Can anyone tell me how many coats of paint should go over Render? Render was meant to be painted today, but they did another runner there for an hour, doing I don't know what, but definately not doing what was on their to do list.
Does anybody know? I have read a few articles and most of them say a primer and then 2 coats, is this right? I'm pretty sure my parents only had undercoat and 1 coating after that. But I wasn't paying full attention lol. They have done the undercoat for mine which has somewhat leveled out the brick.
I think they will do 2 color coats on mine because I have chosen darker colors. Depends on whether they do the render and then paint it or use the render with the colour through. 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. See our project on base coat plastering as the principle here is exactly the same. Polyurethane rendering float — Get one here in our online store. Once the battens have been removed and the voids filled to be level with the rest of the wall, the wall should be left for another hour or so to start the drying out process.
Once it is hard enough to push a rendering float onto the surface without render bulging out around the float, you can begin to float the surface up. Floating has the effect of closing up the render. All the little air holes are filled and the render becomes smoother and more waterproof. The float should be pushed fairly firmly only practice will show you the pressure required onto the surface then moved in a circular motion as you can see in the below video.
Cover the whole wall and then go back and start again. You will end up with a lovely smooth, closed surface. 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. 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.
Fill out to screeds, if necessary in layers. Screed off excess mortar between battens with a wooden straightedge spanning between the battens. When battens are taken down, fill in strips with the same mortar. An alternative is to make running screeds mm.
Scour back and key as usual after initial setting. Check for shrinkage during the first 2 days and, if necessary, lightly dampen the relevant area, tighten back and re-key.
In case of intermediate coats this would apply to each coat. Do not apply finishing coat until undercoat is adequately hardened.
Precautions are necessary and, if in doubt, your St. Astier Distributor will be able to advise further. Early exposure to rain will cause some moisture absorption in the first few millimeters of a fresh render. If frost occurs, there might be damage. The figures given above refer, therefore, to a render that has not been subject to water penetration in its early life. The preferred form of protection is hessian covers that, with re-damping, will also contribute to curing the mortar.
Hessian covers are essential to protect against frost. Plastic sheeting is effective against rain but should be kept clear of fresh work. If too tight it will generate condensation leading to unsightly staining. It will not protect against frost. Frost protection should be provided even if frost is not occurring at the moment of finishing the day's work but is forecast during the early days of a mortar. If the render is too wet, do not use it - discard and start again. As a guide for thickness you can nail wooden battens of the correct thickness vertically to the wall which also gives you a clean edge to work to.
Using your steel float, start forcing the first layer of render on to the wall. Keep applying the render until you have reached the desired thickness. Once the thickness has been reached, use a straight edge such as a metal leveler and screed off the render using a sawing motion.
Gently trowel smooth with a steel float. If you are applying more than one coat, you will need to let each coat dry for at least 3 — 7 days. You will then need to scour each coat with a sharp object to provide a good surface for the second coat of render to bond to.
A number of decorative finishing effects can be achieved using different finishing techniques on the final coat. Trowel Finish - This is achieved by skimming the final coat using a wooden float to produce a smooth dense surface. Sponge Finish - Mopping or sponging the hardened surface with a damp sponge achieves a sponge textured finish. Care should be taken not to let water run down the wall spoiling the finish by washing the cement out of the render.
Roughcast Finish - Throwing and flicking the final coat onto the surface achieves a roughcast finish, no re-touching is carried out, the way it lands is how it looks. Textured Finish - Textured finishes can be achieved by the addition of a coarser aggregate being added to the mix for the final coat. On days where the temperature exceeds 27oC, it is recommended that you either render early in the morning or late afternoon.
If the job needs to be done during the heat of the day, slightly dampen the brickwork with a fog spray before placing the render. This will ensure that the bricks do not suck the water out of the render mix before it has time to adhere to the brickwork.
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