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Posted by Wayne Whitney on April 12, 2006, 1:54 pm
Hello,
As part of a remodel project and reconfiguring an exterior wall, I
need to drill some 7/8" holes in my foundation to epoxy in 3/4"
threaded rod. So I got an SDS rotary hammer and an 18" long 7/8"
carbide hammer bit. I've never done this job before, so I'm looking
for some advice.
For example, how will I know if I hit a piece of the foundation rebar?
Hopefully this won't happen as long as I keep the new holes in line
with the existing anchor bolts. If I do hit a piece of rebar, is
there a way to drill through it? Most of my holes I could just move
over a bit, but two of them are tightly constrained and would be a
major design headache to move.
Thanks, Wayne
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Posted by BobK207 on April 12, 2006, 4:48 pm
Wayne Whitney wrote:
show/hide quoted text
> Hello,
> As part of a remodel project and reconfiguring an exterior wall, I
> need to drill some 7/8" holes in my foundation to epoxy in 3/4"
> threaded rod. So I got an SDS rotary hammer and an 18" long 7/8"
> carbide hammer bit. I've never done this job before, so I'm looking
> for some advice.
> For example, how will I know if I hit a piece of the foundation rebar?
> Hopefully this won't happen as long as I keep the new holes in line
> with the existing anchor bolts. If I do hit a piece of rebar, is
> there a way to drill through it? Most of my holes I could just move
> over a bit, but two of them are tightly constrained and would be a
> major design headache to move.
> Thanks, Wayne
Wayne-
I done this a LOT, that is, drilling into concrete with rebar.
"For example, how will I know if I hit a piece of the foundation
rebar?"
The bit will stop advancing. With a good rotary hammer (Hilti,
Miluakee) the bit will make steady progress into the concrete. Don't
push hard on the tool, let it do the work.
You CAN drill by the rebar IF you only hit it "partially". If you hit
it dead on it will be nearly impossible to drill through with a rotary
hammer (unless it's only a #3 or 4 bar and you are very stubborn)
But do you reall want to sever the rebar?
Most epoxy anchoring goop allows for oversized holes, not a great idea
since it can lower the tensile valves if the hole is REALLY big but
much better (IMO) better than severing the rebar.
The worst thing that can happen is that you just barely nick the rebar
& the bit "corkscrew" passed it.
When you go the withdraw the bit, the drilling debris will cause the
bit sieze up in the hole.
A pair of vise-grips will be helpful but clearing the hole as you go by
withdrawing the bit often is the best bet. Even better blow & vac
it..
You'll get a feel for the rebar depth so you'll know when you in the
"danger zone".
Getting a bit stuck is a major PITA and can take a long time to futz
with to get out.
If you hit rebar with a bit I suggest that you stop, re-drill the hole
with a larger bit such that the smaller bit now can be "moved over" &
sneak passed the rebar.
SImpson & Sika both make good products for this sort of app; Sika works
in a regular caulking gun, Simpson needs a special one ($$'s)
Both products spec hole sizes; the SImpson website gives info about
oversized holes
http://www.simpsonanchors.com/catalog/adhesives/application_guidelines.htm
SImpson reports no stenght reduction for holes up to 150% larger than
desired hole.
The SImpson website (& Sika for that matter) has a wealth of info
Long winded answer.........my bottom line, avoid severing the footing
rebar, work around it, over size the holes if need be & load them up
with goop. :)
Make sure you blow AND brush the hole.............the correct sequence
is brush, blow, brush (at a minimum) but ALWAYS end with "brush".
cheers
Bob
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Posted by Wayne Whitney on April 12, 2006, 5:58 pm
show/hide quoted text
> I done this a LOT, that is, drilling into concrete with rebar.
Thanks for all the info. I just received the item requiring the
precisely placed 3/4" threaded rod (a Simpson Steel Strong Wall
SSW12x8). I now see that the bottom holes to bolt it to the
foundation are oval shaped, so I do have some leeway to move the hole
if I hit some rebar.
BTW, is drilling a 3/4" hole any easier than drilling a 7/8" hole?
Most of the holes I need to drill are for anchor bolts, which only
have to be 5/8", so they would only need a 3/4" hole. But I figure it
would be simpler to just do everything with 3/4" rod in 7/8" holes.
Cheers, Wayne
P.S. Why does everyone use epoxy to grount in the anchors, instead of
a cementatious grout like hydraulic cement? Is epoxy stronger, or
just easier to work with?
