Pilings in the frozen north

[RobS]

<font color=blue>was hoping to do this without buying another tool that will rarely see use</font color=blue>

Ah Pete, you need to get to know your local tool rental place. I go through these phases where I must own every tool known to man but in reality that just isn't possible. One trip to the rental yard and I'm happy again. How else can you experience the thrill of a hammerdrill against granite for $20 a day /w3tcompact/icons/smile.gif

 

[yooperdave]

Hi Pete,

I had a similar foundation for a technical college in Door County, Wisconsin.

The earth was excavated to exposed competent bed rock.
Holes were drilled into the rock, and vertical rebar was
epoxied solid into the rock. The foundation walls were poured
directly on top of the rock. Though the bottom of the
foundation walls varied, the top was level.

You may want to reconsider the use of poles for this type
of foundation. Your excavation will be very limited in the
first place.

Just a suggestion.

Yooper Dave

 

[RobertN]

There is a simple way to attach a metal bracket or anchor. Use an concrete anchor. I worked a bit with a guy that installed USPS group mailboxes, ie CBU's and NDCBU's. These were placed on a 4'x4'x8" concrete pad. We drilled 1/2" holes about 6" deep. Then we installed Hilti anchors(you pound them into the drilled hole). When the nut and washer were installed and tighened, a wedge on the anchor "wedged" into the cement for a solid contact.
<A target="_blank" HREF=http://www.us.hilti.com/holus/modules/prcat/prca_fuse.jsp?RANGE_ID=r2509>http://www.us.hilti.com/holus/modules/prcat/prca_fuse.jsp?RANGE_ID=r2509</A>

I've seen where trucks backed into the mailboxes, and tore the base/pedestal right off of the anchors, but the anchors themselves held tight in the concrete. They removed the nuts and washers, installed a new box, and put new nuts and washers on.

Another option is to put concrete on top of the granite. You can drill holes into the granite. Then, pound rebar into the holes you drilled. Allow the rebar to stick up sufficiently into the concrete footing you'll be pouring. If you drill the hole to big, you can epoxy the rebar in too.

you can rent a rotary hammer. I don't know how they charge for bits(we paid about $15 for a 1/2x12 bit). We generally got 100 holes from a bit before it wore down.