ETICS & Rendered Facades: Plinth and Splash Zone XPS

7 July 2026

For ETICS and rendered facade systems in the plinth zone and splash zone, PNP XPS recommends XPS 150 W X-Grip or XPS 300 W — waffled-surface extruded polystyrene boards whose embossed face provides the mechanical key required for adhesive compounds, base coats and decorative renders to bond reliably to the insulation. Both products carry a declared thermal conductivity (λD) of 0.034–0.035 W/(m·K) under EN 13164:2012+A1:2015, long-term water absorption WL(T)0,7 (≤ 0.7 Vol.-%) and dimensional stability DS(70,90), making them suited to the demanding moisture, impact and freeze–thaw conditions at and below finished-ground level.

Why XPS in the Plinth and Splash Zone?

The plinth zone — typically from about 300 mm below finished ground level to 500–1000 mm above it — is the most demanding part of an ETICS facade. It is subject to:

Driving rain, splash-back from paving and standing water after heavy rainfall
Freeze–thaw cycling at the waterline
Mechanical impact from foot traffic, garden equipment and snowploughs
Soil pressure and root moisture below grade

Extruded polystyrene (XPS) is particularly suited here because its homogeneous closed-cell structure resists moisture ingress over time. PNP XPS boards rated WL(T)0,7 absorb ≤ 0.7 Vol.-% by long-term immersion (EN 13164:2012+A1:2015), so thermal performance is maintained even where the board is in periodic contact with water or damp soil.

Freeze–thaw resistance (FTCD1, ≤ 1 Vol.-%) is declared on XPS 300 W, supporting suitability for the seasonal temperature swings typical across Central and Eastern Europe. This supports the choice of XPS in this zone, but the final specification — including waterproofing strategy, drainage detail and transition to below-grade insulation — must be confirmed by a qualified designer using the current TDS and DoP for each product.

For further background, see What Is XPS Insulation?, WL(T) Long-Term Water Absorption Explained and Is XPS Resistant to Freeze–Thaw Cycles?

Recommended PNP XPS Products

PNP XPS offers two waffled-surface boards optimised for adhesive and render systems in the plinth and splash zone. The choice between them depends on the ETICS system provider's specification and the compressive load at the plinth.

XPS 150 W X-Grip — primary recommendation for standard ETICS

XPS 150 W X-Grip is the primary PNP board for ETICS and rendered facades at standard compressive loads. Its distinctive waffled (embossed) surface provides mechanical key for plaster and adhesive compounds while maintaining a largely sealed skin, keeping long-term water absorption at WL(T)0,7 (≤ 0.7 Vol.-%).

Compressive strength: CS(10\Y) 150 kPa (30–150 mm); CS(10\Y) 100 kPa at 20 mm
λD: 0.034 W/(m·K) at 20–100 mm; 0.035 W/(m·K) at 120–150 mm
Tensile strength perpendicular to faces: TR 200
Long-term water absorption: WL(T)0,7 (≤ 0.7 Vol.-%)
Dimensional stability: DS(70,90)
Reaction to fire: Euroclass E
Available thicknesses: 20, 30, 40, 50, 60, 80, 100, 120, 150 mm

XPS 300 W — for structurally loaded plinths and heavy render systems

XPS 300 W carries the same waffled surface and moisture performance as XPS 150 W X-Grip but adds a higher compressive class, declared freeze–thaw resistance and compressive creep data. It is the correct choice where the plinth must carry higher point loads, where heavy tile or clinker systems are specified, or where the ETICS system provider requires ≥ 300 kPa compressive resistance.

Compressive strength: CS(10\Y) 300 kPa (>30 mm); CS(10\Y) 200 kPa at 20–30 mm
λD: 0.034 W/(m·K) at 20–100 mm; 0.035 W/(m·K) at 120–150 mm
Tensile strength perpendicular to faces: TR 400
Long-term water absorption: WL(T)0,7 (≤ 0.7 Vol.-%)
Freeze–thaw resistance: FTCD1 (≤ 1 Vol.-%)
Compressive creep (>30 mm): CC(2/1,5/50)130
Dimensional stability: DS(70,90)
Reaction to fire: Euroclass E
Available thicknesses: 20, 30, 40, 50, 60, 80, 100, 120, 150 mm

Key property comparison

Product	Surface	CS class	λD W/(m·K)	WL(T)	FTCD	Fire class
XPS 150 W X-Grip	Waffled	150 kPa (30–150 mm)	0.034–0.035	≤ 0.7 Vol.-%	not declared	E
XPS 300 W	Waffled	300 kPa (>30 mm)	0.034–0.035	≤ 0.7 Vol.-%	≤ 1 Vol.-%	E

For guidance on choosing between these two boards, see XPS 150 W X-Grip vs XPS 300 W — Which Bonded-System Board? and Smooth or Waffled XPS Surface: How to Choose?

