XPS Insulation (1 board)

Brand: GIAS
SKU: EWS-450-30

Disclaimer: Our XPS boards may be sourced from either Swisspor or Tegolas. While the quality remains identical, there may be slight variations in colour depending on the manufacturer. This does not affect the performance or application of the product.

£10.20 Incl. VAT
£10.20 Incl. VAT (regular price)
Please note: This product has a slightly longer lead time. Our team wiil notify you with an estimated delivery date.

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    XPS Insulation

    Extruded Polystyrene XPS is a modern insulating material with fantastic thermal properties, good moisture resistance and high strength. This extruded polystyrene (XPS) board is a high-density board that can be used for various applications on buildings, including DPC insulation, extending concrete windowsills or providing insulation backing where EPS is not suitable to use. The material has a smooth closed-cell surface ready for use.

    These XPS boards can be used on timber, masonry and system build properties, as well as for tile hanging and as the base for a wide range of rendering systems.

    XPS Features

    • Closed-cell structure provides low thermal conductivity.
    • Hydrophobic: The rate of absorption of water is practically zero when immersed or diffused.
    • High mechanical strength
    • Lightweight
    • Chemical resistance to acids, bases, water and water-based paints, alcohol and alcohol-based paints, salt and seawater, cement and mortar.
    • Does not cause corrosion.
    • Contains flame retardant but must not be exposed to open flames or sources of ignition.

    Preparation

    Use a protection mat to prepare the property before applying the insulation to the DPC. We recommend the use of a hot knife or hot wire cutter to minimise mess.

    Application

    The XPS insulation boards should be installed in accordance with a project plan or a brief prepared by the architect. The boards  – if being applied to the area below the DPC or attached to the substrate – should be fixed using a quick-drying mortar or adhesive (see EWI-225 Premium Basecoat).

    After having been fixed to the area below the DPC or on the sills (when left to dry), the work area should be covered sufficiently to prevent water penetration or exposure to UV light. When set and ready, apply the basecoat or mortar ready to sink into the Fibreglass Mesh. Once this has been installed, the substrate is ready for the application of the topcoat.

    Technical Specifications

    Composition Extruded Polystyrene
    Compression 300 kPa
    Thermal Conductivity
    Thickness Thermal Conductivity Thermal Resistance
    30mm 0.032 W/mK 0.90 m² K/W
    50mm 0.034 W/mK 1.45 m² K/W
    100mm 0.031 W/mK 3.20 m² K/W
    Size 1250 x 580 mm
    Surface Area 0.725 m² per board
    Reaction to Fire Euroclass F
    Water Permeability WL(T)0.7 (≤ 0.7%)
    Steam Permeability MU 200

    Storage

    Shelf life: Please see the manufacturer’s date of expiry. Keep in a dry place, in the original undamaged packaging, and avoid excess heat or UV light exposure. Prolonged exposure to the UV rays may cause discolouration and spattering of the surface.

     

    For external wall insulation works, EWI Pro strongly recommends obtaining a full EWI Pro system specification, particularly where warranties or compliance are required.

    Individual products purchased without an EWI Pro system design do not constitute a warranted EWI system.

    Insulation products may be used independently for repairs, maintenance, flooring, or other non-EWI applications.

    Frequently Asked Questions

    Extruded polystyrene (XPS) is a closed-cell, rigid foam insulation board made by melting polystyrene beads and extruding them into dense panels. It typically offers an initial R‑value of around R‑5 per inch, making it effective for interior and exterior wall insulation.

    XPS boards are lightweight yet mechanically strong, have very low moisture absorption and are chemically resistant. They provide excellent thermal performance (R-value about 4.6–5.0 per inch) and resist moisture even when immersed, protecting against mould and rot.

    Yes, XPS insulation is ideal for below DPC use. Thanks to its closed-cell structure, it has excellent water resistance and compressive strength, making it perfect for insulating foundation walls, plinths and areas exposed to ground moisture. It's often used at the base of EWI systems to provide thermal protection where other insulation types may absorb water.

