49. Types of Undertile Membranes * Depending on formulation LIQUID MEMBRANES Suitability Membrane Description Comments Acrylic co-polymer water based High Flexibility Acrylic co-polymer cement modified Good External Weathering Modified Polyurethane based Some are Premium * Water based epoxy Semi-Rigid Conditional Polyester resin two parts reinforced with fibreglass mat. Compatibility must be confirmed Bitumen latex Requires a 40mm self supporting screed for tiling Single pack moisture curing polyurethane
50. Types of Undertile Membranes SHEET MEMBRANES Suitability Membrane Description Comments Conditional Butyl rubber sheet membranes Direct Bond with ARDEX Optima APP bitumen compound sheet membranes Requires a 40mm self supporting screed for tiling SBR bitumen self adhesive sheet membranes PVC sheet membranes TPO sheet membranes
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Editor's Notes
Surface preparation is one of the most important and critical parts of a successful waterproof membrane installation and failure to adequately prepare the surface will undoubtedly lead to a membrane failure. Surfaces that are provided to the waterproof applicator are rarely in a suitable condition for membrane installation and the costs associated with surface preparation will normally constitute a large proportion of your total job cost. Because of this careful consideration should be given to the equipment necessary, materials and the logistics of doing the preparation when quoting a waterproofing and/or tiling job.
All surfaces to which the membrane is to be applied must be structurally sound as a whole. That is if a slab has a crack that is moving it is impossible to apply a waterproof membrane over it without proper special design of that membrane installation. All surfaces must also be integrally sound, that is the surface must be strong enough to support a waterproof membrane and whatever goes on top of it. All cracks, construction joints, expansion joints or any joints that may move must be treated in accordance with the membrane manufacturers recommendations. All surfaces must be clean and free from contaminants that may hinder the adhesion of the membrane. Most common contaminants are dirt, dust, concrete curing membranes, form release agents, grease and oil. Remember, a membrane applied to a foreign material only bonds as well as the foreign material bonds and this is normally considerably weaker than is required. All holes in the surface must be repaired to a smooth surface to eliminate any edges. A membrane applied to an edge will, as with all coatings, tend to pull away from the edge as it dries leaving a lower than required dry film thickness at that point. This effect of pulling away from an edge also applied to a highly irregular surface which consists of a large number of corners. Protrusions, or dags on the surface also result in the same pull away effect so they should be removed before the membrane is applied. Essentially, for a sound membrane installation, the surface should be smooth.
Concrete and renders can, and usually do, shrink during curing resulting in the formation of small cracks. If these cracks develop after the fully bonded membrane has been applied there is a high risk of the membrane fracturing regardless of its elongation. There are major fallacies in understanding what a flexible membrane can do and Ardex have Technical Bulletin TB073 available from Ardex explaining this in detail. Essentially, if there is no gap at the time of installing the membrane and a crack develops, even though the membrane has over 300% elongation, 300% of zero is zero. New concrete or renders must be allowed to cure for the required periods, normally 28 and 7 days respectively to allow it to develop these cracks before the membrane is installed. The surface must also be dry before a membrane is installed to avoid the membrane blistering. If water is contained within the substrate when the membrane is installed, this will expand as it vapourises as it gets warmer and cause the membrane to blister. By applying ARDEX WPM 300 HydrEpoxy at 3 square metres per litre and allowing this to dry, a membrane can be applied to both fresh or green concrete as well as wet concrete. The ARDEX WPM 300 HydrEpoxy is a hydrostatic pressure resistant membrane and can withstand the vapour pressures created by water in the substrate after it has cured. Ideally this coating should be applied late in the day while the surface temperature is reducing so there is no vapour pressure during the cure cycle. The ARDEX WPM 300 HydrEpoxy also acts as a very efficient concrete curing membrane preventing water escaping from new concrete and therefore substantially minimising the risk of plastic shrinkage.
There are three essential regulations governing the installation of waterproofing installations, particularly in internal wet areas, throughout Australia and these are: Firstly and primarily is a current version of the Building Code of Australia. At present the basis of these codes is dated 1996 however there are numerous updates that must also be complied with. The second document is the Australian Standard 3740 and the current version is dated 2004. This standard dictates where membranes are to be applied and how they are to be detailed or installed. This document is referenced extensively within the Building Code of Australia. The third document is Australian/New Zealand Standard 4858 that governs the properties required of a waterproof membrane for internal wet areas. This document is of little use to waterproofing applicators other than it classifies membranes into three categories that governs the detailing the waterproofing applicator needs to install at corners. Individual local state regulations apply in several states that must be adhered to within that state only. This presentation does not cover these state regulations but it is necessary that the waterproofing applicator is familiar with and complies with these regulations when working in the relevant state. Notwithstanding these additional state requirements the BCA and Australian Standard requirements are compulsory throughout Australia and overrule any State requirements in the event of conflict. These supplementary requirements are not covered in this presentation although they need to be observed if you are working in one of these states.
