Do solar water heaters, air conditioners and water tanks have to be removed to waterproof the roof?

Apartment building roofs in Athens are almost always crowded with solar water heaters, air-conditioning units, pipes and water tanks. Removing them all would mean calling a plumber and an AC technician for every flat. In practice, liquid membranesLiquid waterproofing membraneA waterproofing product applied as a liquid by roller, brush or spray. Once dry it forms one continuous, flexible membrane with no seams. and sprayed 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. allow the waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks. to go right under the equipment and seal around its supports.

On this roof crowded with solar heaters, the slab was cleaned, patched and levelled. The outdoor air-conditioning unit was propped up on bricks so the primerPrimerThe thin first coat that goes on before the main material. It binds dust, seals the pores and helps paint or waterproofing stick firmly. and waterproof coatingElastomeric waterproof coatingA thick, rubbery waterproof paint for flat roofs, parapets and roofs. It stretches without cracking as the building expands and bridges hairline cracks. could be rolled right underneath it without leaving a bare spot.

With liquid white membrane or sprayed polyurethane foam, the material reaches underneath solar tanks and wraps tightly around each metal leg and pipe. Those support feet need special care, because the bolt holes drilled to anchor solar frames are one of the most common places for water to get into the slab.