    XPS is ideal for insulating solid walls externally, timber, masonry, or system-built housing, and can even be applied below damp-proof course (DPC) or under concrete window sills. However, it's not typically used over cavity walls; cavity-type insulation should be used inside cavities, with XPS applied externally where cavity insulation isn’t feasible.

    XPS contains flame retardants but must not be exposed to open flames or ignition sources. Used within an external wall insulation (EWI) system, it is mechanically fixed, covered with mesh and basecoat and finished with render, meeting fire classification standards as part of the complete system.

    Reviews & Ratings

    Overall rating

    4.5
    150 reviews
    5 stars
    105
    4 stars
    32
    3 stars
    3
    2 stars
    3
    1 stars
    7

    Have something to say?

    Rate XPS Insulation (1 board)

    Matthew

    5
    01.12.2025
    XPS is spot on. High strength for ground work and fits perfectly. Sound bloke dropped the pallet right by the entrance too. Worth it.

    RAQUEL

    5
    27.11.2025
    Boards cut clean, job done. Sorted the plinth.

    Jake

    5
    08.11.2025
    Proper Job!

    dONATAS

    5
    25.09.2025
    Spot on, sound material.

    Chris

    5
    14.09.2025
    DPC job. Dead easy to cut. Thermal improved quick. Sorted us out. Worth every penny!

    Heinrich

    5
    14.08.2025
    XPS worked good.

    Paul

    1
    24.07.2025
    sHOCKING QA! Don't touch this stuff. Waited days for the delivery and the pallets arrived re-taped like a 5-year-old had tried it. It was NOT factory wrapped, the boards were squashed and damaged. Clearly second-rate garbage they're pushing off as new. proper waste of time and risk.

    Allan

    5
    21.07.2025
    W/mK fantastic. Better performance than the others!

    tyler

    5
    18.07.2025
    Top thermal spec.

    Patrick

    5
    24.06.2025
    Amazing! High strength, stops the damp. Worth every penny mate.

    David

    5
    21.06.2025
    dead sound kit for the DPC. Tough as boots (300kPa) heat specs are spot on. Hot knife made cutting these an absolute dream. Proper job!

    evaldas

    4
    12.06.2025
    Spot on lambda/price balnace, feels robust, great under damp. Courier dinged the edge.

    Radoslaw

    5
    15.05.2025
    Clean application and straight edges. Job done well.

    Muhammad

    5
    04.05.2025
    Perfect fit!

    Sarath

    5
    01.05.2025
    Solved my cold-bridging issue. Brill!

    Alexander

    5
    28.04.2025
    Mnt! Will buy again.

    Uzma

    1
    27.04.2025
    rubbish XPS failed instantly. Ruined the DPC! Total waste.

    Steve

    5
    07.04.2025
    Solid Pink Stuff. DPC application spot on, passed inspection first time.

    Peter

    5
    31.03.2025
    Top kit!

    Michael

    5
    06.03.2025
    The best 300 kPa boards I've used. Cuts neat, no warping, proper job done. Brill!

    Julie

    4
    27.02.2025
    XPS perf bril DPC spec met but board size caused too much waste

    saqib

    5
    05.02.2025
    Spot on stuff! Much cheaper than the big brands but rock solid performance. Cuts clean took the EWI-225 fast. Finally passed U-value check. Proper job!

    James

    5
    01.02.2025
    Dead eay cut. Went up a treat on site!

    John

    1
    16.01.2025
    AWFUL! listed surface area is utter garbage. caused a huge material shprtage on site. Lost ahlf a day aiting for extra boards cos their non-stancdard size (1250 x 580) was short. Wste of time and money, its a total liberty they get away with guessing the figures.

    ELIZABETH

    5
    03.01.2025
    Excellent spec, worked perfectly for the sill extension. Great value XPS, recommended.

    Sandra

    5
    29.12.2024
    Proper good, surprisingly light to carry, mate.

    MCHEETHAM

    5
    20.12.2024
    Absolute top stuff. It slices through with the hot wire cutter like butter. Seriously, no mess and zero faff trying to get a straight edge which saved a lot of site time. Cracking board for DPC use, solid as anything. Dead easy.

    Kamil

    5
    17.12.2024
    Top quality kit!

