Buying a grinder versus renting a shot blaster

[Git]

I am still in the planning stage of refinishing my 3 stall garage.

It appears that the best surface prep is achieved by the use of a shot blaster? I called around and only one rental place in the area has one and the cost is $350 per day plus another $70 or so for the media.

I hate renting tools and would rather buy something that I will still have when the job is over, even if it takes me more work - as long as I can get consistent results. (I own a Bosch "Brute" electric jack hammer - but that is another story)

So, can I get good results if I buy a Bosch 1773AK for about the same price as the shot blaster rental?

or

 

[GeorgiaHybrid]

That's an easy one, buy the shot blaster...

With times like they are, have you checked on a price to have someone come out and shotblast it for you? There are a LOT of guys right now that will work cheaply to put some food on the table. I know that at our shop we are back to prices from the early 80's on our work.

No worries, it's done and you don't get tired at all.

 

[AlphaGarage]

If you're one of those guys who looks at the cost of renting, or hiring, then think "Gee - for that cost I could buy the tools, do it myself, and have the tool for other jobs..." Then yes, a 7" grinder will work. But it will take more than just a couple of hours.

If the floor is somewhat smooth, and without any issues, it's pretty straight forward to use a angle grinder with a good diamond cup and prep. I hate to give a time frame, but I'd plan on two days. Those aren't full days, no way would I want to spend a full 8 hours grinding a floor!

I don't have any experience with the Bosch. A flooring contractor I know who's pretty thorough in his tool selection swears by the Matabo 7" grinders.

But -make no mistake about this - a shot blaster or walk behind grinder will be easier, but the results of hand grinding can be equal or better.


FYI:

These projects were done with hand held angle grinders:
http://www.garagejournal.com/forum/showthread.php?t=13347
http://www.garagejournal.com/forum/showthread.php?t=26308

 

[Git]

If you're one of those guys who looks at the cost of renting, or hiring, then think "Gee - for that cost I could buy the tools, do it myself, and have the tool for other jobs..."

Ya, that's me for sure. I don't mind the extra work, now that I am retired - it's a good way of justifying my tool habit...

But honey, look at all the money I saved by doing it myself...

 

[AlphaGarage]

Ya, that's me for sure. I don't mind the extra work, now that I am retired - it's a good way of justifying my tool habit...

But honey, look at all the money I saved by doing it myself...

That sounds familiar! I just need to walk in with the tool and say, "But Honey" and the wife kicks in "yeah I know, look at all the money we'll save."

 

[boiler7904]

If you're one of those guys who looks at the cost of renting, or hiring, then think "Gee - for that cost I could buy the tools, do it myself, and have the tool for other jobs..."

Ya, that's me for sure. I don't mind the extra work, now that I am retired - it's a good way of justifying my tool habit...

But honey, look at all the money I saved by doing it myself...

A lot of guys on this board are that way including me. We wanted to tear out our builder special patio last year and install Unilock pavers and a seating wall. After crunching the numbers; permit fees, materials, plate compactor rental (no one had a good used for sale at the right price), and dumpster fees were about $3,500. Tool purchases including a 14' masonry cut off saw were another $500 give or take. Add in 7 weeks of my time on nights and weekends from May to July and we ended up with a great patio that we love. Neighbors all thought I was nuts for the amount of work to get it done the way we wanted it.

I bought a Milwaukee 14' electric cut off saw. It was a little slower than a gas unit but my cost to buy it was the same as three days rental and there is no way I would have been done in 3 days.

Guy down the street hired a local landscaper to do something similar a couple of months after we were done and spent almost $13,000 but it was done in less than a week.

My problem is that the next house we live in I'll have to do something bigger and better to keep the wife happy.

 

[AlphaGarage]

...we ended up with a great patio that we love.

Mmmm... Pics?

 

[Sebastian]

Git, I did both. My floor had latex paint on 2/3rds or 400 sq feet.

I tried the angle grinder first with the diamond bit. Yes it worked - but it kicked up alot of dust and was slow and painfull. I took me about 4 hours to about 40 square feet. My results with the angled grinder were not consistent, lots of swirls and edges - this is due to my inexperience with the tool and the tedious nature of this process. This was backbreaking work.

A friend convinced me to rent the shot blaster. I rented the tool from Home Depot for about $150 and purchased one bucket of SS shot for about $30. - I rented the tool for 4 hours - it would have cost more if I did a 24 hour rental. I did not rent the vacuum, I attached the machine to my shop vacuum and it worked fine.

