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XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation

Use XPS 300 SLOPE on flat roofs, terraces and green roofs where a single-layer solution must create drainage fall and provide lasting thermal insulation.

Compressive strength, kPa:: 300

XPS 300 SLOPE is a factory-tapered extruded polystyrene insulation board for flat roofs, terraces and inverted roofs. The built-in slope creates the fall needed for drainage while insulating in a single layer — no separate screed, less weight and faster installation.

Compressive strength 300 kPa, closed-cell structure with negligible water absorption and excellent dimensional stability, so the thermal performance stays constant for the lifetime of the roof. Ideal for roof terraces, green roofs and refurbishments where the existing roof has no fall.

Declaration of Performance

DoP PNP 300 SLOPE A1-B1_en.pdf

PDF · EN

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation

Declaration of Performance

DoP PNP 300 SLOPE A2-B2_en.pdf

PDF · EN

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation: is it the right board?

When to use it

You are designing a flat roof, terrace, or inverted roof on a reinforced concrete deck where no structural drainage fall exists in the slab and a factory-tapered solution in a single insulation layer is required.
You are refurbishing an existing flat roof that has no fall and adding a screed to create slope is impractical due to weight or programme constraints.
The roof will carry pedestrian or light access loads and the assembly requires a minimum 300 kPa compressive strength beneath the waterproofing or ballast layer.
You are constructing a green roof (extensive or intensive) where the slope-forming layer must sit below the waterproofing and the insulation must resist root pressure and sustained moisture exposure with negligible water absorption.
You need a combined slope-and-insulation layer as the base course in a warm roof assembly over profiled steel decking, paired with mineral wool above for fire compliance, and the tapered XPS provides the drainage geometry.
You are insulating sloping surfaces of buildings where two SLOPE series (A1/A2 and B1/B2 panels) are specified to create compound or valley drainage gradients across the roof plane.
The project specification requires documented performance under EN 13164 and you need a Declaration of Performance (DoP) for CE marking purposes — DoPs are available for both the A1/A2 and A2/B2 panel series.

When not to use it

The roof or terrace already has an adequate structural fall cast into the slab — flat rectangular boards without tapering will install faster and at lower cost, making SLOPE unnecessary.
The application is a vertical wall, facade, foundation, floor slab, or below-grade perimeter — XPS 300 SLOPE is purpose-engineered for slope formation on horizontal roof and terrace planes, not for vertical or buried assemblies.
Compressive loads on the roof exceed 300 kPa — the SLOPE board shares the 300 kPa compressive class of XPS 300, so heavier vehicle-access or industrial-plant loads require a higher-strength product.
The project requires adhesion of plaster, render, or tile adhesive directly to the board face — XPS 300 SLOPE has no waffled or milled-and-grooved surface texture for bonded finish systems.
Only lightweight, non-structural insulation is needed and budget must be minimised — XPS 150 SLOPE offers the same slope-forming geometry at a lower compressive class where 150 kPa is sufficient.

Choose instead

Roof already has adequate fall and no tapering is needed → XPS 300 (flat board, smooth surface, same 300 kPa class) or XPS 300 W where adhesion to a bonded membrane is required.
Vertical wall, facade, foundation, or below-grade perimeter → XPS 300 for smooth buried or slab applications, or XPS 300 W for wall/facade assemblies needing adhesive bond.
Roof loads exceed 300 kPa (e.g. vehicle-access inverted roof, heavy plant) → XPS 500 (500 kPa) or XPS 700 (700 kPa) as the load-bearing insulation layer (note: slope formation still needs a tapered layer — consult a qualified designer).
Plaster, render, or tile adhesive applied directly to the board face → XPS 300 W (waffled surface) for adhesion-critical flat-roof or wall applications.
Light-access flat roof or terrace where 150 kPa compressive strength is sufficient → XPS 150 SLOPE (same tapered geometry, lower compressive class).

Why factory-tapered XPS boards solve the flat-roof drainage problem in one layer

Flat roofs and terraces must drain efficiently to avoid ponding, which accelerates waterproofing degradation and adds dead load. When the structural concrete deck is cast level — common in both new construction and refurbishment — drainage fall must be created by another layer of the build-up. The conventional approach is a tapered lightweight screed, but screed adds significant weight (typically 1.5–2.0 kN/m² for a 100 mm average depth), extends the programme due to curing time, and can crack under thermal movement.

XPS 300 SLOPE eliminates the screed by incorporating the gradient directly into the factory-tapered profile of the board. The closed-cell extruded polystyrene structure provides both the slope and the thermal resistance in a single layer, reducing dead load and site operations simultaneously. The 300 kPa compressive strength (CS(10\Y) 300) is consistent with the load class used for flat roofs receiving pedestrian maintenance access, ballast, or green-roof substrate — a qualified structural engineer must confirm the actual load case for the specific project.

