STEP 1 - Watertight Envelope and Preparation of the Base
The building envelope should be sealed before preparation commences i.e.; Wind and watertight. Prior to lying down insulation all debris & high spots must be removed. If they are not removed they can imprint on the thickness of the finished screed. In cases where the substrate is particularly uneven, a slurry grout may be required.
STEP 2 - Damp Proof Membrane
Lay a polythene membrane (DPM 1200 gauge or 300mu) on substrate with an approximately 100mm upstand. Ensuring it is free from punctures and lies flat on base. Ensure all lapping joints are a minimum of 100mm and properly taped.
STEP 3 - Insulation
Make sure that insulation is installed on a clean and even bed to prevent the movement and rocking of boards which are to be butt jointed with staggered joints. All joints of insulation need to be taped with a 100mm foil tape.
STEP 4 - Separation Barrier
A thin layer of plastic sheeting should then be placed over insulation, this must be cut as a carpet not turned up the walls, polythene should finish at the edge of the insulation, and any joins must be duct taped.
STEP 5 - Perimeter Strip (Upstand)
Perimeter edging is laid on the edge of the insulation with polythene lip facing down onto the separation barrier. Ensure this is tucked in nice and loose to prevent any gaps around perimeter, in corners cut perimeter strip around 2 inches from top to allow the edging to tuck in tight into corners. (See diagram)
STEP 6 - Final Check
Any dust or debris must be removed from all floors either swept or vacuumed as dust may affect final finished floors. Upon completion of installation, inspect the whole system for tears / holes / damage etc and make sure that the whole system remains watertight to receive liquid screed.
STEP 7 - Floor Screed Installation
During installation of the floor screed and for three days thereafter, the surface of the screed must be protected from severe draughts. If windows have not already been fixed, clear polythene protection should be installed.