Microcement for showers and wet areas on moisture-resistant drywall

1. Materials & Tools

Gather everything before you begin

Purpose:

Gather all tools and materials before starting. Several products have strict working times—you don't want to stop mid-application to find a missing tool.

Mixing & Application Tools:

• Drill with spiral paddle mixer
• Clean mixing buckets (multiple)
• Stainless steel trowel with rounded edges
• Flexible putty knives (various sizes)
• Short-nap rollers and brushes
• Foam roller (for Aquafloor Eco)
• Spray bottle with clean water

Sanding & Cleaning:

• 80-120 grit sandpaper or sanding screens
• Orbital sander or similar (for flat areas)
• Sanding block (for hand sanding edges)
• Shop vacuum with brush attachment
• Clean, lint-free cloths

Preparation & Protection:

• Painter's tape and masking plastic
• Drop cloths
• Work light (for raking light inspection)
• PPE: gloves, safety goggles, dust mask

For wet spaces:

• Ardex SK Mesh seam tape, caulk gun for final silicone at fixtures

2. Surface Preparation- Showers & Wet Areas

Clean, repair, and prepare substrate

⚠️ Substrate Requirements:

ONLY these substrates are acceptable in wet areas:

• Moisture-resistant drywall (green board) — NOT standard drywall
• Cement board (Durock, HardieBacker, or equivalent)
• Schluter KERDI-BOARD or similar rigid foam building panel
• Existing tile (firmly bonded, see below)
• Cement

All Surfaces:

• Clean thoroughly — remove all dirt, soap residue, mildew, and dust
• Surfaces must be completely dry before WATstop application
• Repair holes and cracks greater than 12mm with mortar
• Scrape or sand any loose, peeling, or flaking material
• Remove silicone caulk completely — WATstop won't adhere to silicone

Cement Board/ Drywall Preparation:

• Tape ALL seams with Ardex SK Mesh (non-woven polyester seam tape) or embed directly into mortar.
• Apply Ardex X5 over taped seams
• Feather edges smooth — no ridges or lips
• Allow seam treatment to cure 24 hours before WATstop

Floor & Drain Area:

• Verify proper slope toward drain (1-2% minimum)
• Clean drain flange thoroughly — remove all debris and buildup
• Ensure drain is compatible with waterproofing membrane
• Plan WATstop to extend minimum 150mm beyond shower curb

Niches, Benches & Curbs:

• Round all sharp corners and edges — Safety Joint Roll needs smooth transitions
• Ensure bench and curb tops slope slightly toward drain
• Plan Safety Joint locations: ALL inside corners, transitions, and edges

Protection & Masking:

• Protect fixtures, drains, and shower controls with tape and plastic
• Mask glass panels, doors, and frames
• Protect bathroom floor outside shower zone
• Have ventilation available — WATstop has odor during application

3. Ardex X5 - Cement Board & Drywall Seams

Fill and level all seams, joints, and imperfections

Purpose:

Ardex X5 creates a smooth, continuous surface by filling cement board & drywall seams and leveling imperfections. This step is essential before waterproofing—WATstop won't bridge gaps or fill joints on vertical surfaces.

Corners taped here still receive Safety Joint Roll embedded in the WATstop above: the mesh reinforces the rigid fill against board-level cracking, the Roll carries the membrane's stretch across the moving line. Neither replaces the other.

When Required:

• All seams between cement board panels, niches, benches & curbs
• Screw heads and fastener depressions
• Corner joints at wall-to-wall and wall-to-floor transitions
• Any chips, gouges, or surface damage
• Gaps around penetrations (pipes, fixtures, niches)

Seam Preparation:

• Ensure all cement board is securely fastened—no movement or flex
• Apply Ardex SK Mesh over ALL seams — the 4.75" (120 mm) roll is sized for this
• Tape should be centered on seam with equal overlap on each side
• For corners: fold the tape into the angle. The 4.75" (120 mm) width is sized for exactly this; no pre-formed corners needed

Mixing:

