Substrate & Surface Preparation Guide
Flawless Microcement Starts Below the Surface
Ready-to-use microcement (MyCROCEMENT™) adheres to any rigid, stable substrate, but the key to a long-lasting, crack-free finish lies in proper surface preparation. Because MyCROCEMENT™ is a micro-topping system applied at a total thickness of ~2mm, the final finish is only as stable as the surface beneath it.
Before opening a bucket, use this guide to assess, clean, repair, and prime your specific surface.
Quick Reference Surface Matrix
| Substrate Type | Compatibility | Key Risk factor | Core Prep Requirement | Recommended Primer | Fiberglass Mesh Needed? |
|---|---|---|---|---|---|
| Ceramic / Porcelain Tile | Compatible | Ghosting / Grout lines showing | Deep clean, fill grout joints flush | MyPRIMER | Optional over grout |
| Drywall, Plaster & Blueboard | Ideal | Uneven suction / Joint movement | Tape seams, mud flat, sand smooth | MyPRIMER | Over board seams only if needed |
| Cement Backer Board | Ideal | Joint movement | Screw tight to framing; tape seams with alkali-resistant mesh | MyPRIMER | Required over board seams |
| Concrete & Cement Screeds | Ideal | Cracks & rising moisture | Grind surface, fill structural cracks | MyPRIMER | Over crack repairs if needed |
| Plywood, MDF & OSB | Conditional | Structural flex & moisture expansion | Fasten securely, seal edges, stabilize | MyPRIMER | Optional in case of any uncertainty |
| Waterproofing Membranes (Wedi, Kerdi, Hydro Ban) | Ideal | Uncured membrane / Seam flex | |||
| Laminate & Countertops | Compatible | Slick, non-porous finish | Abrade with 80-grit, degrease | MyPRIMER | Optional (High-impact/High-stress zones) |
| Metal & Glass | Not Recommended | Adhesion / Non-porous flex/Thermal Expansion & Contraction | Strictly climate controlled and stable environment 24/7 only | MyPRIMER | Case-by-case evaluation |
| Unstable or Rotted Wood | Not Recommended | Structural failure | Must be completely removed and replaced prior to application | N/A | N/A |
Detailed Preparation Guidelines
1. Drywall, Plaster, Plasterboard & Cement Board
Drywall and cement backer board provide ideal, uniform surfaces when properly jointed and stabilized.
- Inspect & Stabilize: Ensure all panels are screw-fastened tightly to framing with zero bounce. Screw heads must be fully countersunk.
- Seam Prep: Tape seams and corners with alkali-resistant mesh tape and mud as usual to achieve a Level 4 or Level 5 finish. Sand completely smooth.
- Clean: Ensure the surface is dry and completely free of dust, painter’s tape, silicone, or caulk residue.
- Prime: Apply a uniform coat of MyPRIMER to equalize porosity and create protection between the board face and joint mud. Allow to dry completely (1–2 hours).
- Mesh: Embed fiberglass mesh in MyBASE over board seams to eliminate stress lines.
2. Existing Tile, Porcelain & Masonry
Existing tile is one of the most common microcement substrates, but telegraphing (grout lines showing through the finished coat) must be strictly prevented.
- Inspect: Tap tiles to identify hollow or loose spots. Remove loose tiles and fill voids flush with high-strength repair mortar.
- Clean & Degrease: Scrub thoroughly with TSP (Trisodium Phosphate) or an industrial degreaser to remove soap scum, oils, and waxes. Rinse clean.
- De-gloss: Heavy-sand glazed tiles using 80-grit sandpaper to break the sheen and create a mechanical profile for bonding. Vacuum away all sanding dust.
- Fill Joints & Level: Fill grout lines flush with a non-shrinking joint filler or MyBASE.
- Prime: Apply 1–2 coats of MyPRIMER to establish a solid mechanical key.
- Reinforce: For ultimate ghosting prevention on tile grids, embed alkali-resistant fiberglass mesh into your first coat of MyBASE, troweling and sanding smooth.
3. Concrete Slabs & Cementitious Screeds
Concrete provides an ultra-rigid base, but moisture movement and existing cracks require careful preparation.
- Cure Time: Concrete must be fully cured (minimum 28 days for new pours).
