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hakalugi
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# Posted: 7 May 2012 15:40
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Hi,
one of our possible sites on our land is on a bluff (at the top of the mountain) see attachment. the benefit here is:
1) southern exposure
2) 1700' below to the valley
3) > 180 degree views
4) prevailing winds will come from the NW/backside somewhat sheltered by the small-ish trees above - so we can tap into it when we want with high windows, but we'll be somewhat protected.
the site has challenges:
1) no septic up there, our perc field is about 300' downhill below the cliffs) so looking at things like these: http://sun-mar.com/prod_flush.html
2) we're working on getting an easement to that bluff, we don't have it yet, and approaching from the bottom and climbing a 5 story staircase in the side of the cliff would be a hassle
3) water: people hit water @ 150-180' from where this pic was taken, adding another 100'+ and through rock is going to stink (checking out rainwater systems, and building a test-system at home for the garden now to get to know the basics)
so, this topic: foundation. I'm still all over the place regarding building style:
a) 2x4 stick with mooney wall interior for extra insulation? http://builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm
b) panel housing - wish these guys weren't in hawaii: http://multi-facettedhomes.com/ i can't get a crane up there easily for post and beam octo - so the DIY panel looks nice
c) foundation or some walls using drystack block and surface bonding?
but all come back to slab on earth for thermal mass reasons. and here is my conundrum - i've got between 0" and 10" of topsoil up top, many areas with exposed rocks 'above grade' since this is the top of the mountain after all. thankfully the site above the cliffs is actually flat-ish for 100' wide and 65' deep to the back property line. so my question is - does a traditional site-prep company come and 'scrape away' all of the "biologic" material leaving exposed granite? then you pressure wash, then you decide where to pour footers. vs. leave rocks exposed for interest. not as fancy as this, but here is some exposed rock:
http://www.en-derin.com/wp-content/plugins/wp-o-matic/cache/a8688_contextual-rock-con crete-house.jpg
i've worked with a framing crew in college, and worked on light commercial and residential remodeling and learned a ton during this time, so i get the post/pier/frostline conversations. i'm just not sure if that applies when pouring concrete directly on top of exposed rock - does that heave, too? or is it considered inert since it won't absorb water and expand when frozen?
i'm thinking a lower level 'on the rocks' with an upper level built for views would be interesting.
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brokeneck
Member
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# Posted: 7 May 2012 20:08
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Looks like a great site --we've kicked around the idea of a lookout cabin at the top of our property as well -- I think if we ever do I'd use stone for the walls -- that way I'd just need to haul up some cement --
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MtnDon
Member
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# Posted: 7 May 2012 21:36
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Quoting: hakalugi .....not sure if that applies when pouring concrete directly on top of exposed rock - does that heave, too? or is it considered inert since it won't absorb water and expand when frozen?
That depends if the rock is truly very large contiguous blocks that do really get below the frost depth.
If they appear to be very large and contiguous and do not seem to be breaking up into smaller blocks by frost action then a good solution would be as brokeneck is thinking of. Use local rock to build a stone perimeter foundation. You may need to insert some anchor bolts but you could also build rock s into a solid base that would grip the natural convolutions of the rock face... depending what there is of course. Haul mortar mix and water, maybe some Quickrete/Sakrete pre mix to help level out the top sill. Cement some j bolts in the top of the stone work and bolt PT mudsills to them.
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hakalugi
Member
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# Posted: 7 May 2012 22:20
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thanks guys. I don't think the rocks "stop" in that they're not rocks built into and surrounded by top soil, rather this is a butte
there are cliffs on both sides of the butte, my SE side and the NW side (the ridge runs 8oclock to 2oclock) that spot up top is the, er, top. at the back property line, it goes downhill back down another 1000+ feet.
using local stone - hmm, that may be doable - i pack sackcrete and collect water, and use that to lay out the foundation. hammer drilling into the rock, putting in some rebar to anchor the foundation along the ups and downs you'all are describing building with local rocks.... then j-bolts up if i want to do 2x framing for the 'mud sill' as describe.
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ShabinNo5
Member
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# Posted: 8 May 2012 22:47
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Great site!
In our case we have built into the side of a slope in a similar situation. Our property goes from exposed bedrock to 24 inches of soil. In our case we choose to pour piers (18 in all). For each pier we dug down to the base rock and drilled three 18" holes for rebar. A threaded pin was placed into the cement during the pour for securing the post brackets. In one case there was no soil to be removed. The stucture itself is a balloon frame, tied directly to the piers.
The link below is our thread.
Looking forword to watching your progress.
http://www.small-cabin.com/forum/6_618_0.html
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hakalugi
Member
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# Posted: 8 May 2012 23:06
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wow shabin5 what a view. your grade is steeper than the site i'm envisioning. If i cannot get an easement and we build near where the picture is taken, then i'll have a little more soil, and more shale than granite and your pier idea makes sense.
love the ballon framing. i saw those 6x6 posts and thought, man those look heavy - then saw you had to hand carry them from the driveway 200' away?!? wow.
questions, if you don't mind:
1) how is the "Stoburn incinerating toilet" working out?
2) how did you dig the pier holes, by pick-axe?
3) did you use a pulley/winch system to stand the 6x6 posts?
amazing job.
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ShabinNo5
Member
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# Posted: 9 May 2012 13:55
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hakalugi,
My original plan was to use a pick-axe and shovel to expose the bed-rock for each pier, then use a hammer drill to secure the rebar. However after conducting a test on some of the exposed rock I determined that it would take me all summer to put the piers in myself. So I hired that task. The contractor used a small excavator and I helped with the pour.
Hopefully I can report on the Stoburn later this summer. To my wifes disappointment, it will not be used until properly installed, which has to wait for the bathroom to be tiled. As you noticed there is a bit of a walk to the build site, so for now the bathroom is used to store and secure all of the tools.
As for the 6x6 posts, my step son is a college wrestler and he and his friends were almost too eager to raise the posts by hand 
If you do end up considering the pier on a slope, keep in mind that the bed-rock should be chipped out to create a level flat surface before the pour. This protects against the shear forces that occur as the overall building weight increases from construction and snow loads.
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