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Strawbale Wall Render In South Australia Here we start a semi-regular series to help you choose the best home-mixed paint or render recipe. Whether it’s for an exposed mudbrick wall, a favourite bedroom, or a strawbale shower (yes, we’ve seen that!), any Earth Garden reader is encouraged to contribute to this new series. Please send your favourite render or paint recipe to: Linda Wheeler, Earth Garden, PO Box 2 Trentham, Victoria, 3458. In this issue Bohdan presents his three favourite render recipes for strawbale walls.
Cement lime sand render For a cement render, the mix I’ve always specified (by volume not spade!) is 1 part cement, 1 part lime, and 6 parts sand. The strawbale walls — once aligned and pre-compressed — should be chicken wire wrapped. The chicken wire helps application and also stops lots of surface cracking. Three coats are recommended and the total thickness is usually around 40 mm. Usually we use normal Portland cement for the first two coats (looks grey and ugly!) and then we use white cement (more expensive) for the final coat, giving a pleasant creamy colour. I recommend this mix when there are severe environmental conditions, for example driving rain, or in public locations — particularly where some robustness is required. The cement render tends to be more waterproof than the earth and lime renders. I have found this render ‘gritty’ and the most difficult to apply. Repairs to cracked render are difficult to repair and colour matching is almost impossible. Lime render The lime render mix that seems to work well is 1 part lime putty and 3 parts sand. The lime putty is obtained in a ‘wet’ material in 25 litre bladders. I have found this render relatively easy to apply, and generally have not wrapped the walls with chicken wire. This saves lots of time during the rendering process. What I like is that lime, when it cracks, will ‘self heal’ — that is, it will close the small cracks by addition of moisture. The disadvantage of this render is that lime is highly caustic and great care needs to be taken during application. I always wear long sleeved old shirts, gloves and safety glasses. Earth render The earth render mix that I’ve seen used is a good clay soil and 29 per cent sand. A client who is a potter in South Australia’s Clare Valley used this mixture and found it to be durable, non dusting and a beautiful earthy colour. South Australia has a lot of clay soils and this is a good, environmentally sustainable render to use. It is usually done in four or five coats, and the first coat is a slurry applied to the straw. Then this is followed by as many coats as you enjoy. The thickness should be in the order of 40 to 50 mm. Earth renders are generally the least durable of the three renders so the design of the buildings should incorporate careful detailing, including careful waterproofing around doors and windows and a good roof overhang. Periodic maintenance is required as cracks develop. So what is the best render? Renders should be selected based on: the climate conditions, the expertise of the plasterers, and the aesthetic effect that is desired by the owners. top | FAQ | Resources | Strawbale home | Back to EG |
IT IS always difficult to say which render type is best for strawbale construction. I think different renders suit different environments, so I’ve presented my three favourites here.