• Post Reply
  • Bookmark Topic Watch Topic
  • New Topic

Question- Skid Foundation/Footer- Above ground, no digging

 
Sarah Mae
Posts: 15
Location: SE New Brunswick Canada, Zone 5a
1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi everyone

I am going to be building a 24 x 34' strawbale cabin in May. The land has a lot of water close to the surface and just everywhere- marshes, bogs, streams, etc.... The local building inspector advised me that if I were to not dig at all, and also not run any utilities into my building (fine, I want off-grid, minimal "conveniences" anyway), and keep the interior 600 sq or less, he would not be interested in it whatsoever. So, I am taking his advice.

BUT, I am left with figuring out how to make a solid foundation for strawbale, also knowing that the ground here heaves and we get heavy snowfall. From the inspector's perspective, my building size and weight should make it fairly simple to make adjustments by jacking the building up if it needs to be re-leveled. I supposed the building could crack, but he thinks it is small enough that it would move as a whole. I hope he's right.

Anyway, my idea for how to begin is to clear topsoil only from spots where I will place pads made from local hemlock (very dense, used instead of treated lumber here) on elevated piles of sand/gravel, and then place hemlock posts on the pads, and then four 30' beams (log or 10x10 hemlock lumber). Then joists, subfloor, and bales on that.

The building inspector was fine with the skid foundation, and just urged me to make sure that it was strong enough to bear the weight of the bales. I had planned to have the bales three feet off the ground level.

I could use concrete pads as well, or cinder blocks, which is what the inspector recommended. I could use those and put the beams on concrete pads with cinderblock "posts."

I have been studying natural building, and with an emphasis on strawbale for the past 7 years, and this is my first opportunity to begin an actual building. I had presumed I would do a rubble trnech, so the need to stay above ground is a challenge I wasn't quite expecting. The alternative to become involved in a very large permit and inspection process, which I will avoid at the cost of having to build with logs if necessary, but I really want to use straw, so any advice or experience with having done this or in some way shape or form (literally!) would be very much appreciated. I di do a search and read everything on this forum about foundations for strawbale, but if there's something I missed, please feel free to direct me to it.

I have carpentry experience and I may be working on this building project alone, although I may also have someone (much stronger than me) to help (I really hope so...).

Thanks in advance,
Sarah

 
Brad Vietje
Posts: 66
Location: Newbury, VT (Zone 4)
6
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hey Sarah Mae,

WOW! -- that's quite a challenge! You have already learned that straw bales and moisture are like bulls and China shops -- they want to be kept apart as much as possible!

Big Picture: How natural, durable & sustainable resilient are you hoping for? Are you trying for all natural and/or native materials? Avoiding manufactured materials with high embodied energy? One aspect of resilience is to use local materials wherever possible, and make sure our structures have a close relationship to the land. If your land is marshy, with lots of Cedar and small conifers, they might make a very good building medium, and some (Cedar & Tamarack) have built-in resistance to rotting and insects. In my case, we have a straw bale home in Northern VT, and while surrounded by a mixture of hardwood and softwood (and not so much barley and wheat fields , but they were grown here 100 years ago), we still opted for straw bale walls on top of a rubble filled trench, since the straw is grown only about 70 miles from here, in southern Quebec, and we really liked so many aspects of bale wall systems. Certainly you could do the same, though keeping the moisture out will be a little tougher in your case.

Wall Support W/Out (Much) Digging:
I would look into an Alaskan floating slab, which can rise and fall with frost heaving, though that might mean using a lot more concrete than you would like. This could be a big violation of the natural and low embodied energy goals, but might be the most reasonable and responsible compromise that would allow you to use your preferred building medium of straw. You'd also want a really good moisture barrier below the slab, and wicking barrier(s) between the concrete and the bales. We used an insulated 18" cinder block toe-up to get the bales up and away from most back-splash from rain and snow, with a lot of attention to stopping the concrete from wicking moisture up from below. Details here: http://vtstrawbalehouse.blogspot.com/ This blog needs updating big-time, but the wall and foundation details are there if you keep going back to the older posts.

