For example, it can be used to make a wall finish look fine and smooth, or coarse and textured. Pigment can be applied to render to give your walls a coloured finish, or else a rendered wall can be painted.
Tools such as brushes, trowels and sponges are used on the final coat to further manipulate the finished render into a smooth or textured result. Render needs to be applied to a completely clean and bare wall to help it adhere, so any old coats of paint and render should be removed with a wire brush. If your wall has any mortar on it, be careful not to damage it during this process. A good tip is to mist your wall down with a mixture of clove oil and water - this will inhibit the growth of mould and mildew.
Roughing the surface of the wall in a cross-hatched fashion will help the render to adhere. If your wall is particularly large and you want the render to look flat and even, one option is to attach some thin wooden members at intervals of a metre along the wall. These can be removed and filled in with the same rendering material once you have applied at least two coats of render. Once the walls have been prepared, the render can then be mixed. Cement based renders on both internal and external walls perform a number of functions.
These include better waterproofing, improved fire rating and an improved appearance through the use of coloured or textured renders. To get the best results it is important that the mix is suited to the background surface, that it is properly applied to the correct thickness in the appropriate number of coats and that attention is paid to curing. Before you start you need to ensure that the surface you are rendering is free from dirt, dust, oil, grease, paint, silicone or friable material.
A dash coat is simply a very strong mix of cement and water which is flicked over the wall or metal window frames creating a surface for the render to grip to. Allow the dash coat to dry for at least 24 hours before you start to apply the render. Highly absorbant surfaces like sandstone will normally require soaking down to prevent water loss from the freshly applied render.
Firstly you need to decide on the type of render finish you want. Using the chart below you can determine the correct mix ratios and roughly how much material you will require. All render mix ratios are for standard cored clay bricks. All mix ratios are by volume e. Only use good quality plastering sand. When mixing renders by hand, measure the quantities carefully using the same gauge vessel for all ingredients. Renders should be mixed on a hard flat surface concrete slab or a board, in a cement mixer or wheelbarrow.
Mix up enough render that can be used up in 30 — 40 minutes. Firstly combine all the dry materials until the colour is uniform. Add only small quantities of water at a time while continually mixing the render.
If it is likely to be very cold in the evening with even a hint of frost or ice, then the work must be covered preferably by hessian sacking or even a old blanket to stop the water in the render freezing. 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.
This will also freeze and so the process goes on. See our project on Freeze-Thaw action for more information. 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. Mixing in a wheelbarrow is fine but almost always there is a little unmixed sand and cement at the bottom which does not become apparent until emptying out the barrow. 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. See our project on fixing to masonry to accomplish this. Place them about mm apart and make sure the screws are flush with the face of the timber because you will be using these battens to help you level the render as you can see in the image above. 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.
Dampen the wall before you start if it is not already damp after cleaning down. Apply the render with a steel plastering trowel using a firm hand to press and ensure it sticks to the damp wall.
The first coat of render should be a very thin coat of about 5mm thick. This coat is pushed well into the wall. It can only do this effectively if there is little weight being applied as, if we try and get too much on the wall in one go, gravity will start to pull it off.
Scratch the surface of the first coat to enable the second coat to bond. Professional plasterers use an over-sized comb type tool for this senn in teh image above. 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. There is no need to scratch right down to the original wall surface, just deep enough to provide a key for the second coat. 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.
For the second coat, which should be about 10mm thick, build up the coat to the thickness of the batten and even a little beyond as it can then be levelled it by using a straight-edge as shown above.
Work up the wall from the bottom, moving the straight-edge from side to side as you move upwards. As you drag the straight edge up the wall it is inevitable that you will leave some holes as the render clings together. Fill in any holes with the trowel and repeat the straight edge levelling process using the battens as guides. When the render has been on the wall for an hour or so, remove the battens carefully and fill in the holes left by them.
This is often best done by using a pointing or a gauging trowel. Scrape the surplus render from the straight edge back onto your spot-board. It can be used for plastering or mixing cement. The straightedge are metal sticks with multiple purposes. It is used for smoothening the layers of render after a coating has been applied to the wall. Not having this tool makes the foundation for the render uneven making the wall craggy and curved. So it is an essential tool, unless that is the look you are trying to achieve.
After applying the first layer of render, you have to put these depressions on the wall to use the next layer. When you are done with the first layer you apply the next layer.
The scratching comb is the tool used to make these depressions. This is the perfect tool for putting multiple layers on the walls. The materials that you will be using can be difficult to carry around without help with tools.
Bucket trowels are used to carry render to a bucket or a wheelbarrow closer to your working area. Scraping, carrying, and mixing wall coating, bucket trowels can do all of these.
The rendering tape is a variance of video that is made for rendering walls. When you look for a clean finish or create straight lines in the walls, rendering tape will help you out here. It allows you to fully maximise plastering walls without worrying that the plaster will touch the paint or windows. After applying the render using the trusty trowel you have, there may be trowel lines that will ruin the wall. The sponge float can help smoothen the wall to give it a smooth look.
These are one of the tools used to add the finishing touches to the wall. The buckets are your storage to put the render.
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