Substrate Solutions

Specifying for fast track projects.

By Gareth Lewis Technical and Specification Manager Kerakoll UK.

Every specifier will have projects that need speeding up, either because of unforeseen delays in the approval or build process, or simply because an unavoidable deadline means that the normal timeframes for laying and preparing substrates, and tiling them, need to be shortened as much as possible to allow other trades access to the site and the project to be completed on time. In this article I will examine how to deal with the challenges that this throws up and overcome any issues that may arise.

Where a new screed is called for, a fast drying formulation such as Kerakoll’s Keracem Eco is essential. This is a hydraulic binder for high-performance screeds and heat-radiant slabs that are compatible with any type of finished flooring. It is a standard set product with a pot life of up to three hours and good workability making life easier when laying. However, it dries rapidly and is ready for foot traffic after approximately eight hours, and tiling after only 24 hours when laid at 20oC and a thickness of 50mm. The screed compensates for hygrometric shrinkage, reducing the formation of surface cracks. The binder also compacts easily, giving the finished screed excellent thermal conductivity and making it ideal for use with radiant heating and cooling systems.

With uncured, damp or cracked screeds, or to avoid future problems, an uncoupling membrane should also be used. For most manufacturers’ products, care needs to be taken to choose the correct membrane for the installation, and almost all uncoupling membranes require that existing movement joints in the floor are followed through both the substrate and the tiling layer.

Kerakoll’s Green-Pro is an exception to this rule. It provides uncoupling, anti-cracking, and waterproofing functions all in the same membrane and, when used in conjunction with Biogel Revolution in their Laminate No Crack system as described below, it can be used for laying tiles on any surface without worrying about respecting joints exactly in the subfloor or screed: they can be ‘moved’ to create a more aesthetically pleasing design in the finished surface.

Furthermore, the ‘plastic’ surface of traditional polymeric membranes reduces the performance of C2 adhesives to below the limits of C1 (a declared value of ≈ 0.2N/mm2) and this can lead to the failure of the installation through delamination and lifting of the tiles.

In contrast to these alternatives, Green-Pro is a multi-layer composite polymer-based membrane. The bottom layer is made of a non-woven fabric which allows vapour to be dispersed through the textile’s structured network of channels. The middle layer is made of HDPE, which renders the membrane waterproof and allows it to deform to compensate for the stresses from movements of both substrate and floor covering. The top layer is created using hydrophobic polyamide fibres which are fused to the membrane and provide an excellent surface for the Biogel Revolution to adhere to, ensuring a powerful bond to the tiles.

Every manufacturer offers a rapid set tile adhesive which enables floors to be walked on and grouting to be carried out on both floors and walls more quickly than with a standard set product. With conventional cement-based fast set (C2 F) adhesives, the specifier must take into account the type of substrate and whether it is flexible or not. Classified as C2 FTE S1, Kerakoll’s Biogel Revolution is a next-generation rapid set adhesive made with gel technology that can be used on any type of substrate including those that are deformable by up to 2.5 mm. It is suitable for use on walls as well as floors as it has virtually no vertical slippage (up to 0.5mm). The pot life at 23oC is one hour, but it is ready for foot traffic and grouting after three hours.

With most manufacturers’ adhesives it is essential to ascertain the type of tile that is going to be fixed as not all adhesives can be used with all materials. Here again Biogel Revolution comes up trumps as it is capable of fixing any tile, including the latest very large and thin porcelain. Shear adhesion for porcelain tiles is 2N/mm2 after 28 days, and the tensile adhesion is 2.5N/mm2 after 28 days.

Where an R2 adhesive is more appropriate, Kerakoll offers a hybrid-gel adhesive, Biogel Extreme, which can fix any material to any substrate even in the most extreme conditions, but is solvent-free and non-toxic, unlike traditional epoxy-based reactive resin adhesives. The adhesive strength (4.5N/mm2) is 500% superior to a Class C2 cement-based adhesive after 24 hours, and ten times more deformable (> 50mm) than a Class S2 cement-based adhesive. It is also easy to spread, being five times less viscous than a polyurethane adhesive. It achieves shear adhesion for porcelain tiles, after seven days, of 6.5N/mm2, and tensile adhesion of 4.5N/mm2 after 28 days.

