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bluefin
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# Posted: 4 Oct 2011 11:38
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I am looking at building a smaller cabin ( 14x20 ) on rock. It is in gulf islands in BC, a mild temperate climate on the ocean. I was looking at drilling a hole and inserting a saddle for the 6x6 posts... The other thought was to drill many holes and , using rebar, create a sonnet tube mount for the saddle. That just sounds like more work and would not be as stable. Main concern is that the post on the saddles is only about 6" long...
thoughts?
thx
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TomChum
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# Posted: 4 Oct 2011 14:38
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Why worry about the rock has it been moving around recently? Maybe set a motion-sensitive camera up to verify the rocks aren't moving while you are away. ;-) Sorry couldn't resist.
What is the cause for your concern? Earthquake? Or are you building a strange shape, with cantilevers, overhangs? Is it perched on a slope?
If it's a standard "small cabin", that couldnt get away if it tried, I don't think you have to concern yourself with building methods that exist to allow for insurability of a $500,000 home.
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MtnDon
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# Posted: 4 Oct 2011 15:02
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The main concern when building on rock would be getting the building anchored down solidly so high winds don't shift or overturn it.
Clean up the rock, get rid of all organic matter. Drill some holes into the rock at a couple of opposing angles. Epoxy some rebar in the holes. Build a form around it or use sonotubes, and pour concrete piers to place the main support beams on. Use the set in wet concrete metal post saddles to hold the beams. That should hold it in place.
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bluefin
Member
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# Posted: 11 Oct 2011 18:53
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This rock isn't going anywhere ( although we are in earthquake country :-) ). I am building at the edge of a large angled bedrock which, at the front of the cabin, drops about 7'. My main concern is shear from a quake ( no worry about wind ).
Given people will sleep here.I just want to ensure my foundation is safe ( vs my tool shed which I just built on pier blocks ).
Thanks for the feedback folks.. I like this forum,
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boatguy
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# Posted: 11 Mar 2012 19:00
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My concern has to do with our colder Ontario climate. I too want to build on shield rock and want to use it as thermal mass or insulate from it. Piers are the easiest except when it comes to drawing and expelling water. Perhaps a partial enclosed and insulated vault to pass the water through. This is isolated in forest so excavation isn't that easy.
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akparajack
Member
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# Posted: 12 Mar 2012 03:20
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Quoting: MtnDon Epoxy some rebar in the holes. Build a form around it or use sonotubes, and pour concrete piers to place the main support beams on. Use the set in wet concrete metal post saddles to hold the beams. That should hold it in place.
Going into rock if concrete is not an option due to extremely remote location, what could you do (not code) if you did have the right hammer drill and bit? Would it be possible to somehow go right to a saddle via galvanized all thread epoxied into the rock? What about a series of 4 smaller diameter all thread pieces, say 5/8" or so - let's say an 8" pattern, so that you could bolt a piece of pt 2 x 12 x 12" to the all thread, and then go up with a 6 x 6 post from there? Too far out there? Too much drilling?
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