We supply Celotex PL4000, Kingspan Kooltherm K118 and Gyproc ThermaLine in 2400 x 1200mm boards (2.88m² each), from 22mm to 93mm thick. Orders of £500 or more ex VAT are delivered free across most of mainland Britain.

Insulated plasterboard sizes

Most boards are delivered in 3–5 working days. Kingspan K118 pallets take 5–10.

Insulated plasterboard prices: what changes the cost

The price of each board is on its listing on this page, ex and inc VAT. Two things set it: the type of insulation and the thickness. Polystyrene-backed boards (ThermaLine Basic) cost least, PIR boards (Celotex PL4000, ThermaLine PIR) sit in the middle, and phenolic (Kingspan K118) costs most for a given thickness. Within a range the price rises with thickness.

To price a room, divide the wall or ceiling area in square metres by 2.88, the area of one board, to get the number of boards. Delivery is free on orders of £500 or more ex VAT, £45 below that and £60 below £200, and code TAKE2 takes 2% off orders over £2,000 + VAT.

Which thickness do you need?

The thickness in the product name is the whole board: the insulation plus 9.5mm or 12.5mm of plasterboard. If you are after 50mm, the nearest boards are 52.5mm (Celotex PL4040, Kingspan K118) and 53mm (ThermaLine PIR). There is no 100mm insulated plasterboard: the thickest we list is 93mm.

When more than half of a wall is being renovated, the Building Regulations for England (Approved Document L, Table 4.3) ask for the upgraded wall to reach a U-value of 0.30 W/m²K. On a 215mm solid brick wall, the manufacturers' BBA certificates show that takes 62.5mm Kingspan K118 or 72.5mm Celotex PL4060, fixed on adhesive dabs. Thinner boards still cut heat loss but do not reach 0.30 on solid brick. The regulations allow a lower standard where the full thickness would take more than 5% of the room's floor area, so check the target for your wall with building control.

For the same thickness, phenolic insulates best (0.019 W/mK for K118), then PIR (0.022 W/mK for PL4000), then polystyrene. The thermal resistance of the Celotex PL4000 boards is 1.20 m²K/W at 37.5mm, 1.85 at 52.5mm, 2.30 at 62.5mm, 2.75 at 72.5mm and 3.00 at 77.5mm.

Can insulated plasterboard go on a ceiling?

Yes. Celotex PL4000 and Kingspan K118 are both certified for the underside of rafters and ceiling joists, and British Gypsum lists ThermaLine for walls and ceilings. On a ceiling the boards are screw-fixed to the joists or rafters, never stuck: the PL4000 certificate asks for fixings at 250mm centres or closer, with all four edges supported.

How is insulated plasterboard fixed to a wall?

On a dry, weathertight masonry wall it is bedded on plasterboard adhesive dabs and then pinned with mechanical fixings once the adhesive has set: at least two per board for PL4000 and at least six for K118, whose foil back is primed with a bonding agent first. The alternative is to screw the boards to timber battens or metal furring channels. On an exposed solid wall the PL4000 certificate requires treated timber battens over a breather membrane, not dabs. Joints are taped and filled, or the whole surface is skimmed. Both certificates exclude the external walls of residential buildings with a storey 11m or more above ground.

Related

Plasterboard · Insulation boards · Fixings and screws · Guide: PIR insulation thickness and U-values · Guide: insulated plasterboard thickness, FAQs