Description
This EPS 180mm is a grey graphite polystyrene board for external wall insulation under render, cut 1000 × 500 mm and 180 mm thick. It sits one step below the deepest size in the range, for walls that need a very thick layer but where 200 mm would push the face out too far at the sills or the eaves. It is part of the Renders World graphite board range of eleven thicknesses, all with the same face from 20 mm upwards.
A single board of EPS 180mm covers 0.5 m², and its declared thermal conductivity is ≤ 0.031 W/mK.
EPS 180mm: What You Get
You get a board 180 mm deep with a 1000 × 500 mm face. The grey colour comes from graphite worked into the polystyrene when it is made; that graphite is also what brings the conductivity down, so each millimetre of the EPS does more than plain white polystyrene of the same depth.
| 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 %) |
The fire class in the table belongs to the board as a material. Once the wall is rendered, its fire performance is set by the specification of the whole system, not by one layer of it. For what 180 mm means on your wall, the U-value and insulation thickness guide walks through the sum.
Made for Walls, Not for Floors
Some polystyrene sold in deep sizes is graded flat sheet for floors and general building work. EPS 180mm is not one of them:
- it is a façade board, shaped and toleranced to go on a wall under mesh and render;
- it is not intended for loading under a screed or a slab, or for burying in the ground.
Where the job is a foundation, a plinth or anything below ground or kept damp, use a foundation board instead. The shop carries them as their own products up to the 100 mm foundation board.
Why Choose a 180mm Graphite Board
- Very thick, one step short of the maximum. 180 mm gives most of the depth of the 200 mm board while leaving 20 mm more room at sills, eaves and doors.
- Graphite in every millimetre. A declared λD of ≤ 0.031 W/mK, lower than white polystyrene at the same depth.
- A single layer. One board covers the full depth, so there is no second layer to stagger and bond.
- Accurate edges. Length and width within ± 2 mm and thickness within ± 1 mm let the joints close tight across a big elevation.
- Holds the render build-up. Bending and tensile strength of 100 kPa or more.
- Same face as the thin sizes. 1000 × 500 mm, so reveal strips from thinner EPS meet the main wall cleanly.
Where a 180mm Board Goes
EPS 180mm is used on:
- Solid external walls, bonded and rendered, or fixed by the light-dry method;
- Timber or steel stud walls, on the outside face;
- Cavity walls with an enclosed or ventilated slot of at least that depth.
Good backgrounds for the adhesive are concrete, cement or cement-lime plaster, brick, block and hollow block made of ceramic or silicate, and aerated concrete.
Before you settle on 180 mm, walk round the building with a tape: window sills, roof overhang, door thresholds, pipes and boxes on the wall all have to clear a face that moves out by the EPS plus its render.
How Many Boards of EPS 180mm to Order
Work out the net wall area and double it: that is the number of EPS 180mm boards. They come 3 to a full pack, which covers 1.50 m².
- A 36 m² gable needs 36 × 2 = 72 boards, or 24 full packs.
- Measure each elevation separately and leave out the openings.
- Order the thinner EPS for window and door reveals as a separate item.
Fitting the Board
The EPS is fixed with a cement-based or a polyurethane adhesive, and you will find both among the adhesives and basecoats for insulation boards. The wall underneath has to carry load and be even, sound and free of frost, with dust, dirt, lime, oil, grease, wax and old emulsion or oil paint cleaned off.
- Get the background right. On a thirsty surface, a weak cement or cement-lime plaster, or rough aerated or cinder block, put on Uni-Grunt priming emulsion first. Large dips and voids are made good beforehand with ZW 330 mortar or Plastering Mix M, listed here as One Coat Dash Cover.
- Edge and spots. Run an unbroken band of adhesive at least 3 cm wide all round the board and add 6 to 8 spots, 8 to 12 cm wide, across the centre. Aim for at least 40 % contact before pressing and 60 % after.
- Set it straight away. Bed the board so that no more than 10 mm of adhesive is left behind it. If the wall is even and smooth, a notched trowel across the whole back is an alternative, leaving 2 to 5 mm once fixed.
- Prepare for the mesh layer. The surface must be dry of frost, level, clean and stable; on graphite EPS a light sanding and a dust-off before the base coat is recommended.
Mechanical fixings and the reinforced coat are next, covered by the insulation fixing accessories, the board fixing pattern and spacing guide and the EWI build-up and layers guide.
Keep Graphite Boards Out of the Sun
Grey EPS soaks up sunlight, and that is the reason for these rules on site:
- Fix it cold. Do not put up a board that has been heated, and keep sun off it until the adhesive has made its first set, or the bond may let go.
- Store it in the shade. Leave EPS 180mm in its packaging, away from direct sun, which can bend the boards.
- Mind the weather. Sheet the scaffold and pause fixing in rain, snow or high wind.
A face left out for weeks, especially in strong UV, may yellow; take that layer off with a sanding float before the base coat. Never let acetone, nitro thinners, benzene or similar solvents reach the polystyrene.
For a wall of uncertain strength, test it before the main fix: bond 8 to 10 cubes of polystyrene, 10 × 10 cm each, over the elevation, then pull them off 3 days later. If the polystyrene breaks inside the cube, the bond is good; if the cube pulls off adhesive or the wall surface, it is not, and the insulation design must solve that first.
180mm Among the Other Thicknesses
Eleven sizes are stocked, from 10 mm to 200 mm, and EPS 180mm sits between the 160 and 200 mm boards. From 20 mm up they all share the 1000 × 500 mm face:
| Thickness | Sheets per m² | Full pack |
|---|---|---|
| 10 mm | 2 | order by the sheet |
| 20 mm | 2 | 30 sheets, 15.00 m² |
| 30 mm | 2 | 20 sheets, 10.00 m² |
| 50 mm | 2 | 12 sheets, 6.00 m² |
| 80 mm | 2 | 7 sheets, 3.50 m² |
| 90 mm | 2 | 6 sheets, 3.00 m² |
| 100 mm | 2 | order by the sheet |
| 150 mm | 2 | 4 sheets, 2.00 m² |
| 160 mm | 2 | 3 sheets, 1.50 m² |
| 180 mm (this board) | 2 | 3 sheets, 1.50 m² |
| 200 mm | 2 | 3 sheets, 1.50 m² |
The right depth for a wall comes from a U-value calculation for the whole build-up, so check the figure for 160, 180 and 200 mm before you choose.
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?
Each board measures 1000 × 500 × 180 mm and covers half a square metre.
How many boards are in a pack?
A full pack holds 3 boards and covers 1.50 m².
Can this board go under a floor?
No. It is made for walls. For floors use a sheet made for floor loads; for foundations and the plinth use the 100 mm foundation board.
What is its thermal conductivity?
The declared λD is ≤ 0.031 W/mK. The U-value is worked out for the whole wall, not for the board alone.
Which adhesive should I use?
Cement-based or polyurethane, applied as an edge band and spots that cover 40 % or more of the board, with no more than 10 mm behind it.
Should I choose 180 mm or 200 mm?
Take the 200 mm board if the wall has room for it and the calculation needs it; take 180 mm when sills or eaves leave less depth.
Technical Documentation