How do you waterproof a flat roof that has solar panels or meets a tiled roof along one side?

When a flat roofFlat roof (roof terrace)The flat concrete roof on top of a building. It is the most common kind of roof in Greece and the part that takes the most sun and rain. sits next to a pitched tiled roofTiled roofA pitched roof covered with clay tiles, on a timber frame or a concrete slab. The real waterproofing sits underneath, in the layer below the tiles., it receives all the rainwater running off the tiles. If the old membraneBitumen membraneWaterproofing that comes in rolls of reinforced bitumen. It is torched onto the roof in sheets that overlap at the seams. along that junction has peeledPeeling paintWhen paint loses its grip and lifts off in flakes or sheets. It is almost always a sign of a problem underneath, usually damp or poor preparation. or split, water runs straight underneath the waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks.. The same problem arises on roofs with photovoltaic panels, where dozens of mounting feet sit on the slab.

On this roof with solar panels, the torn old membrane was stripped out completely with the panels kept in place. The slab was primedPrimerThe thin first coat that goes on before the main material. It binds dust, seals the pores and helps paint or waterproofing stick firmly., new screedScreedA layer of sand-and-cement mix or lightweight concrete poured over the slab to create falls and a solid surface for the next material. was pumped and levelled around every mounting base, and once dry it was sprayed with polyurethane foamSpray polyurethane foamA foam sprayed on as a liquid that expands on the spot and sets into one seamless layer. It insulates against heat and cold and closes cracks and joints. right up to the first row of tiles on the adjoining roof.

On another terrace bordering a tiled roof, the old bitumen sheets were pulled up sheet by sheet. White liquid membraneLiquid waterproofing membraneA waterproofing product applied as a liquid by roller, brush or spray. Once dry it forms one continuous, flexible membrane with no seams. was then applied first along the low wallParapetThe low wall around the edge of a flat roof or balcony. The joint between it and the floor is one of the most common places for leaks. beneath the tiles and into the corners, and finally across the whole terrace floor.