bottom of the holes and I got gravel to put around the tubes to hold them in place.

3. I wish I had looked more into glass fibers before the project. After looking into it, I definitely would have used that instead of rebar.

4. I was able to remove that huge rock that wouldn't come out of one of my holes. I wish I could say it was due to my superhuman strength but really it was thanks to mother nature. As I belled out that hole and dug everything around the rock to depth I realized it didn't extend all the way to 48" below grade. So I dug out as much rock and earth as I could underneath it. I left that overnight and I think the little bit of seepage that was going on must have loosened up the soil around the rock. When I some more tamp iron workin the hole the next day I realized the rock was loose and was able to work it out of the hole. Had to put a towel down into the hole, with some strings to bring the ends up to my hands and work the rock onto that so that I could bring it out of the hole. I kind of want to post a picture of it but the one I took has me flipping the bird to the rock. Not sure if that's Permies appropriate.

5. Got one pier done yesterday. It took a LOT longer than I thought it would but it's perfectly level and right at the height of my batter boards so that makes me happy. Just 11 more to go.... uh oh.

ay, I haven't been doing a slump test, I'm hoping to go by the feel/sight (as well as the recommendations for the amount of water). Admittedly that has made things a bit dicey but the cones don't seem to be readily available to buy (for today) so I think I'll move forward without using the slump test. Just to double check, when you say "fully wetted" do you mean that the color of the concrete has all chanced from light gray to dark gray and is damp, with no discolored patches, or do you mean everything should be in a slightly liquid form?

Hi Jesse,

First, videos on the net are questionable at best...especially if not showing the "slump test" or related check. "Feel/sight" is not an acceptable method for gauge OPC work...people do it all the time, and we are also seeing failures all the time...sorry to be so negative, but architecture (especially opc) is not a "feel right" kind of medium. A "cone" can be a kid's beach pail if need be...anything similar is better than nothing.

Fully wetted mean no dry spots. "Balling" is a form of slump test also...but takes a bit more skill to affect.

Good luck..

j

Hi,
Just read this thread. Thanks for posting. I just want to say that I think you're crazy (in the way Paul Wheaton used the word recently) for not digging a continuous trench, drained to daylight. And using so much concrete on a temporary building. Also why not put a couple, or one pier in the middle with a beam so your joists don't have to span all that distance?
Just my two cents. You're the one acting so more power to ya! keep us posted
Tim

Hi all,

Just wanted to post a (much belated) update on this project. Wow. Timber-framing has been taking a lot longer than I thought it would. Plus, I built that drainage ditch after all. It took about a week because I had to go 50 feet to a ridge that allowed me to drain to daylight. Lots of rocks and roots. Anyway, around the end of August I started a new job that been keeping my busy so I haven't made much progress since then. At this point all of the piers are done and the sill and joists are all in. I anchored the sills to the concrete piers using a anchor bolts (after drilling out holes in the concrete with a hammer drill and a masonry bit). That part wasn't nearly as bad as I thought it would be. Pretty much everything else took much much longer than I thought it would. Still, I've loved learning how to work with wood and I can't wait to live in my timber-frame structure.

Looks like I'm going to have to wait until next Spring to make more progress. Fortunately I'll have the summers off so there will be plenty of time to work (and hopefully complete) the project. I'll post some pictures of the progress though I actually don't have any of the very latest developments (having all of the joists in).

Thanks to everyone for offering up their expertise and advice.

Jesse

Hi Jesse,
I am watching your progress with interest! Thanks for posting the update. My husband and I are planning on building our own log cabin, along the same lines as yours down, in South Africa and it's good to see a "one man build" in operation. it gives us the courage to take the plunge, Thank You! Do you have any building background? You seem more clued up than a genuine novice like me- I got lost at "drain to daylight". I'd like to know what resources you used to gain the knowledge you applied- hopefully it will help me.
Regards,
Sarah

Hi Sarah,

I'm excited for you guys! The idea of building your own house is pretty intoxicating isn't it? =)

I'm definitely a novice builder and was almost completely green when I started. I had no idea what "drain to daylight" meant initially either, but that's what Google is for! Probably the most complicated things I had built before I got started on the cabin was a bunk bed or a book shelf (neither of which turned out too well). But I like big projects and was willing to spend time learning. I enjoyed it a lot. I tried to get over my mentality of "just get it done" and adopt the mantra of "it doesn't have to be done now, it has to be done right." Since it felt like any time I skipped steps it wound up just costing me time. Even when you go super slow to get things right at least you're always making forward progress. Everything took much more time than I thought. I was quite confident that I'd get the whole thing done last year and instead with a lot of work I finished the foundation, sills, and joists. But, everything is level and square and solid and I'm hopeful it will all come together this year (I started teaching at a community college so I have the luxury of having the summers off).

