We often get asked if we can explain the difference between monocouche renders such as K-Rend and Parex and Silicone renders, so here is a brief explanation and description if you are trying decide which ones to use.
- Most manufacturers produce or supply both types of render. ‘K-Rend’ has almost become an industry description of a through coloured render much like ‘Hoover’ has for Vacuum Cleaners.
- Monocouche renders are generally applied in two coats. Either two applications of the topcoat or a basecoat such HPX and a coloured topcoat.
- To finish the render, monocouche renders have to be scratched in order to get their preferred appearance. Silicone renders are plastered on and flattened with a plastic trowel.
- Monocouche renders are at the optimum level of scratching when you can “press your thumbnail in to it and but not your thumb”.
- Silicone topcoats have to be applied in dry conditions.
Pro’s and Con’s of each system
- Monocouches render is generally cheaper because of materials costs
- Monocouche render have been used more widely in this country for longer.
- Monocouche render has to be scrathed at the right time and if it isn’t, this can lead to scarring of the system.
- The biggest drawback to monocouche renders is that they are almost impossible to repair, should they be damaged after the application. Because of the beading system it is impossible to reapply the topcoat because the system needs to finish up against a bead nosing. This means that when its damaged then there isn’t much that can be done, apart from to completely hack off the damaged area and reapply. This has it’s own drawbacks because should you be hacking it off near a bead and damage the render on the other side of the bead, then there is another elevation that needs to be hacked off.
- Lime blooming – Monocouche renders contain cement which contains lime. If there is a persistent drip on the surface of the render, it can react with the lime and cause staining of the render. This again can not be patched. It can be painted but then you no longer have a coloured render, you have a painted render.
- Approved Installers – many monocouche renders can be bought off the shelf at builders merchants, which means anyone can use them. Silicone systems general have to be bought from manufacturers and suppliers which means they have to do a course which improves the general level of workmanship. Many plasterers believe they can render but we have seen more than our share of terrible jobs.
- Monocoche render tend to be more brittle if applied incorrectly which leads to more cracking and again this are nearly impossible to repair.
- Colours – There is less of a colour choice with monocouche renders.
- Silicone renders tend to be slightly more expensive as they are generally a four or five coat system. Base coat, Mesh coat, Second base coat, primer coat and topcoat. The working areas require more visits and therefore it is generally 5% or more, more expensive.
- Silicone renders are more forgiving once applied and can be easily patched or fixed, should someone cause damage.
- Silicone render can be made in any colour.
- There are many aggregate sizes so there are more finishes available in silicone. 1mm up to 4mm
- Silicone render are more flexible and less prone to cracking.
- Manufacturers guarantees are widely available
- Silicone renders can be easily applied to insulation.
- Silicone renders are easier to finish generally leaving better finishes.
- Silicone renders are water repellent but allows moisture out of them as a gas. (so let the building breath)
- Silicone renders can be applied to polystyrene, cement particle board, brick, block and can be applied over existing renders and paints using the scrim and pin system. (The new render is bolted to the substrate of the building rather than just being stuck to the face of the substrate)
- Silicone render to not have lime in them so no lime blooming can occur.
- Silicone renders are easy to clean.