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Posted by BobK207 on April 12, 2006, 7:50 pm
Wayne Whitney wrote:
show/hide quoted text
> > I done this a LOT, that is, drilling into concrete with rebar.
> Thanks for all the info. I just received the item requiring the
> precisely placed 3/4" threaded rod (a Simpson Steel Strong Wall
> SSW12x8). I now see that the bottom holes to bolt it to the
> foundation are oval shaped, so I do have some leeway to move the hole
> if I hit some rebar.
> BTW, is drilling a 3/4" hole any easier than drilling a 7/8" hole?
> Most of the holes I need to drill are for anchor bolts, which only
> have to be 5/8", so they would only need a 3/4" hole. But I figure it
> would be simpler to just do everything with 3/4" rod in 7/8" holes.
> Cheers, Wayne
> P.S. Why does everyone use epoxy to grount in the anchors, instead of
> a cementatious grout like hydraulic cement? Is epoxy stronger, or
> just easier to work with?
Too bad you already got you StrongWall I would have suggested a
ShearMax
anyway
"is drilling a 3/4" hole any easier than drilling a 7/8" hole?"
Slightly but it depends on the capaciyt of the hammer, I have a Hilti
TE-52 that can drill up to 1 1/2" so 3/4 or 7/8 not much difference
but my Milwaukee Falcon (nominal 3/4" capacity) would struggle witha
7/8" bit
"Most of the holes I need to drill are for anchor bolts, which only
have to be 5/8", so they would only need a 3/4" hole. But I figure it
would be simpler to just do everything with 3/4" rod in 7/8" holes."
Use the rod size they suggest, the smaller rod with be more forgiving
with respect to placement & fit up
"Why does everyone use epoxy to grount in the anchors, instead of
a cementatious grout like hydraulic cement? Is epoxy stronger, or
just easier to work with"
PourStone, PourRock, etc are fast setting cementious anchoring
compounds that work well. I've used them in some situations but never
for uplift on shear elements. I have no idea of the tensile
properties. I have experience with epoxy; construction & testing. I
know it works
IMO the epxoy goop is easier to work with, esp the Sika AnchorFix that
goes in a standard caulk gun The strengths are in the 5000psi+ range
they sell it at HD in the masonry section, the two parts come in a
single standard caulk cartridge (two plastic "bags" inside the caulk
cartridge)
There is a fast (~5 minutes) & a slow set (~30 minutes) AnchorFix1,
2 or 3 I don't remember the number. Read the tubes.
The fast set stuff with harden in the nozzle for you don't keep
dispensing new proucts every minute or so. I've lost lots of nozzles
by being delayed & setting the gun down; only to find the product
setup!
If you use the fast set, ....................you've got to ready, setup
& quick!
cheers
Bob
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Posted by Wayne Whitney on April 12, 2006, 10:32 pm
show/hide quoted text
> Too bad you already got you StrongWall I would have suggested a
> ShearMax
ShearMax is a wood shear panel? I'm actually using a metal shear
panel with attached wood side bucks, the whole thing is only 12" wide.
Shearmax's website is rather rudimentary, but it seems to indicate
that their smallest product is 16" wide.
show/hide quoted text
> > "Most of the holes I need to drill are for anchor bolts, which only
> > have to be 5/8", so they would only need a 3/4" hole. But I figure it
> > would be simpler to just do everything with 3/4" rod in 7/8" holes."
> Use the rod size they suggest, the smaller rod with be more forgiving
> with respect to placement & fit up
Right, the Simpson Steel StrongWall calls for 3/4" rod, so I know I
have to do 3/4" rod. The other holes are just for anchor bolts for
the 2x6 mudsill (at least every 4', and 6"-12" from each end), which
are required to be at least 5/8". I was planning to use 3/4" anchor
bolts for simplicity.
Cheers, Wayne
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> As part of a remodel project and reconfiguring an exterior wall, I
> need to drill some 7/8" holes in my foundation to epoxy in 3/4"
> threaded rod. So I got an SDS rotary hammer and an 18" long 7/8"
> carbide hammer bit. I've never done this job before, so I'm looking
> for some advice.
> For example, how will I know if I hit a piece of the foundation rebar?
> Hopefully this won't happen as long as I keep the new holes in line
> with the existing anchor bolts. If I do hit a piece of rebar, is
> there a way to drill through it? Most of my holes I could just move
> over a bit, but two of them are tightly constrained and would be a
> major design headache to move.
> Thanks, Wayne