The Building Code of Australia is divided into two volumes covering different types of building structures. Commercial buildings are covered in Volume 1 under building classes 1 and 10. This volume, and therefore the requirements of commercial buildings, requires internal wet area waterproofing be carried out in accordance with Australian Standard 3740. Domestic buildings are covered in Volume 2 under classes 2 to 9. This volume requires that membranes used for these classes of building conform to Australian Standard 4858 and be applied in accordance with Australian Standard 3740. It is expected the duplication that currently exists between the Building Code of Australia and the Australian Standards will be changed, however the content and requirements that exist at present are not expected to change.
The Australian Standard 3740 governs the application of a waterproof membrane within an internal wet area of a domestic dwelling or building. It details the areas that have to be waterproofed and the areas that have to be water resistant within these areas and how they must be detailed in relation to turn ups, membrane overlaps and the extent of a membrane installation. Australian Standard 3740 dictates the minimum requirements that are acceptable in waterproofing an internal wet area however it must be remembered that the Building Code of Australia dictates the overriding performance required which is that the waterproofing installation shall prevent water transferring from one room to another. This means that an installation that meets the minimum standards and fails to prevent water transferring to another room is deemed to have failed to comply with the standards.
Throughout the Building Code of Australia and the related Australian Standards there is reference to areas that should be “waterproof” and areas that should be “water resistant”. The definitions of these terms according to the Code are: - Waterproof does not allow water to penetrate through the film or layer of material. - Water resistant allows some moisture movement but the materials that are water resistant will not degrade under moist conditions. It should be appreciated that all materials, including waterproof membranes and materials will allow the transmission of water vapour which is the gaseous form of water. A waterproof membrane will only allow the transmission of water vapour to an extent that allows that vapour to evaporate from the surrounds faster than it is transmitted under normal conditions. A water resistant material allows the transmission of both water vapour and liquid water but will not degrade under the moist conditions that occur when this happens.
The principal significant changes in the 2004 edition of the AS/NZ 3740 include: Wall to floor junction upturns in showers must now be 150mm compared to 100 mm in the original standard. The complete floor of a wet area with drainage outlet must now be waterproofed in all Class 1 buildings as defined by the Building Code of Australia. The complete floor of a wet area timber floor must be waterproofed. A water stop angle must be installed at the step-down or at 1,500 mm from an unenclosed shower head and this is required to extend to the underside of tile with a silicone tile joint over the angle to form a waterproof system to the top of the tiled surface. Tap and other intrusions must now be totally sealed with a waterproof material. Frameless shower screens are deemed to be unenclosed showers. Differing joint details required for different membranes controlled by the membranes classification under AS/NZ 4858 and these are covered later.
AS/NZS 4858: 2004 provides details of the minimum properties required of a waterproof membrane providing the benchmark for the formulation of a membrane. It is principally directed toward the membrane manufacturers and is of little importance to the waterproofing applicator. One area that is of concern to the waterproofing applicator is the classification system for membranes within that standard. The classification of Class 1, 2 or 3 type membrane is based on the flexibility of the membrane and dictates what type of detailing is necessary to be installed by the applicator at movement joints such as wall to floor, wall to wall joints floor and wall to hob as well as at hob corners.
As was explained previously AS/NZ 4858 classifies membranes into 3 classes based on flexibility measured using a test method that is defined in the standard: Class 1 is low flexibility and includes membranes with 0 - 59% elongation. This type of membrane requires a 75mm bond breaker tape across a joint placed over a backing rod as in the top picture of the slide. This allows the membrane to deflect as the backing rod compresses or expands during joint movement and minimises the reliance on the membrane stretching. Class 2 is medium flexibility including membranes with 60 - 299% elongation. This type of membrane requires a 35mm bond breaker tape across the joint as described in the middle picture of the slide thus spreading the elongation forces over 35 mm and reducing the point of elongation required of the membrane. Class 3 is high flexibility including membranes with 300% or greater elongation. This type of membrane only requires a 12mm bead of flexible sealant across a joint and any movement is taken up by the membrane. Most common undertile membranes should be Class 3 since the other can present difficulties with the subsequent tiling installation.
