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Unitex® Renders & Finishes
UNITEX® RENDERS & FINISHES
Install, Maintain :
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Coating with Unitex Renders and Finishes
Substrate Preparation
Before applying the coating it is essential that the substrate is properly prepared. Strong adhesion of the render or textured coating, to the substrate, can only be achieved if the surface of the suitable substrate is clean, dry and well bound. If the substrate has been previously coated, it is very important that any loose render, flaking paint, etc adhering to the surface is wire brushed and then swept to ensure no loose particles remain. The surface should then be washed with clean water to remove any dust still present on the surface. Allow to dry before applying your Unitex product.
Similarly if the surface has any oil, grease or any other oil-based compounds adhering to it, this contamination must be removed before applying your Unitex product. Typically oils and grease on the surface can be removed by scrubbing with household detergent and warm water. The surface must then be washed down with clean water to remove any traces of detergent, before applying the coating. In the case of poorly bound or overworked render an approved sealer (acrylic) will need to be applied prior to texture coating. Poorly adhering base render must be removed first.
If coating over an existing render with the Unitex Decor range of products, the render surface must be made good before applying the textured coating. This means that any loose or damaged render must be removed and patched prior to coating with the textured finish. In this case, for increased adhesion strength, Uni-Seal (an acrylic sealer) will need to be applied prior to the Unitex Applied Finish.
If old masonry (concrete or brickwork) shows efflorescence or scaling laitance then this must be physically removed as a first step. The cause of the salt 'bleeding' should be investigated and steps taken to prevent its recurrence prior to applying your Unitex coating.
In addition to preparing the substrate so that it is clean and dry (no moisture in the substrate behind the coating), it is also important that the builder nominate and set the expansion/control joints for the applicator before the coating is applied.
Expansion/control joints are the responsibility of, and will be provided by, the Builder or Head Contractor. Unitex recommends, as a mimimum, expansion joints (approximately every 6 metres) to every elevation and between different substrates, to allow for building movements and stresses. On broad walls, Unitex recommends vertical expansion joints at least every six metres and between floor levels. Also allow for extra expansion joints at weak points such as bulkheads at window and door openings, etc.
If such expansion joints are not provided by the Builder or Head Contractor, cracking of the render and/or surface coating, due to movement, may occur. This is not indicative of faulty material but of sub-standard building practice. The builder or Head Contractor is also responsible for the construction of the framing and substrate. They are to be constructed according to the relevant Australian Standards. Failure to do this may result in cracking of the render or finish. Again such cracking is not an indication of faulty product. Substrate movement may be caused by many factors such as timber shrinkage, ground movement, substrate stresses, surface and thermal movement etc.
Applying the products
Before Applying the Render or Texture
It is important to ensure that, as well as the substrate being properly prepared the work area is also made ready. This means masking of windows etc. to avoid marking the glass and frame surfaces with render or texture splatter. Drop sheets should also be used where required to prevent marking of adjoining surfaces - tiles, pavers, downpipes etc.
Spray Application
This is principally, but not exclusively, used for application of dry powder-based renders. The required slump (consistency) is determined in the mixing chamber of the spray machine. The water flow, from mains connections, is regulated at the mixing chamber.
Unitex can arrange the supply of render spray machines. They are robust and compact. They are easily transportable and small enough to pass through standard door openings and can be used inside and outside. They can be used as mixers only or as a mix and spray machine. The pump pressure, aperture of the nozzle, and the consistency of the render determines the thickness applied.
The spray pattern can be in any direction. Whether you use it in a mainly vertical, horizontal or any other pattern depends on the geometry of the surface and the preference of the applicator. Generally, when spraying render, you work from the bottom up and horizontally.
As to how far from the wall the nozzle should be held, this is not a fixed distance. It is largely determined by the degree of 'bounce-back' of the render. If there is a significant amount of bounce-back then the spray pressure should be reduced or the nozzle held further back from the surface. When using a spray application for Unitex renders it is important that a three-person team be available. Whilst one operator is intermittently keeping up the supply of render (out of the mixing chamber), and the second spraying the surface, the third should be following immediately behind the sprayer to trowel off the surface to smooth it over and keep the surface render 'true'. The machine operator has time to mask up and prepare scaffolding ahead of the sprayer. The operator must understand and care for the machine and carry out daily thorough cleaning and maintenance.
Trowel Application
If using trowel application for renders Unitex recommend that the initial trowelling at least be done with a notched trowel. This trowel spreads the render more easily and evens the surface better than straight-edged trowels. The surface can then be finished off with a flat (straight edged) trowel. This finishing is best done with a polystyrene, plastic, steel or wooden trowel. Unitex can supply all of your trowel requirements.
The trowelling can be done in a vertical, horizontal or sweeping action. The preference of the tradesman is the determining factor, so long as it produces an even, tradesman-like finish.
Roller Application
For heavy texture applications the best type of roller to use is a 'spaghetti' roller. This gives a stipple finish. This is a two person application - the first to give even coverage spread and the second to produce the desired effect.
Brush Application
A standard paintbrush can be used for these applications. The only usual situation requiring paintbrush application is for the cutting-in of the flexible membrane coating (Uni-PTC or Uni-Flex Membrane) around windows, doors and edges. If applying a one-coat system (not recommended), cut in first and then roller apply away from these edges to coat the rest of the wall. If it is a two-coat system, roller close to the edges first and then cut in with a brush from the rolled edges. After 24 hours apply the second coat.
Note: Whichever application method is chosen, building regulations may require scaffolding to be erected by a qualified and certified operator.
Cleaning Up
All of the equipment used to apply Unitex renders and textures are cleaned up with water and a little 'elbow grease', immediately after use.
For a more information or a copy of the Unitex Application and Fixing Guide, contact Unitex. |
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