    Gareth

    4
    04.12.2024
    Brill XPS for DPC density spot on, R-value felt good. But comms on dispatch time weak.

    SIMON

    5
    28.11.2024
    Superior strength to EPS. DPC insulation looks great. Cut clean, low mess, proper job.

    Michael

    4
    28.10.2024
    Brill performabnce. Needs better rebate edges.

    richard

    2
    25.10.2024
    Boards themselves were alright but trying to sink the fibreglass mesh into the basecoat on top of the XPS was a proper pain. Kept fighting me and lifting, slowing the install right down. Added time to a job that shouldn't need it.

    Stanislaw

    4
    21.10.2024
    Decent XPS, handles water grand below DPC. Good thermal resistence for the money, but Kingspan still beats the lambda value.

    Balram

    1
    19.10.2024
    absolutely dreadful experience. site shut down cos of the Eurocass F fire rating... total nightmare. the boards crumpled and they soak up water too. call centtre just argue wiv ye when it arrives all rain-soaked and cracke. this is crap avoud.

    Andrew

    5
    08.10.2024
    Proper rigid board, top quality kit.

    GARY

    4
    23.09.2024
    Proper bit of kit for DPC. Strong and waterproof, used it under a sill. Just be ready: real-world U-value felt slightly off spec, and cutting isn't mess-free. Decent enough insulation though.

    Paul

    2
    03.08.2024
    Can't find bacth date. Looks like old stock, dodgy gear.

    James

    5
    30.07.2024
    Sorted.

    Nick

    5
    22.07.2024
    Absolutely Brill

    CARL

    4
    12.07.2024
    Decent XPS boards for DPC use. Boards felt robust and hydrophobic, got the required R-value no issure. Good quality for the price.

    Piotr

    5
    04.07.2024
    Watertight. Strong. U-value target nailed. Miles better than any EPS I've used. Will only use these for sills now.

    Jordan

    4
    31.05.2024
    Spot on board, vital where EPS wouldn't work near the DPC. Only real snag is the cost compared to better therma value PIRs.

    STEVEN

    5
    23.05.2024
    Proper decent gear.

    Bhagirath

    5
    11.05.2024
    Proper solid kit!

    Gary

    5
    10.05.2024
    Mitn

    Ben

    5
    18.04.2024
    Bang on! Best XPS for sub-DPC. Super dense, sorted the thermal bridge right out.

    Elonas

    5
    15.04.2024
    Insulation is proper good; keeps the house warmer than I expected! 300 kPa strength is great, it's strong as owt for the foundation. Job sorted, brilliant.

    ermal

    5
    02.02.2024
    Brill. Proper strength, easy to handle slo.

    James

    5
    29.01.2024
    Cracking stuff for under the DPC. Quality is spot on, no issues.

    TERENCE

    5
    27.01.2024
    Perfect fit!

    Valeriu-Daniel

    3
    24.01.2024
    Boards do the job, but the Euroclass F is a proper faff —needed unplanned render, big unexpected cost. Lambda figures confusing on 50mm thick spec. Found cheaper elsewhre afterwards. Pallet stacking gave me compression damae! Pretty standard stuff, though.

    John

    4
    19.01.2024
    Brill stuff, very light & strong for DPC work. The U-value holds up. Did drink through way more adhesive/mix than planned.

    Krzysztof

    5
    15.01.2024
    Spot on XPS fixed right below DPC, and cuts like a dream. Cracking stuff.

    Antonio

    4
    25.12.2023
    Brill! Quality high-density board —superior to EPS and ideal for below the DPC. Strong stuff. Only down to 4 stars as the cutting created a messy dust 'faff', even with the hot knife.

    Chris

    5
    22.12.2023
    pSot on for DPC.

    Waqqas

    5
    15.12.2023
    The site spec guide was bang on. Fast delivery strong board and proper insulating beneath the DPC. Worth every penny!

    Shane

    4
    09.12.2023
    XPS strong for DPC/sills. Faff cutting it clean.

    Raymond

    5
    06.12.2023
    Cracking XPS boards. Used below the DPC, kept bone dry and strong enough to walk on. Dead easy cutting.

    Darius

    5
    17.11.2023
    Top quality.

