We are obviously not neutral here, so let us start with the part that works against us: there are situations where the kit from the hardware store is the correct purchase, and we will name them.
What is actually in a kit
A typical garage floor kit contains a two part epoxy at fairly low solids content, a bag of decorative flake, an acid etch solution, a stir stick and a roller cover. Some include a small quantity of clear topcoat.
What it does not contain, and cannot, is the thing that decides whether the floor survives: mechanical preparation. The kit substitutes acid etching for grinding, because you cannot put a planetary grinder in a box.
What that substitution costs
Acid etching roughens the very top of the surface and leaves residue that has to be neutralised and rinsed completely. It does not open the concrete anywhere near the profile a coating needs. On a slab that has been power troweled, which describes most garage floors, it barely registers.
So the coating sits on the surface rather than keying into it. It looks correct on day one and usually still looks correct after a season or two. Then it starts lifting at the edges, along the door line, and anywhere water finds its way under.
The second issue is film thickness. A kit spread across a two car garage goes down thin, and thin epoxy is where most hot tire pickup actually comes from.
When the kit is the right answer
A sound slab in a dry space you are not precious about. A basement storage room, a shed, a workshop floor that is going under a bench anyway.
A short horizon. You are selling next year, or the garage is coming down, or you want it to look better this weekend for a hundred dollars.
You enjoy this kind of work. Some people do, and on a small, simple, well prepared floor a careful DIY job can look genuinely good.
In all three cases buying the kit is rational and we would tell you so.
When it is not
A two car garage you intend to keep. The labor to grind off a failed coating later is real money, spent on undoing rather than on building.
A basement with unknown moisture. The can cannot tell you what your slab is doing, and vapor drive lifts a coating from underneath no matter how carefully it was rolled on.
Anywhere with an existing coating. Removing the old one is grinding work, which is exactly where the kit route ends.
Any exterior slab. Epoxy ambers in sunlight, and a yellowed patio looks worse than the concrete it replaced.
The honest cost comparison
The kit is roughly a hundred dollars and a weekend. A professional install on the same garage is a few thousand and one day.
That is not a small gap. If the kit lasts you five years it was excellent value. If it fails in two and has to be ground off before anything else can go down, it was the most expensive option on the table.
Related
- Why coatings peel, which is this argument in full
- What a professional install costs here, published rather than hidden
- Hot tire pickup, which is largely a thin film problem
Reference
The gap between etching and grinding is not a matter of opinion. The concrete surface profile scale, CSP 1 to 10, is defined in Guideline 310.2R by the International Concrete Repair Institute, and manufacturers specify a minimum profile that acid etching does not reach.