SPECIFICATION:
The most appropriate time to specify is at design stage when the reduced
thickness of screed can be accommodated in the overall design of the building
for maximum cost savings.
When installed onto a concrete base calcium sulphate screeds need not be greater
in thickness than 30mm. However, it is often necessary to provide screeds
as a replacement for sand cement screeds which were specified at thicknesses
between 50mm and 75mm. In these cases it is possible to use insulation board
underneath the screed to make up the thickness, and still provide an economic
solution.
When used in conjunction with insulation for either thermal protection or sound
attenuation, the screed will need to be installed slightly thicker with a
minimum of 35mm depending on the thickness of insulation board.
(See table)
Almost without exception, calcium sulphate screeds will provide a stronger,
smoother, faster solution to your screeding needs.
INSTALLATION:
A full method statement is available on request, but briefly, the area to be
screeded should be clean and free of mortar droppings and significant
protrusions. Insulation board, if used, should be installed with tight but
joints and bridging should be avoided.
A 500 gauge polythene slip membrane (not a DPM) is provided with taped joints. A
5mm thick polyethylene expansion strip is provided to most walls and up stands
(10mm thick if under floor heating is installed). NO REINFORCEMENT IS REQUIRED.
A grid of levels is provided by use of levelling tripods.
The screed is delivered to site ready to use in conventional mixer trucks which
discharge into Woodroyd's Putzmeister mortar pump which then delivers it through
a hose to the point of use. This pump is capable of discharging 10m³ per hour.
The material is tested for flow characteristics using the Flow Ring Test. Having
discharged the screed to the levels indicated, the surface is agitated with a
“dappling bar”, a 30mm diameter aluminium rod similar to a tamp. The screed is
then left to cure for about 24 hours before foot traffic.
This is a photograph of an actual section of
Cemex Supaflo showing the density and
uniformaty of the screed.