Regardless of all the regulatory document instructions always remember they form the minimum requirements and the Australian Building Codes have the over-riding clause that a “waterproof membrane must prevent the passage of water between rooms”. If a waterproof membrane installation leaks and allows water to pass through it to another room the applicator is liable regardless of whether the membrane has been installed strictly in accordance with the minimum requirements of all the standards. In other words it is recommended that the standards be considered as the minimum requirements and the waterproofing applicator, if they do not want call backs, should apply the membrane in excess of the requirements. For example Ardex recommend that wet areas be fully waterproofed where water may occur, that is all floors, joints, all walls within a shower recess up to a height of 1.8m or above the shower head and walls adjacent to the baths to a height of 500mm. This ensures that all areas where water may occur in the normal usage of a wet area are fully waterproofed even though this is well in excess of the standards. The small additional costs involved will be saved very quickly if no call backs are received.
The latest version of AS 3740 permits the waterproof membrane to be applied either over or under the screed and there are advantages and disadvantages in each type of application. With the membrane under the tile bed or screed, the screed remains consistently saturated providing a breeding ground for mould, fungi and odours to be initiated and propagate and the membrane is not laid to falls and therefore ponding occurs which can expose weak points in the membrane application. The advantage is that there is less of a logistical problem related to the responsibilities of the tiler and the waterproofer however this is significantly reduced with tilers being authorised to carry out undertile waterproof membrane application. In the case of the membrane being applied over the screed the screed remains dry at all times and the membrane is laid to falls providing better drainage but the adhesive must be compatible with the waterproof membrane. While the compatibility of the adhesive and membrane is an issue with the screed under the membrane system, it should be remembered that the membrane must be compatible with the screed to achieve full bond unless the screed is a 40mm plus self supporting reinforced floating screed.
Priming is essential on all surfaces for a successful membrane application. On porous surfaces priming serves two major functions. Firstly the primer consolidates small amounts of residual dust on the surface providing a sound base for the membrane application to achieve a sound bond. Secondly, it controls the porosity of the surface to avoid the substrate absorbing water from the membrane too rapidly while allowing sufficient penetration of the substrate to achieve a sound bond. If water is absorbed from the membrane too rapidly, the membrane dries too quickly at the interface preventing adequate absorption into the substrate and, with cement modified membranes prevents full hydrolisation of the cement leading to incomplete cure. Wet porous surfaces or freshly laid concrete must be primed with ARDEX WPM 300 HydrEpoxy to hold back water vapour pressures that cause blistering of the membrane as the temperature increases. With fresh ‘green’ concrete the ARDEX WPM 300 HydrEpoxy acts as a barrier coating and concrete curing membrane to form a compatible layer between the fresh concrete and the membrane. The ARDEX WPM 300 HydrEpoxy should be applied while the surface temperature is declining to allow it time to cure and achieve a sound bond before being subjected to increased water vapour pressures.
Moisture in the substrate can cause major problems in the application of a waterproof membrane. As the temperature of the substrate increases from the time of application, the moisture that is in the liquid water from begins to vaporise, that is become a vapour. As the moisture vaporises it increases in volume and creates a positive pressure on the underside of the membrane. As the membrane is curing it does not have its maximum bond strength and the vapour pressure causes the membrane to blister or partially loose bond strength. In the reinstatement of a shower recess the screed is normally saturated because the previous membrane has failed – after all this is normally why you have been contracted to reinstate the shower. A screed normally takes about 7 days to dry so, to avoid excessive delays, a barrier coat of ARDEX WPM 300 HydrEpoxy can be applied and the membrane applied the next day. This problem is not restricted to surface water but the problem can arise with moisture deep in the screed. To avoid problems because of substrate moisture, the first membrane layer, be it a barrier coat or the first membrane coat, should be applied while the surface temperature is declining. When the surface temperature is declining, the water vapour in the screed is condensing or returning to the liquid state thus reducing in volume and therefore creating a negative pressure on the underside of the membrane.
