Clean Garage Floor Prior to Paint?

[Bob B.]

Hi all,

I want to paint my concrete garage floor and have cleaned it a couple of times with garage floor detergent and a steam cleaner. However, there are still some darker spots where oil has spilled in the past. I am afraid the paint will lift if I paint over the spots. Can anyone recommend something to clean these spots or am I overcautious?

Thanks,

Bob

[Chuck S.]

Re: Clean Garage Floor Prior to Paint?

Bob, I wouldn't even consider painting a garage floor without first using muriatic acid to etch the surface. Ideally, you would do this BEFORE you cleaned with detergent...the alkalinity of the detergent would neutralize any acidity remaining in the concrete.

I remember John H describing the floor coating in his new garage shop some time back...I believe the contractor prepped the new clean concrete floorby blasting it with steel shot. It appears the archives are back on; take a look, there's some good info there.

[Gary S.]

Re: Clean Garage Floor Prior to Paint?

Bob,
As Chuck mentioned, cleaning your floor with a heavy duty detergent is the LEAST you should do. I have been reading as much as I can on the various floor systems and they all require some form of floor preparation to remove the oil and other liquid stains that we get. First, I would figure out which product you want to use, then I would figure out how to prep the floor. Most of the products I have looked at will need muriatic acid or something similar. Of course, each manufacturer will have his own instructions.

Again, as Chuck said, John's garage floor article was quite thorough.

Gary

[Bob B.]

Re: Clean Garage Floor Prior to Paint?

Thanks for the tips! I have muriatic acid. Is there a preferred dilution ratio and application method? - Bob

[Gary S.]

Re: Clean Garage Floor Prior to Paint?

Is there a preferred dilution ratio and application method? - Bob

Bob, I can't emphasize enough that the directions of the individual floor covering manufacturer should be your guidelines. ANY acid can be nasty stuff.

[Gary C.]

Re: Clean Garage Floor Prior to Paint?

Bob, here's article I wrote for the Texas Chapter on floor epoxy. Many other members such as John Hinckley and Kent Keech epoxied their shop floors. Good luck, Gary....

[Bob B.]

Re: Clean Garage Floor Prior to Paint?

Thanks, Gary, great article! - Bob

[Grant M.]

Re: Clean Garage Floor Prior to Paint?

Bob,

There's a web site for Precision Epoxy Products out of Douglasville, GA that has a number of application step-by-step articles and prep tips for their floor coating products (the ones John Hinckley had used on his floor--he had it professionally applied, though). I have already bought the materials from Precision and am awaiting the (Ottawa) weather to warm sufficiently before applying it. The owner at Precision recommended BOTH muriatic acid etching as well as steel shot blasting for the best preparation. Precision also offers its own compatible crack filler product.

BTW, another important aspect of coating garage floors is the question of what's underneath them and how much moisture passage occurs. On John's and others' advice I had my floor poured over rigid foam insulation and foil vapour barrier, and I have no moisture penetration issues at present.

Good luck with your floor!

grant

[Mike G.]

Re: Clean Garage Floor Prior to Paint?

the guys that did the epoxy floors at my office did a few things first. some areas got an acid wash. others they rented a shot blaster and went over the floors. in the power house they used a floor sander like the one you rent to sand hard wood floors.

[Chuck S.]

Re: Clean Garage Floor Prior to Paint?

...The owner at Precision recommended BOTH muriatic acid etching as well as steel shot blasting for the best preparation...

Normally, Grant, I don't question the recommendations of people who sell the materials, but frankly, doing both muriatic etch and shot blasting seems way over the top.

Muriatic etch would fall in the category of "good" prep; shot blasting is in the category of "superior" prep, providing a very rough substrate suface for adhesion. Depending on the blasting technique and the number of coats, I doubt the paint will even completely fill shot blasted texture on concrete. If you have the means and access to have it shot blasted, I would skip the muriatic acid etch for two reasons (1) if acid is introduced, you must neutralize it before painting, and (2) you avoid soaking the concrete with water that must be allowed to dry thoroughly before painting.

[Grant M.]

Re: Clean Garage Floor Prior to Paint?

Chuck,

I agree with your perspective on overdoing it, and will not likely do both myself; I'll probably just have the floor shot blasted. As to the paint filling the co**** texture, Pecision Epoxy's product "system" requires an application of sand after one of the primer laters which is subsequently machine sanded and vacucumed to remove the excess, before the two colour coats are applied. Lots of work, but it seems to produce a superior result.

I used just muriatic acid etch on the basement floor in my previous house and had problems thereafter with adhesion of the paint.

[Joe T.]

Re: Clean Garage Floor Prior to Paint?

Why Paint? Has anyone tried those "overlayment" tile solutions that use no adhesive, just snap together?

[Tom S.]

Re: Clean Garage Floor Prior to Paint?

I have had really good luck with stain.I pressure wash the floor first.Then I wash the floor with a solution of 3 parts water to 1 part acid.Wash it again, let it dry for a couple days and good to go. I have had no lifting problems, to tire marks nothing.I would not use any kind of paint, been there done that, it does not work! Tom

[John H.]

Re: Clean Garage Floor Prior to Paint?

I don't know of ANY "garage floor paint" that will last more than a month or two, especially if there is no moisture barrier under the slab. Moisture migration through the slab will affect any coating, whether it's paint or professionally-applied epoxy.

I spent the money to put down a 10-mil poly moisture barrier first, then 4x8 sheets of 5/8"-thick high-density closed-cell foam with heavy foil on both sides before my slab was poured, so I'd have an impenetrable moisture barrier plus insulation under the slab.

Eight years later, the solvent-based industrial epoxy floor (you DON'T want the cheaper water-based epoxy) still looks like it was poured yesterday, and it's warm and dry all winter long.

You'll find a wealth of information on all the floor coatings (and alternatives like VCT tile and RaceDeck), preparation procedures, results, tips, hints, and problems in the "Flooring" section at www.garagejournal.com .

[Larry S.]

Re: Clean Garage Floor Prior to Paint?

Stain is the only way to go. With paint you get maybe three color choices, and none of them is anything to brag about. Paint may adhere if there's perfect prepping and you get lucky. With stain, just wash the concrete, let it dry, and put it on. I've never met a car that didn't leak something, either engine oil, transmission fluid, or coolant, and it stands out like a sore thumb on paint; it's not nearly as noticeable on stain, and neither are hot tire marks.