The shot blaster got the rest of the garage done in 2 hours. The results were perfect and consistent, I did not get any marring or unexpected cuts. It was perfect and I wish I had rented it sooner.

I had never used a blaster before, it was not that diffucult. Make sure you were eye protection, occassional shot will bounce off the floor and hit you in the face.

I did use the angle grinder to clean up all the edges around the periminter, it is a nice tool to own. I bought a Dewalt on sale for about $70. The diamond bit I bought was from Harbor Freight - about $30.

 

[Sebastian]

Forgot to mention, I did get a qoute from a contractor to prep my floor for epoxy - about a $1 per foot! So about $700 for my garage. I am certain I did a better job since I went over every inch of the garage myself.

Dont have any pics of the floor before epoxy but, here is an after pic.

This is a residential garage, I am still moving in...

 

[Git]

Sebastion - that looks really nice, I will have to look into a rental from Home Depot

I hired the wrong contractor and ended up having to demo 22 tons of mostly concrete debris due to improper footing, lack of rebar, etc. (I had to pay the dumpster rental company by the ton, so unfortunately, I know exactly how much it all weighed)

That why I ended up buying the Bosch Brute - in the pic, that was suppose to be a wood burning fireplace which called for a 10' x 10' pad that was 18" thick (it wasn't)

 

[Sebastian]

Ouch... Good luck!

 

[djs]

I could not get the blaster to give consistant results when I did my floor, maybe it was the blaster itself??

I ended up renting a concrete planer with carbide teeth on it that could be adjusted up and down, after a bit of adjustment I set it to barely scuff the floor surface.
It was enough to get the epoxy to adhere to and it took me ~1 hr or so to do 2400sf.

And was half as much as the blaster was.

 

[PoPo]

I just stopped by the local Lowes tonight and talked with a guy about renting their sander, he said it was $37 per day for their floor sander. Sounds like a deal to me.

Definately look into local hardware stores for the rentals.

 

[FFPL]

I bought one of these and it performs very nicely. I think it was well worth the investment although get one of those knee pads, they will thank you.

I did my floor
http://www.garagejournal.com/forum/showthread.php?t=13347

and my neighbors
http://www.garagejournal.com/forum/showthread.php?t=20542

and lent it to another work mate for his. Who didn't post his floor here.

And you can have extra fun and do your walls as well

 

[Git]

FFPL - did you have to buy any other grinding wheels with the Bosch, or does the one that comes with it work fine?

 

[FFPL]

FFPL - did you have to buy any other grinding wheels with the Bosch, or does the one that comes with it work fine?

I used the DC510 wheels. It came with 1 of these in the kit and I subsequently ordered another. There are probably some other brands you can also use but I stuck with Bosch.

 

[Sebastian]

Alpha - the Home Depot shot blaster I rented had what looked like a Matabo grinder as the guts to the machine.

 

[Markgyver]

I work with contractors that do concrete restoration and they will always use a shot blaster for this application I have see grinders used and you can see the gouges in the concrete left from the grinder. The shot blast media is recycleable also.

 

[boiler7904]

Mmmm... Pics?

I'm at work for a few more hours but I have some at home. Would rather not hijack this thread with them though so I can PM a couple to you.

 

[Markgyver]

Also a grider will polish the surface where a shot blaster will open the pours up for a better epoxy bond.

 

[AlphaGarage]

A grinder MAY polish, it all depends on the disc attached.

Helped with a floor a couple of months ago - 2 head Edco with DymaCerts. Removed what was left of an old cheap epoxy coating and knocked down a few high spots. Good rough finish when completed.

 

[Git]

I stopped by my local Home Depot this morning and took a look at their tool rental section.

They do have a Blastrac 8" shot blaster that rents for $150 a day. A couple of bags of shot would be around $60. This is far cheaper then the $400+ for renting the machine at United Rentals.

Not sure what I am going to do now, but at least I have a couple of months until it starts cooling off to think about it

 

[Sebastian]

Git, for my 3 car garage I only used one bucket of shot. You can reuse the shot as go, you get a magnetic broom with the rental and follow behind the blaster - you pick up the shot and reuse it as you go. I also reused the shot that I picked up in my shop vac - just pulled it out with the magnetic broom.

I agree with Alpha, when I tried the grinder I did try different wheels and the only one that actually ground the concrete was the diamond cup wheel.

 

[Irondrive]

You may want to call a few pro installers who have diamond grinders/shot blasters. There is a good chance they may have time to come prep your floor. I do this every now and then for homeowners who don't want to go through the hassle of what you are going through.
The bigger and faster their machines are, the lower the cost will be.

