Blog

As we have written about before, large cracks in render can be an indication of a major problem in the substrate. However, smaller and much less serious fissures can also appear. These fissures tend to be a lot smaller than cracks (around 0.1-3mm in width) 

Origins of fissures in render

Like cracks, fissures can occur due to movement from the building or the substrate the render has been applied to. Whereas large cracks tend to be an indication of a more severe issue, minor fissures usually occur due to minor inconsequential movement in the substrate.

What to do if you find fissures in render

It goes without saying, but you should always seek the advice of a professional before attempting any repairs. Determining the origin of the fissure is essential to ensure that there are no recurring instances of the problem. It is also advisable to wait for a period of at least 6 months to make sure that all fissures in the render system have stabilised.

Repairing fissures in render

Our patented Mendrend Flexible Fissure repair system is specifically designed to repair fissures in render from leading manufacturers and is supplied in a range of colours intended to match render manufacturer colour ranges. We also provide a comprehensive support service for this product. 

Rendit offers expert help and advice on repairing fissures in render – contact us today to find out more

One thing some applicators are better at than others is providing their customers with sample test panels of a finished render product as it can cause big problems with customers who are expecting their render to look exactly like it does in the brochure or even worse on their computer monitors!

The two render samples shown in the above picture are made from exactly the same render from the same bag. The sample on the right was simply scraped much earlier during the drying process than the render sample on the left and the difference that can make on the outcome of the final colour of all cementitious renders can be quite profound. It is for this reason we strongly recommend that you complete customer samples so you can test and verify the colour with them before ordering any materials 

It is very common for applicators to scrape renders early, therefore the colours achieved on site could possibly be much stronger than the colours of manufacturer provided samples which are made in a laboratory under ideal circumstances. It should be noted that all manufacturers of cementitious render products would deem this to be normal behaviour of the product.

We are happy to provide assistance with this, please feel free to contact us!

Most render systems are best applied in optimal weather conditions – ideally between 5oC and 35oC, with no rain, wind or snow. However, some projects may have to be undertaken in less-than-ideal conditions either due to time or budget constraints, so it is vital that the risks and challenges of applying render in adverse weather conditions are fully understood. 

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!

Do we really need to two pass the application of monocouche scraped renders and use a serrated edge? This is a question most applicators will furiously debate. The answer to this question I think depends on whether you ever have any of the below issues with any cementitious render product that you apply, whether it be a basecoat or top coat:

1. Sagging, bulges, tearing or slumping down the wall when trying to level off.

2. Splits that appear during initial set before scraping.

3. Holes or splits that appear and need filling during scraping off.

4. Long wait to scrape times and render setting that seems to "hang."

5. Cured renders that sound hollow in small random areas when tapped.

Some applicators who one pass and then spat straight away when applying through coloured scaped renders seem to accept that these issues are part and parcel of rendering and will work around them by either manually and laboriously filling any defects or resort to buying chemicals from third party manufacturers to try to modify the handling characteristics of the material which may have unknown effects on the render itself. There is an easier way to potentially solve the above problems without compromising the performance of render coating and that is by applying your render either over a basecoat, ensuring that a serrated edge is used to remove any trapped air after the application of each coat and before levelling off, or where a monocouche scraped render is to be applied directly to the substrate primed or not by applying in two level passes with the use of a serrated edge straight after the application of each pass and before levelling off. I recommend the 1st pass be approx of through coloured scraped render to be 6mm thick (ISH) with the second pass 10-12mm. Allow the 1st pass to stiffen slightly before applying the second pass. The use of a serrated edge on thinner layers effectively removes most or all of the trapped air and pulls the render together which usually sets it up lovely for levelling off.

I'll further explain my thoughts below:

Firstly, there has been a huge shift in all industries to green and environmental thinking. There’s been massive regulatory pressure applied to all manufacturers to focus on carbon saving on every aspect of their business and this has had a huge impact in product development labs everywhere. Everyone in the building industry is thinking cheaper, lighter, stronger, less energy for everything whether it be bricks, blocks, plasters, mortars and renders. I think for the render industry it’s had a great effect. From a render applicators point of view, today as I type this I honestly think that if you could buy a bag of render from any of the larger manufacturers and you would have a great product to apply. Gone are the days of the huge heavy trailer diesel powered mud-slinging pumps which could only be afforded by the busiest of applicators. These days due to these modern advancements you can buy a tiny but powerful Ritmo spray machine, plug it in and start firing a buttery, light and fluffy dream of a render at a wall 3 floors up in about 30 minutes. Applicators are positively spoilt in this day and age!

