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Weber Saint-Gobain - Official website of the company

weberfloor 4320 fibre flow rapid

weberfloor 4320 fibre flow rapid
weberfloor 4320 fibre flow rapid

Product Benefits

For levelling bonded, unbonded and floating substrates:

• Concrete

• Sand/ cement screeds

• Anhydrite screeds

• Wooden boards

• Under-floor heating/warming

• Insulation boards

• Existing tiles

• Bitumen

Rapid drying self-smoothing base & renovation screed

  • Domestic & Commercial areas
  • Fibre reinforced for use on underfloor heating and insulation
  • Ideal for receiving tiles or Weber thin topping screeds

Product Features

About this Product

weberfloor 4320 fibre flow rapid is a pump or hand applied, rapid drying, self-smoothing, fibre-reinforced base or renovation screed for floors, which gives a strong base layer for receiving tiles or a thin topping screed. The product is formulated from special cements, aggregates, supplementary binders and chemical admixtures.

weberfloor 4320 fibre flow rapid is designed for the use in domestic and commercial areas. Rapid drying technology allows our quickest overlay compared to traditional sand/ cement, concrete or anhydrite screeds. It is ideal for the renovation of existing floors and floating floor constructions.

Features and Benefits

• For application depths between 5-50mm

• Pump or hand applied

• Rapid drying

• Foot traffic after 1-3 hours

• Tile after 12 hours

• Final floor covering installed after 2-4 days in normal conditions

• Fibre modified for added durability

• Low alkalinity

• Casein-free

• Low emissions

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: 08703 330070 (press 1 for sales)                                                        Fax: (01525) 718988


Send or download the documents

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

Preparation & Application


The surface strength of the substrate must be greater than 1N/mm2

It is essential the substrate is suitably prepared and primed with weberfloor 4716 primer prior to installing the Weber floor screed.

The substrate should be clean, free from dust, grease and other impurities that might prevent adhesion.

Walls and any upstands (pillars, columns etc) should be isolated with 10 x 100mm foam.

Large irregularities in the substrate (>50m) should be filled in with a application of weberfloor 4360 base flow rapid , this should be allowed to harden and then primed before application of weberfloor 4320 fibre flow rapid can begin.

Holes and leaks in the substrate should be sealed. The substrate should be vacuum cleaned, prepared and primed with weberfloor 4716 primer according to the instructions on the data sheet.

Priming improves the screed's adhesion to the substrate and prevents the formation of air bubbles and dewatering of the screed. Priming also improves the flow properties of the screed. Dry and very porous substrates (cast-in-situ concrete floors) may need to be treated twice. If the screed is applied in more than one layer, each layer must be primed.


weberfloor 4320 fibre flow rapid is mixed with clean water using an automatic screed mixer approved by Weber.

The material is mixed with 20% water, which corresponds to 5.0 litres per 25kg bag. It is important to add only the specified amount of water as excess water will reduce strength, increase shrinkage and encourage segregation. Whilst mixing, the water content should be checked continuously by the flow ring test to ensure that the material is correctly mixed and free from separation and lumps of powder. The flow rate should be between 220-235mm . Conversely, reduced water content increases viscosity. The temperature of the mix should ideally be between +15°C and +20°C.For manual mixing thoroughly mix with using a slow speed electric mixer (500 rpm) for at least two minutes. Allow to stand for 2 minutes.


Light ventilation in the working area is necessary but windows and door openings must be closed sufficiently to avoid draughts during and for 3 days after application.

During application, and for at least 1 week afterwards, the substrate and ambient temperature should not fall below +10°C or rise above +25°C. The relative humidity of the substrate must be <95%.

To achieve the best finish, the floor area should be divided into bays of 6 to 8 metres depending on pump capacity and application thickness. weberfloor 4965 barrier foam should be used to form bays and stop ends. Pumping is carried out in sections so that a new section is pumped as quickly as possible and to maintain a wet edge. A wide flat spatula or wobble bar should be used to assist the self levelling process.

In addition to solid bonded substrates weberfloor 4320 fibre flow rapid can be applied to a range of other substrates including flooring grade insulation boards, timber floors, underfloor heating and bitumen. For old and established bitumen only priming is required. However, for other substrates the minimum application thicknesses stated must be observed and weberfloor 4945 fibre mesh may be required. For further information, please contact Weber.


weberfloor 4320 fibre flow rapid is compatible with most common tile adhesives and all Weber thin topping screeds.

In small domestic areas it can be covered with directly with a flexible floor covering such as carpet but a thin layer of either weberfloor 4150 fine flow or weberfloor 4160 fine flow rapid is always recommended.

weberfloor 4320 fibre flow rapid is ready to receive these Weber thin screeds after 3-5 hours (in normal conditions). However the drying time 1-3 days must be observed before the final floor covering can be applied. It should not be painted or used without a floor finish.

Drying time

The screed can receive foot traffic after a drying time of 1 - 3 hours at an ambient temperature of +20°C. If necessary, the surface can be ground after 1-2 days following application. Floor covering can be installed after 1 - 3 days depending on layer thickness and drying conditions. High humidity of the substrate and poor drying conditions prolong the setting time.

Packaging, Health & Safety


weberfloor 4320 fibre flow rapid is packed in 25kg polythene-lined paper sacks.

Storage and Shelf Life

When stored unopened in a cool, dry place at temperatures above 5°C shelf life is 12 months from date of manufacture.

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.