# Painting a 40 year old basement floor



## ric knows paint (Oct 26, 2011)

polarzak said:


> The workshop cement floor in my basement was painted with, I am assuming, an oil based paint some 40 years ago when the house was built. I want to repaint the floor. The existing paint is not flaking, and it good shape except for normal wear and tear. The floor is very dry.
> I went to my big box store and was told all I need to do was to wash it well with TSP and paint it with a later porch/floor paint.
> 1. Will TSP etch paint? I have read that the paint needs etching for anything to stick to it.
> 2. I always understood latex would not stick to oil based paints. Is this so?
> ...


Hiya Polarzak,

If that floor has been painted for 40 years, you're probably right that it is an oil based product. As long as the latex floor enamel is of high quality, you'll have no problem applying over an existing oil coating (that is assuming the floor is exposed to normal traffic - no tow-motors, hard-wheeled pallet jacks etc.). 

I would recommend a slightly different surface prep though. TSP is a very good detergent cleaner and, if mixed to a strong enough solution, it could etch paint - I wouldn't mix it that strong though...nor would I use TSP in this application. I'd recommend washing the floor with a non-sudsing detergent (such as Soilax or Dirtex Powder), because these products are non-sudsing, unlike TSP, they leave no residue and a clean water rinse is not necessary. These detergents aren't as strong as TSP, but the purpose for a detergent wash is to simply clean the floor, not etch it. Since it's difficult to rinse a floor thoroughly (mopping with clean water doesn't cut it), it's best to use a detergent that requires no rinse and won't contribute to mildew growth (as TSP can).

Because the finish has been on the floor for 40 years, and most probably alkyd (oil), the remains of that finish has to be really hard and slick...For best results (whether you use oil or latex), you should sand the floor using a pole sander and medium grade paper - you don't need to remove the finish, just create a profile for a better mechanical bond. After sanding, vacuum to remove any sanding dust and apply 2 coats of high quality acrylic according to mfrs. directions. 

BTW, 40 years ago, that may have been a truer statement regarding the "latex over oil, oil over latex" discussion...Not so true anymore. Acrylics (today's latexes) are so advanced over latex products of the past with much greater durability and superior adhesion (even when compared to oils) - not to mention other advantages when compared to oils (alkyds) such as ease of application, more environmentally friendly, easier to re-coat, usually less expensive, less apt to harbor mold/mildew growth, better UV resistance, etc. You'll be good with this system.


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## user1007 (Sep 23, 2009)

If it is a painted concrete floor and has lasted 40 years it is likely NOT alkyd or oil based paint on there. The alkalinity in the concrete would have caused it to fail ages ago. Apply a good urethane reinforced latex/acrylic floor paint and you should be good to go. Obviously you want it spotlessly clean before you apply.


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## polarzak (Dec 1, 2008)

ric knows paint said:


> Hiya Polarzak,
> You'll be good with this system.


Thanks ric. Very good information.


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## polarzak (Dec 1, 2008)

sdsester said:


> If it is a painted concrete floor and has lasted 40 years it is likely NOT alkyd or oil based paint on there.


Thanks sdsester. 
Latex then...on a cement basement floor...in 1969? It sure doesn't "look" or "feel" like latex. I am no paint expert though.


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## ric knows paint (Oct 26, 2011)

polarzak said:


> Thanks sdsester.
> Latex then...on a cement basement floor...in 1969? It sure doesn't "look" or "feel" like latex. I am no paint expert though.


Hey Polar...

Latex floor paints were around in 1969, but again, they weren't anywhere near the same product as today's acrylics. Not that it really matters (to repaint, the procedure and recommendation would be the same), but it wouldn't be unusual at all for an oil/alkyd to last 40 years (or longer) even on a concrete floor. What SDSester said about alkalinity might be true if moisture were a constant, continual problem in your basement. You said the floor was dry - alkalinity will really only wreak havoc on a system when moisture (ground moisture in this case) is present beyond just the occasional or incidental exposure. 

SD did make a good point about urethane modification though - most of your quality lines of acrylic floor enamels will be modified with urethane or epoxy - this modification adds an element of hardness and/or resiliency that is not so common with just a straight acrylic. This modification also provides a scoche more resistance to moisture and chemical exposure (chemicals = _mild_ household cleaners and solvents) than a straight acrylic would. Good luck, you'll enjoy working with these acrylic products.


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## polarzak (Dec 1, 2008)

Thanks ric. The basement is dry as a bone, as they say. Thanks so much for your help.
Thanks to all. Happy Holidays.


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## mustangmike3789 (Apr 10, 2011)

sdsester said:


> if it is a painted concrete floor and has lasted 40 years it is likely not alkyd or oil based paint on there. The alkalinity in the concrete would have caused it to fail ages ago. apply a good urethane reinforced latex/acrylic floor paint and you should be good to go. Obviously you want it spotlessly clean before you apply.


very good point. I also feel that it is not an oil/alkyd based coating. Oxadative cure coatings should not be applied over alkaline surfaces such as concrete or over a zinc coating such as inorganic zinc or hot dipped galvanizing because they can soponify. Soponification happens when the oils in oxygen cure coatings react with alkali and form soap (lye soap)and usually disbond from the substraight immediately. Many alkyds produced today are modified alkyds and may be more resistant to soponification.


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## Brushjockey (Mar 8, 2011)

I don't agree with the guys above- if it wasn't oil- what else could it be at the time? 
But nonetheless- the prep and finishing is the same- to which I will add- vacuum before washing- vacuum after washing, and then vacuum again. It is amazing how little stuff will remain and get in your finish.
In this situation i have used with great success Ben Moores Latex epoxy modified porch and floor paint. it is a strong hard finish- but not glossy, kind of an eggshell finish.
And if you ever have any wear down, chip off- easy to touch up if needed.


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