• Use clean, cool water in a clean bucket
• Small batch: 1 kg powder + 330 ml water
• Medium batch: 5 kg powder + 1.65 L water
• Full bag: 18 kg powder + 5.68-6.6 L water
• Add powder to water gradually, mixing 2-3 minutes until smooth and lump-free
• Pot life: 3 hours at 21°C — if it stiffens, re-stir with the drill; never add more water

Application:

• Apply Ardex X5 over mesh tape with flexible putty knife or flat trowel
• Press firmly to embed tape and fill seam completely
• Feather edges 50-75mm (2-3") beyond tape on each side
• Fill all screw heads flush with surrounding surface
• Inside corners: apply in layers if needed—don't build up too thick at once
• Remove excess before it sets

Curing & Finishing:

• Allow to cure per manufacturer specifications (typically 24 hours)
• Check for shrinkage—apply second coat to any cracks or low spots
• Sand or scrape lightly to smooth any ridges or high spots
• Vacuum all dust before proceeding to WATstop

4. WATstop Moisture Barrier

Epoxy-cement moisture barrier

Purpose:

WATstop at 1.0 kg/m² creates a barrier that protects against moisture migration through substrates. This 1.0 kg/m² build is sufficient for substrates not subject to pooling water or rising moisture from below substrate. If risk or concern of this is present-proceed with 2kg/m².

Mixing (3-Component System):

• Mix Component C (cement powder) with the water first, into a smooth paste — roller/brush application: 30-40% water by weight; trowel application (floors only): 10-20%
• Add Component A (epoxy resin) and mix for 1 minute
• Add Component B (liquid catalyst)
• Mix with spiral paddle for 3-4 minutes until smooth and lump-free
• Consistency should be like thick paint—flows but doesn't drip

Application:

• Apply with short-nap roller for large areas, brush for edges and corners
• Work in one direction for even, consistent coverage
• Target coverage: 1.0 kg/m² total
• Best results come from two coats of about 0.5 kg/m², the second within 24 hours
• Ensure complete coverage—no pinholes, thin spots, or holidays
• Pay extra attention to seams, corners, and around penetrations
• Check coverage in raking light to spot any missed areas

Safety Joint Integration:

• While WATstop is still wet, embed Safety Joint Roll at all corners and junctions
• See Safety Joint step for complete placement requirements

Curing:

• Touch dry: 5-12 hours at 23°C / 50% RH
• Ready for Decorkrete: minimum 24 hours, maximum 48 hours
• Do not allow foot traffic during curing

5. Safety Joint Application

Reinforcement tape for corners, junctions, and transitions

Purpose:

Safety Joint Roll is a non-woven polyester reinforcement tape that bridges corners, junctions, and transitions where movement or cracking is most likely to occur. Embedded in WATstop, it creates a flexible, crack-resistant waterproof membrane at every critical point in your wet area installation. This is the most important waterproofing step—skipped corners lead to failures.

Where Required (Do Not Skip Any):

• Inside corners: All wall-to-wall and wall-to-floor junctions, plus wall-to-ceiling wherever the membrane runs onto the ceiling (full wet rooms and steam spaces)
• Outside corners: Curbs, bench edges, niche openings
• Floor-to-wall transition: Entire perimeter of shower floor
• Around penetrations: Pipes, valves, shower controls and drains get the fixture maker's own sealing kit, or an off-the-shelf seal such as Schluter KERDI-SEAL-PS for pipes and KERDI-SEAL-MV for mixing valves
• Shower niches: All four inside corners plus the back edges
• Benches and seats: Where bench meets wall, floor, and all edges
• Curbs and thresholds: Both sides and top of curb, corner transitions
• Expansion joints: Any control joints in the substrate
• Material transitions: Where cement board meets drywall, different substrates meet

Preparation:

• Map out ALL locations requiring Safety Joint before mixing WATstop
• Pre-cut pieces to length—label them if helpful (e.g., "left wall," "niche top")
• For inside corners: cut pieces 50mm (2") longer than the run to ensure full coverage
• For outside corners: cut separate pieces for each face, overlapping at the corner
• Have a putty knife, trowel, and clean rags ready

Application Sequence:

