Cement based Lytag® LWA levelling screed
To specify Lytag® LWA screed the following format may be used to develop a specification.
Lightweight Aggregate supplier: Lytag Ltd. 4 Bramley’s Barn, The Menagerie, Escrick, North Yorkshire, YO19 6ET. Tele: 01904 727922, Fax: 01904 720181
email: sales@lytag.net, website - www.lytag.net
Product Reference:
LYTAG BS EN 13055-1
(insert size)
Standard: BS 8204 -1 Annex A
Substrate:
Screed construction:
Partially bonded construction: (if applicable) - Generally in accordance with BS 8204 – 1. Remove surface laitance and any friable areas, thoroughly brush the surface to achieve a texture suitable to achieve a bond over the complete area.
Bonding coat: (if applicable) (insert type of bonding coat)
Application: (If applicable) - Shortly before laying the screed, remove any deleterious matter and thoroughly wash clean the substrate. Keep wet for several hours. Remove any free water and brush in the bonding coat. Complete screeding while slurry is still wet.
Mix proportions:
Mixing: In accordance with Lytag Ltd recommendations.
Surfacing layer: (insert the surfacing layer details)
Other requirements:
(insert any further requirements or comments)
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Notes
Product reference
Insert the required aggregate size, 4/8mm, 4/14mm. Normally for thicknesses less than 100mm 4/8mm should be used.
Substrate
Insert the layer onto which the no-fines screed will be laid i.e. 150mm concrete slab, 100mm insulation etc.
Screed construction
Insert partially bonded, unbonded or floating. For a no-fines screed partial bonding is acceptable and achieved using a proprietary bonding agent or cement / water slurry.
Partially bonded construction
Removal of the laitance can be achieved by grinding, scabbling or abrasive blasting.
Bonding coat
Insert type of bonding coat required. Cement slurry as a minimum, polymer modified cement slurry or proprietary bonding agent
Thickness
For a partially bonded screed the minimum thickness is 25mm. For an unbonded or floating screed the minimum thickness is 50mm. If the maximum thickness exceeds 300mm the screed can be laid in one operation but compacted each 300mm of depth.
Mix proportions
Insert the appropriate mix proportions i.e. 6:1, 8:1, 10:1 aggregate: cement ratio by volume. The mix proportions selected will depend on the application. A 6:1 will be for critical applications whereas a 10:1 will be for light, non trafficked areas.
Surfacing layer
If the final flooring requires a smooth surface i.e. vinyl or carpeting, a smooth topping layer of 15-20mm of cement: sand will be required. The minimum should be a 1:4 mix by weight placed ideally within 24 hours.
Other requirements
Other requirements such as an insitu crushing resistance (ISCR), flatness / surface regularity, finish to surfacing layer may be specified here.
Please note it is the responsibility of the specifier to ensure that all the information in the specification is suitable for the construction. Lytag Ltd accepts no responsibility for errors or omissions in the compilation of the specification.
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