Even though some wet area undertile membranes are internally reinforced sufficiently to cope with normal building movement it is recommended that external reinforcement also be added to corner joints. The reason for this is that during application there is a tendency to brush the membrane away from the corners resulting in a reduced dry film thickness in these areas. This tendency of brushing away from the corners is extremely difficult to avoid and can frequently result in membrane failures at the corners. By incorporating the external reinforcement ensures that the required dry film thickness is achieved in these areas. It should be noted that Ardex recommends against using fibreglass as the external reinforcement and prefers the woven polyester mat. The reason for this preference is that fibreglass tends to ‘wick’ which causes the rigid glass fibres to protrude from the surface of the membrane. As the membrane dries it shrinks very slightly leaving a mini-micro gap between the membrane and the glass fibre through which water can be absorbed into the membrane through osmotic forces and then leading to premature membrane failure. In addition fibreglass has very good longitudinal strength properties however also has very low transverse strengths. Polyester cloth possesses high strengths in both the longitudinal and transverse directions.
It is critical that external reinforcement, either polyester or fibreglass, be fully wetted out without air inclusion. Therefore, as required with normal fibreglassing, the reinforcement must be completely wetted out from the underside. If a partially wetted reinforcement then has more membrane material applied to the top surface, air is trapped within the membrane reinforcement this significantly reducing the effectiveness of the membrane at this point. By using an aluminium fluted roller to wet out the reinforcement substantial reduces the time necessary and the efficiency of the wetting process. This type of roller is commonly used in the manufacture of fibreglass items such as surface boards and boats for exactly the same purpose. Applying sufficient material before placing the reinforcement is essential for proper wetting. The fluted roller will not wet out the reinforcement on its own, it needs enough liquid membrane under the reinforcement to pull through the reinforcement.
The finished dry film thickness of a waterproof membrane is critical in achieving the desired performance. The dry film thickness nominated by manufacturers is not arbitrarily fixed nor is it designed to sell more product. The dry film thickness nominated by the manufacturer is the thickness of membrane necessary to achieve a water vapour transmission rate that enables the product to be classified as a waterproof membrane and act as a vapour barrier. Thicker films than those recommended simply improve the efficiency of the membrane while lower thicknesses reduce the properties to a level where they do not function as required. It must also be remembered that the minimum membrane thickness recommended must be applied over the whole surface for the membrane to work. One area of low film thickness can make the whole membrane ineffective. Pinholes also make the whole membrane application ineffective and it is to avoid this situation that manufacturers normally recommend a two coat application. A good smooth surface is necessary for the successful application of a uniform film thickness. A membrane applied over a highly irregular surface is going to drag or flow away from the high points leaving a reduced film thickness at the point.
Because dry film thickness is so critical during membrane application and non-destructive testing of the dry film is difficult, of low accuracy and expensive the only time an applicator can control this property is by controlling the wet film thickness. To determine the wet film thickness required multiply the dry film thickness by the percentage volume solids. Therefore to achieve a 500µm dry film thickness with a membrane that has 50% volume solids requires a wet film thickness of 500 multiplied by 50 over 100, or 0.5, which equals 1000µm. To measure the wet film thickness, a wet film thickness gauge, as shown in this slide, provides a very good indicator. The two outer teeth on each side are level while the inner teeth are set back a controlled distance. When this gauge is place vertically into the film the outer teeth sink very closely to the hard underlying surface be it substrate or the previous dried coating. The last tooth or the tooth with the highest indentation that has membrane on the tip is taken as an indication of the wet film thickness. Several wet film thickness measurements should be taken each time to get a true reading since high spots in the membrane, from roller or brush marks, will lead to false results.
All Ardex Undertile membranes are safe within the context of a workplace product. Obviously, this does not mean you should drink or bath in the products however they can be safely used taking into account normal safety measures. There are two main safety issues with the Ardex products. Breathing and contact with cement dust should be avoided with the cement based products. ARDEX WPM 300 HydrEpoxy can cause chronic skin sensitisation in some people so contact with the skin should be avoided. Don’t fall into the false belief that contact caused you no problem the first time so its not going to cause problems in the future. Some people can go for months or years without getting itchiness and rashes before suddenly becoming sensitised to epoxies. Once a person becomes sensitised there is no gong back and rashes will appear as soon as that person gets near an epoxy. This generally only happens with regular continuous contact but everybody is different and there is no forecasting a persons reaction. Use epoxies safely and sensibly and there is no problem.
The most common cause of failure in an undertile waterproofing installation, other than surface preparation, is improper of inadequate detailing of the membrane. Detailing practices required are spelt out in much detail in Australian Standard 3740 and the Building Code of Australia.