The push for green advancements does have a minor downside, especially when we look at the aerated concrete blocks available on today’s market, the push for cheaper, lighter and stronger does mean essentially that there’s more air in them, which in turn means more suction, or variable suction. Too much suction on a render that’s applied to thick on the first pass could result in accelerated drying backwards as the moisture is drawn quickly into the background and there’s potential for random splits occurring in the skin of the render due to the pressure of this pull. Whilst this won’t happen all the time, the risk of it happening is quite high and it is one of the reasons most renders are manufacturer would prefer their material to be applied in two passes. The first pass takes the initial suction hit and quickly pulls in which then protects the second pass from too much background pull. Most manufacturers still suggest a primer or a key coat on very lightweight blocks though as the suction on those things can be huge. Dense blocks need priming also but that’s because there’s not enough suction for the render to create its bond, but that’s for another article!

Secondly, renders in most of the country they have to be finished to a depth of a minimum of 15mm thick to achieve product specification. (20-25mm in some areas.) At this depth it's very easy to trap air deep in the material when one pass finishing as it is being applied with a spray or a trowel. This air may be difficult to remove at this depth, even with a serrated edge so you there may be a risk of air pockets forming underneath the skin of the render which show up as hollows or splits during the set / scrape or the material may sag when it tears at the air pockets during levelling off. You may not even see these problems happening until the scraping process at which at that point of no return they reveal themselves as random horizontal splits, holes, or hollow sounding areas across the wall. Our Mendrend Render Repair technicians can fix this if need be, but it needs a fair bit of work. 

Thirdly, two passing may improve the wait to scrape time, substantially if our site tests are to be believed, as the first pass being thinner will set very quickly which in turn will help the second pass set quicker too instead of one thick insulating pass which may retain moisture for longer.

You should find that the above advice may help with any product that you buy and may be struggling with the above issues but every gang works differently at the end of the day if you have methods that work for you for any given product there's not need to change for the sake of. 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!

There are many factors to take into account when selecting a render. From the type of building to weather conditions, it is important that the the correct type of render is chosen. Between aesthetics and functionality, there is a vast range of different renders to choose from, so how do you go about selecting the correct render?

The material of the building that is to be rendered plays a large part in selecting the most appropriate type of render to use. Older buildings tend to be made from materials that have a lot of movement, so will need a flexible render which is able to move with the building. At the opposite end of the spectrum, newer buildings are constructed with stiffer materials so will need to be coated with a more rigid render. 

Renders both help improve the exterior appearance of a building and can help in both protecting against the elements (weatherproofing) and insulating the building itself

Types of render

Lime render tends to be more expensive than other types of render. Its flexibility makes it more suited to older buildings. One other thing that needs to be taken into account is that lime render should be maintained with frequent coatings of lime-wash.

Cement render is a more rigid render and is available in a variety of bold colours. Being relatively quick to apply and cure, cement-based renders are the go-to choice for most modern buildings.

Method of Application

There are several methods of applying render to a substrate, and their preparation is something that needs to be considered before making a choice. Renders can be applied via hand or spray gun. Hand-applied renders require more work in their application, whereas spray guns allow for a quick and easy method of applying render. 

One final point to consider is local planning regulations. Render can be a stark contrast against non-rendered, brick buildings which can sometimes be an issue with occupants of surrounding properties. There are however, various types of render and their application - such as brick render - which offer a subtler solution.

I regularly hear people proclaim that their monocouche or through coloured scraped renders are "non maintenance," when they speak to me and they are a little flabbergasted that they are getting told that their render needs cleaning. This is a common misconception because of the misunderstanding of what "non maintenance" actually means.

Modern renders are incredibly hard wearing; a correctly applied system will withstand many years of whatever the elements throw at them even in sometimes extreme circumstances. Everyday I drive past a rendered property that was rendered nearly 30 years ago which even though the property has been subject to heavy flooding over 8ft deep at numerous points in history still looks great today, with no sign of the render falling off anytime soon.

On that basis, all modern renders are almost certainly expected to be non-maintenance. Once they are on, you'll have a hell of a time to get them off and re-applying anytime of the next couple of decades and beyond certainly should not be needed.

This doesn't mean that some, not all, will need some kind of regular cleaning. This is the case for all properties in the UK, regardless of what the walls were made up of. Thankfully its not a overly difficult task to either take preventative measures to minimise the amount of cleaning needed in the first place or to clean after things start to look a little dirty.

If you have signs of algae growth, we'd recommend you be proactive and kill it with a good algae cleaner before it gets chance to spread, we have them available on our site here or here. These tend to incredibly easy to apply as they simply are sprayed through a normal garden low pressure spray. Algae is stubborn stuff, it can grow on anything given the right conditions and its better to nip it in the bud before it spreads. 