1. Apply WATstop base coat: Brush or roll WATstop onto the corner/joint area, extending 50-75mm (2-3") on each side of the joint
2. Position tape: Center Safety Joint Roll over the joint while WATstop is still wet
3. Embed tape: Press firmly into wet WATstop starting from the center and working outward
4. Remove air bubbles: Use putty knife or trowel to smooth tape flat, pushing air bubbles toward edges
5. Saturate tape: Tape should be fully wet through—dry spots indicate insufficient WATstop beneath
6. Top coat: Apply additional WATstop over the tape to fully encapsulate
7. Feather edges: Blend edges into surrounding surface—no ridges or lips

Inside Corner Technique:

• Apply WATstop to both surfaces of the corner
• Fold tape lengthwise to create a crease; the fold is the technique, no pre-formed corners needed
• Press into corner, ensuring tape contacts both surfaces fully
• Work from one end to the other—don't start in the middle
• Use putty knife to press tape firmly into the corner crease
• Apply top coat, working WATstop into the corner

Outside Corner Technique:

• Apply WATstop to the corner and both adjacent surfaces
• Cut separate pieces for each face of the corner
• Apply first piece, wrapping slightly around the corner edge
• Overlap second piece onto first by minimum 25mm (1")
• Press firmly and apply top coat over both pieces

6. Decorkrete Application

Apply decorative microcement coating

Purpose:

• Decorkrete is the decorative microcement coating that creates your finished surface. Applied in two thin coats totaling approximately 2mm thickness, it develops the characteristic depth, texture, and organic beauty of microcement.

Coverage Rate:

• Total coverage: 1.20 kg/m² (both coats combined)
• First coat: approximately 0.60 kg/m²
• Second coat: approximately 0.60 kg/m²
• Set and work time: Initial set 30 min · work time 60 min at 20°C or cooler

Mixing (Bicomponent Kit):

• Decorkrete is a pre-dosed two-component kit — Component A (fine-cement powder) : Component B (elastic latex resin liquid) = 10:3 by weight. To mix part of a kit, follow the Batch Mixing Guide. Never batch by eye.
• Pour Component B (liquid resin) into the mixing pail first
• Add colour toner to the resin and mix briefly to disperse - both coats are toned
• Gradually add Component A (powder) while mixing with a spiral paddle
• Mix on low-medium speed (300-500 rpm) for 3-4 minutes
• Consistency should be like thick yogurt — a small splash of clean water can adjust consistency once per batch, at mixing or later while it's still workable. Water only adjusts the consistency; the kit ratio stays 10:3.

First Coat:

• Hold the trowel at about 45° with a little material on the edge and lay it on in short, slightly curved strokes
• Change direction constantly: up, across, on the diagonal, then back over at another angle. Each stroke covers the tails of the ones before it
• Keep it thin, about 1 mm. This coat covers; the second coat builds the finish
• Cover the whole surface, corners and edges included
• Work a section you can finish in 15-20 minutes and keep the edge wet. Blend each new stroke into the last before it skins
• Three or four passes over a spot is enough. Past that the trowel drags and darkens the colour
• Why the directions matter: every stroke leaves a faint line where the blade starts and stops. Strokes in one direction line those marks up into stripes. Strokes crossing each other break them into the soft, cloudy variation microcement is known for, and each pass catches the light a little differently
• The first coat's marks show through the second, so apply it the way you want the finish to look. For a smooth or cloudy finish, apply it as if it were the last coat. For a rustic stone look, leave ridges and crests in it on purpose: the height differences give the second coat its dimension

Between Coats:

• Wait 4-6 hours—surface should be firm but not fully cured
• Sanding between coats is only for large ridges you did not want: knock those down with 80-120 grit and vacuum. Otherwise leave the first coat alone

Second Coat:

• Same motion, same thickness: about 1 mm for 2 mm total. Its strokes cross the first coat's marks in fresh directions, which gives the surface its depth
• Hold the blade a little flatter and pull a little tighter for a smoother skin. Finish each section with light passes, the trowel almost flat, to compress the surface
• Smooth and even: tight overlapping strokes in every direction, light final passes
• Cloudier: vary pressure and stroke length a little. Once the coat begins to set (20-30 minutes), mist the surface until saturated and spread the water with the trowel; more water lightens the tone. This works best on darker colours; the cloud effect is hard to achieve on light or white colours
• Stone: over a first coat left with crests, lay this coat on smooth and even. Then set the trowel flat on the wet surface and lift it straight off: the pull leaves peaks and ridges, different every time. Knock them down with a light, flat pass that lays the peaks over without wiping them out. Sanding later creates the stone effect
• Stop when it starts to set. Reworking a stiffening area leaves dark streaks that only sanding back and recoating will remove

