Minimum order £500.00 Ex-VAT - Delivery Vehicle Access: 28 ton curtain-sided lorry off-load requirement.

    Shopping Basket

Knauf Earthwool DriTherm Cavity Slab

Knauf Dritherm products in popular densities / sizes are generally available for delivery in many of our depots, depending upon the popularity of these products in that area. We always recommend allowing four to five working days, and suggest that customers be prepared to accept Rockwool Cavity Slabs as a possible alternative.

Product Functions Celotex TB4000 installed in a wooden stud partition wall application

Earthwool DriTherm Cavity Slabs are for the thermal insulation of masonry cavity external walls and are installed to fully fill the cavity. They are approved for use in buildings up to 12m high in any exposure zone and for use in multi-storey applications up to 25m in height.

Product Description

Earthwool DriTherm Cavity Slabs are semi-rigid or rigid slabs of non-combustible, water repellent, glass mineral wool. They are 455mm wide to suit standard vertical wall tie spacings, ensuring a closed joint with adjacent slabs.

Knauf Insulation mineral wool products made with ECOSE® Technology benefit from a formaldehyde-free binder, which is up to 70% less energy intensive than traditional binders and is made from rapidly renewable bio-based materials instead of petroleum-based chemicals.
The technology has been developedfor Knauf Insulation’s glass and rock mineral wool products, enhancing their environmental credentials without affecting the thermal, acoustic or fire performance. Insulation products made with ECOSE Technology contain no dye or artificial colours – the colour is completely natural.

Product Benefits

Earthwool DriTherm Cavity Slab is suitable for use as partial and full fill cavity wall insulation and is effective in reducing the thermal transmittance (U value) of cavity walls with masonry inner and outer leaves where masonry includes clay and calcium silicate bricks, concrete blocks, and natural and reconstituted stone blocks

British Board of Agrément approved for use in all exposure zones
Excellent thermal and fire performance
Water repellent

Slabs ‘knit’ together, thus eliminating air gaps between adjacent slabs


Earthwool DriTherm Cavity Slabs are odourless, rot proof, non-hygroscopic, do not sustain vermin and will not encourage the growth of fungi, mould or bacteria.

Moisture resistance

Tests by the British Board of Agrément confirm that Earthwool DriTherm Cavity Slabs will not transmit water to the inner leaf. Nor will they transmit moisture by capillary action across the cavity or from below damp proof course level.

Vapour resistivity

Earthwool DriTherm Cavity Slabs offer negligible resistance to the passage of water vapour and have a water vapour resistivity of 5.00MNs/g.m.


Earthwool DriTherm Cavity Slabs are guaranteed* for 50 years to resist the transmission of liquid water from the outer masonry leaf to the inner masonry leaf in new cavity walls and to have a thermal conductivity of 0.032 to 0.037 W/mK at normal building temperatures *Available by application to Knauf Insulation Ltd


Earthwool DriTherm Cavity Slabs are certified by British Board of Agrément Certificate 95/3212. Approval can be sought from Knauf Insulation Ltd and the British Board of Agrément for Earthwool DriTherm Cavity Slab’s use in buildings over 25m high.

Handling and storage

Earthwool DriTherm Cavity Slabs are easy to handle and install, being lightweight and easily cut to size, where necessary.
They are supplied in polythene packs which are designed for short term protection only.
For longer term protection on site, the product should either be stored indoors, or under cover and off the ground.
Earthwool DriTherm Cavity Slabs should not be left permanently exposed to the elements

Universal Slabs are odourless, non-hygroscopic, rot proof, do not sustain vermin and will not encourage the growth of fungi, mould or bacteria.

Product Price List and / or Add to Cart

Product availability indicators

Knauf Dritherm Cavity Slabs - Price and Availability Advisory:

Presently there are no availability restrictions.

Excellent = Product Availability Excellent  Good = Product Availability Good  Fair = Product Availability Fair  Poor =  Product Availability Poor  Undetermined = Product Availability Undetermined
Availability relies on stock levels at closest depots and upon transport logistics to effect deliveries

Technical Data

Dritherm Cavity Slab 37 Standard

Product Code

Thermal conductivity (W/mK)

Thermal resistance (m²K/W)

Length (mm)

Width (mm)

Slabs per Pack

Area per Pack (m²)

150 0.037 4.05 1200 455 8 4.37
125 0.037 3.35 1200 455 6 3.28
100 0.037 2.7 1200 455 12 6.55
85 0.037 2.25 1200 455 8 4.37
75 0.037 2 1200 455 8 4.37
65* 0.036* 1.75 1200 455 10 5.46
50* 0.035* 1.4 1200 455 12 6.55
* 50mm and 65mm DriTherm “37” products are manufactured to 0.035W/m2K and 0.036W/m2K lambda respectively. This higher specification allows the thinner 50mm and 65mm materials to achieve a robustness normally associated with thicker materials and so allows for easier installation.

Dritherm Cavity Slab 34 Super

Product Code

Thermal conductivity (W/mK)

Thermal resistance (m²K/W)

Length (mm)

Width (mm)

Slabs per Pack

Area per Pack (m²)

150 0.034 4.4 1200 455 5 2.73
125 0.034 3.65 1200 455 6 3.28
100 0.034 2.9 1200 455 8 4.37
75 0.034 2.2 1200 455 10 5.46

Dritherm Cavity Slab 32 Ultimate

Product Code

Thermal conductivity (W/mK)

Thermal resistance (m²K/W)

Length (mm)

Width (mm)

Slabs per Pack

Area per Pack (m²)

125 0.032 3.9 1200 455 4 2.18
100 0.032 3.1 1200 455 6 3.28
85 0.032 2.65 1200 455 5 2.73
75 0.032 2.3 1200 455 6 3.28

Thermal Properties

The thermal conductivity of Earthwool Building Slabs varies with density from 0.035 to 0.037W/mK.

