Natural EWI Basecoat

Raso Top Bio - Natural EWI Basecoat

Transpiring NHL5 lime-based natural EWI basecoat and adhesive for eco-friendly insulation systems

Raso Top Bio is a transpiring, fibre-reinforced natural EWI basecoat and adhesive from Licata — based on NHL 5 natural hydraulic lime with additives and inert materials of natural origin. This natural EWI basecoat is specifically designed for eco-friendly ETICS systems using breathable insulation panels — rock wool, cork and wood fibre — whilst remaining compatible with EPS and XPS systems. Ideal for projects requiring natural, biocompatible materials.

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Product Type Natural EWI Basecoat

Application Interior & Exterior

Thickness per Coat 3–10mm

Fire Rating Class A1

Standard UNI EN 998-1 R / 998-2 M5

Features & Benefits

Why specify Raso Top Bio natural EWI basecoat?

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Eco-Friendly Natural EWI Basecoat

Formulated with NHL 5 natural hydraulic lime and additives and inert materials of natural origin — this natural EWI basecoat is the correct choice for eco-friendly and environmentally sensitive ETICS projects.

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Highly Transpiring

The high vapour permeability of this natural EWI basecoat makes it ideal for use with breathable insulation panels such as rock wool, cork and wood fibre — where maintaining vapour permeability through the system is essential.

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Water Repellent

Combines transpiring properties with water repellency — protecting the insulation system from moisture ingress whilst allowing water vapour to pass freely through the natural EWI basecoat layer.

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Dual Function — Adhesive & Basecoat

Raso Top Bio functions as both an adhesive for bonding insulation panels and as a reinforced natural EWI basecoat for skim coating — reducing the number of products needed on eco-friendly EWI projects.

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High Adhesion on All Substrates

Despite its natural formulation, this natural EWI basecoat delivers high adhesion on all common construction substrates — exceptional for styling applications and suitable for new build and renovation.

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Class A1 Fire Rating

Achieves a Class A1 reaction to fire classification — making this natural EWI basecoat suitable for use in systems on buildings where non-combustible materials are required.

Product Description

Raso Top Bio — Natural EWI Basecoat for Eco-Friendly Systems

Raso Top Bio is Licata's natural EWI basecoat and adhesive — a transpiring, fibre-reinforced product based on NHL 5 natural hydraulic lime with additives and inert materials of natural origin. It is specifically designed for eco-friendly ETICS systems, particularly those using highly breathable insulation panels such as rock wool, cork and wood fibre.

The transpiring and water repellent properties of this natural EWI basecoat allow the creation of lightweight, easy-to-work mortars that maintain the full breathability of the insulation system. High adhesion on all substrates makes it suitable for both bonding insulation panels and skim coating any lime or cement-based surface.

Raso Top Bio natural EWI basecoat is also compatible with EPS and XPS panels, making it a versatile choice across the full range of insulation system types. It can be left exposed, though a protective finish coat will significantly extend its useful life.

Standards & Classification

UNI EN 998-1 Class R renovation mortar · UNI EN 998-2 Class M5 masonry mortar · Class A1 reaction to fire (EN 13501-1)

Supported Substrates

Natural EWI basecoat compatible substrates

Rock wool, cork and wood fibre insulation panels

EPS and XPS insulation panels

Lime-based plasters

Lime/cement-based plasters

Clay brick

Precast and cast-in-place concrete

Autoclaved aerated concrete

Old paint and coatings (clean, sound and well adhered)

Technical Data

Raso Top Bio natural EWI basecoat — technical specification

AppearanceHazelnut colour powder

Particle size<1.0mm

Consumption — bonding (full surface)4–5 kg/m²

Consumption — bonding (points/perimeter)3.5–4.5 kg/m²

Consumption — skim coating3.5–4 kg/m² (1.1–1.2 kg/m²/mm)

Mixing water5.5–6L per 25kg bag (22–24%)

Workability at 20°C40 minutes

Application thickness per coat3–10mm

Dry bulk density1,470–1,530 kg/m³

Compressive strengthCS II (EN 1015-11)

Capillary water absorptionW0 (EN 1015-18)

Water vapour permeability (µ)≤12 (EN 1015-19)

Thermal conductivity (λ)0.4 W/mK

Reaction to fireClass A1 (EN 13501-1)

Packaging25kg bags

Shelf life12 months (sealed, dry store)

Bonding

Using as an EWI panel adhesive

Substrate preparation: The substrate must be cured, clean, flat and cohesive. Prime to even out absorption. Resolve any capillary or saline rise in advance with Neutral Antisale or Injecto Gel.

Mixing: Pour the natural EWI basecoat into a container with three quarters of the mixing water. Mix for 3–4 minutes at low speed until a homogeneous, lump-free mixture is achieved. Use only clean water.

Bonding on rough surfaces: Apply in 2–3 central crowns (approx. 10cm diameter) and along the perimeter of the insulation panel.

Bonding on flat/rendered surfaces: Apply the natural EWI basecoat as a full bed using a toothed spatula for maximum adhesion.

Skim Coating

Using as a natural EWI basecoat

First coat: Apply a first coat evenly and flat using a smooth American spatula — priming or moistening the substrate before application.

Embed reinforcement mesh: Drown the licataTHERM 160 reinforcement mesh vertically into the first coat, overlapping at joints by at least 10cm.

Second coat: After at least 24 hours, apply a second coat of natural EWI basecoat covering the reinforcement mesh entirely. Finish with a sponge trowel as the product begins to dry.

Thicknesses over 10mm: Apply an additional layer on the hardened first coat. The natural EWI basecoat can be left exposed, but a protective finish coat will significantly extend its service life.

Note: Workability time is 40 minutes at 20°C — shorter than most basecoats. In hot or dry conditions this may reduce further. Protect fresh material from rain, wind and direct sunlight for at least 48–72 hours. Temperature must be between +5°C and +35°C.

Buy Raso Top Bio natural EWI basecoat

Available from all six Licata branches across the UK. Speak to our team about pricing and technical support.

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