After Second Coat:

• Allow 24 hours minimum before sanding
• Protect from foot traffic and moisture during cure
• Application range: +5°C to +30°C; ideal working band 15-25°C, 40-60% humidity

7. Troweling Techniques

Laying on, crossing and closing each coat

Trowel Selection:

• Stainless steel trowel with rounded corners. Sharp corners dig in and leave lines
• Keep the blade clean. Dried material on it scratches the coat; wipe it often with a damp cloth
• Have a second trowel ready so the work never stops while one is being cleaned

Laying On:

• Hold the blade at about 45° with a little material on its leading edge and lay it on in short, slightly curved strokes
• As the Decorkrete spreads, let the blade drop flatter, to 15-30°. The steeper angle lays material on; the flatter angle spreads and compresses it
• Even light pressure from the start of the stroke to its end. Bearing down hard with the steel blade burns dark marks into the coat as it sets
• Change direction constantly: up, across, on the diagonal, then back over at another angle. Each stroke covers the tails of the ones before it and overlaps the last by about half
• Why the directions matter: every stroke leaves a faint line where the blade starts and stops. Strokes in one direction line those marks up into stripes; strokes crossing each other break them into the soft, cloudy variation microcement is known for
• Keep it thin, about 1 mm a coat. A lightly loaded blade and more strokes beats an overloaded trowel
• Three or four passes over a spot is enough. Past that the trowel drags and darkens the colour
• Work a section you can finish in 15-20 minutes and keep the edge wet. Blend each new stroke into the last before it skins

On Walls:

• Work from the bottom up, never top down as material will easily fall off the trowel
• A hawk (or a second trowel) carries the material up the wall and catches what drops off the blade
• Load the blade lightly: a thick pass sags and drops

Finishing:

• Finish each section with light passes, the trowel almost flat, to compress the surface into a smooth skin
• Smooth and even: tight overlapping strokes in every direction, then the light final passes
• Cloudier: vary pressure and stroke length a little. Once the coat begins to set (20-30 minutes), mist the section until saturated and spread the water with the trowel; more water lightens the tone. This works best on darker colours; the cloud effect is hard to achieve on light or white colours
• Stone: over a first coat left with crests, lay this coat on smooth and even. Then set the trowel flat on the wet surface and lift it straight off: the pull leaves peaks and ridges, different every time. Knock them down with a light, flat pass that lays the peaks over without wiping them out. Sanding later creates the stone effect
• Stop when it starts to set. Reworking a stiffening area leaves dark streaks that only sanding back and recoating will remove

8. Sanding Decorkrete

Prepare surface for sealer application

Purpose:

Sanding smooths high spots, removes trowel marks, and creates a uniform surface texture before sealing. This step also opens the surface to accept D20 Fixative and Aquafloor Eco. Light, even sanding—not aggressive removal—is the goal.

Readiness Check:

• Wait minimum 24 hours after final Decorkrete coat
• Surface should be completely firm and dry to touch
• Cold or humid conditions extend cure time significantly

Tools Required:

• 80-120 grit sandpaper or sanding screens
• Orbital sander for flat areas (optional but faster)
• Sanding block for hand sanding
• Shop vacuum with brush attachment
• Clean, lint-free cloths
• Work light for raking light inspection

Sanding Process — Flat Areas:

• Use orbital sander with 80-120 grit disc or sanding screen
• Keep sander moving—never stay in one spot
• Use light, even pressure—let the sandpaper do the work
• Work in overlapping circular or random orbital motions
• Sand entire surface uniformly—don't focus only on visible high spots
• Check progress frequently by wiping away dust
• Stop when surface feels uniformly smooth

Sanding Process — Edges, Corners & Details:

• ALWAYS hand sand edges and corners—orbital sanders remove too much material
• Use 120-grit sandpaper wrapped around sanding block
• Work slowly with light pressure
• Check frequently—edges thin quickly
• For inside corners: fold sandpaper and work carefully
• For detailed areas: use smaller pieces of sandpaper by hand

How Much to Sand:

• Sand to smooth the surface; take off as little as possible
• High spots and trowel ridges should flatten
• Surface should feel uniformly smooth when you run your hand across it
• Some texture variation is normal and desirable—don't sand to perfection
• If you see primer or substrate, you've gone too far—touch up with Decorkrete

9. Dust Removal

Prepare surface for sealing

Purpose:

Dust contamination is the leading cause of sealer adhesion failure. Sanding creates fine particles that settle into the microcement's texture and pores. These particles must be completely removed before D20 Fixative—any remaining dust creates a barrier that prevents proper bonding and causes peeling, flaking, and delamination.

Tools Required:

• Shop vacuum with soft brush attachment
• Clean, lint-free cloths (microfiber works well)
• Clean water in spray bottle or bucket

Step 1 — Initial Vacuum:

• Vacuum entire surface thoroughly with brush attachment
• Work systematically—don't skip areas
• Pay extra attention to inside corners where dust accumulates
• Vacuum edges, transitions, and textured areas carefully
• Vacuum surrounding areas—dust on adjacent surfaces will migrate back

Step 2 — Damp Wipe:

• Dampen cloth with clean water—wring out thoroughly
• Cloth should be damp, not wet—excess water can damage uncured microcement
• Wipe entire surface in overlapping passes
• Rinse and re-wring cloth frequently as it collects dust
• Use fresh cloths as needed—dirty cloth just moves dust around
• Wipe corners and details with smaller cloth or folded edge

Step 3 — Dry:

• Allow surface to dry completely—typically 30-60 minutes
• Do not apply D20 to damp surface
• Warmer, drier conditions speed drying
• Ensure good ventilation during drying

Step 4 — Final Vacuum (If Needed):

• If a clean dark cloth wiped across the dry surface still picks up dust, repeat the vacuum and the damp wipe
• Do not proceed until the surface wipes clean
• Better to spend extra time cleaning than to have sealer failure

Environmental Considerations:

• Close windows and doors to prevent airborne dust settling
• Turn off HVAC if it circulates dust
• Remove any dust-generating activities from the area
• Apply D20 Fixative as soon as possible after final cleaning
• If significant time passes, re-inspect and clean again before D20

10. D20 Primer Application

Consolidating primer before final sealer

Purpose:

• Binds any remaining dust particles
• Consolidates and strengthens Decorkrete surface
• Provides ideal base for Aquafloor Eco adhesion
• Never skip this step - critical for durability

Application:

• Apply with short-nap foam roller
• Thin, even coat - avoid pooling
• Coverage rate: 0.15 kg/m²
• Work in one direction
• Ensure complete coverage

Drying:

• Dry time: 3 hours at 23°C / 50% RH
• Surface should be dry to touch
• Do not proceed if still tacky

11. Aquafloor Eco Sealer

Protective polyurethane coating

Before You Mix - Plan Your Batch:

• Pot life is 2 hours - only mix what you can apply in that window
• A full 6.25 kg kit covers about 31 m² (336 ft²) across all three coats - do NOT mix the whole kit for a smaller area
• For a partial batch, weigh out 80% Component A + 20% Component B (example: 800 g of A + 200 g of B)
• Reseal both containers immediately - unmixed product keeps for the next coat

Mixing (2-Component):

• Pour your measured Component B into the measured Component A
• Mix thoroughly for 2-3 minutes until homogeneous with no streaks
• Use immediately after mixing

Coat 1 - Diluted:

• Dilute the mixed product 30% with clean water (example: 1 kg of mix + 300 g water)
• The diluted first coat penetrates and grips the primed surface
• Coats 2 and 3 go on undiluted

Application - Three Coats:

• Apply with hand sprayer and back roll with foam roller (short-nap microfiber)
• Thin, even coats - avoid heavy application
• Work in one direction per coat
• Coverage: approximately 0.07 kg/m² per coat, 0.20 kg/m² total for 3 coats

Between Coats:

• Wait minimum 2 hours between coats