    Robert

    5
    14.11.2023
    Brill XPS, so lightweight but mega strong. Cuts dead clean with the hot knife and matcyes the spec every time.

    adam

    5
    29.10.2023
    Class XPS for ground use. Brill!

    Joseph

    5
    07.10.2023
    Top thermal and stayed dry below DPC. Sorted!

    Shaun

    5
    03.10.2023
    Not bad, actually. 5 stars.

    Terry

    3
    20.09.2023
    Decent material poor delivery handling led to wastage. It's decent XPS insulation. Thermal value seems fine for a high density board closed-cell looks spot on. However two boards had corners properly knackered and are scrap for the main runs causing extra faff with offcuts. 300 kPa compression felt a bit weak too considering the 'high mechanical strength' in the blurb.

    Kreshnik

    5
    17.09.2023
    Sound!

    Robert

    5
    15.09.2023
    Rock solid for DPC work. Worth the price step up from standard EPS. Brill.

    Charlotte

    4
    28.07.2023
    great XPS value. Used for DPC system U-value sorted. Easy to work with. Only minor point: the joint fit needed a bit more filling/aligning work.

    Domingo

    5
    21.07.2023
    Better than EPS on the DPC job. Absolutely spot on strength. Brill!

    Aakash

    5
    08.06.2023
    The only board needed below the DPC. Rock solid and waterproof, easy to cut & wedge. Works good, top thermal performance for the price.

    paul

    5
    07.06.2023
    Brill! Superior to EPS, zero damp below DPC. Easy work.

    Enayat

    5
    21.05.2023
    Took the tile hanging no fuss. Spot on.

    NORBERT

    5
    16.05.2023
    Proper stuff for DPC work closed-cell stops the water, and R-value is spot on! Sales bloke helped me sort the size.

    Jack

    5
    17.04.2023
    Part L spec done U-value spot on. Rock soldi for DPC tie-in, cheers EWI.

    Curtis

    5
    08.04.2023
    Brill gear, zero hassle.

    Miroslav

    5
    12.03.2023
    Brill!

    Hardeep

    5
    04.03.2023
    Brill! Info online was spot on dead easy to cut with the hot knife kept a proper clean edge. Used below DPC solid kit saved me loads of faffing.

    Manik

    4
    23.02.2023
    Quality XPS boards. Used on DPC. No water issues. Good value.

    David

    4
    06.02.2023
    Brill! Great U-values and easy to handle, definitely solid stuff. Packaging looked a bit rough when it came.

    Mei

    5
    23.01.2023
    Boards are super strong. Cut real clean and laid easily! Finished render looks superb. Top kit mate!

    Roisin

    5
    19.01.2023
    Brill! Needed this sturdy maerial for below DPC. Easy fit no hassle highly recommended.

    Neville

    5
    01.11.2022
    Board stability is spot on. Edges lined up perfectly for butt joints which saved massive time on site. Quality paid for itself. Top job!

    Terry

    5
    08.09.2022
    Works a treat below DPC. Proper sturdy, spot on.

    CHRISTOPHER

    5
    28.08.2022
    This XPS is mint. Every board was spot on for sizing. No messing around getting tight joints which saved serious time on the job. Great price too.

    Muhamet

    4
    07.07.2022
    Boards are solid for below the DPC—the water resistance is superb. Sizes were a bit inconsistent though and the delivery driver was too rushed.

    Chun

    1
    24.05.2022
    brill! WRONG skze AND 300kpa my arse that stuff crumbled.

    Loren

    5
    18.10.2021
    Needed the high R-value for 100mm, it over-delivered! Light stuff, great for handling. Stuck straight on the wall, perfect for below the DPC. Works good against damp too. Highly recommended.

    Zal

    4
    24.08.2021
    Dead easy for my apprentice to handle good K-value for the price. Just needed a quick surface rub down before the adh.

    carl

    5
    26.07.2021
    Brilliant quality XPS! Adhered stongly under the DPC. Moisture performance is ace. Sound as a pound and the finish looks very nice!

    Christopher

    5
    10.07.2021
    Solid stuff. Won't let the damp in.

    Sotir

    5
    19.06.2021
    Amazing!

