Can the concrete around a hot tub be coated, and what does it need that a patio does not?
Yes. The surround takes the same kind of system as pool deck and patio coating, a UV-stable aliphatic coating over ground concrete, with grit broadcast into the top coat. What the tub adds is how the slab gets used. The feet on it are bare and wet, and its busiest month is January.
The system itself is usually polyaspartic or polyurea over a primer, the same family a pool deck gets in a warmer town. The decisions particular to a tub come after the chemistry, in how coarse the texture is, which top coat goes on the splash side, and where the water from the tub ends up.
Most of that happens in a strip a few feet wide. The ring of concrete right beside the tub takes the splash and the drain water, and the path to the back door takes the footprints. The rest of the patio is coated like any other patio.
How much grip does a wet slab need under bare feet in January?
More than a garage floor and less than a sidewalk. A coated surround gets a fine aggregate broadcast into the top coat, or a flake floor with a textured clear over it, so a wet foot holds on it. The trade is comfort and cleaning. A coarser grit grips better, feels rougher on bare skin, and holds more grime in its texture.
On a tub surround the usual answer is a finer grit than a front step gets and a little more than a covered porch gets. Stand on a sample with bare feet before it is chosen. Nobody walks a garage barefoot, so the texture spec written for one is the wrong starting point here. The garage version of the slip question, a clear coat with no grit in it, is covered in the guide to the downsides of an epoxy garage floor.
One honest limit. No coating grips ice. The texture is for a wet surface, and once the water on it freezes the slab is as slick as any other. Look at the walk back from the tub on a cold night. The wet footprints between the tub and the door are a line of ice ovals by the time anyone goes out again, coated or not. Snow and ice on a surround still get cleared.
What does splashed tub water do to bare, sealed and coated concrete?
Tub water lands on the same strip of concrete every time someone climbs in or out, and it carries chlorine or bromine with it. On bare concrete it soaks in and dries to a pale crust along the edge. A sealed slab beads it off until the sealer wears thin. A coating keeps it on the surface, where a hose takes it off.
The pattern is easy to find on an older surround. There is a drip line on the side people climb out on, darker than the rest of the slab when it is wet and chalky when it dries, and it often starts to scale before any other part of the patio. That band is where bare concrete takes the most water, and the treated water drying in it over and over leaves its residue in the pores each time.
A coated surround handles that splash with its top coat, and the top coat is picked for it the way a pool deck’s is. An aliphatic finish chosen for pool water holds up to repeated splashing and drying, and the texture in it is set so the residue rinses out instead of building up. Rinsing the splash side with plain water now and then, mostly in summer when the tub gets used with the cover off for hours, keeps it that way.
Where does the water go when the tub is drained or the cover comes off?
Wherever the slab sends it. A full drain empties the tub onto the yard a few times a year, and every time the cover folds back in winter, the snow on it slides off one side in a heap. Both land right beside the tub. If the concrete there dips instead of falling away from the house, that dip is an ice sheet by evening.
The drain is the easier one to control. A hose run off the edge of the slab to the lawn or a drain sends the water where it can soak away, and a hose left lying across the patio sends it across the coating, down whatever slope the concrete has, and often toward the foundation.
The cover is harder. It lifts the same way every time, so the snow it sheds piles up on the same few square feet all winter. That pile melts a little in the afternoon sun and refreezes at night, which is how one corner of a surround turns into a skating rink while the rest of the patio is dry. Shovel the pile away from the tub after the cover comes off, and keep that corner in mind when the slab is measured.
A surround that holds a puddle after a hose test has a slope problem, and a coating will not fix it. A film on top of a low spot holds the water the same way the bare concrete did. The slope gets sorted first, falling away from the house and off the slab, and then the coating goes on.
What about the shoveled path from the back door?
Coat it in the same visit as the surround. It carries the same wet bare feet all the way to the door. After that a coated path takes a plastic blade, a push broom and a light hand with de-icer for as many winters as the coating lasts. It does not take a steel shovel edge scraped across it every morning or ice chipped off with a spade. Those are the habits that gouge any film, and every gouge is a place for water to get under it.
The path from the back door to the tub gets cleared after every snowfall, often in the dark and often in a hurry. A few habits keep it in good shape:
- A shovel with a plastic blade or a plastic wear strip, never bare steel
- Clearing before the snow is packed down, so nothing needs chipping
- Sand or a thin scatter of de-icer on a glazed patch, swept off once it has melted
- Shoveled snow thrown onto the yard, not piled at the edge of the path where it melts back across it
De-icer is mostly a question of how much and how long it sits. A thin scatter swept off after it has done its work is a small thing on a good top coat. A heavy layer left to dry into a crust, day after day, is the same problem the garage floor has with mag chloride and a coated floor, outdoors. Rock salt also feels like gravel under a bare foot.
When can the surround be coated if the tub runs all winter?
In spring. Exterior coatings here go down between May and September, and the tub stays in service until then. Fall is the time to measure the surround, get the spring date in writing, and put a penetrating sealer on the bare concrete before the snow if the forecast still allows it.
That sealer is a stopgap. It slows the water and the splash down through one more winter, and the coating goes over the slab after a grind in spring. The details of sealing concrete before the first freeze are the same on a surround as on a driveway.
Whether the tub stays where it is and the coating is finished up to its skirt, or the tub is moved so the concrete under it gets coated too, is settled at the measure. Most of the time it stays put. Either way the tub is drained and its water sent somewhere other than the fresh coating.
Exterior coatings run $7 - $11 per square foot installed, with the slip texture and the top coat included. A surround of a few feet around a small tub can come in under the $1,200 minimum on its own, which is why the path to the back door and the rest of the patio usually go on the same spring visit.