Fire Resistance Properties

Earthwool Building Slabs are classified as Euroclass A1 to BS EN 13501-1

Product Information and Certification

Links to manufacturer's information. Click to download in a separate browser window.

Knauf Universal Slab Datasheet | Knauf Earthwool Flexi Slab Datasheet | Knauf Earthwool Handy Guide |


Knauf Building Slab Range - Certification

Earthwool Building Slabs are manufactured in accordance with BS EN 13162,ISO 50001 Energy Management Systems, OHSAS 18001 Occupational Health and Safety Management Systems, ISO 14001 Environmental Management Systems, and ISO 9001 Quality Management Systems, as certified by Bureau Veritas.

CE marking
The Certificate holder has taken the responsibility of CE marking the Earthwool DriTherm Cavity Slab in accordance with harmonised European Standard BS EN 13162 : 2012. An asterisk (*) appearing in this Certificate indicates that data shown are given in the manufacturer’s Declaration of Performance.

Knauf Insulation Products CE Markings

Important to note is that products that are currently CE marked or have been CE marked before July 1st 2013 are deemed to comply automatically with the CPR (Construction Products Regulation). All of Knauf Insulations building insulation products are CPR ready, additionally the CPR does not apply to fire protection and acoustic insulation products so they are unaffected by this new legislation.

The most important part of the CPR is the Declaration of Performance (DoP) which contains all of the key information about a product`s characteristic`s, when compiling the DoP the product manufacturer assumes responsibility that the product is in confirmation with its declared performance characteristics.
Knauf Insulation can provide a DoP for each product which can be able to find online via a unique web address to be found on the product label, packaging or invoice - this is not a service that we undertake on Knauf's, our our customer's behalf.

  • Knauf Building Slabs

    Knauf Earthwool Building Slabs are a range of rigid and semi-rigid, resilient, non-combustible rock mineral wool slabs.

    View Full Detail

    Earthwool Building Slabs are a range of rigid and semi-rigid, resilient, non-combustible rock mineral wool slabs, available in densities from 33 to 140kg/m3.
  • Rockwool RW Slabs

    Thermal / acoustic slabs suitable for roofs, ceilings, walls, partitions, floors, and can be fitted between timber and metal frames.

    View Full Detail

    RW Slab Range is used for thermal, acoustic and fire insulation in general building applications. The product range consists of high quality resin bonded slabs in a variety of thicknesses and densities.
  • Acoustic Partition Rolls

    Designed for metal and timber stud partitions, APRs are flexible, resilient, unfaced roll of glass mineral wool.

    View Full Detail

    Isover Insulation acoustic insulation rolls have been especially developed to utilise the sound absorption properties of glass mineral wool
  • Earthwool Loft Rolls

    Ceiling joist level loft rolls that are flexible, lightweight, low density, resilient and non-combustible glass mineral wool quilts.

    View Full Detail

    Knauf Insulation have specially designed our loft insulation products for the thermal insulation of loft and attic spaces, when insulating at ceiling level between or above joists

Product Installation

Knauf Insulation Building Slab Installation Examples

Example: Building a bedroom extension above an existing garage.

Building an extension to create a new first storey over an existing attached single-storey garage built with masonry cavity walls. The external walls and the pitched roof of the extension are new build. The roof of the garage has to be removed and a new intermediate floor constructed with deeper floor joists and at a level to coincide with the first floor of the house.

In order to minimise the additional load on the existing foundations, the example applies timber frame for the inner leaf of the external walls of the second storey, and raises the brick facing of the garage to be the outer leaf of the timber frame structure.

The floor structure will be timber joists and the roof will be insulated at ceiling level. The example proposes U-value of 0.30 W/m2K for the new external walls exceeds the standard elemental U-value of 0.28 W/m2K for new wall elements, but the area-weighted average heat loss for the thermal elements is less than using the standard elemental U-values

Pitched roof

Roof insulated with two layers of Earthwool Loft Roll 40, 100mm between the ceiling joists and 200mm over the ceiling joists achieves a U-value of 0.13 W/m2K.

External wall

Cavity wall with brick outer leaf and insulated timber frame system with 90mm Earthwool FrameTherm 32between the studs and a low emissivity breather membrane achieving a U-value of 0.30 W/m2K.

New floor

Two layers of 100mm Earthwool Flexible Slab between 200mm deep timber joists at 600mm centres achieves a U-value of 0.19 W/m2K.

Contact Manufacturer

Knauf Insulation Limited

PO Box 10, Stafford Road, St Helens, Merseyside, WA10 3NS

Knauf Technical Advisory Service

Telephone: +44 (0) 1744 766666 - Fax: +44 (0) 1744 766667
Web sites: Knauf Home Page / Knauf Insulation Solutions iPad App.

Contact us

Insulation Online Limited

Sales Office only:39 Normandy Road, Worthing, West Sussex, BN14 7DX, UK

Telephone: 0333 8000 828


Web site: - we always deliver top quality products, competitive pricing and an efficient caring service