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M13 Calcium sulfate based levelling screeds

TYPES OF LEVELLING SCREED

120 PROPRIETARY SELF SMOOTHING LEVELLING SCREEDSgenerally
• Substrate: site specific.
• Manufacturer: Contractor's choice.
- Product reference: Contractor's choice.
• Screed construction: site specific.
• Thickness:
- Nominal: site specific.
- Minimum: site specific.
- Maximum: site specific.
• In situ crushing resistance (ISCR) category: A .
• Flatness/ surface regularity: SR3.
• Finish: Unsanded.
- To receive: site specific.
• Movement joints: Sealent movement joints with metal edgings.
• Services: site specific.

GENERALLY/ PREPARATION

220 SUITABILITY OF SUBSTRATES
• General:
- Within tolerances for level and surface regularity.
- Moisture content: To suit type of screed.
- Sound, clean and even textured.
• Concrete strength: To BS 8204-1, table 2.
• Penetrations/ Outlets: Completed.
• Movement joints: Correctly installed.

230 CONDUITS UNDER FLOATING SCREEDS
• Requirement: Haunch up on both sides of conduits in 1:4 cement:sand mortar.
• Timing: Before laying insulation.

250 UNBONDED CONSTRUCTION
• Separating layer: Polyethylene sheet minimum 65 micrometres thick (250 gauge) .
- Installation: Loose lay.
- Joints: Lap and seal with tape to prevent penetration of self smoothing screed .
• Edge strips at perimeter abutments: 5 mm thick resilient polyethylene foam .
- Installation: To full depth of screed.
- Joints in strips: Lap with separating layer and seal with tape .

RotF generic (intermediate) NBS 2014 6118-AEW-XX-XX-NBS-A-01