As I took a walk around the centres at Amaroc I remember having one common thought – why do we have so many basecoats? Six from K Rend, three from Jub, five from Fassa Bortolo and three from Weber - why? I took it upon myself to find out from one of the technical members of our team. Complicated? Well, Yes & no - I narrowed it down to two things:
- Understanding the makeup of the render
- Understanding the nature of the substrate (the wall to be rendered).
What do I mean by “makeup of a render” - At Amaroc we stock a number of scraped textured renders, all of which perform differently. The answer is down to where/how they are manufactured. For example, a cementitious render has a more aggressive drying time after a certain point, where lime based renders has a slower consistent drying time. Both types of renders achieve a very similar finish but if the substrate receiving a render finish is not understood it can lead to poor adhesion and hair line cracking.
By understanding the nature of the substrate and the curing/drying process between render manufacturers, certain brands may offer significant cost savings over others. For example a render made from natural lime has a more consistent curing process than cementitious renders and as such can be applied directly to certain substrates without the need for a basecoat and/or additional bonding aids.
The main factors to consider when rendering on to your substrate are:
- Strength – the substrate, including joints, must be stronger than the render and should be able to adequately support and restrain it.
- Suction – good adhesion of a render is dependent on good porosity of the substrate. If the suction is too high the render will not hydrate sufficiently. If it is too little there will not be a good bond.
- High porosity – this is particularly the case with low density blocks. The substrate should be lightly sprayed with a fine mist of clean water evenly before the render is applied. Saturation should be avoided as this will cause excessive shrinkage.
- Low porosity – this is particularly the case with concrete or brickwork. A splatter or tight coat should be used to provide a controlled level of porosity and a mechanical key.
For further information contact the Amaroc team who are trained to advise the correct base coat for the best finish. We will ask four important questions
- What is the substrate you are rendering over?
- What finish does your customer want to achieve? For example, scratch render, thin coat render, dashing.
- Is the substrate inside or out? Area’s more exposed to adverse weather conditions are advised to use either silicone based thin coats or lime based products with a protective sealant
- How many square metres do you need to render?
With this key information, Amaroc can provide you with a competitive quote and manufacturer specification, to ensure you have another happy client. Contact one of our centres at Bristol, Cornwall and Swindon today!