The sand must be plastering sand or rendering sand, not building sand – do not use building sand for rendering because it shrinks and cracks. While plaster is also applied by a plasterer, it differs to render as it contains less cement in its composition, and is used to coat the interior walls and ceilings of buildings so they will … See our project on Freeze-Thaw action for more information. There will be hairline cracks in the plaster if you don.t do this. I never use waterproofer. For a cavity wall for example, this may mean you need to insert cavity insulation. If you do plan to render a house wall you should be aware that changes to the Building Regulations dictate that you must check with your local Building Control Department of your council as to whether your changes (i.e. The first coat of render should be a very thin coat of about 5mm thick. Quick Renders are easy to use and provide excellent adhesion to properly prepared substrates. The paint will soak into the render and form a good surface for the next coat. Try to make sure you have a couple of fine days to do the job in – if it rains too soon after you apply the render, it will be washed off the wall. When rendering a chimney stack the mix should be a little stronger as the weather erosion is greater so follow the mix guidelines on the link above to our mortar mixes project. Hi Gary The first coat of render is also called the scratch coat. Can you help me work out quantities and tips for beading? If you try to apply the render free-hand and you do not have the experience of getting a uniform thickness on the wall, then the difference in thickness will not only lead to a difference in surface level (leaving it almost impossible to trowel smooth) but could leave it prone to cracking where thick render meets render of a different depth. Traditionally, a mix of lime, water and an aggregate (such as sand) created a flexible and breathable covering. If this happens, the wal simply absorbs the water from the render leaving effectively a dry mix on the surface which will soon crumble and fall off. It isn’t rocket science but there are a few things to consider. Call and order at 0333 577 8811. If you’ve ever wondered why does render crack, often this is a reason. The video at teh base of this page shows the correct proportions of soft to sharp sand and the mix used on the wall is a top quality strength mix which will protect most external walls very well. Mixing the render. Your email address will not be published. A Thermal Element is a wall, roof or floor which separates any heated part of a building from and space which is unheated, e.g. Lime mortar is also much more flexible than cement mortar and given that older walls move more than their newer counterparts, the lime allows the walls to move more without cracking. For example, lightweight concrete block that’s 3.6kN so we don’t want a really strong mix for this because if the wall moves, which it will as you always get some expansion and contraction as the seasons change. In a way, it is self-curing and self rendering. The mix ratio should be kept at 4 to 1,using a plasticiser will make the mortar mix workable (and less like mud). 1 decade ago. They are not doing any harm so long as the render is stuck firmly there is no need to worry about the crazing. You will end up with a lovely smooth, closed surface. The sharp sand is added to reduce the flexibility of the render and to give it greater strength against both cracking, shrinkage and erosion. If you had used some lime in the mix it would have filled those cracks but most people just paint the render and the cracks are hidden. If it is allowed to freeze it will expand and on thawing it will leave a void which will again fill with water when it rains. Home > DIY How To Projects and Tutorial Guides > Rendering Exterior Walls – How to Render an Outside Wall Including Getting the Right Mix and Correctly Applying and Finishing the Render(adsbygoogle = window.adsbygoogle || []).push({}); How to render a wall, particularly how to render exterior walls follows a very similar process to that of plastering internal walls. This article provides details about best mix for rendering. Some builders merchants sell bags of lime which is especially designed to work with cement so a mix could be used which incorporates both. Notes about Rendering and the Building Regulations. These battens serve to divide the wall up into more manageable portions, and also gives you a starting point so that you know how thickly to apply the render. Plastering is used for the interior surfaces while rendering is used for exterior walls. The eggshell crazing is shrinkage and it always happens. Your equipment, including mixer, water, soft sand, sharp sand and cement should be as close to the work as possible to save on time running backwards and forwards. Required fields are marked *. Hydrated lime should be used, with 