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85mm Residential Dufaylite Clayboard (Clay Heave Protection)

85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Residential Dufaylite Clayboard (Clay Heave Protection)
  • Strength grade up to 30kn/m2
  • Superb strength to weight ratio
  • BBA Certified Product
  • Easy on-site applications - Increased cost savings
  • Sustainable, manufactured from recycled materials
Estimated delivery:
In Stock
£ 117.20
Ex VAT: £ 97.67
  • Brand: Dufaylite®
  • Model: Residential 85mm
  • Dimensions: 2,440mm x 1,000mm x 85mm
  • SKU: 85mm Dufaylite
  • Product code: P1-1899
  • MPN: 85mm-Residential-Clayboard

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85mm Dufaylite Clayboard Residential Void Former is a sustainable, 100% recyclable maximum strength honeycomb board designed to solve ground movement issues and prevent structural damage caused to foundations by clay heave.

Dufaylite Residential Clayboard Void Former 85mm is a BBA certified, lightweight but strong specially designed material which will increase your cost savings on-site applications.

Specifically designed to work in commercial and domestic environments, the technical properties of environmentally friendly Clayboard void former system means significant savings in both time and money.

Due to its unique construction, Clayboard creates very little compression and virtually no uplift, allowing for a lighter slab, less reinforcement steel.

This void former also reduces soil excavation, muck-away costs and deliveries to the site as the product is up to 30% thinner than any other product on the market.

Dufaylite Clayboard Void Former is available in two standard strengths, KN30 (Residential Grade) and KN90 (Commercial Grade). 

KN30 residential clay-board has a nominal compressive strength of 30kN/m² when dry and is designed to support the weight of wet concrete up to 1000mm thick. 

KN90 commercial clay-board has a nominal compressive strength of 90kN/m² when dry and is recommended for concrete slabs thicker than 1000mm.

When the core is wetted, both KN30 and KN90 Dufaylite Clayboard will collapse under nominal compressive load of approximately 3kN/m².

There are three key steps to installing Clayboard Void Former: Preparation, Laying and Forming the void.

Delivered direct to site in a weatherproof seal.




Thickness: 85mm

Length: 2440mm

Width: 1000mm 

Board Coverage: 2.44m2

Residential: strength grade up to 30kn/m2


Key points:

 · Sustainable, manufactured from recycled materials.

 · Superb strength to weight ratio.

 · Easy on-site applications.

 · Increased cost savings.

 · BBA Certified Product.


Preparing the site:

 · Important - the product remains dry on site at all times.

 · Remove all water from the foundation zone.

 · Lay a 25mm, flat, dry, level sand blinding.

 · Lay a polythene sheeting (minimum 500g) onto the blinding.


Laying the system:

 · Lay the Clayboard, printed face up, making sure the adjoining panels are positioned up closely together.

 · Seal all the joints with Dufaylite Waterproof Tape.

 · Lay polythene (minimum 500g) on top of the Clayboard, overlap and tape all joins and leave an overlap at the edges of the Clayboard.

 · Lay steel reinforcement.

 · Prepare for later introduction of water by using the Clayboard voidpak System.


Forming the void:

 · When the concrete is totally self-supporting, insert hosepipe and introduce a slow flow of water into the Clayboard. 

 · Leave water for approximately 2 hours.

 · After 24-28 hours, strike through the bottom facing of the Clayboard to allow excess water to drain away. 

 · Seal the pipes with cement or waterproof sealant.


*Further information may be found in our Downloads section.

Fairly easy access to all PDF files.

Datasheet ǀ Declaration of Performance - DoP ǀ BBA Certificate ǀ Installation Guide ǀ Certificates ǀ Brochure ǀ SPEC Sheet


For more information:


Board covarage 2.44 m2
Length 2440mm
Material Honeycomb
Profile Residential
Thickness 85mm
Width 1000mm 
Coverage 2.44m2
Shipping method Courier
Grade Up to 30kn/m2
Applications Foundations ǀ Ground Heave
BBA Certified Yes (no. 98/3528)
Features Strong ǀ Up to 30% thinner material
Shrinkage Category Low-Medium
Manufacturer DUFAYLITE®
Plasticity Index 20-40

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We deliver insulation materials to Mainland UK only. Deliveries to Highlands, Northern Ireland, Isle of Wight etc.. might be possible at additional cost.
We offer free delivery on most of the orders above £300 (excluding VAT) (except special products - shipping cost via courier - products marked ''Request A Quote'')

Delivery of some insulation materials might be extended due to the current situation (Covid-19, stock shortages, allocations).
If you need materials quickly please contact us - we will do our best to help you source materials needed.

We do not deliver on weekends and bank holidays. Sometimes we can deliver on Saturdays - please check with us before placing the order.
If you need any further information please contact us tel. 02081910776

We can help to calculate price per m2 or linear meter (one meter in length) cost, please just contact us via phone 02081910776, email or live chat. Alternatively, you can work it out yourself quickly and easily: to get cost per meter square please divide price shown in orange area by ''Required area (m2)'' Example price of £28.80 divided by board coverage 2.88m2 = cost of £10.00 per m2.


No matter whether you choose a local installer or a national company, there’s a few tips to help you find the right installer for your home insulation improvements, such as asking for recommendations and making sure that they’re part of a certification scheme. This makes sure that they have the right skills and standards of workmanship to carry out the installation, and you can be sure that they know exactly what they are doing.


1. Thermal inspection picture in portfolio

It’s worth seeing a installer’s previous work. There’s no harm asking if you can see any properties nearby that they’ve installed insulation in. Best way would be to see Infrared Thermal Imaging Inspections. Thermal cameras spot small, but key changes in temperature in different areas of a house, identifying problematic areas that the human eye never could and some that a visual inspection could only hypothesize.

2. Reviews

Along with checking recommendations and previous work, finding reviews online can often be a great way to find out if they provide a good service or not. However, it’s best not to solely rely on reviews you may find or review websites, as there’s no controlling who writes them.

3. Compare prices

Comparing prices will also ensure companies can’t take advantage of you and give you a fair price. 

4. Word of Mouth

The best way to find a great insulation installer is through recommendations. Make sure you ask friends and family. They will most likely give you their honest opinion and can tell you from first hand experience.


Whether you require a wall, cladding, external wall, loft or floor insulation fitted, you can find and hire your local insulation installers from popular UK web pages. A simple internet search will return thousands of potential installers near your area.



We are the stockist of construction materials and related products for both trade and DIY from most recognizable brands in the UK like Cordek, RCM, Promat, Rockwool, Isover, Celotex, Xtratherm, Ursa, Low-E, Cedral, Kingspan, Dufaylite, British Gypsum, K-rend, Ecotherm, Iko enertherm, Kay-Metzeler, Terrawool to allow you to complete your insulation job on time at competitive prices and the highest standards.


Whether you are a large company or a DIYer, if you need a large amount of insulation materials, we can offer quantity discounts at the best prices. Please contact us and our friendly customer service will try to find the best and cheapest solutions for you. We value your time and we will try to deliver the products as soon as possible at a reasonable price to your construction site or house. The UK's leading insulation supplier near you and your needs. Price List available upon request.
85mm Dufaylite Clayboard - Residential - Clay Heave Void Former Board - 2.44m2
85mm Residential Dufaylite Clayboard (Clay Heave Protection)
£ 117.20