Use Quikcrete tube for purple matin house on solid rock

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Old 08-14-15, 10:25 AM
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Use Quikcrete tube for purple matin house on solid rock

I'm thinking of using a quick Crete tube to create a birdhouse base on solid rock (granite) next to the lake. Seems like if I clean the rock, put it a long post in ( make sure it's vertically level) and pour the concrete and let it sit should be fine. Am I missing something?

Thanks

Rick
 
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Old 08-14-15, 11:08 AM
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It depends a lot on how tall your post will be and how large diameter the tube is. Concrete will stick to the rock somewhat but a lot of its stability will simply be it's mass. If you really want it to stick you can drill into the rock and install a couple concrete anchor bolts and leave them protruding so the concrete has something to mechanically grab.
 
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Old 08-14-15, 12:48 PM
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Since it is a marten house, it could be quite large and pick up a lot of the wind pressure. There is big difference between a 4 family and 24 family house.

You could need a concrete base anchored to the wall, since shallow soil over the rock offers little resistance and the concrete might not weigh much.

How far down to rock from the surface, how high is the post above rock and how big is the house?

Dick
 
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Old 08-14-15, 02:01 PM
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It's bare rock, a small point in a lake. Those good points: I don't know how many families but it is pretty heavy- I'd say 20 lbs...I was thinking of a 12 foot pole.
 
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Old 08-14-15, 02:17 PM
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I'd core the granite and fix the pole in grout.
 
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Old 08-15-15, 07:59 PM
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Core the granite?? Come on, chandler, he's not building a bridge.

An easier but just as effective method would be using an elephant's paw on the bottom of a sonotube, with a vertical No. 5 bar running full-length to resist bending forces. Making sure the rock is reasonable clean/moist before concrete placement, to ensure adequate bond.
 
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Old 08-15-15, 08:20 PM
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So you advocate an ugly basketball goal base above ground, sitting on the rock? I'd rather build a bridge
 
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Old 08-15-15, 08:40 PM
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Okay, I'll bite. What the heck is an "elephant's paw"? I tried Google but all I got was related to an actual elephant.
 
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Old 08-15-15, 08:44 PM
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Original footing forms & the best pier footings - concrete volume calculations for the bf36

It is used quite a bit up nawth, where the ground heaves. Letting my redneck show, sorry.
 
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Old 08-15-15, 09:19 PM
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Thanks, Larry. I am familiar with those footing forms but never heard them referred to as an elephant's paw.
 
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Old 08-15-15, 09:45 PM
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If you really want it to stick you can drill into the rock and install a couple concrete anchor bolts and leave them protruding so the concrete has something to mechanically grab.
This is probably the best, easiest and quickest solution. Another alternative would be to drill holes into the rock and epoxy pieces of rebar into them. You're going to have to do something to mechanically attach the concrete to the rock in order for this to work.
 
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Old 08-15-15, 10:36 PM
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Furd

Google Bigfoot Systems, where you'll learn all you need to know about elephants' paws. I guess a more correct, technical term would be sonotube extensions, but I've only known them to be elephants' paws ever since first seeing them used, starting in the 70s or 80s, either in Colorado, New Mexico or Wisconsin (can't remember exactly where, it's been too many years ago. I often don't remember what I walk to the refrigerator for any more--have to go back to the table and start over).

So could anyone explain why I still can easily recite the alphabet backwards, or why I can still rattle off the combination to the first padlock I was issued in my 7th grade phy ed class, more than a half-century ago?
 
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Old 08-16-15, 04:29 AM
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I do that with phone numbers I remember numbers from my childhood, 50 years ago. Where I laid my reading glasses???? Not so much.
 
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