Polished concrete can look incredible in wetrooms, walk-in showers, and spa spaces — offering a seamless, durable, and water-resistant finish. But polishing concrete for wet areas isn't the same as polishing standard floors. Extra attention is needed to ensure the surface stays slip-safe, moisture-resistant, and long-lasting under constant exposure to water. In this guide, we’ll show you how to polish a wetroom concrete floor properly — for safety, beauty, and durability.
Before polishing, verify that the slab is dry and properly cured. Wetrooms often have concrete installed over waterproof membranes or sloped surfaces. Use moisture meters (Tramex or similar) to test moisture vapor emission rates (MVER). Ideally, MVER should be below 3lbs/1000 sq ft/24 hours for sealing success. Check for cracking, movement joints, or signs of poor installation that could allow water ingress later. A sound, properly cured slab is essential before polishing begins.
Wetroom floors must slope correctly to drains — but they still need to be flat at micro-levels to polish properly. Begin with 50 or 80 grit metal bond diamonds. Grind carefully, maintaining any designed slope toward linear or point drains. Avoid over-grinding at edges, especially near drains or walls. Outdoor-type rough broom finishes must be flattened fully before polishing. Dust collection must be excellent indoors — use HEPA vacs or wet grind with water control measures.
Wet environments demand tight, dense surfaces. Apply a lithium silicate densifier after initial grinding. Lithium formulas penetrate deeply without blocking breathability — critical in wetrooms. Mist lightly, spread evenly, and allow full absorption. Avoid pooling densifier near drains, as it can leave whitening or streaks if not spread properly. Densification improves surface hardness, scratch resistance, and polishability without sealing off moisture vapor pathways.
After densification, hone the floor carefully with 100 grit, then 200 grit resin diamond pads. Keep water use minimal to avoid ponding or lifting surface fines. Wet polishing is acceptable with excellent water recovery, but dry polishing provides better visibility in confined wetroom spaces. Aim for a smooth, satin finish — not high gloss. The 200 grit stage is crucial: too low and the floor will dust and stain, too high and it may become dangerously slippery.
After reaching 200 grit, pause and test slip resistance. A wet DCOF (Dynamic Coefficient of Friction) value above 0.42 is desirable for wet areas. Use slip meters if available, or perform informal wet foot testing if needed. If the surface feels slick, stop polishing further or plan to apply anti-slip treatments. Never continue blindly to higher grits without checking grip levels — safety is critical in wetrooms and bathrooms.
If needed for slight extra sheen, polish up to 400 grit but no further. Going beyond 400 grit in wetrooms risks creating a hazardous surface when wet. A 400 grit finish produces a pleasant low sheen that still maintains good grip. Use light passes and avoid aggressive dry buffing, which can glaze the surface and reduce traction. Maintain consistent speed and overlap patterns to create a uniform appearance throughout the wetroom floor area.
Choose a penetrating silane or siloxane sealer designed for wet areas — not topical guards or acrylics. The sealer should repel water while allowing vapor permeability to avoid trapping moisture beneath the slab. Apply thinly and evenly with microfiber pads. Allow full curing per manufacturer guidelines. A second coat may be needed in very wet environments like spa floors. Proper sealing protects against stains, mold growth, and freeze-thaw spalling where applicable.
Pay special attention to edge polishing around drains, walls, and transitions. Use handheld grinders fitted with the same resin grits used on the field area. Maintain drainage slopes carefully — polish by hand if needed at slope breaks. Ensure drain surrounds have clean, tight finishes without overgrinding, which could cause water pooling issues. Drain zones are the most visually scrutinized parts of wetroom floors — precision here makes or breaks the final look.
After all polishing and sealing, clean the surface thoroughly with a pH-neutral cleaner and remove all dust or sealer residues. Allow full curing before exposing the surface to standing water, showers, or cleaning chemicals — typically 72 hours minimum. Protect finished floors from trades and foot traffic until fully cured. Early exposure to contaminants can cause permanent staining, slippery patches, or visual blemishes that are difficult to fix once the wetroom is operational.
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