The pot life at 23oC is 110 minutes, with an open time of 180 minutes, but it is still ready for foot traffic or grouting after four hours.

Grouting and sealing
Specification of a rapid set grout will enable the tile fixer to finish, clean off and leave the site available for other trades more quickly. Fugabella Eco Flex is a rapid setting and hardening mineral grout suitable for internal and external use. The pure NHL in its formulation makes it naturally bacteriostatic and fungistatic as well as extremely colour-fast. It resists water damage by creating a water-repellent water-drop effect. It has a pot life of 30 minutes and is ready for foot traffic after three hours when used at 23oC. After 28 days its flexural strength is ≥10N/mm2 and resistance to abrasion is ≤ 358 mm2.

The final step in any installation is to ensure that all movement joints are filled with a suitable silicone sealant such as Kerakoll’s Fugabella Eco Silicone. This is an anti-mould organic sealant with a high level of elasticity.

Laminate No Crack
Kerakoll has developed a system designed to take the headache out of specifying for projects with time constraints where the screed may not have time to dry out before installing tiles or there are other issues present. This system uses two of their most innovative products, the Green-Pro membrane and Biogel gel adhesives, and allows tile installation even when substrates have problems that would normally cause failure, such as cracks, movement or vapour pressure from insufficient curing. Christened “Laminate No Crack”, the system forms a laminated surface composed of adhesive, membrane, adhesive and tiles with a very high shear strength of ≥ 1.8N/mm2. It can be used for both uncoupling and waterproofing over all screeds including heated ones. The use of fast setting screed, adhesive and grout allows speedy installation.

There are two versions of the system: the first, Laminate No Crack Uncoupling is as an uncoupling, anti-cracking solution for cracked screeds or to compensate for hygrometric shrinkage in uncured substrates, especially in fast-track projects. It is also ideal for use with underfloor heating systems as the Green-Pro membrane has thermal resistance of 1.030 m2 K/W, thus does not impede the passage of heat. The system is also suitable for use in industrial settings subject to high-impact and extremely heavy loads, having passed the Robinson Test for resistance to dynamic stress (ASTM Standard C 627 tested with 10mm thick porcelain tiles).

The uncoupling system can be laid on any suitable (or Keracem Eco) screed, followed by the Green-Pro membrane on top of a layer of Biogel Revolution to create a bond between the membrane and screed. On top of this is applied another layer of Biogel Revolution to fix the chosen tiles without having to wait for the previous adhesive used to fix the mat to dry. The system is finished with Fugabella Eco Flex grout and Fugabella Eco Silicone in the movement joints. As previously noted there is no necessity to follow joints in the screed through the tiling installation so the tiles can be laid in any pattern desired.

The second version, Laminate No Crack Waterproofing is specifically for installations that require waterproofing, such as balconies, terraces, or external surfaces of any size, whether new or old, damp or dry, cracked or subject to dimensional movements.

Here the system can be laid on any suitable (or Keracem Eco) screed followed by Biogel Revolution and the Green-Pro membrane in exactly the same steps as the Laminate No Crack Uncoupling system. Next, Aquastop Fix is used to install Aquastop 120 waterproofing tape is applied to the joins in the Green-Pro membrane and around edges and corners to ensure water-tightness. Aquastop Fix is a waterproofing product which uses nano-technology to make it totally water-repellent and give it high chemical stability.

There is no waiting time before laying coverings on top of Aquastop Fix, so installation of tiles can then proceed promptly with Biogel Revolution used to create a secure adhesive bond between the tiles and membrane, Fugabella Eco Flex grout used to grout the joints and Fugabella Eco Silicone to fill the movement joints as before.

Technical advice and problem solving
With the Biogel adhesives and Green-Pro membrane, Kerakoll has developed products that are simple to specify as they are multi-purpose and easy to use. However, every project is unique and it is important to take into account any particular issues that may be present. The best way to do this is to get the manufacturer involved at the specification stage, so that the most suitable products can be chosen, and to ensure that they are consulted should an unforeseen issue occur on site. Kerakoll’s technical team is pleased to offer their help and advice at all stages of any project.

Kerakoll UK is a subsidiary of Kerakoll, one of the leading Italian suppliers of environmentally friendly chemical products for tiles and construction work.

For further information please
contact Kerakoll UK on:

T: 01527 578000