Before starting any project, it is important to do a few pre-start checks to make sure the products you select are the correct ones and the environment in which you are to work is suitable. Selecting the correct system is vital to ensure the integrity and performance of the flooring when in use.
The products should be chosen after considering different aspects of the project. Considerations on the environment, the type of floor covering you are laying and what the flooring will be exposed to are just some of the points to consider. By following the guide below, you will be able to build your system, confident that it will perform well and with the knowledge that the potential for any flooring issues will be minimised.
Environment
We all know the environment plays a key factor in the installation of floor coverings. This is why we acclimatise all flooring products before installation. But is the job site ready? It is important that the conditions on site are similar to the conditions that are expected once the area is occupied.
However, it can often be the case that the environment is not suitable yet for the project to commence. Time constraints and deadlines can sometimes mean that the project does not have a controlled heating source or even be weathertight. Knowing and understanding the temperature requirements of the products and the guidelines set by the industry codes of practice allows you to assess the environment and advise as to what improvements are needed before the project is ready to proceed. Preparation products all have a minimum and maximum application temperature. Application outside of these temperatures can significantly impact drying and curing times, and may even hinder the performance of the products irreparably. The industry code of practice advises that installations take place in a stable environment, between 180C and 270C, and as close to the anticipated building conditions when in occupied use.
Laitance/contamination
On site, laitance and contamination are often present on the substrate surface. Laitance is a weak upper layer of cement dust, additives and fine sands that float to the top of the surface. This can happen by overwatering or overworking a product. If left in place when products are applied, it does not provide a suitably strong surface to bond any product to.
This soft layer needs to be removed. Depending on how difficult to remove or widespread the laitance is, this can be done either by hand or using mechanical equipment, but in all instances, it must be removed.
Contamination of the surface can also result in the same problems. Contamination can be caused by many different means. It may be other trades dropping plaster, paint, dirt, etc., or it may just be general debris that gets worked into the substrate surfaces. These contaminants must be removed before the application of subfloor preparation products. If we do not remove these contaminants, we will never have a strong bond, vastly increasing the likelihood of floor failures.
The goal is to have a laitance/contamination-free and textured surface before we apply any floor preparation products. This allows the products to bond to the surface, providing excellent adhesion for the build-up of your system.
Cracks/joints
It is always good to identify what cracks need to be repaired, and not just fill them with a patching compound. Applying the correct crack repair system is vital to provide long-term protection of the floor. There are many ways to treat cracks – utilising mesh and/or a resin to treat the cracks is commonplace.
Understanding which type of crack is present and why they are there will give you a better understanding of how to treat them. For instance, we need to know if the crack is structural or non-structural. Structural cracks indicate there has been movement in the building fabric, leading to cracking. This can be seen by the crack running not just into the floor but also into the walls, tending to be wider in definition. Non-structural cracks indicate that shrinkage has occurred during the curing process of supplementary products and can be identified by their appearance, which resembles lightning bolts, usually hairline in width.
For the repair of shrinkage cracks, Bostik have a fast-track system in RENO P520 EASY, which allows for quick repair, 20-30 minutes before smoothing compound application and 24 hours before resin application.
For repairing structural and non-structural cracks, as well as weak friable surfaces, Bostik’s RENO E742 STRUCTURE is recommended due to its unique properties. Once cured, the epoxy repair resin dries to a compressive strength of 82N/mm². Due to its low viscosity, it penetrates the cracks fully and soaks in laterally across the cracks, providing a solid bond.
Moisture
It is well known in the flooring industry that we need to measure the relative humidity (RH%) to understand whether we need to control the moisture in the substrate or whether the substrate has sufficiently dried out. Measurements above 75%RH will indicate that a moisture vapour barrier (MVB) is required, and anything below, will not (if installing resilient or textile flooring). For wood installations, the indicative RH% figure is lower, at 65%RH.
This can be measured with the Hygrometer test, which can be performed using either the non-invasive box method or the invasive drill and plug method. This is the test stated in BS8201, BS8203 and BS5325.
It is good to mention that some screed manufacturers advise that the moisture test is done via the carbide bomb test. This is because you get an instant result and there is no need for a return visit to the site. However, the test itself is invasive due to the process involved. In the test, a sample of the substrate is removed using a hammer and chisel, and then weighed out to a required amount. This is then placed in a CM testing container and calcium carbide is added. Then, the container is sealed and shaken. This allows the calcium carbide to react with the moisture in the sample, providing us with an instant moisture reading. It is important to make sure that the substrate does not contain underfloor heating (UFH) before this test is done.
Once we have our moisture reading, we must identify the type of moisture we want to control – is it ground moisture or residual construction moisture? Ground moisture is where the building has no structural DPM and the RH% can fluctuate throughout the seasons. Residual construction moisture is the water put into the mixture of the substrate at the time of application.
Conclusion
When building your flooring systems, remember what the project is going to be used for! Is it a new project, or is it a refurbishment? What is the substrate? Is it a cementitious or calcium sulphate base? Are there any contaminants/laitance on the surface that need removing? Is the base covered in crack or joints? If so, what type of cracks are they? What is the moisture content, and which type of moisture control do you need? Do you need to deep-fill any sections? Are there large format windows that will create areas where you need an adhesive to resist high solar gain, like Bostik’s STIX A930 MULTI FIBRE?
Correct adhesive selection is a major part of any project as you want to select the right adhesive for the job, not just because you have it in the warehouse, or it was on offer. With new products coming out all the time, it is good practice to carry out test areas on projects to ensure that the system you’ve chosen performs as required. By performing a test area, you are giving yourself the advantage of trying new products and, more than likely, finding a more efficient and cost-effective system.
In all instances, these are the questions you or your estimator should be asking when you visit your next project. The answers will give you an indication of what system build you need, whether it is a fast-track installation on a site that is only live for an afternoon, a timber renovation system where the project has had an extension and you want to have a seamless finish across a timber and concrete surface, or a new-build system where you are applying onto a brand new flow screed.
At Bostik, our technical team offers this kind of support and more. Get in touch to book our free Bostik Academy training to learn why and how to use our products, and how they can solve your flooring issues.