- Moisture Testing: Subfloor moisture content must be below 4% (Relative Humidity < 75%, or MVER < 3 lbs / 1,000 sq ft / 24 hrs).
- Abrasion: Mechanical grinding or etching is required to remove laitance, old sealers, paint, or curing compounds, achieving a concrete surface profile of CSP 1–2.
- Crack Repair: V-cut any hairline or structural cracks, fill with epoxy gel or rigid repair mortar, and cross-stitch with carbon fiber staples if active movement is suspected.
- Prime: Apply MyPRIMER to seal porous screeds or power-troweled concrete.
4. Waterproofing Membranes (Showers & Wet Areas)
Sheet membranes (e.g., Schluter-KERDI, Wedi) and liquid membranes (e.g., Laticrete Hydro Ban, RedGard) make excellent backings when handled correctly.
- Cure Check: Ensure the membrane system is installed strictly to manufacturer specs and fully cured.
- Clean: Wipe clean of jobsite dust, oils, or thinset residue.
- Prime: Apply MyPRIMER evenly across the surface.
- Mesh Reinforcement: Embed alkali-resistant fiberglass mesh into MyBASE across all corners, transitions, niches, and change-of-plane seams. Full-coverage mesh is strongly recommended in direct water-contact zones.
5. Wood Substrates (Plywood, MDF, OSB)
Wood expands, contracts, and flexes with ambient humidity. Overcoming this movement requires strict mechanical locking and full-coverage reinforcement.
- Rigidity: Subfloors and countertops must be a minimum of 3/4” thick, tongue-and-groove, screw-fastened every 6 inches along joists/framing with zero flex under footprint or heavy load.
- Seam Sealing: Fill seams between sheets with polyurethane sealant or epoxy filler to prevent edge swelling.
- Moisture Barrier: Seal all exposed bare edges and undersides of wood panels to prevent ambient moisture absorption and warping.
- Full Mesh Reinforcement (Mandatory): Because wood moves dynamically, you must embed an alkali-resistant fiberglass mesh into MyBASE across the entire wooden surface to bridge expansion movements across joints.
- Prime: Apply MyPRIMER thoroughly before base coating.
6. Countertops, Laminate & Formica
Transforming existing laminate or solid surface countertops requires breaking the factory sheen for a permanent bond.
- Check Bond: Ensure the laminate is firmly glued down and not delaminating from the core substrate underneath.
- Degloss: Thoroughly scuff-sand the entire surface using 80-grit sandpaper to create a rough, open texture.
- Solvent Wipe: Wipe down completely with acetone or denatured alcohol to eliminate lingering dust, waxes, or silicone residue.
- Prime: Apply 1 to 2 coats of MyPRIMER.
Universal Golden Rules for Substrate Preparation
- Rigidity is Essential (The Tap Test): Tap your substrate. If it sounds hollow, flexes underfoot, or crumbles under pressure, fix the structural flaw first. MyCROCEMENT™ is flexible, but it cannot structurally hold together a failing base under stress.
- Never Skip Primer: Priming neutralizes suction differences, prevents pinholing, extends troweling working time, and guarantees a chemical/mechanical bond to the substrate.
- Respect Movement & Expansion Joints: Never bridge active building expansion joints or concrete control joints with MyCROCEMENT™. Honor all structural expansion joints by carrying them up through the finished microcement layer or filling them with a color-matched flexible polyurethane sealant.
- Cleanliness Drives Adhesion: Dust, grease, and silicones are bond-killers. Always vacuum thoroughly using HEPA filtration right before priming.
- In presence of thermal variations, microcement application is not recommended on metal, glass and similar materials as the surface is not stable and could lead to stretching of the microcement coating and therefore cracking.
Need Assistance?
Technical Support: Have a unique surface, commercial spec, or custom substrate? Contact our US Technical Support Team or order a Sample Kit to test your prep process firsthand.
Jobsite Checklist: Download and print our handy Substrate & Surface Preparation Checklist – PDF for quick reference on site.
*PPE & Cleanliness Notice: Sanding and mixing powders create airborne dust hazards. Always wear appropriate personal protective equipment (PPE), including a fitted dust mask/respirator (N95+), protective eyewear, and gloves. Use adequate ventilation or active dust extraction. Wear suitable footwear to avoid transferring dust outside the work area.