Drilling through old garage slab

[Sukhoi]

I'd like to drill a line of holes along the interior edges of my attached garage slab to do a preventive termite treatment. The slab was poured in 1965, so do I need to be careful about drilling through any sort of vapor barrier? Not sure if they did that sort of thing back then. The crawlspace under the rest of the house is just a plain dirt bottom.

 

[Greenman]

My guess would be no vapor barrier as it's unconditioned and ventilated space. I'd also guess that there is no rebar either, probably 6x6x10 wire mesh.

 

[IronWing]

Be prepared to chew up drill bits. 50+ year old concrete has had a long time to cure.

 

[Greenman]

Be prepared to chew up drill bits. 50+ year old concrete has had a long time to cure.

A single carbide bit in a rotohammer will do the job. I have bits that have drilled hundreds of holes in concrete and still work fine.
Just as important as the bit is the tool that's turning it. Using a hammer drill will take forever and kill the drill. A rotohammer is an absolute must have when you're drilling multiple holes.

 

[Micrornd]

A single carbide bit in a rotohammer will do the job. I have bits that have drilled hundreds of holes in concrete and still work fine.
Just as important as the bit is the tool that's turning it. Using a hammer drill will take forever and kill the drill. A rotohammer is an absolute must have when you're drilling multiple holes.

I assume you mean something like a TE72.
That and the bit would be a rental for him 😉

Or most termite treatment companies (Orkin, Terminex, etc.) can do it from outside the slab AND give a guarantee.

 

[Sukhoi]

The cracks all over the slab support the no rebar theory. 😀

Years ago I got a great deal on a Hitachi DH38MS SDS Max rotohammer for $199. Used it to clean up all the crack edges for patching, and also drilled four 3/4" x 9" holes for anchoring the shear walls I installed on the sides of the garage door. It went through the stem wall like butter so I'm not concerned about the tool for this job.

I need to buy a new, longer, bit for this job. Does it matter much between 2- and 4-cutter carbide? I'll have around 20 holes to do. Would it be appropriate to dip the bit in a bucket of water after each hole to keep it cool?

@Micrornd no access to the side of the slab so gotta drill vertical holes.

 

[Greenman]

The cracks all over the slab support the no rebar theory. 😀

Years ago I got a great deal on a Hitachi DH38MS SDS Max rotohammer for $199. Used it to clean up all the crack edges for patching, and also drilled four 3/4" x 9" holes for anchoring the shear walls I installed on the sides of the garage door. It went through the stem wall like butter so I'm not concerned about the tool for this job.

I need to buy a new, longer, bit for this job. Does it matter much between 2- and 4-cutter carbide? I'll have around 20 holes to do. Would it be appropriate to dip the bit in a bucket of water after each hole to keep it cool?

@Micrornd no access to the side of the slab so gotta drill vertical holes.

The four cutter bits last a little longer, for 20 holes a two cutter will absolutely do the job. The two types of failure I had were the carbide cutter breaking lose from the bit, and the outer edges wearing down causing the bit to bind in the hole. You'll never see those failures. I saw them because the project had over 3000 (yes, three thousand) 3/4" holes 12" deep. I don't recall how many bits we went through, but it was certainly less than a dozen. We burned up 3 rotohammers doing the job. The guys doing the drilling weren't kind to the tools.

Btw. 5' bits are available, but they ain't cheap. Mine was $365 about ten years back.

 

[herm0016]

should drill fine. I have drilled 100s of holes with my Makita carbide bit set and my battery Ridgid SDS hammer drill in all ages of concrete, stone, precast panels, etc. i find the aprox. 12 in long bits are the most usefull for my work. Not many slabs to drive ground rods through or walls thicker than that will drill.