Quick answers
Our roof is covered with old paving slabs. Can waterproofing or polyurethane foam be applied over them?
Yes, provided the slabs are firmly bedded. The surface is ground and pressure-washed, joints and post bases are sealed, and either a liquid waterproof membrane or sprayed polyurethane foam is applied directly on top.
Many older apartment buildings in Athens have concrete paving slabs on the roof with bitumen or mortar in the joints. Over time the joints open up, weeds take root and water gets underneath the slabs. As long as the slabs themselves are solid, there is no need to rip them up and haul tonnes of rubble down from the roof.
On this slab-paved terrace, the surface was ground and cleaned, the metal column and railing bases were sealed, primer was rolled on and the entire roof was coated with white liquid waterproofing.
When thermal insulation is needed alongside waterproofing, the slabs are pressure-washed to clear every joint and sprayed with a continuous layer of polyurethane foam that bridges all the joints and seals around solar heaters and rooftop equipment.
Jobs that show it
Paved Roof Insulated with Spray Foam
The roof was washed, sprayed with polyurethane foam over the old paving, and became one light-coloured surface around the solar water heaters and machinery.
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Slab-Paved Terrace Waterproofed with a White Coating
The old terrace slabs were ground and cleaned, the bases of posts and railings were sealed, and the whole surface was coated in white waterproofing.
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Worn Tiled Terrace Waterproofed by Spraying
On a terrace with loose tiles and peeling old coatings, the joints and holes were sealed and a blue-grey waterproofing was sprayed over the whole surface.
See the job step by step