ISOVER Cavity Wall Slabs 36

The ISOVER Cavity Wall Slab (CWS) 36 is a glass mineral wool slab providing thermal performance in external masonry cavity walls. Manufactured with a water repellent binder, the strong, resilient and flexible slabs are 455mm wide to fit between standard wall tie spacing.

Key Considerations:

• When using Isover Cavity Wall Slab (CWS) 36, you need to satisfy yourself that the use of the product meets all relevant national Building Regulations and guidance as well as local, national, and other applicable standards relevant for your construction or application, including requirements in relation to fire and applicable height restrictions.

Important information about this product:

• Length: 1200mm
• Width: 455mm
• Thickness: 50mm, 75mm, 100mm
• Material: Mineral wool slab manufactured from up to 82% recycled glass with a water repellent binder
• BBA Approved: Certificate 18/5560
• λD Declared thermal conductivity (W/mK): 0.036
• Fire Classification: Euroclass A1 Reaction to Fire classification according to EN 13501-1.

RD Declared thermal resistance (m².K/W):

• 50mm: 1.35
• 75mm: 2.05
• 100mm: 2.75

Key Features & Advantages

• Thermal Performance – Thermal conductivity of 0.036 W/mK. Helps to reduce heat loss within the building envelope and decrease energy costs.
• Sustainability – Manufactured from up to 82% recycled glass on a plant that uses 100% renewable electricity. For further details, visit insulation-uk.com/CSR.
• BBA Certified – Cavity Wall Slab (CWS) 36 has been assessed by the BBA as fit for use in defined full fill and partial fill masonry cavity wall applications if installed, used and maintained as set out in the certificate. Please read the certification under the documents tab or at insulation-UK.com/BBA for full details and restrictions.
• Fire Classification – Achieves a Euroclass A1 Reaction to Fire classification, according to EN 13501-1.
• Easy to Install – Slabs are 455mm wide to fit standard wall tie spacing for straightforward installation. No requirement for retaining discs when filling the cavity.

Do you offer Free Delivery?

Yes! On most insulation orders over £400 excluding VAT, we can offer free delivery*. 

Delivery depends on stock availability and location. If stock is not available at your local branch and must be delivered from another branch, this may affect lead time or delivery charges. In this case, one of our advisors will contact you to confirm any changes. 

You can also send your enquiry via Contact Page or WhatsApp, and we will calculate the costs for you. We always aim to have your order travel the shortest distance possible to ensure free or the most economical delivery option. 

Orders below £400 excluding VAT are usually subject to a delivery fee of £50 excluding VAT. 

*Orders into central London (inside the North Circular and South Circular) will be charged on orders up to £1,000 + VAT due to increased shipping costs and congestion charges. Orders must also be above £350 + VAT to be processed.

Where do you deliver to?

We can deliver to 95% of the UK, using our branches across England, Wales, and Scotland. To check if you are in our delivery area, see the map or your postcode. 

London postcodes: BR, CR, DA, E, EC, EN, HA, IG, KT, N, NW, RM, SE, SM, SW, TW, UB, W, WC, WD. 

Other postcodes: AL, B, BA*, BB, BD, BH*, BN, BS, CA, CB, CM, CO, CT, CV, CW, DA, DD*, DE, DG*, DH, DL, DN, DT*, DY, EH*, EX*, FK*, FY, G, GL*, GU, HD, HG, HP, HU, HX, IP, KA*, KY*, L, LA, LE, LL, LN, LS, LU, M, ME, MK, ML, NE, NG, NN, NR, OL, OX*, PA*, PE*, PH*, PL*, PO*, RG, RH, RM, S, SG, SK, SL, SN*, SO, SP*, SR, SS, ST, SY, TA*, TD*, TF, TN, TQ*, TS, WA, WF, WN, WR, WS, WV, YO. 

Limited areas (PO – Mainland only; BA, BH, DD, DG, DT, EX,  EH, FK, GL, KA, KY, OX, PA, PE, PH, PL, SN, SP, TA, TD, TQ & PL) may have restricted delivery coverage depending on distance from the branch and order size.

Where will you deliver my order to?

All deliveries are kerbside only. It is your responsibility to move items from the kerb onto your property. The courier decides where the order is left, so please ensure there is ample space to offload.

Delivery access and site restrictions

These items are typically delivered on large 18T or 26T rigid lorries, approximately 10–12 meters long, 4 meters high, 2.6 meters wide, carrying 12–14 pallets.

Please inform us of any access restrictions or site issues in advance; failure to do so may result in extra delivery charges.

When do you dispatch orders?

If your order is placed before 12:00 PM, we aim to process and dispatch it on our lorries the next working day. Occasionally, lorries may be full, or stock may need to be brought in from another branch, which can extend delivery up to 10 working days. Some areas are subject to set delivery days due to distance from the local branch.

Please ensure to leave a mobile number so that we can contact you with your delivery date once we have received confirmation from the local branch. This also allows ourselves or the delivery driver to contact you if there are any issues with your delivery.

Why do we need your contact number?

It is essential to provide a mobile number so we or the delivery driver can contact you if there are any issues. For orders of this nature, we may contact you after ordering online to discuss delivery options, site restrictions, or offloading requirements.

How much will my delivery cost?

For orders over £400 excluding VAT, we can offer free delivery*. 

Delivery costs vary depending on the product and delivery location. When you add items to your basket and proceed to checkout, the delivery price will be displayed. We keep delivery costs as low as possible and only pass on the rates charged by our delivery partners.

How long will my delivery take?

Each product page shows the usual lead time below the “Add to Basket” button. These times are a guide only, and we aim to deliver your items as quickly as possible.