Anyway... you asked about resources. Here are the ones I found to be the most helpful.

Books
Timber Frame Construction - Jack Sobon - I based the plans for my cabin on an expansion of his woodshed (he includes instructions for making modifications).
Building The Timber Frame House - Tedd Benson
A Timber Framer's Workshop - Steve Chappell
Serious Strawbale - Paul Lacinski (Which is great for building with strawbale in the NorthEast US which is a wet and cold climate).
The Natural Building Companion - Jacob Deva Racusion (Which I'm planning to use to help with the earthen walls / floors.)

Videos
The YouTube by Wranglestar where he is building a timberframe were helpful to watch just to get a sense of how the details of how to timberframe: https://www.youtube.com/watch?v=LTwV5Je7BKQ&list=PLu9l40IymKw_lJnc6t6PU2IvTJ-TveOBN

Websites
I found this website to be quite helpful for getting started on the foundation: http://www.theyearofmud.com/2012/04/06/concrete-pier-foundation-layout/

One other note from me. I don't regret building a timberframe cabin, but I think I thought it would easier than convential 2x4 construction. I think it was easier to wrap my head around a few big pieces of wood rather than lots and lots of little ones. My sense now is that timberframing means taking a lot more time, especially on your first project. If I had to build something quickly I wouldn't timberframe it. That being said, I've loved learning the craft a bit and I'm looking forward to getting more experience. Understanding wood and how to work with precision brings a tremendous sense of competence and more than a bit of wonder (and also a great sense of anxiety that I might make a mistake). I also think timberframes are just beautiful. Anyway, I wish you the best whichever way you go, just wanted to let you know about my experience.

Hope that was helpful and best of luck!
Jesse

Hi Jesse,
Thanks for taking the time to answer my question. I must admit, I am a bit daunted by timber framing and as we are pretty timber poor down south I'm thinking of weight bearing straw bale construction on a raised timber platform. And yes, the desire to "get it up" definitely needs to be tempered with "rome wasn't built in a day" and to learn to enjoy the process instead of seeing it as a chore! I think I have a few of the books you mentioned but I still need to unpack my boxes to be sure.

Please keep posting your updates, they make very interesting reading.
Thanks
Sarah

Hi all, just wanted to quickly write an update.  I don't have a ton of time but I don't want others considering similar projects to get discouraged thinking I wasn't able to complete this one.

The project has changed a lot from my original conception. Here are the aspects of the project that have stayed the same:

Timber-Frame
Pier Foudation
Off-Grid (Solar):  Array = 1200W (48V), Battery Bank = 500AH AGM (24V), Inverter = 2000W)
Composting Toilet

However, a number things have changed:
Strawbale in-fill became reused 3" poly-isocarbonate balloon framed around the timberframe.  This basically required creating a second frame around the timberframe to to given enough anchor points for the foam and allow doors and windows. For what it's worth I was able to find all of my insulation, windows, and doors used on craigslist which made them reasonably affordable.  Doing this method gave me an extra 15% of floor space.  I wanted to do strawbale but it just didn't make sense given the dimensions I planned out for my frame and the primary use of the building (as a living space for myself, my wife, my (newborn) son, and my dog.  
The RMH I had planned on became a vented propane heater from Rinnai.  I felt like I would lose too much floor space with a RMH and also worried about safety and having to tend the fire too often.  I've been very happy with my propane heater though I think an RMH would have been more interesting and sustainable.

I ran out of time on this project and it became necessary to just get it done as soon as possible so that my wife and I could move into it ahead of the birth of my son this past June.  We moved in about a week before he was born (and a few days after his due date) so there wasn't any time to spare. Actually, a number of things aren't finished but it was livable and we needed a place to live so in we went. We've been living in the cabin for almost six months now and we've been quite happy there though it hasn't always been easy. I'll post some pictures and write whatever I can think of that would be helpful to others about my experiences with various aspect of our living situation when I get more time (hypothetically at least) later.

I just realized that I don't have recent photos available right now so I'll post a couple of old ones to show some of the progress and append some more later.

Aha!  Just found some more recent pictures in my e-mail.  

Hi Jesse,
Looks like a sweet little cabin. I'm curious how you finished the underside of the floor joists.
Did you cover the bottom with planks or plywood? How did you critterproof?
I'm also wondering if you considered using helical piles, rather than concrete piers. That may not have been a possibility given your soil type and water table.
Thanks,
Tom