As explained previously AS/NZS 4858: 2004 classifies membranes into 3 classes based on their flexibility. These Classes are: Class 1 – semi-rigid membranes with an elongation of 0 - 59%. Class 2 – semi flexible membranes with an elongation of 60 - 299%. Class 3 – flexible membranes with an elongation of 300% or greater. The class a membrane falls into governs the type of movement joint necessary and the design of that movement joint. Class 1 semi rigid membranes don’t have a lot of flexibility and require a 75mm bond breaker joint or bond breaker tape over a backing rod as indicated in the slide. With the backing rod the membrane does not have to stretch on joint movement but rather deflects by compressing or releasing the backing rod to accommodate the joint movement. Class 2 semi-flexible membranes require a 35mm bond breaker joint or bond breaker tape allowing any movement in the joint to be spread over a wide distance thus reducing the point stretching required of the membrane. If a 5mm joint moves 1 mm this is a 20% move – of that 1 mm is spread over 35 mm the movement in the membrane is only 2.9%. Class 3 flexible membranes require a 12mm bond breaker joint or silicone sealant on the basis the class 3 membrane has sufficient flexibility to cope with essentially the full joint movement.
The simplest detail is the standard shower with hob. Important points: The membrane must extend up the perimeter walls at least 25mm above the level of the hob. That is the standard requirement is 150mm up the perimeter walls, however if the hob is 150mm high the membrane must extend at least 175mm up the walls. The membrane must extend to the outer edge of the hob under and past the shower screen door as a minimum. That is the shower screen must be removed to carry out a waterproofing installation. It is recommended in the standard that the membrane extend right over the hob and out onto the surrounding floor.
An internal hob membrane detail is where the membrane goes up and over the inside face of the hob forming the waterstop inside the shower recess. An external hob membrane detail is also acceptable where the membrane goes under the hob and extends up the external face forming the waterstop on the external of the hob but this is not common. Important points: The shower screen must be positioned on the internal side of the shower hob. The shower screen to hob joint must be sealed with a flexible sealant along the outer edge of the screen. It is a good idea that the internal edge is also sealed to prevent water collecting under the screen causing corrosion. If a pre-formed shower tray is used the edges must extend to the outside edge of the hob. The height of the base of the shower screen must be at least 25mm or 100mm above the finished shower recess floor level. That is, if the hob is only 50mm high the shower screen base height must be 50mm.
The most common undertile membranes are acrylic copolymer types in either the mastic one part or the cement modified two part. Provided these are supplied by a reputable manufacturer these are premium performance undertile membranes. Another older version of a co-polymer that is available is the Styrene Butadiene Rubber or SBR type however they all perform similarly. The mastic coating has excellent flexibility and is most suited to internal application while the cement based provides good external weathering for external applications but is still quite suitable for internal applications. Modified polyurethane dispersion membranes are generally one part mastics and provide the premium performance of the liquid undertile membranes particularly in regard to chemical resistance. It should be noted that the percentage of polyurethane dispersion used in the formulation is important to achieve these improved results. Using a premium undertile membrane comes with a premium price however, this price premium should be considered as a percentage of the total cost of the job and the savings incurred in avoiding call-backs. These three waterproof membranes are the most commonly used undertile membranes and have a long history of solid performance in this application. Water based epoxy membrane offer excellent waterproofing properties however, they are a semi rigid and should only be used on structurally sound surfaces where there can be no movement between the surfaces. Water based epoxies can be used as a prime coating because some possess resistance to hydrostatic pressures and may be used on wet of green freshly laid concrete as a barrier coating for other membranes. Polyester fibreglass membranes have been used for ages and while most of these can be tiled over provided proper surface preparation is first carried out, the compatibility of the proposed tile adhesive should e confirmed before proceeding. The water based bitumen type are a common economy membrane for planter box internals and below ground applications however they are not suitable as an undertile membrane because they don’t have the strength properties to withstand tile movement. Moisture cured polyurethanes are excellent waterproof membranes however have one major problem in that it is not possible to adhere tiles to them. The use of these membranes in applications where they are intended to be tiled over has increased over the past 1 or 2 years and failures are beginning to become significant. Adhesion may appear sound initially however, in wet conditions the bond fails completely when using conventional tile adhesives.