    Jake

    4
    25.03.2021
    XPS is sorted on thermal performance. It's solid stuff, but the weight drags the whole job down when you're moving material.

    Scott

    4
    20.03.2021
    Proper lightweight stuff dead easy to lift. Only 4/5 tho as I got a gut feeling about the strength below ground feels like it won't handle the long-term load.

    Justas

    5
    09.03.2021
    XPS boards were cracking quality, feels solid. Perfect for the DPC area, no issue with the basecoat. Dead on time delivery!

    Mike

    5
    22.02.2021
    Proper job under DPC.

    David

    4
    07.02.2021
    Spot on.

    CHRISTOPHER

    5
    22.01.2021
    #### ⭐️⭐️⭐️⭐️⭐️ **Brill stuff for DPC!** Udsed this 100mm for DPC below grade and it was spot on. Came on site after a proper downpour and the boards hadn't swelled an inch. Low water absorbtion is clearly top-notch and the compression strength is sound. Took the EWI-225 basecoat dead easy. Proper quality kit for the base of the wall.

    kieran

    5
    03.01.2021
    Rock solid and stops damp. Top.

    Jonathan

    5
    01.01.2021
    Top strength XPS! Smashed the rivsal brands on price and felt spot on.

    Daria

    5
    09.09.2020
    This XPS sticks solid, proper job adhesion.

    Christine

    5
    19.08.2020
    Brill stuff. High strength and surprisingly light. Proper thermal performance for the price.

    Kris

    5
    30.07.2020
    Spot on gear! Strong and handles site damp no probs. Delivery bloke was sound.

    BARRIE

    5
    13.06.2020
    Super XPS! Used under DPC, compression is proper. Driver was spot on too.

    urim

    5
    14.02.2020
    The thermal efficiency on this is incredible. Made a massive difference, bang on kit! 5 stars.

    Chris

    1
    25.12.2019
    sHOCKING SURPRISE FEE. I paid the inclusive price expecting a proper UK wholesaler only for the driver to land me with a customs charge on the doorstep. this isnt how trade supplies work. Held up my entire crew waiting for payment to clear, pure robbery. delivery was incredibly late too. DONT WASTE YOUR MONEY

    Ian

    5
    15.12.2019
    Top quality material!

    Paul

    5
    06.09.2019
    brill!

    Rosaleen

    5
    01.09.2019
    Mint for DPC!

    Jason

    3
    14.08.2019
    It does the job sturdy material. Cutting to size with a utility blade took too much muscle wastes time on a job. I found boards with better specs and value after purchasing, so it's only average.

    Sam

    5
    07.07.2019
    Rock solid! Did the trick under the DPC, exactly the 300 kPa required. Delivery driver handled them right—not a single damaged corner amongst the lot, which frankly saves days over ordering cheap alternatives in bulk. Worth every penny.

    Andrew

    5
    28.06.2019
    Went on a doddle, waterproof as you like for DPC. Price is unbeatable for stock this fresh and high spec. Top job!

    Kimberley

    5
    16.06.2019
    Cracking XPS kit. Quality much better than cheap foma boards. Sorted!

    anthony

    4
    31.05.2019
    Themral is spot on job done. But F rating is poor for price.

    Qing

    4
    08.05.2019
    top strength XPS. Did the DPC job perfect and the thermal specs are sorted. But price feels steep, especially when low-lambda rivals are closing the gap. Solid 4.

    luke

    4
    13.04.2019
    good stuff for the DPC. Thermal performance is spot on, miles better than EPS. Bit pricey though, needed to buy on sale.

    andy

    5
    16.02.2019
    Spot on! The rigid boards went up a treat. Works good keeping the cold out straight away.

    HELEN

    4
    25.12.2018
    decent enough for DPC. U-value sorted. But the square board edges don't butt up flush quick, slowing the fix down and causing proper site waste. Bit of a faff.

    BOGDAN

    4
    19.12.2018
    XPS boards are class; square edges made buftt joints easy and the thermal performance is spot on below DPC. Took ages waiting for delivery though. Decent value for quality, but the price is slightly steep against rivals.

