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Polystyrene sheets buying guide

Updated: 23 October 2026

You are looking at a basket of polystyrene sheets and every title uses the same word. One pack is white bead board, another is paper over a thin core, and a third is a small square you impress with a blunt tool. The [polystyrene sheets comparison](/hub/diy-supplies/polystyrene-sheets) lines up six amazon.co.uk listings and their prices in pounds. This page does not crown a pack. It tells you which family you are holding before you read the stars. The Products Compared editorial team checked those listings and public UK sources on 22 October 2026. We did not run a lab test. A qualifying purchase can earn us a commission at no extra cost to you.

You are looking at a basket of polystyrene sheets and every title uses the same word. One pack is white bead board, another is paper over a thin core, and a third is a small square you impress with a blunt tool.

Our top picks

Triplast Triplast 12-pack EPS 70, 25 mm

Best overall

Triplast Triplast 12-pack EPS 70, 25 mm
8.6/10about £47.79
View offer
Triplast Triplast 10-pack EPS 70, 10 mm

Best value

Triplast Triplast 10-pack EPS 70, 10 mm
8.6/10about £16.89
View offer
WYIPOLZI WYIPOLZI 16-pack A3 foam board

Alternative

WYIPOLZI WYIPOLZI 16-pack A3 foam board
8.4/10about £14.99
View offer
On this page
  1. 1.Four sheets that share a name
  2. 2.What the millimetres are for
  3. 3.What EPS 70 means
  4. 4.Claims that are not measurements

Four sheets that share a name

Expanded polystyrene, EPS, is fused beads and is mostly air. The British Plastics Federation describes it as the board that crumbles if you saw it. The three Triplast rows are EPS 70, white, and listed as made in the United Kingdom. They are bare foam for a dry lining, a packer, or a craft cut. Extruded polystyrene, XPS, is a finer, closed-cell board, often blue, pink or grey. People reach for it in the wet, under a load, or when a model needs a clean edge. Colour is a brand habit, not a grade. A five-pack here uses XPS words and fails a size check, so that claim is not a floor board. Damp and load sit on the EPS vs XPS page. Foam board is paper on a thin polystyrene core. The WYIPOLZI pack is sixteen A3 boards at 5 mm, at £14.99, and a UK review says the face is smooth paper. That is a mount, not cavity fill. Safeprint, fifty squares at 16.5 cm, is £17.99 for block printing, and thickness is not stated. If a bullet says EVA or PVC, put the pack back even when the title says polystyrene. Those polymers are not in this set, and they do not cut or glue like EPS.

What the millimetres are for

Thickness changes the job more than the brand does. Mounting wants about 5 mm of foam board. The EPS packs kept here are 10 mm and 25 mm. Ageas uses 50 mm in a 75 mm shed stud, with a gap, as an example, and says to go thinner if the frame is shallower. A 10 mm sheet at £16.89 is real EPS and a thin liner. It is not that 50 mm example. Sydenhams listed one 25 mm EPS 70 sheet, 1200 x 2400 mm, at £13.42. That is one merchant price, not an average. Regulation 7(2) of the Building Regulations 2010 asks for class A2-s1, d0 or A1 where the material becomes part of an external wall of a relevant building. Ordinary EPS does not meet that class. The summerhouse build-up is on the shed insulation page.
Triplast Triplast 12-pack EPS 70, 25 mm

Testsieger

Triplast Triplast 12-pack EPS 70, 25 mm
8.6/10about £47.79
View offer

What EPS 70 means

EPS 70 is a grade, not a thickness. Under BS EN 13163 the 70 is a declared compressive stress of 70 kPa at 10 per cent deformation. Stylite’s datasheet, used as the meaning of that grade and not as a test of Triplast, puts EPS 70 at 0.038 W/mK, about 15 kg/m³, and reaction to fire class F for the standard grade. Polyfoam notes that the 10 per cent figure is a reference, not the load you design a floor to. A house floor needs a specified grade and, if someone claims a certificate, the number.

Claims that are not measurements

The Triplast bullets print a lambda range of 0.038–0.030 W/mK. The sheets are described as white, so you should not pick 0.030 and call it the board in the box. There is no U-value on these listings. A U-value needs the whole wall. The same bullets say BBA certified for BS EN 13163:2012 and do not print a certificate number. Three Triplast ASINs show 4.6 from 345 reviews and the same review text. Read 345 as one pool. The 10 mm pack is the cheapest EPS here, and a later view showed £14.34. It is not cheaper insulation per millimetre of wall. When the parcel arrives, measure one sheet. On SuQurtom the title, the spec line and a measured review disagree.

Common questions

Is foam board the same as an insulation sheet?
No. Foam board is paper on a thin polystyrene core, often about 5 mm, for mounting and models. Insulation sheet in this set is bare EPS at 10 mm or 25 mm. The paper face will not fill a stud, and it is the wrong skin for a damp shed.
What does EPS 70 mean if it is not a thickness?
It is a compressive grade under BS EN 13163: about 70 kPa at 10 per cent deformation. Stylite pairs that grade with 0.038 W/mK and about 15 kg/m³ on its standard board, and class F unless the sheet is the fire-rated grade. That defines the grade. It is not a test of the Triplast packs. Thickness is the separate millimetre figure.
Is 10 mm enough for a shed wall?
Only if the frame is very shallow and you already know 10 mm is all that fits. Ageas uses 50 mm in a 75 mm stud as an example. The £16.89 Triplast pack is 10 mm of real EPS. It is a thin lining, not that example. A 25 mm sheet is closer and still leaves a gap if the stud was planned around 50 mm.
Does BBA certified on the bullet replace the PDF?
No. The Triplast bullets claim BBA certification for BS EN 13163:2012 and do not print a certificate number. Without the number you cannot match the claim to a certificate. If the job needs that approval, get the number or buy a board that publishes it.
Are the 345 stars about the size on the page?
Not on their own. The same 4.6 from 345 and the same text appear on three Triplast ASINs here, and a review can name another size. One review title does name the 25-sheet, 600 x 400 mm pack. That is a marker inside the pool, not a separate test.
What should you measure when the parcel arrives?
Measure length, width and thickness on one sheet, and check whether the face is bare foam or paper. If the title and the spec line disagree, the tape decides. Shared Triplast comments mention damaged outer sheets, so check the first and last board in the parcel.

Related pages

Best polystyrene sheets

Polystyrene sheets

EPS vs XPS for damp, a floor load or a carved edge

How to cut polystyrene sheets with a knife or wire

Insulate a shed with polystyrene sheets, frame and fire

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Updated 23 October 2026.

  1. British Plastics Federation, EPS and XPS (retrieved 23 October 2026)
  2. BSI, BS EN 13163 (retrieved 23 October 2026)
  3. Building Regulations 2010, regulation 7 (retrieved 23 October 2026)
  4. GOV.UK simpler recycling (retrieved 23 October 2026)
  5. Which? insulation boards (retrieved 23 October 2026)
  6. Polyfoam XPS, compressive strength (retrieved 23 October 2026)
  7. HSE PPS1, hot-wire cutting (retrieved 23 October 2026)
  8. Stylite expanded polystyrene datasheet (retrieved 23 October 2026)