One-Part vs Two-Part Water-Based Polyurethane: Which One a Recoat Needs

What 'one-part' and 'two-part' mean

• The water leaves. About a third of the gallon is solids. The rest is mostly water, and it evaporates as the coat dries.
• The resin fuses. The resin particles join into one clear film across the floor.
• The crosslinker locks it. Part B ties that film together into a hard network. That is why a two-part finish cures hard instead of just drying.

A one-part finish comes ready to use. You open the can, stir it and roll it on. As the water evaporates, the resin particles fuse into a clear film. Nothing else happens after that. The film is as hard as it will ever be once it has dried.

A two-part finish comes as two containers. Part A is the finish itself, in the gallon. Part B is a small bottle of crosslinker that you pour into the gallon on the job, right before the coat goes down. With FloorIt Two-Part Finish it is 1 ounce of crosslinker per gallon, so there is nothing to measure.

Once the two parts are mixed, the finish cures in three steps.

Dries vs cures: what it means on a real floor

• Abrasion: 45 mg lost after 1,000 cycles on a Taber abrasion test. That is about the weight of a couple of grains of rice ground away by 1,000 turns of abrasive wheels. Less lost means tougher.
• Hardness: 90 on the Koenig scale. A hard coat that resists scratches and scuffs.
• Rating: commercial grade, rated for homes, businesses and sport floors.

A one-part finish has no hardener, so it stays softer. You can often chip it with a fingernail. In the busiest walkways, from the front door to the kitchen and in front of the couch, it wears through sooner.

A two-part finish is built for that wear. FloorIt Two-Part Finish has these numbers on its data sheet:

Oil-modified one-part finishes and yellowing

Some one-part water-based finishes are oil-modified. Even some pro lines are one-part, oil-modified polyurethanes. That is a one-part finish with no crosslinker.

Oil-modified finishes can amber over time. On a honey oak floor nobody may notice. On a light, gray or natural floor, the homeowner notices, and they remember who put it down.

FloorIt Two-Part Finish is non-yellowing. It stays clear for the life of the coat, so light and gray floors stay the color the homeowner picked.

Two-part is a class of finish, not a brand

Do not mix up 'two-part' with one brand. The big-brand pro finishes are two-part too, and they are good. Two-part finishes are the class the pros use. They go through flooring suppliers, not the shelf next to the mop at the big-box store.

So when you compare two-part finishes, compare them on their own published numbers. The big-brand pro finish's data sheet lists 350 to 400 square feet a gallon. FloorIt Two-Part Finish covers 500 to 600, so a gallon goes about 50% further. It lists 0.5 for slip resistance. Ours tested at 0.87. At the partner price, ours runs about 24 cents a square foot per coat against about 30 to 43 cents for the big-brand pro finish, about 40% less per foot.

None of that makes one two-part finish tougher than the other. The wear tests use different standards, so those numbers cannot be set side by side. What changes is what each coat costs you and how much floor a gallon covers.

• The full spec sheet for the finish

How to tell which one you are holding

Look for the second container. A two-part finish always comes with a separate crosslinker or hardener that goes into the gallon. A one-part finish has nothing to add.

Read the label and the data sheet. A two-part finish tells you how much Part B goes into each gallon and how long the mix stays usable. FloorIt Two-Part Finish stays usable for about 8 hours once it is mixed.

Where you bought it is a clue too. Big-box stores mostly sell one-part finishes, plus polishes and restorers, which are not a finish at all. Pro two-part finishes go through flooring suppliers.

What a two-part finish asks of you

• Mix only what the job needs. Once mixed, the clock is running, and leftovers harden in the container.
• Wear gloves and goggles when you pour in the crosslinker. Part B is the hazardous part of the product until it is mixed in.
• Never pour leftover mixed finish down a drain. Let it harden in an open container outside, then throw it out as solid waste where your local rules allow.

A two-part finish is one more step on job day, and it asks for respect.

Which one a recoat business should carry

A homeowner pays you to make the floor look right and stay that way. A soft coat that wears through in the hallway in a short time turns into a callback. A callback costs you a day of work and maybe a review.

A two-part finish also bonds into the old finish after the floor is screened, so it becomes part of the floor instead of a layer sitting on top. Because it bonds to the finish layer and not to the wood, the same product recoats solid hardwood, engineered, factory-prefinished floors and LVP. That is one finish in the van instead of several.

That is why FloorIt partners use FloorIt Two-Part Finish, a two-part, water-based urethane, on every recoat.

• More on two-part, water-based polyurethane

Common questions

Is two-part water-based polyurethane harder to apply than one-part? It is one more step: pour the crosslinker into the gallon, shake it and let it rest. After that it rolls on the same way. FloorIt Two-Part Finish takes 1 ounce of crosslinker per gallon, so there is nothing to measure.

Can you put a two-part finish over an old one-part finish? Yes, if the old finish is cured, clean and free of wax and polish. Screen it until the whole floor is evenly dull and the dust comes off as a fine white powder. That powder means a cured finish the new coat can bond to.

Does two-part water-based polyurethane turn yellow? FloorIt Two-Part Finish is non-yellowing and stays clear. Oil-modified finishes are the ones that can amber over time.

Is a two-part floor finish the same as epoxy? No. Epoxy is for concrete and garages. A two-part floor finish like this one is a water-based urethane with a crosslinker, the family of finishes flooring pros use on wood.