Light pressure washing is something that can be done also as long as care is taken not to apply too much pressure to the surface of the render which may damage the surface. Industrial washers may have too much power for this job, but your average consumer grade washer that you buy from B&Q should be fine. Good quality non-acidic patio cleaners applied before washing down will also help with dirt removal. 

If you are looking to prevent dirt and algae build up completely you could use a special sealer for these types of surfaces. We will shortly be launching a new product we have developed called ProtxSeal which is incredibly easy to apply, again using a low pressure sprayer. Using a formula containing Siloxanes, ProtxSeal completely repels water and seals the render with a lotus leaf effect seal whilst still allowing the walls to breathe. Dirt and algae simply gets washed away as it can no longer stick to the surface. This sealer is easy to apply through a normal garden spray, does not change the appearance of the render at all and can be used on ANY porous masonary surface. We will also shortly be offering application services also for this product, please contact us for more details.

If you need any advice on how to keep your render looking fantastic for years to come do not hesitate to give us a call. 

Its that time of year when we regularly get asked "do we scrape same or next day?"

In all honesty its a tough question as all render have slightly differing setting attributes. I understand the eagerness to move to same day scrapes but its not something that can be rushed. Trying to scrape off a wet, sticky render will throw off the colour and create nasty texturing issues which are difficult to resolve. 

As a general rule if the air is dry and temps are predicted to be in the double figures from the minute you start until the end of the day then your render should be good to scratch the same day, but expect maybe a late finish if the temps are at the lower end of that scale. Get the pumps and trowel working early too!

If you like more specific advice on the K Rend or Parex products we supply then please feel free to contact us.

I don't normally do reviews as applicators tend to like what they like but I felt the need to write a bit about the new K Rend Silicone K1 because I rarely get such good feedback from my customers from a product as I have over the past few months than I have with this one, so I decided to get onto site to see it for myself.

I've seen it running through Ritmo and G4 spray machines as well getting hand applied applied by some of the guys who were staunch users of the Silicone FT and I've got to say I was pretty much blown away! Anyone who's traditionally used silicone mineral renders will tell you that they aren't as easy to apply as the other standard renders on the market, including those from K Rend themselves and I'd have to agree. They are usually harder to mix, dusty and heavy under the trowel or straight edge with a tendancy to split if not mixed correctly.

That is no longer the case with the silicone K1! Through the pumps you honestly can't tell the difference from the standard K1 and those who hand apply will be pleased to know that you too can have a light, fluffy and easy to manipulate render as your machine hugging colleagues tend to hog!

Now, we have a render where customers can have the benefits of K Rends unique silicone enhancements and the applicators don't have to worry that they may be having a late night to get the job done. Everyone who has tried the new Silicone K1 has made the switch from the Silicone FT on the first try of the material! Check out our video below! Thanks to Russ Downing at Lord and Downing Render Systems for allowing me to spend time on site with the guys.

K Rend Silicone K1, 3 floors up flying through PFT G4 Spray machine. Cracking! @KRendRenders pic.twitter.com/05RYdrV2DQ

— Rendit (@RenditLtd) January 27, 2016

Verdict: 5 out of 5! 

Applying render to the exterior of a building is an attractive way to improve its appearance. A number of modern renders go even further and can be used as a method of further insulating a building. However, there are several problems that can occur in both newly-applied render and render that has been on a building for years.

Where do cracks come from?

Cracks forming are one of the most common problems associated with external render applications and can form for several different reasons. Slight movement of the ground ann the foundations of a building can cause it to move. As render isn't elastic, this movement causes cracks to appear. If the render was applied in less than ideal conditions, or a previous repair was carried out inadequately then the probability of cracks appearing increases. Finally, movement may even occur in the substrate itself.

Why it's a problem

Cracks in render are unsightly, which defeats one of the main purposes. However, render with cracks in it can be even more of an issue - left untreated, cracks can develop into larger ones, providing an ingress point for moisture and dirt. Over time these will damage the render, enlarging existing cracks, causing new ones to form leading to blown or complete failure of the render system.

Solutions to the problem of cracks in render

The best solution is to seek out the advice of a professional. More importantly, do not hack away at the render without first identifying the cause of the problem. Doing so may damage the surrounding render and can make a colour-matched, invisible repair extremely difficult. Most cracks in render can be repaired using a non-maintenance crack repair system such as Mendrend.

How to repair the cracks in render

We suggest using a professional crack repair system such as Mendrend, which allows you to repair your render whilst allowing it to retain the appearance of the existing render. Mendrend comes as two components: a flexible crack fissure infill and a flexible penetrating acrylic. Detailed instructions on how to repair cracks in render can be found on our Mendrend Application Guidelines page.

If you are unsure about repairing cracks in render, contact an expert today