Page 373 - McD_6118-AEW-XX-XX-NBS-A-001_Neat

330 IN SITU CRUSHING RESISTANCE (ISCR)
• Standard: To BS 8204-1, table 4.
- Testing of bonded and unbonded levelling screeds: To Annex D.
- Testing of floating levelling screeds: To Annex E.

335 FLATNESS/ SURFACE REGULARITY OF SCREEDS
• Standard: To BS 8204-1, table 5.
- Testing: To Annex C.
• Sudden irregularities: Not permitted.

345 LAYING TROWELLED SCREEDS
• Trowelled screeds: Lay continuously using 'wet screeds' between strips or bays.
Compact thoroughly.
• Joints generally:
- Defined joints: Minimize.
- Daywork joints: Form with vertical edge. Wet with activated water before
continuing screeding.

355 LAYING SELF SMOOTHING SCREEDS
• Self smoothing screeds: Lay continuously. Agitate thoroughly.
• Joints generally:
- Defined joints: Minimize.
- Daywork joints: Form with vertical edge. Prime before continuing screeding.

375 STRIP MOVEMENT JOINTSgenerally
• Manufacturer: named supplier.
- Product reference: site specific.
• Size: site specific.
• Colour of insert: site specific.
• Installation: Centre over joints in substrate. Fix securely to exact finished level of
floor.
- Fixing: site specific.
• Accessories: site specific.

FINISHING/ CURING

410 TROWELLED FINISH TO SCREEDS
• Surface on completion: Uniform and smooth but not polished, suitable to receive
specified flooring material.

420 SANDED SELF SMOOTHING FINISH
• Finish: Sand to remove laitance.
• Surface on completion: Uniform and smooth, suitable to receive specified flooring
material.

430 CURING TROWELLED SCREEDS
• General: Prevent premature drying. Immediately after laying, protect surface from
wind, draughts and strong sunlight. As soon as screed has set sufficiently, closely
cover with polyethylene sheeting.
• Curing period: Keep polyethylene sheeting in position for a minimum of 48 hours.
• Drying after curing: Allow screeds to dry gradually. Do not subject to artificial drying
conditions that will cause cracking or other shrinkage related problems.

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