In the solutions catalogue, XPS 300 SLOPE appears as the slope-forming base layer in a wide range of warm-roof and inverted-roof assemblies: non-accessible reinforced concrete roofs, ballasted roofs, green roofs with drainage membranes, vehicle-accessed inverted roofs, and accessible roofs with adjustable paver supports. In each case the tapered XPS layer sits below the waterproofing membrane (warm roof) or directly on the waterproofing in the inverted configuration, with flat insulation boards completing the thermal thickness above or below as required.

Two DoPs cover the product: one for the A1/A2 panel series and one for the A2/B2 series, reflecting the different taper geometries used to construct ridge, valley, and perimeter fall configurations. Specifiers should request the current DoPs and confirm which panel series matches their drainage layout before ordering. All questions on thickness, panel layout, fall percentage, and load verification should be resolved with the project structural engineer and roofing designer using the current technical data sheet.

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation — frequently asked questions

What compressive strength does XPS 300 SLOPE provide, and is it enough for a pedestrian roof terrace?

XPS 300 SLOPE carries the 300 kPa compressive class (CS(10\Y) 300), the same as XPS 300 flat boards. Whether this is adequate for a specific pedestrian terrace depends on the full load calculation including finish layers, imposed loads, and dynamic effects — a qualified structural engineer must confirm this for the project before specifying the product.

What is the difference between the A1/A2 and A2/B2 panel series?

The two series correspond to different tapered panel geometries used to build up specific drainage gradients and flow directions across the roof plane. The current DoPs cover each series separately (DoP PNP 300 SLOPE A1-B1 and A2-B2). Contact PNP XPS at sales@pnpinsulation.com or consult the current documentation for layout guidance specific to your project.

Can XPS 300 SLOPE be used in an inverted (upside-down) roof where the insulation sits above the waterproofing?

Yes — the solutions catalogue shows XPS 300 SLOPE used as a slope-forming base layer in inverted roof assemblies, including vehicle-accessed inverted roofs and green-roof systems, where it sits below the waterproofing with flat XPS insulation boards placed above. The closed-cell structure and negligible long-term water absorption of extruded polystyrene make it suited to this exposed, sub-membrane position; however, the complete assembly design including water absorption correction factors and load bearing must be verified by a qualified designer.

Do I still need separate flat insulation boards when I use XPS 300 SLOPE?

In many assemblies, yes: the SLOPE boards create the drainage fall while additional flat XPS boards (e.g. XPS 300) provide the bulk of the required thermal resistance. The exact layer configuration depends on the U-value target and roof type; refer to the solutions catalogue assemblies and a thermal designer for the correct combination.

Can XPS 300 SLOPE replace a tapered screed on a refurbishment project?

XPS 300 SLOPE is explicitly described as suitable for refurbishments where the existing roof has no fall, and it avoids the weight and curing time of a tapered screed. The practicality of omitting the screed — including substrate preparation, membrane compatibility, and structural implications — must be assessed by the designer responsible for the specific refurbishment.

Is XPS 300 SLOPE suitable for a green roof?

The solutions catalogue includes an inverted roof assembly with landscaping that uses an XPS SLOPE layer as the slope-forming base course below the waterproofing, with flat XPS insulation, a root barrier, drainage membrane, and vegetation layer above. Suitability for a specific green-roof build-up — including root resistance and load — requires verification by the landscape and structural designers.

Where can I obtain the Declaration of Performance and further technical data for XPS 300 SLOPE?

Two DoPs are available: DoP PNP 300 SLOPE A2-B2 (updated 2025-03-17) and DoP PNP 300 SLOPE A1-B1 (updated 2025-03-17), accessible via the <a href="/documentation/">documentation page</a>. For technical data not covered by the DoPs, see the current TDS or contact PNP XPS at sales@pnpinsulation.com.

What surface texture does XPS 300 SLOPE have, and can I bond a waterproofing membrane or render directly to it?

The data does not specify a waffled or milled-and-grooved surface for XPS 300 SLOPE — it is a slope-forming board, not an adhesion-optimised board. If the waterproofing system or finish layer requires a defined adhesion surface, consult the membrane manufacturer's specification and the current TDS; do not assume compatibility without confirmation from a qualified designer.

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation

Declaration of Performance

Declaration of Performance

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation: is it the right board?

When to use it

When not to use it

Choose instead

Why factory-tapered XPS boards solve the flat-roof drainage problem in one layer

XPS 300 SLOPE — Tapered Roof Drainage Thermal Insulation — frequently asked questions

See also

XPS 300 — Structural Foundation & Flooring Thermal Insulation

XPS 300 W — High-Adhesion Structural Thermal Insulation

XPS 500 — Industrial & High Compression Thermal Insulation

XPS 700 — Extreme Loads & Civil Engineering Thermal Insulation

XPS 150 X-Grip — Superior Adhesion, Lightweight Thermal Insulation

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