Choosing the Right Waterproofing Membrane, Room by Room
By Wall Boulevard
Waterproofing fails quietly. By the time you see it, whether that is blistering, peeling, a stain on a ceiling or tiles lifting off a balcony, the damage underneath has been running for a while. Rot, mould and structural repairs follow, and none of it is cheap to put right. Most of those failures come down to the right membrane in the wrong place.
Liquid applied membranes go on like paint and cure into a seamless, flexible coating. Because there are no joints, they handle corners, junctions and complex shapes better than anything else. The catch is that they have to be applied at the correct thickness and cured in the right conditions, so they are unforgiving of a rushed job.
Sheet membranes come in rolls of PVC, TPO or butyl rubber. They are extremely durable and hold a consistent thickness across the whole area, which makes them the pick for large exposed surfaces. Seams have to be sealed or welded properly, and they are awkward around detailed work.
Bituminous membranes are the heavy duty option for below ground and external work. They are durable, have a very long service life, and suit retaining walls and similar constant moisture exposure, though they are less flexible than liquid systems and need professional application. Cementitious waterproofing is a cement based slurry that bonds exceptionally well to concrete, performs under pressure and suits basements, tanks and pools. It is not the answer for anything that moves.
Inside the house, liquid applied is usually the answer. In a bathroom it copes with moisture, steam and humidity, adapts to thermal expansion, bonds to walls, floors and screeds, and can be reinforced with mesh at junctions. It also works around plumbing penetrations and multiple angles without a seam. Laundries and kitchens are splash zones rather than full wet rooms, and liquid membrane suits them for the same reasons plus speed of installation.
Outside, exposure changes the calculation. Balconies take intense weather, constant UV and structural movement, so a sheet membrane or a reinforced liquid membrane is the right call, with sheet generally preferred across large areas. Rooftops deal with ponding water and heavy rain on top of the UV, which is where sheet membranes in TPO, butyl rubber or EPDM, or a bituminous system, earn their thickness.
Below ground the enemy is pressure, not weather. Basements face groundwater pressure, soil moisture and seepage through concrete, so bituminous or cementitious systems are used for their adhesion to concrete and their ability to resist hydrostatic pressure. Retaining walls sit in permanent soil contact and suit bituminous membranes, which work alongside drainage boards and geotextiles.
Planter boxes are their own problem, with permanently wet soil and roots actively looking for a way through. A sheet membrane, or a reinforced liquid membrane, creates a fully waterproof liner that resists root damage. Whatever the area, check the system against current Australian waterproofing guidelines; the Australian Institute of Waterproofing is a sensible starting point.
Talk it through with us at either store. 19 Mantell Street, Coburg North VIC 3058, (03) 8683 6514. 1/8 Lakewood Blvd, Carrum Downs VIC 3201, (03) 9005 5027.
