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There’s no doubt that cracked render can be incredibly disappointing and frustrating, especially for homeowners that have just had their houses re-rendered. There are many reasons as to why render might crack, be it due to weathering, the incorrect use of materials, rising damp and the like. As a renderer, it’s important to ensure that all your bases are covered to prevent cracking and achieve a long-lasting finish. In today’s post, we’re going to give our best installation tips to ensure that cracked render is a matter of the past!
Prevent Cracked Render with Substrate Absorptivity Tests
The first step in any render installation is to check the absorptive capacity of the substrate. This is an essential step because porous substrates can absorb water out of your render very quickly, which can in turn affect its adhesion and ultimately – you guessed it – cause cracked render.
The substrate absorptivity test that we recommend is to wet the wall with water and check the rate at which it is absorbed. You don’t want the substrate to be oversaturated with a low absorptive capacity because the render won’t stick but, equally, you don’t want it to immediately absorb the water.
If your substrate is highly absorptive, we recommend lightly dampening the walls with a fine mist of water, then performing the test again. Be careful not to oversaturate the walls!
Use the Right Primer
Following this, a good primer is essential for limiting the absorptive capacity of the substrate and ensuring that it is stable, thereby preventing cracked render. We recommend using the EWI-301 Water-Based Primer or the EWI-302 Deep Penetrating Primer which is ideal for newbuild brick and blockwork.
A good primer will also work to ensure that the substrate doesn’t absorb too much water from your materials. The EWI-310 Universal Primer, for instance, contains quartz aggregate which helps to create a mechanical key to aid adhesion.
Reinforce with Fibreglass Mesh
We recommend using Fibreglass Mesh in all the render systems that we offer; you can embed the mesh in the first pass or within the basecoat layer.
Fibreglass Mesh enhances the tensile strength of the render, keeping it nice and sturdy so that it can withstand any movements within the building structure and therefore resist cracking. The mesh is cut into strips and overlapped on all sides so that there are no gaps where cracks can form.
If you want to take the crack resistance up a notch, we highly recommend using Panzer Mesh within your system as this is incredibly high-strength.
Don’t Forget Your Beading
We sell lots of different types of beading, all designed to be embedded within the render to reinforce certain areas. For example, our Corner Bead helps to provide a nice sharp finish at the corners of the render system whilst also providing reinforcement against impacts. Also, our thin-coat render system beads tend to have a mesh wing to spread the reinforcement across a larger surface area, while the scratch render beads have just the hard uPVC without the mesh. Other types of bead we offer include:
Movement Joints
Movement joints need to be reinforced using a render movement bead. These are used where there is a large expanse of render (more than 12m). It’s installed vertically and is embedded within the basecoat layer to stabilise the render and ensure that any cracking is prevented.
Stress Patches are Essential
Areas above and below openings (around windows and doors) need to be reinforced with strips of Fibreglass Mesh to distribute and resist stresses. The mesh should be cut into strips that extend past the stress patch by at least 50cm. It should be embedded in the middle of the basecoat or the first pass.
And, there you have it! We hope you found these tips useful for preventing cracked render. If this has been an issue for you in the past, be sure to refer to these tips to prevent it from occurring again in future. If you have any questions, do not hesitate to contact our experienced sales team who will be happy to help!
EWI Store are the leading UK render specialists, offering a range of high-quality Render and External Wall Insulation products. We take a whole-system approach to external wall insulation, stocking all the materials required to help installers achieve a stand-out result. Our selection of products is constantly growing as we strive to offer our customers the best possible choice of materials from trusted manufacturers and established brand names.