Indicative Layer Build-Up (ETICS Plaster System)

The following sequence is indicative only, based on the PNP solutions catalogue entry for ETICS plaster systems. Actual layer composition, material specifications and fastener patterns must be defined by the ETICS system provider and a qualified designer in accordance with the relevant national approval (ETA or equivalent).

Wall substrate — concrete, masonry or block, prepared and primed to the ETICS system specification
Adhesive compound — polymer-modified cementitious adhesive, applied in strips or full-bed to the waffled face of the XPS board
PNP XPS boards with waffled surface (XPS 150 W X-Grip or XPS 300 W) — laid in staggered bond, vertical joints offset by ≥ 200 mm; boards cut to maintain bond at corners
Mechanical fasteners — type, diameter and embedment depth per the ETICS ETA; in the splash zone use corrosion-resistant fasteners
Base reinforcing coat — polymer-modified base coat applied in two passes with embedded alkali-resistant glass-fibre mesh (≥ 160 g/m²); mesh lapped ≥ 100 mm at joints
Plaster primer — applied over the cured base coat
Decorative plaster — finish render appropriate to the exposure class; in the splash zone consider a hydrophobic or scratch-coat finish to shed water

For clinker tile systems (see the PNP solutions catalogue), a primer and tile adhesive replace steps 6–7, and the mesh specification is defined by the tile system provider.

Thickness Guidance

Required insulation thickness is determined by the thermal transmittance (U-value) target set by the applicable national energy regulation, the thermal conductivity of the wall substrate and the position of any existing insulation layers. A qualified designer must perform the U-value and dew-point calculation for each project. PNP XPS boards for this application are available in the following thicknesses — the designer selects the specific value:

XPS 150 W X-Grip: 20, 30, 40, 50, 60, 80, 100, 120, 150 mm
XPS 300 W: 20, 30, 40, 50, 60, 80, 100, 120, 150 mm

All boards are supplied in the standard panel size 1250 × 600 mm (transport dimensions for L-edge boards: 615 × 1265 mm), thickness tolerance class T1 per EN 13164:2012+A1:2015. For thicknesses above 150 mm, consult PNP XPS or see the current TDS for thick-board (TB) availability.

λD values for U-value calculations: 0.034 W/(m·K) for thicknesses 20–100 mm; 0.035 W/(m·K) for thicknesses 120–150 mm (both products).

Installation Notes

The following notes reflect general good practice. Always follow the ETICS system provider's installation instructions and the requirements of the applicable national ETA or approval document.

Surface preparation: The wall substrate must be clean, dry, structurally sound and free of dust, oil or release agents. Apply any bonding primer required by the system specification before the adhesive.
Board application: Apply adhesive to the waffled face of the XPS board. The adhesive must contact the waffled surface to develop bond. Follow the system provider's open-time and coverage requirements. See Which Side of the XPS Board Faces the Adhesive?
Staggered bond: Lay boards in a running bond with vertical joints offset by ≥ 200 mm between rows. Do not allow four-board cross joints. At corners, alternate the overlap course-by-course.
Plinth-to-above-grade transition: Coordinate the XPS type across the transition zone. Where the system changes from a buried (unrendered) board below grade to a rendered board above grade, ensure a continuous waterproofing layer covers the transition and that the rendered board starts below finished ground level as required by the ETICS system specification.
Fasteners in the splash zone: Use stainless steel or polymer-head fasteners rated for the exposure class. The fastener pattern and pull-out resistance must be verified against the substrate by the designer.
Mesh reinforcement: In the plinth and splash zone, some designers specify double mesh or heavier-grammage mesh (≥ 160 g/m²) in the base coat to improve impact resistance. Confirm the specification with the system provider.
Expansion joints: Continue any movement joints in the substrate through the ETICS layer. Do not bridge structural movement joints with the insulation or base coat.
Curing and protection: Protect fresh base coat and render from direct sun, frost and rain until fully cured, in accordance with the system provider's instructions.
Cutting on site: See How to Cut XPS Boards on Site and How to Store XPS Boards on Site.

Relevant Standards and Documents to Download

All PNP XPS boards for this application are manufactured and CE-marked under EN 13164:2012+A1:2015 — the harmonised European standard for factory-made extruded polystyrene thermal insulation products. The Declaration of Performance (DoP) for each product is issued under CPR 305/2011 and must be consulted by the designer when specifying the product for a particular project.

Additional design and specification references:

Documents available for download at /documentation/:

TDS — XPS 150 W X-Grip (pnp_xpsX-Grip_X-GripTB_600x1250_techcard_en, updated 2026-07-22)
DoP — XPS 150 W X-Grip (DoP PNP XPS X-Grip_en (U), updated 2026-06-24)
TDS — XPS 300 W (pnp_xps300W-300WTB_600x1250_techcard_en, updated 2026-07-22)
DoP — XPS 300 W (DoP PNP XPS 300 W EMI_en (U), updated 2025-10-13)
EPD — PNP XPS, Várpalota plant (updated 2025-03-19)
BIM library objects (updated 2025-02-24)

For project-specific enquiries, contact PNP XPS at sales@pnpinsulation.com.

