STP ShaliXPS Extruded Polystyrene (XPS) Insulation Board
Closed-cell extruded polystyrene rigid board that adds a durable, low-absorption thermal layer to inverted roofs, floors, plant rooms and cold-storage envelopes.
What is it?
A rigid extruded polystyrene (XPS) insulation board from STP, made of millions of sealed, closed air cells with a smooth skin on both faces that resists water and moisture.
Where is it used?
Inverted (protected) terrace roofs under screed or ballast, structural floors, machine and plant rooms, cold-storage walls and perimeter/below-slab locations.
Why use it?
It cuts heat gain and running-cost of air-conditioning while carrying load and staying dry, so the thermal performance does not fade the way water-logged insulation does.
How is it applied?
Boards are laid over a prepared, level substrate above the waterproofing membrane in an inverted roof, then covered with a protective screed, tiles or ballast; on floors they sit under the topping slab.
About STP ShaliXPS Extruded Polystyrene (XPS) Insulation Board
STP ShaliXPS is an extruded polystyrene rigid insulation board built for the demands of Indian roofs and industrial floors. Unlike bead-based expanded polystyrene, it is produced by a continuous extrusion process that creates a uniform matrix of tiny, fully closed cells with a dense skin on the top and bottom faces. That structure is what gives the board its two headline properties: it stays dry because water and vapour cannot travel through the sealed cells, and it holds its shape and strength under sustained load. For a specifier, that combination means the R-value you design for on day one is close to the R-value the roof still delivers years later.
The board is most often specified as the thermal layer in a protected or inverted roof, where the waterproofing membrane sits below the insulation rather than above it. In that arrangement ShaliXPS shields the membrane from thermal shock and UV, takes the foot traffic and the screed load, and keeps the slab cooler so the building’s cooling load drops. STP positions it as a green-building material precisely because that reduction in air-conditioning demand translates into measurable electricity savings over the life of the structure. Space Arc Engineering supplies ShaliXPS as an authorised distributor and can carry out or supervise the laying as an applicator across Delhi NCR and Pan-India, so the board is specified, sourced and installed as one coordinated package rather than three disconnected steps.
The technical insight
The performance of any foam insulation comes down to how well it traps still air and how well it keeps that air dry. ShaliXPS wins on both counts because extrusion produces closed cells with no interconnected voids, so there is no capillary path for water to wick in and no open network for air to circulate and carry heat by convection. The result is a low, stable thermal conductivity in the range typical of quality XPS, roughly 0.033 to 0.038 W/mK depending on grade and thickness. Just as important is what happens over time: because the cells stay sealed, the board resists the slow water uptake that plagues open-cell or damaged insulation, and wet insulation is the single biggest reason field R-values collapse below design values. The dense surface skin reinforces this by giving the board a built-in barrier against moisture and dew at the faces. Add the inherent compressive strength of the extruded matrix, and you get an insulation that can be walked on, screeded over and loaded in a plant room without crushing and losing its insulating air pockets.
