When installing ceramic tiles, vinyl, carpet, and other floor coverings. Self-levelling screed level out uneven substrates, leaving a flat, smooth surface to connect to.
Before laying self-levelling screed, its suitability has to be assessed. Most projects will consist of three kinds of substrates, that are as follows:
Bonded is a crucial aspect of the self-levelling screed laid because it is based on the bond that is formed with the substrate. Self-levelling screeds are appropriate for this kind of construction.
Unbonded is when you have an elastomer between the screed and the substrate. This kind of screed is not one that would be appropriate for this kind of screed.
Floating construction refers to the fact that the screed is placed on insulation, whether it’s thermal or acoustic insulation. This kind of construction is not one which is suitable for this kind of screed since bonding is usually required.
When it comes to bonding, I think it is essential to draw attention to the process. When we look on the surface, it must to be solid. When we talk about “sound,” it needs to be sturdy. If you notice cracks, crumbling, or other issues, you must take action prior to placing the screed. It is not a good idea to placing self-levelling screed on something that’s not stable as it could cause the screed to crack or separating.
It is important to make sure that the substrate has not been affected. Contamination could be caused by a range of things like dust, grease, oils and anything else that could have entered the crevices in the screed (the capillaries of the screed). If there’s contamination, it could require some type of mechanical surface preparation. This could involve grinding, scabbling, or shot blasting. If there are any traces of paint on the substrate, it should be removed prior to the installation of self-levelling London.
The surface should be cleaned and vacuumed in the event that there are dirt or dust particles in the substrate. Before you lay self-levelling screed, a primer must be placed on the substrate in order to aid in the fusion of the self levelling screed with the substrate. Sometimes, it is possible to lay without primer. Always check the instruction before you lay. In any case, you’re going require some penetration into the surface. It has to be bonded and it could be that you have to grind away the first few millimetres of matrix to reduce it to a level that can be bonded.
In the case of made of power floated concrete and the top layer of the matrix has to be removed in order to allow for the more open-textured concrete which allows the primer to get into. Certain products can be poured directly on the surface that is power floated however you must examine the requirements for each specific product. In general, you’d be considering changing the mechanical properties of the surface in order to facilitate more adhesion between screeds and substrate.
Self-levelling Screed Thickness
When you lay self-levelling screed the thickness will vary from one product to the next however, as a general rule of thumb, check the depths below:
The minimum depth is typically 2-3mm There are products that are able to be lowered to “featheredge”
Maximum depths are about 10-15mm However, when you add bulking aggregates (normally kiln-dried sand) when you lay self-levelling screed, it can be as deep as a of 30mm.
Generally speaking, when you lay self-levelling screed, the substrate must be at 75 percent absolute humidity, or lower. in the case of the threshold of a liquid damp proof membrane may be required to reduce the moisture available.
I would suggest that the surface be checked for moisture prior to proceeding.
If you are completely satisfied by the surface, you’re in a position to use the primer, which helps in bonding the screed and the substrate.
Each product comes with an approved primer that has been tested and may come with different ratios to water. Always confirm the manufacturer’s guidelines prior to implementing.
The primer generally needs to be dry prior to the laying of self-levelling screed. However, it shouldn’t typically be left for too long (always make sure to read the directions).
Applying the primer, use a brush and make sure that there isn’t any concentration in the prime.
When mixing by hand with an electric drill you add the powder to appropriate quantity of water (again take note of the manufacturer’s instructions for the product they sell) while mixing until a non-clumpy mortar is formed.
It is laid on the substrate and laid out to self-level. screed. It is then spread with a trowel made of steel or floating floats to distribute the mortar and to finish.
The screed is likely to self-smooth within during the initial 15 mins. It will work for a total time of about 30 minutes dependent on the temperature of the site.
Conditions on the ground can affect drying times, but 3mm of screed will typically be dry within 24 hours and walkable in 3-4 hours.
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