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boomhaeur
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# Posted: 29 Jul 2016 11:55am - Edited by: boomhaeur
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Hi folks - first post here but have been lurking for a while.
In the process of starting a small cabin (plans here). While not blessed with a perfectly level surface all six footing locations have solid granite beneath them.
Of the 6 footings locations, 3 of the granite faces are completely level, 1 has a slight slope and 2 have severe slopes (1 is a flat surface but on a ~30-45deg angle, the other on a pointed top where two sides meet - 20-30deg angle sloping on either side of the point.)
The land slopes along the 8' side of the building so the footings on the downhill side are about 18-24" lower than the uphill side. Here's some pictures of the site (the frame was just a template to help us choose the site/place footings properly - not intended to provide 'structure' and we need to dig out the footings spots a bit better still).
So my questions:
1. Given granite is about as solid as I can get can I avoid concrete forms and drill straight into granite and epoxy the footing brackets drag to resize or shift-drag to move
into the rock directly?
1a. Would this only work for the level footings or is there some leeway with the off angle ones? (ie as long as base where pin is meets the rock?)
1b. Any particular epoxy type product you'd recommend? for securing the pins?
2. Would 4x4 be sufficient or should I go with 6x6? (3 footings down each long side, single story with small loft building.)
- (Edit: From doing more digging, 6x6 seems to be the wise choice)
Appreciate any advice - thanks!
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bldginsp
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# Posted: 29 Jul 2016 09:55pm
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Hi boomhauer
Not sure I understand what you intend to do with the brackets, but here's a few thoughts-
Epoxing into granite should work fine- use Simpson Set type epoxy which is used to glue rebar into concrete.
I think you are fine with 4x4 for such a small cabin.
If you attach the post bases directly to the granite, then the post bottoms will end up an inch or so above the rock. If you clear all dirt and debris from around the posts, you might be okay, but in general you want your wood at least 6-8 inches above the ground to prevent rot, pressure treated or not.
I would bore into the granite and epoxy in rebar, build forms around the rebar, and pour concrete footings. 3-4 pieces of rebar sunk into the granite at each pier will keep it from shifting. More in the slanted granite, with bigger footings.
Post pics!
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sparky30_06
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# Posted: 30 Jul 2016 06:39am
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I'm a Hilti man myself.
https://www.us.hilti.com/anchor-systems/injectable-adhesive-anchors
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boomhaeur
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# Posted: 30 Jul 2016 07:42am
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Thanks Bldginsp -appreciate the insights... Will definitely share pics when we're done.
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bldginsp
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# Posted: 30 Jul 2016 07:20pm
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You're welcome boomhauer, look forward to seeing your pics
Sparky- yeah Hilti is just as good as Simpson, but Simpson is more widespread- you tend to see Hilti on large commercial jobs, and Simpson everywhere else. You can always get Simpson at the Homeless Despot, Lowes, etc. at least here on west coast. Don't know about east
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sparky30_06
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# Posted: 1 Aug 2016 06:49am
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bldginsp
I'm familiar with Hilti from working in the Midwest and now down here in the Oil & Gas industry. Guess I've never looked for that stuff at the big box stores
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MouldyJoe
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# Posted: 30 Aug 2016 02:06pm
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I had a similar situation and hammer drilled/epoxied 4, #4 rebar into the stone with some pre made home depot rebar bands into 3' columns and put sonotubes around them filled with concrete and used them like piers with my post bases on top of them. Worked well
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