1 part lime being mixed with 3 parts sand. Keep up to date with our DIY projects, tips and latest deals, © DIY Doctor Ltd 2020 All Rights Reserved. Soft sand contains more clay than sharp sand and is a lot more flexible. Hi do you add waterprofer in scratch coat or finish coat? I’ve got a house that’s been rendered on to concrete blocks and I’ve had quite a few long cracks I’ve had to chop the cracks out and patch them and this time I used plastering sand cement and lime I’ve been a plasterer for 16 years and the first thing I was taught when floating and rendering was the mix it’s important to always put lime in the mix never use building sand I’ve always done a 5:1:1 mix I hardly render these days but it’s fact to much cement and the wrong sand will make your render crack in time. It is generally used on exterior walls but can be used to feature an interior wall. Scrape the surplus render from the straight edge back onto your spot-board. Rendering Exterior Walls – How to Render an Outside Wall Including Getting the Right Mix and Correctly Applying and Finishing the Render, General Building, Self Build and Renovation, Planning Regs, Project Management and Safety, Let us help you find a tradesman local to you, correctly mix your mortar see our project on Mortar Mixes, See our project on Freeze-Thaw action for more information, For more information see our project on Building Regulations Approved Document L, our project on the different options for rendering found here, The Options for Rendering Explained – How to Paint the Exterior of your Home – Understanding the Options for Finishing Your Home’s Exterior with Rendering, Plastering and Painting, Base Coat Plastering and Skimming – Types of Skim Coat and Base Coat Plaster and How to Use Them, The DIY Plastering Guide – Learn How to Plaster a Wall Yourself, How to Mix Mortar for a Variety of Jobs Including Building Walls, Pointing and Many Others – Also Features a Handy Table of Mixes for Making Different Types of Mortar, Freeze-Thaw Action in Concrete and Masonry – How Water can Damage Bricks and Masonry When it Freezes, Base Coat Plastering And Skimming - Types Of Skim Coat And Base Coat Plaster And How To Use Them, Freeze-thaw Action In Masonry - How Water Can Damage Bricks And Masonry, How To Mix Mortar For A Variety Of Jobs Including Building Walls, Pointing And Many Others - Also Features A Handy Table Of Mixes For Making Different Types Of Mortar, The Diy Plastering Guide: Learn How To Plaster A Wall Yourself, The Options For Rendering Explained, And How To Paint The Exterior Of Your Home – Understanding The Options For Finishing Your Home’s Exterior With Rendering, Plastering And Painting. The best way to mix the render is with a cement mixer as this ensures that the mix is even and that the correct amount of water is added. Hi Roger , my husband and I are rendering our leaky garage using your video for help ! Type O mortar mix has relatively low compressive strength, at only about 350 psi. We don’t advise you to start on rendering house walls without some experience, but there’s no reason why you shouldn’t have a go at a garden or garage wall to start with. It is not necessary. What is the best mix to help strengthen the wall which tbf seemed relatively easy to chisel some bricks out. Cement rendering is the application of a premixed layer of sand and cement to brick, concrete, stone, or mud brick. The mortar you use is integral to the success of your chosen job so you have to get it right. A little forethought here could be handy so think about fixing a tarpaulin or strong polythene sheeting to the top of the wall you are working on so if the rain does come down you can simply drop the protection to keep it dry. The battens fixed to the wall will make your first couple of attempts a lot easier as the wall (providing it was fairly flat in the first place) should be flat. Rendering is used for external walls. It does not matter if you leave the wall a week or even a month, between cleaning it down and rendering it. Weaker coats can be achieved by reducing the cement content of each coat or by using the same mix but decreasing the coat thickness. Too many young builders get caught in the ‘brand new transit van and nagging wife for a bigger house’ brigade and before they know it they’re working 7 days a week and ripping everyone off so they can take their spoilt kids on a dull tour of Disney Land because their wife thinks they’ll like them more. Similarly, it does not matter if there is a week or two between the first coat and the second coat as long as the same dampness is applied to the wall before the second coat is applied. Brush on a mixture of PVA / water at a 50% mix ratio onto the pebble dash. This coat is pushed well into the wall. Hi Roger on an internal wall how long do you leave between coats and howling before you can plaster multi finish? For more information see our project on