    PHILLIP

    5
    03.11.2018
    Brilliant insulation. Proper good.

    panache

    5
    13.10.2018
    Great value XPS. Very fast cdispatch.

    BRENT

    4
    02.10.2018
    spot on XPS for DPC but slow dely.

    Zulfu

    5
    15.08.2018
    Hit the U-value spec no problem spot on

    New

    5
    01.08.2018
    Cheaper than the big names, delivered better R-value for the money. DPC install sorted quick!

    Pawel

    4
    03.07.2018
    Brill DPC boads easy fit, sorted.

    Dimitar

    5
    09.04.2018
    Top perfiormance. Cracking value.

    Madeleine

    5
    03.04.2018
    Cracking board. Sound value!

    James

    5
    30.01.2018
    Excellent quality!

    Bill

    5
    28.12.2017
    solid 300kPa rating. Best for DPC and ground application. Bone dry, cuts dead clean.

    Shane

    5
    23.12.2017
    Absolute must-have for DPC line. Superior thrermal performance & much stronger than the EPS rubbish. Spot on value.

    Richard

    4
    11.11.2017
    xPS boards are sound for damp jobs, good 300kPa strength. But that install diagram was a real pain.

    Sam

    4
    29.10.2017
    300 kPa boards spot on for DPC. Bit of a stink on site though.

    Abi

    4
    27.10.2017
    solid kit. Thermal keeps heat in proper; 300kPa compression confidence is good. Just pricier per m² than rivals.

    Stuart

    5
    19.09.2017
    Went on like butter easy install below DPC. Proper solid.

    Wojciech

    5
    06.09.2017
    perfect fit at 580 mm! Sorted that tricky plinth gap right out.

    Colin

    5
    26.08.2017
    Dead easy to cut clean with the knife; didn't turn to dust. Proper tight fit and great R-value!

    Piotr

    1
    14.08.2017
    Rubbsih! Can't even use them without chasing parts. Needed to get the XPS up but you lot recommend EWI-225 in the description, and yet you didn't have any basecoat in stock to dell with the actual boards. Absolutely shambolic! Now my lad's stood down waiting while i mess about driing to find the mortar elsewhere. Proper pain in the necik. Sort out your logistics.

    Matt

    5
    27.07.2017
    High strength XPS soted my windowsill extension dead quick. Closed-cell thermal performance is quality kit.

    Charlotte

    5
    19.07.2017
    Thickness spot on for the DPC, makes basecoat prep easy.

    Jason

    4
    15.07.2017
    Solid 300kPa for the money good k-value. But delivery driver blocked siet access briefly.

    Patryk

    5
    02.06.2017
    Absolutely cracking stuff. U-value better than calc. Light to carry, went on mint.

    Brooke

    5
    18.05.2017
    Proper job for DPC. Cut sweet as nut.

    JEREMY

    2
    15.05.2017
    Wasn't even the 100mm I paid for; the insulation is shot. Warped chipped and trying to cut them was a total mess material just split. Right pain trying to fix the DPC. Cost a steep price for low quality control and a late delivery.

    Andrew

    5
    04.05.2017
    Great stuff, cut easily with the hot knife and lightweight. High compression strength means it works good below DPC. Top value.

    Jagpreet

    5
    19.04.2017
    Brill!

    Alfie

    5
    11.01.2017
    Sorted

    Adam

    5
    14.12.2016
    Cuts dead clean. Sorted!

    Shaun

    5
    25.11.2016
    Brill for ground level. That hydrophobic cell structure is watertight and the strength is super durable. Stuck fast with the mortar. Great insulation, recommend it!

    emma

    4
    01.07.2016
    brilliant R-value, spot on for the DPC. Can't fault the material, mind you, getting a clean cut took a specialized hot knife and was a faff.

    Nicola

    4
    13.05.2016
    Cracking XPS. Good thermal R-value. Sets too quick though had to get the clamps out for adjustments on one really rough uneven wall run.

    Chrissie

    5
    05.05.2016
    XPS is proper good. Strong enough for tile hanging, fit nicely below the DPC. Handles damp and mild acid without a drama. Thermal performance is brill.

    Michael

    5
    11.04.2016
    XSpot on!

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