 

[AlphaGarage]

Here's a pic with the four things that will make the job go real quick and easy... A ride along shotblaster, a magnetic broom to collect wayward shot, and two guys to operate them.

But with the choices you have I'd go with either renting the shot blaster, or picking up a nice 7" angle grinder. If the Bosch comes with the wheel - all the better, FFPLs space, along with the walls and the sculpting he did, is easily twice the area you'll face, so one wheel will probably do the entire job.

Both methods will adequately prep the floor, so it comes down to how much time and wear and tear on the body is worth having a angle grinder in the tool bin when the job's done.

btw The pic is from a Motor City project that was interesting to say the least. Can't talk about it for now - but there will be film at eleven, or nine central.

 

[Irondrive]

Here's a photo of what a pro installer may have that can help you out. You can get a 3 car garage prepped in less than 2 hours, +/- depending on hardness.

 

[Irondrive]

BTW, I'm not trolling for business, grinding for DIYers is not high on my list of things to do, just trying to help. I admire all you guys for doing your research.

 

[B&H]

I just went through this deal myself. I have a customer of mine (I own a small auto repair shop) that works for a large flooring company. They mostly do floor coatings in food/bev plants across the country. After the cure and seal didn't "make the program" on my new concrete floor, I decided to hire him and one other person on the side to do an epoxy coating.

Their thoughts on shot blasting vs diamond grinding was that sometimes after shot blasting, you have to grind anyway to get rid of the corn rows, and that blasting near edges still required edge work afterwards. Also, depending on what's on the floor, shot blasting would be difficult to remove it. In my case, there were areas where gas had taken up and moved into a pile, old sealer. The thick sealer is difficult to remove with a shot blaster because it is rubbery (ever try to sandblast something with grease on it?).

Anyway, they charge by the square foot, and I didn't have to rent a shot blaster (twice, as we had to split the shop in half to keep the business open).

I don't think there is a right or wrong answer here. It all depends on the conditions and factors at each job.

 

[Jaguar Fan]

That sounds familiar! I just need to walk in with the tool and say, "But Honey" and the wife kicks in "yeah I know, look at all the money we'll save."

My 17 year old daughter saves me a ton of money every time she goes clothes shopping. If I only had a dollar for each of my dollars she "saved" on clothing...

 

[Jaguar Fan]

Here's a photo of what a pro installer may have that can help you out. You can get a 3 car garage prepped in less than 2 hours, +/- depending on hardness.

Hi Ironclad, what is that machine?

 

[Irondrive]

It's a Werkmaster Raptor 1600. Very pricey but it's FAST. I have only ground concrete with it no polishing etc. It's made in Canada so it's a bit of a hassle getting parts etc with customs and all that.

I'm checking out Kutrite and National for a second machine. I think I can live with it being slower to save $6K!

 

[drsifu]

i got a quote in San Diego for a contractor to come out and prep my 400 sq feet 2 car garage with stem walls for $500.00

he has not responded to my inquiries as to how he goes about prepping the floor, whether it is with a grinder or shot blaster.

but if with a shot blaster, does the price sound reasonable?

for those looking to rent, try to see if there is a Hertz rental near by. Home Depot rents out the Matobo grinder for $25-$40 for 4 hrs. Hertz will rent you the Bosch pictured above for $10 a day or $30 per week.

 

[Sebastian]

drsifu, I live in SD as well, the quote I got for prepping my floor was $700 for a 3 car garage.

 

[Irondrive]

The average in Az is about $1 sq ft. Labor appears to be cheaper here than in most parts of the country. I do it for less because my machine is pretty fast and there is virtually no hand work, as it gets to within 1/2" of the wall.

I hate to take $ out of contractors pockets but make him/her a reasonable offer. These days there are more holes in the schedule. A smaller chunk of something beats 100% of nothing. Some guys will tell you to take a hike, others need to make the truck payment due 10 days ago.

 

[drsifu]

the guy called back and he said they grind the floors. tried negotiating considering the economic times we are in, but he will not go lower in price.

so i am very tempted to rent a grinder for $30/week, buy a diamond cup and use my shop vac to prep my garage.

 

[Docklobster]

Not to hijack the thread but I am also in San Diego and hoping to start my floor next week. I have been debating renting the concrete grinder versus buying a 7" angle grinder as well. I have 400 sq/ft plus stem walls. Wonder if there is a way to split the cost of a rental and do 3 floors in a day???