Waterproofing a terrace roof: layer order and membrane selection

Conventional terrace: layer order

• The reinforced concrete slab is cleaned and a cold-applied asphalt emulsion primer conforming to TS 113 is applied
• A bitumen-based vapour barrier is laid, with joints fully bonded
• Thermal insulation boards are laid with staggered joints
• Waterproofing: two layers of polymer-bitumen sheet (torch-applied) or a single-layer synthetic sheet; if the insulation is not hard and heat-resistant, a screed is laid first
• A reflective or UV-protective top coat

Inverted terrace

On the reinforced concrete slab, a screed with a fall of at least 2 percent, a primer and waterproofing are applied; the thermal insulation is laid loose on top of the waterproofing without bonding, and a filter layer is placed over it. On a non-trafficked roof, washed river gravel of Ø16-32 mm is used; on a trafficked roof, Ø4-7 mm gravel and tiles on plastic pedestals.

Membrane types and where they are used

• Bituminous (polymer-bitumen): the most common type; two layers on a flat roof, with the top layer required to be mineral-surfaced
• PVC and TPO: high UV resistance, suitable for large roof areas
• Plastic or rubber-based synthetic sheet: laid in a single layer, joints hot-air welded, must be UV resistant
• Liquid membrane: forms a seamless elastic layer by brush, roller or spray, suited to detail points
• Polyurethane: high elasticity; used on terraces and balconies that move
• Applied coating systems (cement, acrylic, polyurethane-based): for inverted terraces and wet areas

What this information is and is not for

The sources convey technical principles; product selection and thickness depend on the roof type, its use and the manufacturer's specification. Because the sources do not reference EN standards, we do not make up standard numbers here.