Overview (TL;DR)
Floor screed is a pre-blended cement-based levelling mortar — just add water and trowel it flat to level rough or uneven concrete floors, forming the base before laying tiles or flooring, and to create falls. Compared with traditional site-mixed sand-cement, pre-blended screed has a fixed ratio and consistent quality, and most are shrinkage-compensated, greatly reducing shrinkage cracks and "hollowness" (debonding). It comes in general, waterproof and insulating types. For an ultra-smooth base, pair it with the self-levelling range.
What is floor screed?
Floor screed is a factory pre-blended cement-based dry mortar of special cements, graded aggregates and additives. On site you only need to add water and mix, then trowel it flat over the concrete floor. Its role is base levelling — providing a flat, solid base for subsequent finishes such as tiles, flooring and stone; it can also form falls (drainage slopes) in bathrooms, kitchens and rooftops.
Pre-blended floor screed vs traditional sand-cement: why the switch?
Traditionally the tradesperson mixes cement and sand on site by ratio and lays it flat. That method is long-proven and low-cost, but quality depends on skill and the site's sand — small differences in sand moisture or ratio affect strength and shrinkage. The advantages of pre-blended floor screed:
- Consistent quality — a fixed factory ratio, just add water, avoiding inconsistent site batching.
- Shrinkage-compensated formula — counteracts drying shrinkage, reducing shrinkage cracks and debonding (hollowness).
- Convenient — mix a bag with water and go, saving on-site sand and additive batching.
Neither is simply "better" — for large build-ups or budget-led jobs, traditional sand-cement still has its place; but for consistent quality with fewer cracks and hollow spots, pre-blended floor screed is increasingly popular. For the full "sand-cement vs pre-blended screed vs self-levelling" comparison, see the complete self-levelling guide.
Floor screed types: general, waterproof, insulating
- General levelling — for levelling interior/exterior concrete floors before tiles or flooring. Examples: Optimix FS151 floor screed, Weberfloor Easi Screed.
- Waterproof — contains a waterproofing component so the screed is water-resistant, suiting bathrooms, kitchens and rooftops. Examples: Optimix FS161 waterproofing floor screed, Weberdry WP Screed. But remember: a waterproof screed is not a complete waterproofing layer — wet areas still need proper waterproofing per a professional's advice.
- Insulating — a lightweight formula that also insulates, replacing the traditional "insulation board + screed" in one step, for rooftops and slabs needing insulation. Example: Optimix FS191 insulation floor screed.
Bonded or floating? Hong Kong mostly uses bonded screed
Floor screed is generally applied as a bonded screed — laid directly onto the concrete base, with a bonding agent (e.g. SBR slurry) brushed on first to strengthen the bond; this is the most common approach in Hong Kong home renovation. Floating or insulating screeds (e.g. an insulating grade) are more common where sound or thermal insulation is needed. Applying the bonding agent is the key step against "hollowness" — see bonding agents (SBR).
Common Hong Kong floor problems: hollowness, cracking, dusting
Hollowness / debonding (most common)
The screed separates from the base and sounds hollow when tapped. The most common cause is a substrate not cleaned/abraded and no bonding agent applied, weakening the bond, or too much water. Fix: thoroughly clean and abrade the substrate, apply a bonding agent, and use a shrinkage-compensated screed.
Cracking
Surface cracks — common when poured too thick in one pass, with active cracks in the substrate, or with insufficient curing. Fix: apply in layers per the grade's thickness, keep movement joints, choose a shrinkage-compensated formula, and cure per the TDS.
Dusting / sanding
The surface rubs off as sand or powder — usually from too much water lowering the strength. Fix: strictly follow the product's specified water dosage.
Installation basics (simplified)
- Clean and abrade the substrate — remove dust, grease and loose material; make sure it is sound.
- Apply a bonding agent — brush on SBR bonding slurry to strengthen the bond and prevent hollowness (per product instructions).
- Add water and mix — to the specified dosage, evenly; don't over-water.
- Level / form falls — trowel or pull an aluminium straightedge to level; form drainage falls where needed.
- Cure — per the TDS; only lay the finish once fully dry.
A great pairing: floor screed + self-levelling
Floor screed and self-levelling are good partners: floor screed handles the build-up, levelling and correcting large differences (it can go thick), while self-levelling lays a thin, smooth finishing layer on top so the surface is smooth enough for SPC, vinyl and other thin coverings. For old floors with big drops, "screed to build up + self-levelling to finish" is often the most practical. To go deeper on self-levelling base prep, see the self-levelling underlayment guide.
Product recommendations (by use)
Not sure which to pick? Use the pairings below; for grade, thickness and curing time, follow the product TDS.
General floor levelling
Optimix FS151 floor screed, Weberfloor Easi Screed — pre-blended cement levelling screeds that replace site-mixed sand-cement, shrinkage-compensated and consistent.
Waterproof floors (bathroom, kitchen, rooftop)
Optimix FS161 waterproofing floor screed, Weberdry WP Screed — floor screeds with a waterproofing component for wet areas (used with proper waterproofing).
Insulating floors
Optimix FS191 insulation floor screed — a lightweight insulating grade that levels and insulates in one step.
Matching bonding agent (against hollowness)
bonding agents (SBR) — brush on a bonding agent (SBR slurry) before laying to strengthen the bond and reduce hollowness.
To see the full range, visit the floor screed range.
FAQ
What is floor screed? How is it different from site-mixed sand-cement?
Floor screed is a factory pre-blended cement-based levelling mortar — just add water and trowel it flat to level rough, uneven concrete floors. Compared with sand and cement mixed on site, the pre-blended formula has a fixed ratio and consistent quality, and most are shrinkage-compensated, which reduces shrinkage cracks and debonding (hollowness).
Why does "hollowness" (debonding) happen and how do I prevent it?
Hollowness (the screed separating from the base — a hollow sound when tapped) most often comes from poor substrate preparation, skipping the bonding agent (e.g. SBR slurry) so the bond is weak, or too much water in the mix. Prevention: thoroughly clean and abrade the substrate, apply a bonding agent, use a shrinkage-compensated pre-blended screed, and cure as instructed.
Does a waterproof floor screed count as doing the waterproofing?
No. A waterproof-type floor screed is water-resistant and suits wet areas, but it generally does not replace a complete waterproofing layer / system. For bathrooms, rooftops and similar wet areas, follow a relevant professional's advice to install proper waterproofing before laying the finish — don't assume a waterproof screed alone is full waterproofing.
What's the difference between floor screed and self-levelling? When do I use which?
Floor screed is hand-troweled and suits medium-to-thick levelling, correcting larger differences and forming falls; self-levelling is poured and self-levels, suiting thin layers and a fine, smooth base for SPC / vinyl. They combine: use screed to build up and level, then a thin self-levelling layer for the smooth surface. See the complete self-levelling guide.
How thick can floor screed be applied?
Each grade has a recommended thickness range; apply larger differences in layers rather than pouring too thick in one pass. For actual thickness and curing time, follow the product Technical Data Sheet (TDS).
Where can I buy floor screed?
Wah Hing stocks general, waterproof and insulating floor screeds from brands such as Optimix and Weber, most typically in stock. Visit our Canton Road shop in Mong Kok or ask us on WhatsApp.
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Ready to buy? Wah Hing stocks the floor screed range, self-levelling range and matching bonding agents, most typically in stock — visit our Canton Road shop in Mong Kok or ask us on WhatsApp.
