Liquid Screed Tile Guide
Several issues have previously been raised regarding flooring failures and the difficulty of identifying the exact point of failure within the substrate build-up. The information below provides a brief overview of the correct controls that should be followed to help ensure a defect-free finish prior to tiling over the existing screed.
Southern Screed’s scope of works is the installation of the screed only. All preparation works prior to floor covering installation remain the responsibility of the flooring contractor.
Although Cemfloor is a laitance-free product, many flooring installers still choose to lightly sand the surface as part of their own preparation process to key the area prior to laying the finished floor. This forms part of their standard preparation works to ensure correct adhesion and installation.
It is also the responsibility of the flooring installer to ensure that all necessary preparation steps are carried out, including priming where required, prior to the installation of any floor finishes.
Make sure the Screed is dry
The time it takes for any screed to dry is purely based on surrounding conditions.
If there is good airflow with a reasonable temperature the screed will dry a lot faster.
Run the Underfloor Heating through a complete cycle (after 7 days and begin at the lowest temperature).
Results from an independent test found that a 50 mm Screed with good airflow and ambient temperatures will dry within as little as 21 days.
For Cemfloor screed, typical drying times are:
- Up to 50mm thickness: around 21 days
- Above 50mm up to 75mm: around 28 days
The building must be fully sealed against all weather conditions, either by installing windows and doors or by securely covering all openings with plastic sheeting. Where glass windows or doors are present in the screeded area, these should be protected during the curing process. This is particularly important where direct sunlight can pass through the glass and heat the screed surface, as this can cause rapid drying and may lead to shrinkage or cracking.
It is good to allow airflow throughout the day. If a building is sealed with no open windows, moisture has no effective way to escape. Good airflow is therefore essential to allow proper drying of the screed. However, care should be taken to ensure that rain, damp conditions, or other weather elements do not enter and adversely affect the screed during the curing process.
When the windows have to be kept closed then dehumidifiers should be used.
What products can be used?
As Cemfloor is cement based, this is suitable for all primers and adhesives- no specialised products required.