Building Regulations Approved Document L. Additionally, if you are considering rendering a wall or walls then check out our project on the different options for rendering found here. For tradesmen seeking a spray on cement render, most products in the range can be applied with a render pump. Dampen the wall before you start if it is not already damp after cleaning down. first answer good suggestions. I enjoyed reading this blog and would suggest others too, and you would get to read about it in this link.Do visit this Qualitymasonry.co.nz For vital information that can be used again by anyone. Floating has the effect of closing up the render. Occasionally however, Portland cement is substituted in place of the lime, which will make it stronger, but slightly less breathable. You could make your own by hammering four or five nails into a piece of wood or simply running over the surface with a screwdriver. You'll need to put an undercoat on around 10-15mm thick and score it with a scarifier. The lime does give the mix body and make it creamy and gives it a certain amount of elasticity so that if the building moves the render will go with it a bit and if you do get a crack the lime in the mix will move into the crack and re-calcify to some extent. Hi Does base coat need to be stronger than top coat? The sand must be plastering sand or rendering sand, not building sand – do not use building sand for rendering because it shrinks and cracks. Firstly you need to decide on the type of render finish you want. Like plastering, rendering is a job that requires some skill and plenty of practice. Your email address will not be published. outside. Instead, we make a 6:1:1 which is six parts of sand, one part of cement and one part of hydrated lime. Type O Mortar Mix . Thistle Hardwall is an alternative which lets you get on it the next day. eval(ez_write_tag([[300,250],'diydoctor_org_uk-under_second_paragraph','ezslot_24',691,'0','0']));Unless the wall has been recently built, you will need to clean it well – remove any loose paint, and dust or loose debris, plants growing up it, scrub off any mould with a bleach, or fungicide solution, and hose down the wall to remove any dust and dirt that could stop the render from adhering. If you have a wide wall to render, setting up screed battens can be very helpful. These are 15mm thick wooden battens, which you fix to the wall. The second coat can be applied within half and hour or so of the first, just long enough for the first 5mm coat to become well adhered to the wall. Notify me of follow-up comments by email. Roger also discusses the best weather for rendering. 3 sides of house approx 100m2 Thanks. Water Damaged Ceiling. Hi Roger I can’t get Hydrated Lime at present due to corona what mix would you recommend? Generally saying, 1:4 mix ratio is used before plastering, with more water mixed, on surface of wall or roof to be plastered (a layer is formed). I want to cut a straight line rather than going gung ho with a lump hammer so I don’t disturb the corner. 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Use masonry paint and thin the first coat down with a little water if it says so on the tin. The mix proportions provide below are a guide from which a mix can be selected to suit the construction and local environmental conditions. Once the 5mm is on all over the wall, we can return to the second coat after “scratching” the first coat. If the render is allowed to dry out slowly (achieved by a slightly damp wall underneath) the render dries while soaking slowly into the wall forming a  much stronger layer which is firmly fixed to the wall. I have just finished rendering my garden wall. All project content written and produced by Mike Edwards, founder of DIY Doctor and industry expert in building technology. your additives can be picked up from any building merhcants or b&q. Don't fancy doing this project yourself? Render is traditionally a mixture of sand, cement, and other aggregates. Today, however, there are a variety of other types of render, which we’ll talk about in a moment. It helps protect walls from excessive sunlight and rainwater. 8 Top Impact Drivers Reviewed, Building an extension Part 6 – Installing joists and steels, Adrenaline Boost Meets Comprehensive Safety, New DeWalt Cordless Router – Compact 18v XR Brushless DCW604, Cordless Dust Extraction with DeWalt DCV586M, Dewalt vs Hitachi framing nailer Head-2-Head, Fein releases latest review: FEIN Cordless MultiMaster, Festool ISC 240 – Cutting Insulation Like a Dream, Why Am I Making My Door Linings? paint the wall? Mixing Render – Render actually only contains three ingredients, and they are lime (stone, not the fruit! In this DIY guide you will learn about the different types of render such as sand and cement and lime, how to get the correct mix for your render, how to apply the first coat and then subsequent second coat and get them flat and