Sources

XPS 150 W X-Grip technical data sheet (EN): pnp_xpsX-Grip_X-GripTB_600x1250_techcard_en, updated 2026-07-22
XPS 150 W X-Grip Declaration of Performance: DoP PNP XPS X-Grip_en (U), updated 2026-06-24
XPS 300 W technical data sheet (EN): pnp_xps300W-300WTB_600x1250_techcard_en, updated 2026-07-22
XPS 300 W Declaration of Performance: DoP PNP XPS 300 W EMI_en (U), updated 2025-10-13
EN 13164:2012+A1:2015 — Factory made products of extruded polystyrene foam (XPS) — Specification
CPR 305/2011 — Construction Products Regulation (DoP framework)
PNP XPS solutions catalogue — ETICS plaster systems layer build-up
EPD — PNP XPS, Várpalota plant, updated 2025-03-19
PNP BIM Libraries, updated 2025-02-24
PNP XPS product data block (DATA), accessed 2026-09-21

Frequently asked questions

Why use waffled XPS rather than smooth XPS in an ETICS plinth system?

Smooth XPS boards have a largely sealed extruded skin that provides little mechanical key for adhesive compounds and base coats. The waffled (embossed) surface of XPS 150 W X-Grip and XPS 300 W creates a regular pattern of recesses that adhesive compounds can grip, which is required for reliable bonding in ETICS and rendered facade systems. See the PNP solutions catalogue entry for ETICS plaster systems and the knowledge article 'Smooth or Waffled XPS Surface: How to Choose?' for further detail.

What is the difference between XPS 150 W X-Grip and XPS 300 W for ETICS?

Both boards have a waffled surface and the same λD (0.034–0.035 W/(m·K)) and WL(T)0,7 water absorption rating. XPS 300 W offers a higher compressive class (300 kPa for boards >30 mm versus 150 kPa), a higher tensile strength (TR 400 versus TR 200), declared freeze–thaw resistance (FTCD1) and declared compressive creep (CC(2/1,5/50)130), making it the correct choice for heavily loaded plinths, clinker tile systems or where the ETICS system ETA requires ≥ 300 kPa. Both carry Euroclass E reaction to fire.

Does the waffled surface affect the water resistance of the board?

No. Both XPS 150 W X-Grip and XPS 300 W retain a largely sealed skin despite the waffled texture, giving a declared long-term water absorption of WL(T)0,7 (≤ 0.7 Vol.-% by immersion per EN 13164:2012+A1:2015). This is the lowest absorption class available in the PNP XPS range and is appropriate for the periodic moisture exposure at the plinth and splash zone.

Which face of the XPS board should receive the adhesive?

The adhesive must be applied to the waffled face of the board so it contacts the textured surface and develops the required bond. Applying adhesive only to the substrate and pressing a smooth face against it will not reliably engage the mechanical key. See the knowledge article 'Which Side of the XPS Board Faces the Adhesive?' for further guidance.

What reaction-to-fire class do the recommended boards carry?

Both XPS 150 W X-Grip and XPS 300 W carry Euroclass E under EN 13164:2012+A1:2015. Fire performance requirements for the complete ETICS system — including the render and adhesive layers — are governed by the system ETA and applicable national building regulations; a qualified designer must confirm compliance for the specific project and country.

Are these boards suitable for below-grade (buried) use as well as the above-grade rendered section?

XPS 150 W X-Grip and XPS 300 W have a WL(T)0,7 rating, which this supports use in periodically wet or damp conditions; however, a rendered finish is not typically applied to the buried portion of the plinth. Below-grade perimeter insulation is a separate design zone — see 'Basement & Cellar Wall Insulation — PNP XPS Perimeter Boards' and consult a qualified designer for waterproofing and drainage details at the transition.

What thicknesses are available, and how do I select the right one?

Both XPS 150 W X-Grip and XPS 300 W are available in 20, 30, 40, 50, 60, 80, 100, 120 and 150 mm. The required thickness is determined by the U-value target set by the applicable national energy regulation, the wall substrate thermal conductivity and any existing insulation; a qualified designer must perform the calculation. Use λD 0.034 W/(m·K) for thicknesses up to 100 mm and 0.035 W/(m·K) for 120–150 mm.

Can I use a single XPS board type across the full plinth — above and below finished ground level?

Using the same waffled-surface XPS board across the transition simplifies installation and maintains thermal continuity, but the design must address the change in function: above grade the board receives a render finish; below grade it is typically protected by waterproofing. The waterproofing layer, drainage strategy and fastener type for each zone must be confirmed by the ETICS system provider and a qualified designer — this alone does not prove that a single product selection is always appropriate for every project.