Blog posts of '2016' 'April'

Modern waterproof render systems are designed to cope with the changing weather conditions we regularly experience in the UK, but correct application is still essential. Even high-performance silicone render systems and monocouche renders can suffer from issues if they are applied during heavy rain, freezing temperatures or excessive heat.

Most waterproof render systems need stable drying conditions to cure correctly. If fresh render is exposed to rain too early, it can lead to streaking, patchiness or weakened surface strength. On hot days, rapid drying can increase the risk of cracking and inconsistent texture.

When carrying out silicone rendering for external walls, it’s important to follow manufacturer guidance carefully and protect freshly rendered elevations where needed.

Know your conditions

It goes without saying that before you begin the application process of any render, you should read and fully understand the application instructions supplied by the manufacturer.

The type of render system being applied is another factor to consider. Dry dash systems are more resilient to wet and cold weather than their silicone counterparts.

It is also advisable to check the weather forecast for your planned application dates – try to avoid any days with excessive rain, wind, heat or cold. Extreme weather conditions can severely affect the both the application and drying / curing times of the render. 

Simple Solutions

In hot weather, do not apply render on walls which are exposed to direct sunlight. Instead, start on an adjacent wall in the shade and follow the sun around the building. This method allows you to work in sunny weather, whilst avoiding any curing issues direct sunshine may cause.

Certain weather conditions will slow the curing process down – usually due to colder temperatures (less than 5oC) or high humidity (90% and higher). If this is the case, then the render will retain moisture for a longer period of time and if sustained will become more susceptible to damage from trapped moisture so it is essential that the render system is protected during this stage.

Ask an expert 

At Rendit, we offer a 2-year crack free guarantee on our Render Systems, so if you need any help applying your render contact Rendit today!

It’s one of those debates that always gets people talking on site.

Do we really need to two pass with K Rend and Parex, or are we just making more work for ourselves?

The honest answer is that there’s no single rule for every wall, every day or every product. A lot depends on the background, suction, weather conditions and how the material is behaving once it’s on the wall.

With systems such as K Rend one coat render and Parex one coat render, the term “one coat” can sometimes be misleading. Yes, these products are designed to achieve a through-coloured finish without traditional sand and cement backing coats, but that doesn’t always mean a single-pass application is the best option in every situation.

Some renderers are happy to apply monocouche render in one pass all day long, especially on consistent blockwork with manageable suction. Others prefer a two-pass application to help control thickness, improve consistency and reduce the risk of cracking or hollowness later on.

Personally, I think it comes down to reading the wall properly.

If the background is pulling hard or conditions are drying the render too quickly, splitting the application into two passes can sometimes give you a much cleaner and more reliable finish. On the other hand, if conditions are right and the material is sitting nicely, there are jobs where a single-pass application works perfectly well.

A lot of this also depends on experience. Some applicators know exactly how far they can push a wall, while others would rather play it safe and build the material up gradually.

The weather also plays a massive part. Warm temperatures, wind exposure and direct sunlight can all affect how quickly monocouche render starts to firm up. Trying to rush larger areas in difficult conditions usually causes more problems than it solves.

Whether you’re using hand application or spray on render methods, timing is everything. Getting enough material on the wall while still being able to rule and scrape it correctly matters far more than trying to save a bit of time.

There’s also the question of finish quality. Two-pass application can sometimes help create a more even appearance across larger elevations, especially when working with lighter colours or areas with inconsistent suction.

At the end of the day, most experienced renderers already know there’s no magic answer. Some jobs suit single-pass work. Some don’t. The important thing is understanding the wall in front of you rather than blindly following what somebody else says online.

K Rend and Parex are both solid systems when they’re applied correctly. Whether that ends up being one pass or two often comes down to site conditions, experience and personal preference more than anything else.

 If you would like more specific advice on the K Rend or Parex products we supply please contact us.

What is a "Halo Ring?" It's a renderers nightmare that's what it is! 

Halo rings in render are formed during the scraping process when an applicator unwittingly scrapes through the finish coat to the much harder base coat or first pass resulting in a flat textured area that cannot be matched into the rest of the wall. The worst cases may even go as far to reveal the mesh embedded into the first pass as the below picture shows:

Can they be avoided?

Most renderers I speak to have a story about a halo ring in either K Rend, Parex or other manufacturers mineral renders that caused them real headaches. Whilst we have had some success in correcting them with our Mendrend Render Repair System we cannot guarantee success under all circumstances as they all tend to be different. This is one of the most common issues we are asked to look at and if I'm honest the one we struggle with the most so if we can provide guidance to avoid it in the first place it suits us!

1. Before starting application check the walls with a long straight edge. If any bows or bellies over 3-4mm are present in the substrate then seriously consider the use of a K Rend or Parex base coat instead of just priming to level the walls out ready for the finish coat.
2. If applying a base coat ensure this too is level with a straight edge before applying the finish coat. Ensure that the K Rend or Parex finish coat is applied to a depth of at least 12mm over the top of the base coat to allow 2mm to be scraped with little risk of scraping too much away.
3. If you aren't applying over a base coat and instead applying the finish coat in two passes, do not apply the first pass too thick, we advise the first pass should be around 6mm maximum and level for both K Rend and Parex. The second pass should be at least a further 12mm on top of that applied wet on wet.
4. It is common for suppliers to under estimate the amount of material you will need in an effort to look like they are the cheapest or doing you a favour. They know that you will be straight back on the phone if you are running out of material and trying to get a job done. What generally happens instead is that the inexperienced applicator starts to take risks by spreading thinner. Always ask your supplier to justify the quantities quoted, backed by a manufacturers specification document. It's always better and cheaper to have a few bags left over at the end of the job rather than running out of material. Always ensure you allow 5-10% additional material for wastage on top of manufacturers quoted consumption figures as that doesn't tend to be included. You'll figure out how much you will need to allow for this yourself once you get a feel for the material after using it for a while. 
5. Every applicator uses a slightly different amount of material to the next due to differing working patterns. Keep a record of material consumption over a few jobs to see if you get consumption rates that suit you.

Avoiding this issue is as simple as that! Hopefully you find this of help and avoid the renderers curse in future!