Description
This 50mm EPS is a grey graphite polystyrene board, 1000 × 500 mm, made for external wall insulation finished with render. At 50 mm it is a board for the wall face where the depth of the insulation is limited, and for returns that a thicker board would not fit. It is one of eleven thicknesses in the Renders World graphite board range.
50mm EPS: What You Get
One board is 1000 mm long, 500 mm wide and 50 mm thick, which is 0.5 m² of wall. The graphite added to the polystyrene in production turns the board grey, and it improves the insulation, so a thinner board reaches a better thermal resistance.
| Property | Declared value |
|---|---|
| Thermal conductivity λD | ≤ 0.031 W/mK |
| Reaction to fire | Class E |
| Thickness tolerance | T1 (± 1 mm) |
| Length and width tolerance | L2, W2 (± 2 mm) |
| Squareness | S5 (± 5 mm per 1000 mm) |
| Flatness | P5 (5 mm) |
| Bending strength | BS100 (≥ 100 kPa) |
| Tensile strength perpendicular to the faces | TR100 (≥ 100 kPa) |
| Dimensional stability, normal conditions | DS(N)2 (≤ 0.2 %) |
| Dimensional stability, set temperature and humidity | DS(70,-)2 (≤ 2 %) |
| Compressive strength | not declared |
The fire class is the board's own. A rendered wall is rated as a complete system, so its fire performance comes from the system specification, not from this line. The data sheet gives the thermal conductivity, not a thermal resistance for each thickness; turning 50 mm into a wall figure is a build-up calculation, set out in the U-value and insulation thickness guide.
A Wall Board, Not a Floor Board
Much of the 50 mm polystyrene offered in the UK is floor insulation in large 2400 × 1200 mm sheets. This board is not that. No compressive strength is declared for it, so it does not go under a screed, under paving or into the ground.
The board's data sheet sends damp and below-ground work to a separate foundation-grade board made from a more water-repellent polystyrene: foundation walls below ground, floors in damp rooms, plinths and cellar walls. Renders World lists a 50 mm foundation board of its own as a separate product; check its declaration before using it in place of this one.
Where a 50mm Board Goes
The data sheet lists where these façade boards are used:
- External wall insulation by the bonded and rendered method, and by the light-dry method.
- Reveals, lintels, loggias and balconies.
- Stud walls, on the surface of the stud wall.
- Cavity walls, in the enclosed slot or the ventilated slot.
- Expansion joints, as a filling.
The boards can be bonded to concrete, to cement and cement-lime plaster, to bare brick, block and hollow block, ceramic or silicate, and to aerated concrete.
How Many Sheets of 50mm EPS to Order
Each board covers 0.5 m², so a square metre takes a pair of boards. The data sheet packs the 50 mm board 12 to a pack, which covers 6.00 m². That packing table is one table for all the façade boards on the sheet, set out by thickness.
Worked through for a typical order:
- A 20 m² wall takes 20 ÷ 0.5 = 40 boards.
- 40 boards are 3 full packs of 12 and 4 boards more.
- Add the boards that reveals and returns will be cut from, and keep the cut strips as a separate line on the list.
Fitting the Board
The data sheet allows cement-based and polyurethane adhesives; the range is in adhesives and basecoats for insulation boards. The wall has to be free of frost, stable, even and sound, and clean of dust, dirt, lime, oil, grease, wax and old emulsion or oil paint.
- Prepare the wall. Prime a very absorbent surface, weak cement or cement-lime plaster and rough aerated or cinder block with Uni-Grunt priming emulsion. Fill larger hollows and gaps first with ZW 330 mortar or Plastering Mix M, listed in the shop as One Coat Dash Cover.
- Apply the adhesive. Run a continuous bead at least 3 cm wide round the edge of the board and place 6 to 8 patches, 8 to 12 cm across, over the face. The adhesive must cover at least 40 % of the board, and 60 % once it is pressed on.
- Press it in place straight away, so that the adhesive under the board is no thicker than 10 mm. On an even, smooth wall the adhesive can instead be combed over the whole board with a notched trowel, to a layer 2 to 5 mm thick after fixing.
- Sand before the base coat. The face has to be frost-free, even, clean and stable, and dusted off if it was sanded. Sanding and dusting graphite boards before the base coat is advised.
Fixings and the reinforced layer that follows are covered in the insulation fixing accessories range, the board fixing pattern and spacing guide and the EWI build-up and layers guide.
Keep Graphite Boards Out of the Sun
- Do not fix a heated board. Protect it from heating up during fixing and while the adhesive first sets; a board that heats up in either phase can loosen the adhesive.
- Store it shaded. Keep graphite boards in their original packaging and out of direct sunlight, which can deform them.
- Cover the scaffold. Use scaffold covers, and do not fix boards in snow, rain or strong wind.
Boards left exposed for a long time, especially to UV, can turn yellowish on the face; remove that tarnish before the base coat. Keep the boards away from anything that dissolves polystyrene, such as acetone, nitro thinners and benzene.
Where the wall's strength is hard to judge, the data sheet advises a bonding test before the 50mm EPS goes up:
- Fix 8 to 10 cubes of polystyrene, 10 × 10 cm, at different points on the façade.
- Pull them off after 3 days.
- A cube that breaks within itself shows a wall strong enough to bond to; a cube that tears away with adhesive or a layer of the wall shows one that is not.
50mm Among the Other Thicknesses
The data sheet makes the board from 20 mm in steps of 10 mm. In the shop's range:
- the 20 mm board is the thinnest inside that range;
- the 80 mm board is the next thickness stocked above this one.
The thickness a wall needs comes from the calculation, not from the board.
The product photo is the same image on several thicknesses in the range; it shows the grey board, not this thickness.
Ordering, Delivery and Returns
Renders World processes orders the same day when the stock is there.
- Delivery: quoted by the team after the order; parcels up to 25 kg go next day, pallets next day or in two business days on the economy option, always kerbside.
- Collection: from the counter at Unit 9A, Central Trading Estate, Southampton SO14 5JP, Monday to Friday 7am to 5pm and Saturday 7am to 12pm.
- Returns: goods bought directly from Renders World can go back within 14 days in their original condition; special orders and promotion purchases are excluded.
FAQ
What size is one board?
1000 × 500 × 50 mm, which is 0.5 m² of wall. Two boards cover one square metre.
How many boards are in a pack?
The data sheet packs the 50 mm board 12 to a pack, covering 6.00 m².
Can I use it for floor insulation?
No. No compressive strength is declared for this 50mm EPS. For floors and ground contact use a board declared for compression.
What is its thermal conductivity?
The declared thermal conductivity λD is ≤ 0.031 W/mK. The wall's U-value comes from a calculation of the whole build-up.
Which adhesive should I use?
A cement-based or a polyurethane adhesive. Bond it with an edge bead and patches covering at least 40 % of the board, with no more than 10 mm of adhesive under it.
Technical Documentation