With the exception of Ardex Butynol butyl rubber sheets most, if not all, require a floating self supporting screed of a minimum thickness of 40 mm. A floating self supporting screed is a minimum 40 mm thick screed placed on a slip sheet of polyethylene or similar with 5-8 mm diameter reinforcing wire in the centre. The installation of a 40 mm screed needs to be accounted for in the design stage of the concrete pour to provide the necessary step down otherwise it can’t be installed because the tiled surface will be above the surrounding floor. Direct bonding of tiles can be achieved to ARDEX Butynol, but only using ARDEX Optima adhesive. If Butynol is used as an undertile membrane care must be taken with the detailing. Where the membrane and/or associated tapes overlap, the substrate must be recessed to accommodate the additional thickness at the lapping sections. If this is not done there will be a step in the thickness of the membrane which will affect the adhesive bed thickness or the level of the tiles.
The Ardex preparatory products consist of two basic primer systems. Firstly, ARDEX WPM265 Water Based Primer is ideal for interior applications because it has virtually no odour and is non-flammable. This primer is very easy to apply and dries quickly, particularly when applied to a porous surface. The main purpose of the primer, as has been described previously, is to reduce, but not eliminate, the substrate porosity and to consolidate any loose dust particles that may hinder the adhesion of the membrane. The second primer is the ARDEX WPM 300 HydrEpoxy which is a two part water based epoxy primer system. The main benefit of this product as a primer is that it will resist very high vapour and hydrostatic pressures. This product also has virtually no odour and is also non-flammable. ARDEX WPM 300 HydrEpoxy normally requires overnight curing before the membrane is applied. This product does not achieve a resistance to vapour pressures until it has set and partially cured and therefore when applied over wet substrates or fresh or green concrete, it should be applied later in the day as the surface temperature is declining so that it has cured before the vapour pressures start to rise .
There are three main Ardex products specifically designed as an undertile membrane. The first is a one part acrylic mastic coating that produces excellent flexibility and strength properties to withstand movement normally expected in a dwelling. This membrane contains internal fibre reinforcement and while external reinforcement is not essential, Ardex recommend its use in corners since the tendency is to brush away from the corners and the external reinforcement acts as an in-built film thickness gauge. The second type of undertile membrane is a two component cement modified acrylic which is a harder membrane that does not soften under heat as much as the mastic membrane and offers better weathering properties. They are therefore better suited to external applications rather than the mastic type. The third type of undertile membrane is a polyurethane modified mastic membrane that offers excellent resistance to chemicals and weatherability. All three of the Ardex undertile membranes are classified as Class 3 under AS/NZS 4858 and therefore only require a bead of silicone spread 12mm across a joint as the bond breaker system. All these three products are specifically designed as undertile membranes and are compatible with conventional tile adhesives. It is important to note that, with the exception of ARDEX D2 in certain circumstances, mastic or one part liquid adhesives should not be used over a waterproof membrane because of extended drying times.
ARDEX WPM 001 (Superflex Premixed) membrane is a 100% acrylic water based material and is, and has been over a long time, the most extensively used membrane for internal wet areas. Easy to apply with no wastage or residual odour, this product is internally reinforced with micro-fibres to provide additional strength. Because WPM 001 is a mastic coating, it is necessary for the carrier water to evaporate before the membrane film is formed. Recoating can normally be carried out the next day and tiling can normally be carried out after 48 hours but a longer drying time may be necessary when the membrane is applied over non-porous surfaces such as bond breakers, because water is not absorbed from the coating into the substrate, or where greater thicknesses have been applied . When checking a surface to see if recoating or tiling can be started, always check the corners as they are normally the last to dry properly. ARDEX WPM 001 will not re-emulsify when wet. After the film has cured it is totally resistant to exposure to water. ARDEX WPM 001 conforms to AS/NZS 4858 as a Class 3 membrane thus requiring only a 12mm bead of silicone at movement joints and has a CSIRO Appraisal.
ARDEX WPM 002 (Superflex 2 Part) is a cement based 100% acrylic membrane that dries faster than the mastics because the carrier water not only evaporates but also reacts with the cement in the formulation. Although faster drying, this membrane will also be the slowest in corners over non-porous surfaces or in thick films so always check the corners to see if the membrane is dry enough to proceed. ARDEX WPM 002 is internally reinforced with micro-fibres for added strength. It conforms to the Class 3 requirements of AS/NZS 4858 for flexibility on the condition that a 16mm bond breaker is used. Principally designed for external applications because of its excellent resistance to weathering, this membrane can also be used for internal wet area undertile installations. Only mix up as much as is necessary because working time is relatively short compared to mastic or pre-mixed type membranes and the product should be mixed by mechanical means using an Ardex mixing paddle and low geared high torque drill.
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