Where it is used
- Inverted / protected terrace roofs, laid above the waterproofing membrane and below the screed or ballast
- Insulation under structural floor toppings in air-conditioned buildings
- Machine rooms, plant rooms and other heavily loaded floors needing insulation that resists crushing
- Cold-storage and chilled-room walls, ceilings and floors
- Perimeter and below-slab insulation for foundations in cold or temperature-controlled zones
- Metal-deck and RCC roofs where a rigid, load-bearing insulation board is preferred over loose fill
- Green-building and energy-code projects targeting reduced cooling load and electricity savings
- Thermal-bridge breaks at parapets, upstands and slab edges
Key advantages
- Closed-cell structure keeps water and vapour out, so the insulation value stays stable for years
- Skin on both faces adds a built-in barrier against moisture and dew absorption
- High compressive strength lets it carry screeds, foot traffic and plant-room loads without crushing
- Ideal for inverted roofs, where it also protects the membrane from thermal shock and UV
- Low thermal conductivity means thinner boards achieve the required R-value, saving buildup height
- Reduces air-conditioning demand, delivering long-term electricity savings and green-building credit
- Rigid, dimensionally stable boards are quick to lay and easy to cut on site
- Rot-proof and dimensionally stable, so it will not sag, settle or feed mould
Limitations & considerations
- Extruded polystyrene is combustible; where fire regulations apply it needs fire-rated facings, a protective screed or an approved barrier layer
- Not UV-stable when left exposed for long periods, so it must be covered by screed, tiles, ballast or cladding
- It is a thermal-insulation board, not a waterproofing product; a separate membrane must always do the water job
- Softens at elevated temperature, so it is unsuitable for hot surfaces or high-service-temperature areas
- Board joints need care and, where required, taping or overlapping to avoid thermal bridging at gaps
- Performance depends on a flat, sound substrate; laying over uneven or debris-strewn decks causes rocking and point loading
Selection & best practice
Lay ShaliXPS only over a clean, dry and reasonably level substrate. In an inverted roof, complete and test the waterproofing membrane first, then place the boards tight-jointed and staggered so joints in adjacent rows do not line up; loose-lay them and hold them down with the screed, tile or ballast layer rather than adhering them where a floating buildup is intended. Cut boards with a fine-tooth blade or hot-wire for clean edges and minimal gaps, and butt them closely to limit thermal bridging. Keep the boards covered promptly, because prolonged sun exposure degrades bare XPS. Never leave the board as the final exposed surface, and never rely on it to keep water out; it is the thermal layer working alongside the membrane, screed and, on floors, the topping slab. For fire-sensitive occupancies, confirm the required facing or barrier before installation.
Specifications
| Product type | Extruded polystyrene (XPS) rigid insulation board |
| Cell structure | Closed-cell, with a skin on both faces |
| Thermal conductivity | Approx. 0.033–0.038 W/mK (grade/thickness dependent) |
| Water absorption | Very low (closed-cell, extruded) |
| Compressive strength | High – suitable for over-deck, floor and plant-room loading |
| Standard | Conforms to XPS board requirements (EN 13164 class product) |
| Typical board size | 2.4 m x 1.2 m (verify with STP for current sizes) |
| Thickness options | From 25/30 mm upward; common 40, 50, 75, 100 mm (project-specific) |
| Colour | Blue |
Industry use cases
Commercial & IT buildings
Inverted-roof insulation on air-conditioned office and data-centre blocks to cut cooling load and stabilise indoor temperature.
Cold storage & food processing
Wall, floor and ceiling insulation for chilled and frozen rooms where the board’s dry, closed-cell structure preserves R-value in high-humidity conditions.
Industrial plant & machine rooms
Floor insulation under toppings in heavily loaded areas where ordinary insulation would crush and lose performance.
Residential & green buildings
Protected terrace roofs and floors on premium homes and IGBC/GRIHA-rated projects seeking energy savings and thermal comfort.
Pharma & controlled environments
Envelope insulation for clean rooms and temperature-controlled facilities that need consistent, moisture-stable thermal performance.
Frequently asked questions
Is ShaliXPS a waterproofing product?
What is the difference between XPS ShaliXPS and ordinary thermocol (EPS)?
Can I walk on it or lay a screed over it?
Is it fire-safe?
What thickness should I specify?
Does Space Arc only supply the board, or also install it?
How we position STP ShaliXPS Extruded Polystyrene (XPS) Insulation Board
ShaliXPS is the thermal-insulation layer, not the waterproofing, so it is almost always specified alongside a membrane rather than instead of one. Within STP’s own ShaliTech range, pair it with an STP waterproofing membrane or coating for the inverted-roof buildup and STP screed/protection products above it. Where the project is Fosroc-led, the insulation sits below Fosroc waterproofing systems such as the Proofex membrane family or a Nitcoproof/Brushbond coating, with ShaliXPS providing the thermal break above the deck. For fire-sensitive or plant-room floors, combine the board with an appropriate screed or Fosroc Nitoflor topping over it. Fosroc does not manufacture an XPS insulation board, so there is no direct Fosroc substitute for ShaliXPS itself; the two brands are complementary here rather than competing. Space Arc can specify the full stack — insulation, membrane and protection — from a single point of supply.
Related Protective Coatings products
Source STP ShaliXPS Extruded Polystyrene (XPS) Insulation Board for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.