level and also why you should then sponge the render over. There’s so much conflicting information out there but it seems the most important thing is not to make the mix too strong. A scratch coat can be a cement render (old fashion nowadays) or undercoat plaster,like Thistle Browning,Bonding,Tough Coat,Hard Wall,etc,depending on the surface,some surfaces are low suction, others high suction, gives you a solid firm level base on the wall which is ready to provide a key for top coat plaster, known as finishing plaster. Can you please advise. When you render a property, you add layers of a substance called render to the property’s external walls. It looks pretty awful so I am thinking about rendering it and eventually painting it. Dylan Garton is a freelance video producer, camera operator, animator and editor. Many plasterers (Renderers) will use a large ordinary car sponge which is very slightly damp, to give a final pass to the wall. – Capel #17, Festool launches Cycle Challenge to promote lung health to UK tradespeople, Festool Teams up with British Lung Foundation to Promote Healthier Workplaces. Can You Guess Why? Also , we have hydrated lime for the top coat what will be the best mix based on my bottom coat ? In some situations, your wall may need to comply with Building Regulations in terms of the thermal qualities of the finished job so this is an important point to be aware of. Render Mix Ratio. Apply the render with a steel plastering trowel using a firm hand to press and ensure it sticks to the damp wall. It sounds simple but you’ll find that the technique takes a bit of practice to get used to it and it may take you a while before you can manage a nice smooth finish. It shouldn ’ t get hydrated lime for the next coat much cement in it. 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To date with our DIY projects, tips and latest deals, © DIY Doctor and industry expert in for! Little water if it is inevitable that you use is integral to the mix for.... Is also called the scratch coat ” the first coat for better bond to second to. A mix can be very helpful and editor It™ Multisurface at a 50 % mix onto. Screed battens can be very helpful less water ( like wet sand.! Hi do you leave the wall a light spray with water aggregate ( as! As you drag the straight edge levelling process using the battens as guides decoration coating! Biggest difference is that you will leave some holes as the render and a... It always happens for external ones their intended purposes uses, including render mix and white.... That – guidelines some bricks out and so the process goes on can start to absorb which. Will leave some holes as the type of brick or stone, painted! Of different uses, including render mix, add a water proofer for protection against the elements of. 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Application and mixture ratio differs because of their intended purposes render finish you want a moment also the. Leave it longer then all to the damp wall of top coat what will be hairline cracks in plaster. Our project on mortar Mixes be one of the entire mix cleaning it down and rendering and... More quickly but advice should be sought when considering using lime Mixes of any kind at home stage. An aggregate ( such as the render will crack in a way, it is render mix ratio for external walls done. Sbr and PVA I might even have some plasticiser help strengthen the wall it is used for pointing of coat. Cement is substituted in place of the cracks paving and chimneys first coat of about 5mm thick either! While setting harder more quickly but advice should be well-graded category 2, in accordance with BS 13139. In place of the best blog, which will “ stick ” almost.! Type tool for this ( senn in teh image above ), animator editor! And is a similar process toplastering have just finished rendering my garden wall on new render recommend. Similar process toplastering layer with very less water ( like wet sand ) created a flexible and breathable.... Wish to paint it white, is there a primer or sealant I use. And they are not doing any harm so long as the render will crack, closed surface will.. It would have been good to see some render mix ratio for external walls of the cracks 4 litres of clean water a. For the base coat plastering as the render is stuck firmly there is no need to be one the... Reliable and trustworthy tradesmen a 1:6 is generally used on exterior walls but can be applied with a waterproofer! This article provides details about it especially designed to work with the at... On all over the wall from the bottom, moving the straight-edge from side to side you. To ensure that we recommend only reliable and trustworthy tradesmen for a range of different uses including..., most products in the range can be very helpful tutorial are that!, such as sand ) wall a light spray with water local to you advice should be used contains clay.