Driven Piles (?): Another technique I've seen is to drive rot-resistant posts down into the swampy ground and get them well below the frost line -- maybe 6-8 feet down... I've only seen that used with stick-built structures, so I'm not at all certain how that could be incorporated into a bale wall system. This involves penetration of the ground, but not exactly digging and excavating (per se) so maybe this would pass muster?

Great Reference Book: Natural Building Companion, by Jacob Deva Racusin & Ace McArleton Link here: http://www.chelseagreen.com/bookstore/item/the_natural_building_companion:paperback%20+%20dvd

If you have not already run into this new book, it is really good, and has all sorts of details about natural building techniques in a cool, damp environment. Ace & Deva both worked on my house, so I can recommend their work and their expertise very highly!
 
Sarah Mae
Posts: 15
Location: SE New Brunswick Canada, Zone 5a
1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi Brad Thanks so much for your thoughtful reply. It is a challenge, and I just found out that my budget will be half of what I was expecting... so I'll be building a lot smaller: 16 x 20'. Then I may add on next year or over time. I'll see.

I absolutely cannot dig into the ground at all if I want to live in this cabin this year (which I do) and don't want to have to build to strict code (which I don't). The cabin's future site is very dry, but the landscape is generally very watery and we have high humidity being so close to the ocean and all of its attendant inlets. The problem for me with concrete is that I have not seen even one home anywhere here where the concrete is ever dry if it has any contact with the ground at all- new homes, custom-built with extra attention to staving off water leakage... doesn't seem to matter; water gets in, up, through, etc... And yes, it would be a major pain to get concrete back there; I don't want to make a huge road to accommodate a big truck or even a small one. I like a walking trail back from the parking close to the road, so the cabin will be tucked away. This is also why I won't be hiring a well-driller. I don't mind enough width for a horse or an atv, but I really want to avoid wide driveways all the way back to where I'm building about 450' from the dirt road). And carting concrete by the wheelbarrow-full also seems more hassle than its worth if I can just haul beams through the brush with an atv. And pavers.

I know that strawbale can work very well here; good hat, good boots. There are several bale homes closer to the ocean even, but they have the wet concrete basements that everyone seems to have, and I don't want a basement at all, so I can't look for their solutions to bale-building for that. So it's the boots I'm concerned about. If I can figure out a way to build completely off the ground, that would be so excellent and solve a lot of problems all at once. The other option that most people take here is to build on skid, but with construction lumber or log. Both of those would be fine for me but I really want the qualities of straw. My thoughts are that straw is not too much heavier if at all, than the 12-16" logs used for homes here, some of which are on skid foundations as well. So I think the weight is still not a huge issue as long as there's enough reinforcement.

Anyway, I think that with my building being so reduced in size, my skid foundation plans would be fine. So if I had waited just a few days, my dilemma wouldn't ever have existed... 16x20' can't go too wrong in too many places, haha.

As for preferences for materials, I definitely prefer to use local materials, and I could skip the pavers as well, but I also have to consider that I have about 7 weeks to get the foundation and shell of the cabin up and moderately habitable (even if in camping style). It will be much faster to get beams on pavers than anything else that I can think of. The trees here are water-acclimated and even lumber suppliers use the local wood in place of pressure treated stuff, which has fallen out of favour here in general, not just because it's toxic, but also because it is also unnecessary.

So, I'll build on a four-20'-beam-on-pad foundation. I lived in a 2-storey log cabin in Yukon (18x20) on tree stumps placed on concrete pavers at 6' intervals. It was fine and had been there for over a decade with no shifting. Of course, even though there is heaving there, the permafrost reduces it significantly, which is not the case here. I am so unfamiliar with this environment... I'm sure I am going to learn a lot as I go, and rely on lots of book-learnin'... and hoping it applies! Building begins in May!

I am going to obtain a copy of that book you recommended and take it as an expense, unless I can get it from the library. Thanks, Brad. Wish me good luck!
 
Sarah Mae
Posts: 15
Location: SE New Brunswick Canada, Zone 5a
1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I don't know how much time/effort I'll be able to spare to document this process (I am just one woman), but if I can, I will post my process here. I always benefit from and love seeing pictorials or process pics anyway of others' projects, so if I can, I'll offer mine too.
 
  • Post Reply
  • Bookmark Topic Watch Topic
  • New Topic