How to Install Insulated Plasterboard on Battens, Studs and Ceilings

Insulated plasterboard lets you insulate and line a wall or ceiling in one go. How you fix it depends on what you're fixing to. This guide covers the three mechanical methods: timber battens on a masonry wall, timber stud walls and ceilings, and metal wall-lining systems. The fixing figures come from Kingspan's installation guidance for Kooltherm K118. If you're bonding boards straight onto a solid wall with adhesive dabs, see our separate guide on how to fit insulated plasterboard to a solid wall.

Which insulated plasterboard?

• Mannok Therm Laminate-Kraft (MLK) is PIR insulation (λ 0.022 W/mK) bonded to plasterboard, 1200 × 2400mm. Mannok says it can be dot-and-dabbed or mechanically fixed. We stock 37.5mm to 92.5mm.
• Kingspan Kooltherm K118 has a phenolic insulation core (λ 0.019 W/mK) bonded to 12.5mm plasterboard, so it's thinner for the same performance. Kingspan says it contains an integral vapour control layer. We sell it in full packs.

Prices are ex VAT, at the time of writing:

Mannok MLK thickness	Price per sheet
37.5mm (25mm + 12.5mm)	£37.91
51mm (38.5mm + 12.5mm)	£42.91
62.5mm (50mm + 12.5mm)	£50.83
72.5mm (60mm + 12.5mm)	£55.41
82.5mm (70mm + 12.5mm)	£65.41
92.5mm (80mm + 12.5mm)	£73.74

Always follow the fixing instructions for the board you're using. The figures below are Kingspan's for K118, and they're a useful benchmark for mechanically fixed insulated plasterboard generally.

Before you start

• Make sure the wall is dry. Deal with any damp first. Kingspan is clear that internal wall insulation must not be used to isolate dampness.
• Plan the services. Sockets, switches and pipes need to come forward by the thickness of the new lining. Decide where new services will run before you start.
• Allow for the lost space at window reveals, door linings, skirtings and ceiling height.
• Seal existing gaps at floors, ceilings, corners and around openings, using a continuous bead of drywall adhesive or flexible sealant.

Method 1: timber battens on a masonry wall

1. Fix the battens. Use treated softwood battens of at least 25 × 47mm, backed with a strip of damp-proof course, fixed vertically at a maximum of 600mm centres. Add battens around the perimeter (at floor and ceiling level) and around openings and services. Fix each batten about 75mm from its ends. Pack battens with shims to get them plumb.
2. Add noggins wherever a board joint wouldn't otherwise land on timber.
3. Cut the boards about 5mm short of the floor-to-ceiling height, and fit them with the long edges vertical.
4. Position each board centrally over the battens, so each sheet laps the timber by at least 19mm at joints. Butt the boards lightly together.
5. Fix the boards with drywall screws at 300mm centres (200mm at external corners), or with large-headed galvanised clout nails at 150mm centres. Keep fixings at least 10mm from the bound edges.
6. Get the screw length right. Fixings need at least 22.5mm penetration into the battens but must not go through them. Drive screws straight, with the heads just below the surface, and don't overdrive them.
7. Seal the perimeter and the 5mm gap at the base of the wall with flexible sealant.

Method 2: timber stud walls

On a timber frame the method is the same as for battens, with studs at a maximum of 600mm centres, noggins behind unsupported joints, and the same screw or nail centres. The difference is penetration: Kingspan specifies at least 25mm into a timber frame. Our guide to what size drywall screws you need explains how to work out screw length from board thickness.

Method 3: metal wall-lining systems

A metal lining system, such as the Gypliner components we stock, lets you line an uneven wall and leave a cavity for services. Metal framing systems are proprietary, so follow the system manufacturer's guidance first. Where there's none, Kingspan's K118 guidance is:

1. Fix the metal tracks to the floor, ceiling and perimeter at a maximum of 600mm centres.
2. Fix the stand-off brackets to the wall at 800–900mm vertical centres (check the system details), in line with the channel positions.
3. Fit the lining channels into the tracks at a maximum of 600mm centres and screw them to the brackets.
4. Put a channel or track tight into internal corners and around the perimeter of openings, and use fixing straps behind any unsupported board joints.
5. Cut the boards about 5mm short of the floor-to-ceiling height and fix them centrally over the channels. Use self-tapping drywall screws at 300mm centres (200mm at external corners), at least 10mm from the bound edges, with at least 10mm penetration into the metal.
6. Seal the perimeter and base gap with flexible sealant.

We stock GL1 channels, GL8 track, and GL2 and GL9 wall brackets.

Method 4: ceilings

1. Run the boards across the joists. Fit sheets with the long edge at right angles to the joists or rafters, with all edges supported. Add noggins where a joint would otherwise be unsupported.
2. Lap the timbers by at least 19mm at sheet joints, and butt the boards lightly.
3. Fix closer together than on walls. Kingspan specifies drywall screws at 230mm centres on ceilings, or large-headed galvanised clout nails at 150mm centres, at least 10mm from the bound edges, with at least 25mm penetration into the timber.
4. Seal the perimeter with flexible sealant.

Insulated plasterboard is heavy overhead, so use a board lifter or a second pair of hands.

Finishing

Once the boards are fixed, tape and fill the joints or skim the whole surface, just as you would with standard plasterboard. You'll find tape, beads and jointing compounds in our beads, tapes and fillers range and finish plaster in our British Gypsum plaster range.

Frequently asked questions

Can I screw insulated plasterboard straight onto a brick wall?

Not directly. Fix it to battens or a metal lining system, or bond it with adhesive dabs, following the manufacturer's method.

Which way should insulated plasterboard go on a ceiling?

With the long edges running across the joists, and all edges supported on joists or noggins.

Do I need a separate vapour control layer?

Kingspan states that K118 has an integral vapour control layer. For other boards, check the manufacturer's guidance, and see the FAQ in our solid wall guide.

What thickness do I need?

It depends on the wall and the U-value you're aiming for. Our guide to what thickness of PIR insulation you need covers solid walls and drylining.

Order insulated plasterboard

Browse our insulated plasterboard and drywall screws and fixings, or use the plasterboard calculator to work out quantities. Prices are shown ex VAT. We are delivery only (no collection) and deliver to mainland England and Wales, with a £400 ex VAT minimum order and free delivery on every order (see delivery information). Call us on 03330 908479 (Mon–Thu 8am–5pm, Fri 8am–12pm), email sales@insulationwarehousedirect.co.uk, or order online.

Sources: Kingspan Kooltherm K118 brochure, Sitework sections; Mannok Therm Laminate-Kraft (MLK) product page; Kingspan Thermapitch TP10 brochure (K118 integral vapour control layer). Figures are indicative and correct at the time of writing.