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275 CEMENT SLURRY BONDING
• Slurry type: SBR polymer modified cement.
• Application: Shortly before laying screed, thoroughly wash clean the surface and
keep well wetted for several hours. Remove free water then brush in cement slurry
bonding coat of creamy consistency.
• Screeding: While slurry is still wet.

280 UNBONDED CONSTRUCTION
• Separation: Lay screed over a suitable sheet dpm or a separating layer.
- Type: Polyethylene sheet, minimum 125 micrometres thick (500 gauge).
• Installation of separating layer: Lay on clean substrate. Turn up for full depth of
screed at abutments with walls, columns, etc. Lap 100 mm at joints.

290 FLOATING CONSTRUCTION
• Insulation:
- Type: Site specific mm expanded polystyrene boards to BS EN 13163, grade EPS
150.
- Installation: Lay with tight butt joints. Continue up at perimeter abutments for full
depth of screed.
• Separating layer:
- Type: Polyethylene sheet, minimum 125 micrometres thick (500 gauge)..
- Installation: Lay over insulation and turn up at perimeter abutments. Lap 100 mm
at joints.

BATCHING/MIXING

302 CEMENTS
• Cement types: In accordance with BS 8204-1, clause 5.1.3.

305 AGGREGATES
• Sand: To BS EN 13139.
- Grading limits: In accordance with BS 8204-1, Table B1.
• Coarse aggregates for fine concrete levelling screeds:
- Standard: To BS EN 12620.
- Designation 4/10.
• Lightweight aggregates: To BS 8204-1, Annex A.

306 PROPRIETARY POLYMER MODIFIED SCREEDS
• Cement types: In accordance with BS 8204-3.
• Sand: To BS EN 13139:
- Grading limits: 0/4 mm (MP) category 1.
• Aggregates: In accordance with BS 8204-3.

307 ADMIXTURES
• Standard: In accordance with BS 8204-1, Table 1.
• Calcium chloride: Do not use in admixtures.

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