Preparation for liquid screed
The building should be weather tight prior to commencement. The roof should be covered and all external doors and windows in place. Alternatively all openings are to be made weather proof with polythene or another suitable material.
Clean the floor and remove all dust and debris from the surface so it is free from contamination.
Insulation
Ensure that all high/low points are removed from the sub-base and that insulation boards are laid flat. Where there are service pipes running across the floor, the insulation should be fitted around the pipes, so that the boards are sitting flat.
Insulation boards should be tightly butt jointed with staggered joints.
Edge expansion strip
Perimeter isolation upstands should be provided to all abutments. We recommend the use of either 20mm extruded polystyrene board insulation for cold bridging or a proprietary 8mm expansion strip to the full depth of the screed.
Membrane
All liquid screeds require a 500 gauge/125 micron (MU) grade polythene separating membrane. TPS is not suitable. Ensure that perimeter isolation details are installed as above.
Note Screedflo screed reacts with aluminium.
Lay polythene membrane ensuring that it is free from punctures and creases. Lap joints a minimum of 100mm and where necessary continue the polythene up the face of all abutments to finish slightly higher than the depth of the screed.
In order to avoid leakages thoroughly tape all joints and abutments, using waterproof gaffa tape (but not aluminium backed tape), to ensure that the area is 100% watertight. Take care to remove air pockets and voids beneath the separating membrane particularly at abutments and corner details.
Exposed edges such as door openings or level changes should be provided with temporary formwork.
Please note that when installing Screedflo liquid screed, it is imperative that the preparation is carried out to the highest standard.
Underfloor heating
When installing underfloor heating , this must be laid on top of the membrane and cables are to be securely fixed down using proprietary fixings, at least every 300mm.
Water systems should be filled prior to the application of Screedflo to reduce the risk of pipes floating when the screed is poured.
When setting out the floor areas consideration must be given to the minimum recommended thicknesses for Screedflo as listed below.
- On slip-sheet 500 gauge polythene laid direct to substrate 30mm
- Floating on insulation (Domestic) 35mm
- Floating on insulation (Commercial) 40mm
- Cover to conduits/underfloor heating pipes 25mm
For underfloor heating systems we recommend an optimum overall thickness of 50mm Screedflo standard screed or 40mm Screedflo Thermal.
Please make an allowance for tolerances and any isolated high spots in the substrate. These will dictate the minimum thickness of the screed and therefore impact upon the overall depth and material usage. Carry out a level survey on the floor to check the depth of screed required.
Please telephone 01621 874781 if you have any questions or require any further advice.