Building the Saltbox with alternative methods...

[vjharr]

Hi all! Just looking for some feedback and comments. Nothing is set in stone. I'm just toying around with some ideas.

First a little background...my husband and I will be doing almost all of the work ourselves. Some help from family and friends, but that will be few and far between. We will not be subbing out any of the work. There will be a slight learning curve, but we both do have some experience with construction. Building site is in west central Alabama (frost line is 6"), and there are no required permits or inspections.

I have always been interested in "alternative" building (strawbale, adobe, cob, etc.), and would like to incorporate some of those methods in our build. We have pretty much set our hearts on the Saltbox, with a few layout changes. We will also not have the massive chimney or the plenum space. It will be simple and straightforward in regard to the basic shape...no nooks or alcoves, etc. What I am looking for feedback on are: #1 building the house on a rubble trench foundation. #2 rammed earth/adobe floors (basically the house would sit on a perimeter foundation and the floor would literally be the ground underfoot (properly prepared and sealed) with no slab, no floor framing, etc.), but would include radiant heating. #3 earth tubes for cooling the house. I also don't want the upstairs floor cantilevered over the lower floor (I've played around with rearranging the layout of the upstairs bedrooms/bathroom). The hot water heater would be behind the stairs as is in the original floorplan. The "utility" room would not be necessary as I only want a washing machine (prefer to hang clothes outside), and the washer would be placed in the space where the current pantry is (I want the kitchen/dining room on the north side of the house where the current living room is. U-shaped kitchen where the wood stove and chimney are and dining table in front of the bay window). Any thoughts/suggestions? Anyone with any experience on rubble trench foundations/earth floors/earth tubes?

Thanks,
Jenn

[Ernest T. Bass]

Sounds like a really cool project, Jenn! We used a rubble-trench foundation for our cob/cordwood home here in MI's UP. I'm perfectly happy with it, but it ended up costing us more than we anticipated since the washed stone was a rather hard-to-come-by commodity in our locality. In hindsight, I think I would have done more of a frost-protected/rubble-trench hybrid, with a shallower trench and a 4' foam skirt around the perimeter.

[vjharr]

Thanks, Earnest! I've been to the U.P. a few times. Beautiful up there! My mother was born and raised up there. I love cob and cordwood. We've considered both, but with 5 kids and 2 full time jobs, we'll be weekend warriors. I'm afraid we'd never get it done, lol. Luckily, we have a sand/gravel company less than a mile from our property One of the big deciding factors for wanting to do rubble trench! I'm not terribly familiar with it other than what I've read online. We have very rocky soil with a lot of clay. Dig down 3 feet, and its really wet. Not sure how well the trench will work with that. Foundation work is, unfortunately, our least knowledgeable area We had thought about buying a house before we found our piece of property, and have viewed several. Have been surprised to see that a lot of them are built on piers resting directly on top of the ground (basically the same as piers under a manufactured home). We're still obviously in the planning/research stage, so any thoughts, comments, or questions are welcomed and appreciated!!

Jenn

[Ernest T. Bass]

Good deal on the local rock.. Our clay soil is quite hard, and any hole that you dig fills up with groundwater.. The rubble trench w/ drain tile seems to do a good job of keeping us dry, and our extra-wide trench gives me a good feeling considering our soil's terrible bearing capacity. The wetness you speak of could be problematic if it isn't just runoff.. Might want to get it tested if that isn't already required for the permit.

Yes, the cordwood is slow going.. It's also too drafty for the brutal winter we are still finishing up.. An outer shell of earthen plaster is on the agenda for this summer.

[vjharr]

Definitely going to do some testing. Plan on doing our own perc and LBV tests, and if there are any concerns from our own results we'll have the local office do more in depth. It's been raining off/on the last several weeks, so hopefully it's just runoff. There used to be a mobile home there so testing would have been done when the septic tank was installed. The home site is actually "cut in" to a hill. If nothing else, I think we'll need a French drain on the inside of the "cut-in" in addition to the rubble trench to drain run off coming from up the hill. We live in an area where no permits or licensing are required. You can build whatever you want however you want as long as it's for your own personal use for a minimum of 1 year.

Earnest, how did you determine the size your rubble trench needed to be? From what I've read, most of them are a minimum of 16" wide, and go down to 4" below frost line (with our frost line being only 6" I'm not sure I trust only going down 10"). Did you have an engineer work up the specs for you? If so, what kinda cost is involved? Thanks again for your replies!!

[UK4X4]

Just because it aint code does not mean is a good idea to ignore it.

You have mentioned 4 things about your location that stand out as issues for cheap and cheerfull foundations

hillside
Cutin
run off
and clay

They are all factors that seriously effect foundation stability long term

I had run off, clay and hillside

You will either need to build a foundation strong enough to resist the movement or one flexible enough to jack the house up from when things move

the post method means you have a foundation that you can jack adjust and wedge to keep the house level

a strong foundation means if things move the house stays in one piece and you jack and wedge up the offending corner

the rubble in stable solid is fine, my neighbor had rubble. his house shifted 14" from end to end.

We have 48" of crushed rock under ours just to remove the clay and provide clear drainage of anyfluids before they chanel and move the silts and sands.

thats not just perimeter thats the whole foundation plus 4ft arround....

Realy depends on not whats easiest but what will provide you with a stable building for its expected lifetime.

[vjharr]

Thanks for the reply, UK. It's not necessarily about what's easiest. Rubble trench would by far be the most difficult from where I'm standing. I'm leaning in that direction because I want earthen floors (again, not easy, lol). Finding out there was easy access just kind of drove it home, so to speak. Basically, the floors will be layered and tamped inside the bond beam (plus a little more depth down beyond the beam). There won't be a crawlspace. Was also thinking that with the poor drainage (and LBV) of the mostly clay soil, the rubble trench would benefit in the drainage (plus a French drain depending on the results of the perc test). The biggest problem I'm having is determining the size of the trench. Of course, we'll have to get an engineer's determination before it's all said and done, but I'm trying to do as much research and plan as much as possible in trying to put together a budget. With the earthen floor inside the bond beam, it would take some SERIOUS natural disaster to shift the house, at which point, the house shifting would be my least concern! However...it might sink if I don't get this right, lol. The only other option I have for foundation (considering the type of floor that I want) is to pour footers with a stemwall around the entire perimeter. Because of the poor drainage and LBV, that's going to be a ridiculous amount of concrete. Not to mention all the "rubble" to go under that concrete. And this is all assuming that the perc will fail or that the entire home site is clay. We've only really dug down in one spot, and that was to remove the existing utility pole. Hopefully we'll be getting some soil samples next weekend from several locations of the home site. Thanks again for the replies UK and Earnest! I'm glad I found this site. I'm learning a LOT!

[Ernest T. Bass]

The width of the trench is usually about the width of the scoop used to dig it.. Technically I think 16'' is already overkill in most situations, but our trench actually ended up more like 30'' from the wide bucket our contractor used. Another reason it cost more than anticipated...

[vjharr]

LOL! I just figured it was 16" to cover the width of the "alternative" (read TRADITIONAL) building materials like straw, cob, and cordwood. One of the concerns I had with doing stick frame was where to put the walls on the bond beam to keep the weight centered over the trench. One "green" builder that I talked to said that you would put the wall on the outside edge as in normal foundation. BUT, With a "normal" foundation the footer spreads the weight that is on the stemwall, so it's still centered over the footer. I do have some fear of the bond beam turning up to the inside if I do it that way. If I center the wall (2x6) on the bond beam (even as narrow as 12" - we are digging the hard way, lol), then I'm gonna have a huge drip edge that won't be very aesthetic.