Why is it better to strengthen the substrate with primer layer with fibreglass mesh and not with epoxy resin

Good preparation of the substrate for microcement is the key to success. The material itself is flexible and does not crack – on one condition: the substrate on which it will be applied, must be of good quality and we must prepare it properly. In many cases it will be necessary to strengthen it, which is most often done with layer with a glass fibre mesh or epoxy resin.

When should the substrate for microcement be strenghten?

We recommend reinforcing the substrate in the following cases:

• floor with underfloor heating
• existing floor with tiles or cement boards
• slippery substrate surface (eg terrazzo, polished concrete)
• uncertain substrate (eg with cracks, floor in a new building that is still bedding down)
• self-leveling screed on the floor

Why is it recommended to reinforce the substrate with a fibreglass mesh and not with an epoxy resin?

When it is necessary to strengthen the substrate, investors and contractors eagerly reach for the epoxy resin. Some customers are so fascinated by the resin that they do not seem to see any other (often more advantageous) solutions.

So what is epoxy resin? Epoxy resin is a kind of one and two component synthetic resins. It is fused and soluble in its uncured form. Coatings made of epoxy resin are waterproof and durable. Thanks to the above properties, the resin works well as a microcement base coat.

However, it has a number of disadvantages, the most important of which are:

• Unhardened resin is highly toxic. On contact with the skin causes allergies, inhaling its vapors results in damage to the airways and other organs. Working with resin requires special protective measures and work outfit (protective masks and goggles).
• Working with resin requires a special outfit. In addition to these personal protective equipment, you also have obtain spiked boots.
• The hardening time of the resin is at least 24h, which delays the proper work related to the microcement application.
• The resin is extremely durable – that’s true. The resin has, among others very high compressive strength. However, it should be remembered that the biggest problem of floors is cracking, which arises as a result of insufficient bend strength (flexural strenght). Flexural strength can be obtained by gluing a glass fiber mesh into the resin, which is unfortunately not remembered by customers. The resin itself is not enough.
• Resin is expensive.

Alternative to epoxy resin: coating with embedded glass fibre mesh

FESTKontakt is a dispersive, ready-to-use adhesion promoter with the addition of polymers and quartz aggregate with very high adhesion. It is suitable both for leveling the substrate and for priming all building substrates (plasterboards, ceramic tiles, smooth plastered concretes, plasters, OSB boards, etc.). It is ideal for use before future plastering works (microcement, fine plasters, mosaic plasters, organic plasters, etc.). After application, the surface is rough, which greatly increases the adhesion when applying subsequent layers. In the bridge, we recommend to paste the glass fiber mesh.

On the other hand, FESTFLOOR BASE is a two-component material that, like the bonding bridge, is used to strengthen the substrate. With it, we also recommend using a fiberglass mesh. We primarily advise the use of FESTFLOR BASE with mesh on floors with underfloor heating, on cracked substrates and on all kinds of cement, anhydrite and self-levelling screeds.

Such a set will protect against cracks on the surface of the microcement due to temperature changes on the floor heating, it will eliminate any unevenness and prevent the joints from old tiles from piercing (see also: A quick bathroom renovation with microcement Festfloor).

Advantages of ground reinforcement kits with fibermesh:

• high bend strenght
• non-toxic, does not require specialized work clothes
• easy to apply
• allows for quick work and application of at least one microcement layer on the same day as the adhesion promoter, which is impossible with the resin. The bridge FESTKONTAKT and FESTFLOOR BASE primer cures in about 4-6h, so 6-4 times faster than resin!
• the adhesion promoter is about 30-50% cheaper than the resin.

Watch our video “How to test and prepare the substrate for microcement”:

You need still more information? Read technical data sheets of the products.