Sher-Crete BU is a pumped industrial protein free underlayment base screed applied as a self-levelling industrial grade flooring system. It is extremely durable and functions as a base screed in both industrial and commercial applications.

Applied by pump or by hand up to 50 mm’s in thickness and be topped with Sher-Crete BU wearing screed or overcoated with resin coatings in situations where an aesthetic finish is required and where protection is required from chemicals, oils and other liquids or if an improved slip resistant texture is required.

Because it achieves strength quickly Sher-Crete BU is ideal for overcoating with Sherwin-Williams Resuflor, Resudeck, Resupen, Elladur and SofTop resin coating systems.

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• Features & Benefits
• Surface Preparation
• Priming
• Mixing and Application
• Joints and Curing
• Technical Information

Features & Benefits

• Single application base screeds
• Pump or trowel applied
• Suitable for underfloor heating systems
• Contains recycled material
• Fast installation
• Excellent adhesion
• Moisture tolerant
• Suitable for resin flooring toppings
• Recommended for use in:
• As a base screed for Sher-Crete BU or SW resinous seal coats and toppings
• Warehouse areas
• Food production areas
• Aviation and automotive areas
• Factory areas
• Pharmaceutical processing areas
• Concrete substrates with no DPM

Surface Preparation

Power floated concrete: The surface must be clean, sound, dry, fully cured and surface laitance removed by vacuum enclosed shot blasting or mechanical grinding, a minimum strength of 30N/mm² is required. Remove all dirt, oil, grease, old paint or any other surface contaminants. Fats, oils or greases must be removed by mechanical means and detergent washing and making sure all residue of detergent is washed and removed by rinsing with clean water.

Tamped or pan floated concrete: Should be treated as porous. Any laitance or weak material should be mechanically removed to ensure a sound, dry and dust-free surface. Two applications of Cemcrete Primer are recommended normally because of porosity.

Cementitious subfloor screeds and Industrial Floors: The absorbency of these floors/screeds can vary significantly, this is to be assessed by personnel on site. Up to 3 coats of Cemcrete Primer may be required according to substrate porosity.

Calcium Sulphate/Anhydrite/Hemihydrate Screeds: These screeds must be confirmed dry, below 75%RH when tested in accordance with BS 8203, and have a compressive strength of greater than 30N/mm². Sher-Crete BU should not exceed 10mm on these substrates. Mechanically remove any laitance or weak material to leave a clean, dry and dust-free surface. An STG machine is recommended with suitable mesh grinding disc of 60-100 grade grit. Apply 2 coats of Cemcrete Primer.

Existing Floors (previously coated): All previous coatings and loose floor paints must be removed by mechanical preparation as described in the above section and primed as specified. If the old resin flooring cannot be removed then please consult with our technical team for advice on intercoat adhesion and suitability, as it may not be compatible with the existing floor coating.

NOTE: Where warm water UFH (Underfloor Heating) systems are incorporated, they must have been fully commissioned and brought up to their maximum temperature, and ideally switched off 48 hours before application. In the absence of other heat sources, the UFH may be set to ‘cutback’ position to achieve an air temperature of 15℃. Any expansion or movement joints must be carried through to the finished floor surface.

Priming

Sher-Crete BU is designed as a finished wear surface it is important that correct and thorough priming and preparation takes place to ensure that no pinholes or blemishes are present in the finish cured surface.

Cemcrete Primer is the recommended primer and this should be applied by roller, brush or spray where there are good drying conditions. The ambient temperatures of the area and substrate should not be allowed to fall below 10℃ throughout the application and the curing period. Where possible it is recommended that the application area is <75%RH, heated to a minimum temperature of 15℃ and time is allowed for the ambient and substrate temperature to stabilise prior to installation.

On highly porous surfaces a very dilute (1:1 with water) wash may be applied to obtain maximum penetration Once dry this should then be followed by an application of the standard material (neat) to the surface to build the film thickness. Applications should be in a thin uniform coating avoiding pooling and puddling of primer. The dry film should be a translucent colour.

Where the Relative Humidity of a substrate exceeds 85% ERH Resuprime MVT should be specified and selected on the basis of hygrometer readings in accordance with BS 8203:2017. Where Resuprime MVT is applied to masonry/concrete surfaces, this must be fully scattered with aggregate (around 1mm in size) and the number of coats to be applied is chosen in accordance with the following table:

Mixing and Application

When mixing by hand pour 4.25 litres of clean ambient temperature water into a clean oversized bucket (20+ Ltrs), and then gradually add the Sher-Crete BU 25 kg powder bag whilst mixing continually with an electric drill with power whisk. When all powder is added mix for a further 2 mins, keeping the whisk below the surface (to minimise air entrapment), until a lump free creamy material is attained. The product can then be poured onto the floor and, using a smooth steel trowel, spread out to the desired application depth. A spiked roller can be used whilst the product is still fluid to minimise air entrapment and “marry” wet edges together to give a uniform finish.

NB Warm water should not be used as this will reduce working time and may result in shrinkage.

For pump application follow pump manufacturer’s recommended set up guidelines. Ensure the correct water ratio is used by carrying out a flow tube test at the beginning of the project and at regular intervals throughout (ideally once per pallet) to check that ideal flow is being maintained. It is recommended to log flow test results, site conditions, batch numbers and pump equipment for future reference.

Using a flow tube of capacity 200ml (106 mm height/ 48 internal diameter) the flow rate should be around 250 to 280 mm. When using other flow tubes we recommend that a single unit be mixed by hand as above and the flow rate of the mixed unit be assessed with the specific flow tube. For large projects it is recommended that the area be sectioned off into manageable sized bays where a wet edge can be maintained throughout the pumping process.

Joints and Curing

Joints

All joints within the subfloor that are designed for movement MUST be followed through the surface of the Sher-Crete BU. It is recommended that subfloor joints should be marked out prior to applying Sher-Crete BU and re-established by disc cutting after 24 -48 hours. It is also recommended that a movement joint also be incorporated at all perimeters, columns and at door thresholds to ensure building movement does not result in the Sher-Crete BU cracking.

Curing

All curing and drying times are based on a 5mm application of Sher-Crete BU in good ambient conditions of 20℃, 65% air humidity and good ventilation. Cold, humid or damp sites, or those with poor airflow, will prolong curing and drying times, so make adequate allowances for such. Drying times are only relevant to the application of Sher-Crete BU. Applications of underlying subfloors must be considered separately.

Sher-Crete BU is ready to receive foot traffic after 2 to 3 hours and forklift traffic after 36 hours, and can receive a resin coating after 24 hours at 15mm @ 20℃. The substrate should have achieved a compressive strength of 25N/mm before applying resin coatings. The resin coating applicator needs to determine that the Sher-Crete BU has achieved this strength. It is also recommended that the substrate be tested for moisture before applying resin coatings. Typically a moisture content of 5% or lower is required.

While Sher-Crete BU is a resilient material designed to accept vehicular traffic, it will need to be surface protected against staining from spillages such as oils and other chemicals.

It is recommended that a minimum of a light sanding of the Sher-Crete BU is undertaken followed by vacuuming prior to the application of a resin coating.

NB: Sherwin-Williams FasTop systems are not suitable for application on top of Sher-Crete BU

Technical Information

References to BS EN13813:2002 confirms the minimum compressive and flexural strengths that the product will attain when tested to the standard.

The above figures are based on tests carried out under quality controlled environments using Sher-Crete BU with the correct water ratios. Actual results attained will be subject to site conditions and allowances should be made accordingly.