Drilling concrete for Seismic retrofit tips tricks please.

[skylarkguy]

So I decided that my house, originally built in the 1930's, needs a seismic retrofit. Basically the premise it that keeping the house on the foundation is the best way to have the structure survive a slip fault earthquake. Before 1974 there were no requirements to bolt the sill plate to the foundation, thus the need for a retrofit.

What is required it basically screwing/bolting a series of plates to the foundation and sill plates. I'm using a simpson strongtie UFP10. The bolts require that 2 holes 1/2 inch diameter by about 2.5 inches deep be drilled in the concrete foundation for each bracket. An expansion bolt then is placed in and bolts the plate down. Each plate requires 2 bolts and I have 40 plates for the size of my house.

Drilling has been a difficult and tedious affair. Keep in mind I'm working in the crawl space on my belly or side. I've managed to install 8 plates in about 10 hours...brutal. So I need some suggestions on how drill concrete. What I have is a Porter cable PC70THD, hammer drill (7amp, 2 speed), I've tried several different bits (standard concrete "ace" brand, a dewalt branded one, and a dewalt with 4 cutting surfaces. I've tried just using the 1/2 inch bit, I have also tried drilling with a 1/4 inch bit first. Most of the time I have been spinning the bit fairly slowly, a couple I when full speed and it really chewed the concrete...but man it got hot.

Any suggestions would be appreciated.

 

[KevT]

Try using a small SDS drill such as a Bosch Bulldog. What you have is made for occasional concrete, use a drill dedicated to concrete. Your arms/hands wont tire as easily either.

 

[Egon]

As per KevT on the drill. You may also try and make a support or hanger for the drill to take the weight off your arms.

 

[skylarkguy]

Thanks guys. I did find out there is a difference between a hammer drill (what i have) and a rotary hammer (what i need).

 

[Paddy]

Renting or buying a real tool will be quickly justified. My drill will drill 1/2 holes 4 in deep in 10 sec.

 

[skylarkguy]

Paddy...do you recall a make and model?

 

[EddieWalker]

Like already mentioned, you need a SDS drill. They are fairly cheap at the box stores. I have a Makita from Home depot and it just melts through the concrete. Get a good quality bit and you will be amazed at how easy it is. I also have Makita bits, which I highly recommend. But for such a small number of holes, you should be fine with just about any name brand.

One of the nice things about the SDS drills is they can be used as small jack hammers, or for digging in really hard clay. It is a tool that has multiple uses that makes it very worthwhile owning. I also have a SDS max drill that is the same thing, just a lot bigger, heavier and more powerful that I use for holes bigger then half an inch, but mostly for jack hammering out concrete on remodel jobs. It also has a nice attachment for driving in ground rods that makes that a fun project

 

[Cord]

I upgraded from a Hilti TE30 to a TE76 and I can't believe the difference in power. The bigger drill is a SDS max and it pounds 1/2" holes through concrete like you were drilling in wood. No joke. These are too expensive to buy new so try shopping on Craigslist or Ebay. Otherwise just rent the tool for a day.

 

[skylarkguy]

So do you guys think something like this would be sufficient...

Makita 8-Amp 1 in. SDS-Plus AVT Rotary Hammer-HR2621 - The Home Depot
Milwaukee 7/8 in. SDS D-Handle Rotary Hammer-5262-21 - The Home Depot
Bosch Bulldog Extreme 1 in. Rotary Hammer-11255VSR - The Home Depot

Or move up to something like this...
Bosch 1-1/8 in. SDS-Plus Drop Down Rotary Hammer-RH328VC - The Home Depot

or this:
Milwaukee 1-1/8" Heavy Duty Corded Electric Rotary Hammer

I don't usually do the pawn shop route but could in this case.

 

[Cord]

My Hilti is a 15a unit; here are the specs for a similar model: https://www.us.hilti.com/drilling-&-demolition/combihammers/r1021424 You can always get by with something smaller, but as you have discovered it comes at the cost of time.

 

[EddieWalker]

For what you are doing, I would be careful about buying something too big and heavy. SDS Max is a lot more weight. For small holes, you really do not need all that extra power. There is a reason I have both a SDS and a SDS Max. One I use all the time, the other I only use when I absolutely have to.

