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Weber Saint-Gobain - Official website of the company

webercem keycoat

webercem keycoat
webercem keycoat

Product Benefits

  • To act as a holding primer prior to the application of webercem mortar.
  • To enhance the bond of webercem mortar.

Polymer modified, cementitious bonding aid

Product Features

About this Product

webercem keycoat is a single component polymer-modified cementitious bonding aid. It requires only the addition of clean water to produce a bonding slurry for webercem mortar. 

This product has been formulated to comply with the requirements of BS EN 1504-3.

Features and Benefits

  • High initial grab to improve the build of the repair mortar and promote the bond to the concrete.
  • This product has been formulated to comply with the requirements of BS EN 1504-3 as a bonding primer.
  • Contains fibres for improved thixotropy.
  • Cementitious, contains no solvents.
  • Single component; simply mix with water.

Technical Services

Weber's Customer Services Department has a team of experienced advisors available to provide on-site advice both at the specification stage and during application. Detailed specifications can be provided for specific projects or more general works. Site visits and on-site demonstrations can be arranged on request.

Technical helpline
Tel: (01525) 722110
Fax: (01525) 718988

Sales Contact

Weber products are distributed throughout the UK through selected stockists and distributors. For UK sales enquiries and overseas projects, contact Weber's Sales office.

Sales office
Tel: (01525) 722100
Fax: (01525) 718988


Send or download the documents

You can either send the documents to an email address, or download it

Preparation & Application


Surfaces must be clean and free from laitance, mould release oil and other surface coatings.

Thoroughly soak the concrete and remove all surface water prior to application.

Concrete substrates must be adequately prepared either by use of a suitable mechanical method such as grit blasting or needle gunning, or by such other means as appropriate to give a clean freshly exposed surface. 

Old concrete surfaces contaminated with oil or grease require suitable preparation such as steam cleaning in conjunction with a suitable detergent. Care must be taken to ensure that the oil or grease is removed from the surface and not simply spread over a large area. 

New concrete should be at least 14 days old. 

Steel substrates
Steel substrates should be cleaned by a grit blasting treatment to Swedish Standard Specification SA 2 1/2 immediately prior to bonding. However, in many instances where corrosion is absent, wire brushing to obtain a clean surface may be adequate.

Where exposed reinforcement is contaminated with chloride or other material which may cause corrosion, the whole of the circumference of the contaminated reinforcement shall be cleaned in accordance with BS EN 1504 Part 10: Clause 7.3.2 (e)


25 kg bag - 9 litres of water 

Mix webercem keycoat with the correct quantity of clean water by adding the powder to the potable water and stirring continuously until a brushable slurry consistency is obtained. 

Use a pallet knife or rigid flat stick and mix to a creamy consistence.  The ideal mix should allow a stipple finish.

For small quantities, mix 3 parts webercem keycoat with 1 part clean water by volume. 


Note: Mix only enough webercem keycoat to be applied to a given surface. In warm weather, quantities to be mixed need to be smaller. In cold weather do not apply when temperature is 5°C or is likely to fall below 5°C.

To steel reinforcement

Apply one full, unbroken coat of webercem keycoat, ensuring the back of the cleaned reinforcing bars are coated. 

webercem keycoat can be used as a holding primer for steel.  Apply a 2-coat application to ensure a pinhole-free coating, making sure that the back of the steel bars are fully coated.  The holding primer can be left for up to 3 days before reapplying the keycoat to the protected coated steel bars and the substrate and before applying the repair mortar.

To damp concrete substrate
Apply webercem keycoat to an area that can be covered with webercem mortar within 30 minutes.

After mixing, apply immediately to the prepared concrete surface.

Use a stiff brush to scrub the slurry well into the surface. Stipple finish the applied slurry coat.  Place the mortar on to the slurry while it is tacky.

In hot weather the slurry will dry quickly once it is applied and it is prudent to mix the mortar ready for application just prior to applying the slurry. If the bonding slurry dries prior to the application of the mortar, it must be removed mechanically and a further coat applied.

Packaging, Health & Safety


webercem keycoat is supplied in 25 kg bags.

Coverage / Yield

20kg will cover approximately 4m² to 5m² depending on surface profile.

Yield is approximately 15 litres. 

Storage and Shelf Life

Shelf life is 12 months from date of manufacture if stored properly in unopened and undamaged packaging in dry conditions within the temperature range of 5°C to 25°C.  If stored at higher temperatures and high humidity, the shelf life will be reduced.  Use within 3 days once the bags are opened.

Health and Safety

Contains cement (Contains chromium (VI).
May produce an allergic reaction). Harmful by inhalation. Irritating to eyes and skin.
Keep out of the reach of children. In case of contact with eyes, rinse immediately with plenty of water and seek medical help. After contact with skin, wash immediately with plenty of soap and water.
Wear suitable protective clothing, gloves and eye/face protection.

For further information, please request the Material Safety Data Sheet for this product