 

[PILOON]

For sure a SDS max is the way to go.
We built a 60' X 200' barn for a client and engineers wanted structure "bolted down".
Two guys installed 200+ 6" x 1/2" expansion bolts in one day!
One worker would drill the hole followed by a second that installed them with an electric hammer drill and 1/2" body washers.
That hammer drill (a Hilti) never knew the difference between wood or concrete.

And, LOL, the Hilti was a $100. pawn shop purchase that included about 12 bits.
I still have it after some 15 years of tough usage.
I also obtained a 2 1/2" core bit for it that became very useful for sump exit hoses and occasional hydro installations.
B4 I used to rent Kango's but they always seemed to break down on the job. (might be due to rental lack of maintenance)

 

[NorEaster]

For prepping stem walls for sills we use a HR3210 from Makita, probably bigger than you need.

Expansion bolts are archaic compared to the Titan HD concrete screws made by Simpson. We don't even use J bolts anymore, it's easier to set the entire sill, tack in place with a ramset, and then drill and screw.

 

[dstig1]

My take is very similar to Eddies. An SDS is great for most uses (I think everything is labeled SDS-plus nowadays - that is what most people mean when they say SDS). The bits are easy to find at all decent hardware and home centers (Lowes/Menards/HD/etc), so that is a big plus. Bits aren't too expensive either, until you get into bigger sizes. You can also do things like getting a wide chisel and use it to pop loose tiles and mastic and stuff like that in hammer only mode (these typically have 3 modes - drill only, hammer and drill, and hammer only). When you need big power or, my favortie, driving ground rods, I just rent an SDS-Max for the day. They are pricey, and so are bits. SDS drills can be under $100 to 300, but the Max drills are $4-900, sometimes more. I bought a ground rod driver bit years ago (hard to find) and that is worth it's weight in gold, but it is an SDS-max only bit. Most holes you need will be in the sweet spot for the regular SDS drill. 1/2" in concrete is a perfect example for that. If you ever drill for Tapcons, you will be surprised how fast those tiny holes go in. ZIP!

 

[Tompet]

My take is very similar to Eddies. An SDS is great for most uses (I think everything is labeled SDS-plus nowadays - that is what most people mean when they say SDS). The bits are easy to find at all decent hardware and home centers (Lowes/Menards/HD/etc), so that is a big plus. Bits aren't too expensive either, until you get into bigger sizes. You can also do things like getting a wide chisel and use it to pop loose tiles and mastic and stuff like that in hammer only mode (these typically have 3 modes - drill only, hammer and drill, and hammer only). When you need big power or, my favortie, driving ground rods, I just rent an SDS-Max for the day. They are pricey, and so are bits. SDS drills can be under $100 to 300, but the Max drills are $4-900, sometimes more. I bought a ground rod driver bit years ago (hard to find) and that is worth it's weight in gold, but it is an SDS-max only bit. Most holes you need will be in the sweet spot for the regular SDS drill. 1/2" in concrete is a perfect example for that. If you ever drill for Tapcons, you will be surprised how fast those tiny holes go in. ZIP!

Good description. I bought this Makita in 2010 and it is very solid. This is a pretty good price on the same one with the included grinder. You can find it for a less online w/o grinder. The short overall length of this style vs straight d handle style works well in tight positions and it is pretty light. As stated above make sure it has all three modes including hammer only.

Makita 1-1/8 in. SDS-Plus Rotary Hammer with 7.5-Amp 4-1/2 in. Angle Grinder-HR2811FX - The Home Depot

 

[ultrarunner]

Did exactly what you are doing about 15 years ago and bought a Bosch Bulldog SDS hammer drill... it was like butter drilling.

Also bought the right angle attachment because some places had almost no clearance.... not quite as effective in that it was slower.

Drilled thousands of holes with that little SDS and still going strong... 1/2 is right in the middle of capacity or 7/8 listed

Here is a similar model rated at 1"

11255VSR 1" SDS-plusｮ BULLDOG Xtreme Rotary Hammer | Bosch Power Tools

I also have larger Hammer Drills... but for retrofit... the small SDS can't be beat.

 

[skylarkguy]

Thanks for the suggestions.

To button this up i found a used milwaukee model 5303-2 11/8 rotary hammer.

I installed 20 brackets in half the time it took to put in 8 with the hammer drill. The holes were not only faster but straighter and cleaner. Probably the best $50 i ever spent.

I still have 5 more to install but first have to figure out how to squeeze myself through a small passage.