Water leaks in around our roof skylight when it rains. Can the base be sealed without replacing the skylight?

Roof skylights over stairwells, lightwells or interior rooms sit on a raised curb above the slab. Over time, the mortar or old sealant around the foot of that curb cracksCrackA split or gap in render, concrete, a wall, a coating or wood. Fine cracks are usually only on the surface; ones that grow, keep reopening or run diagonally need attention. from sun exposure and thermal movement, letting rainwater run down into the building below.

On this roof with two skylights, the curbs had cracked and crumbled while the skylight domes themselves were still sound. All loose, broken material around the base was chipped away and cleared until only solid substrate remained.

The perimeter was then cleaned, repaired and coated in successive layers of white liquid waterproofingLiquid waterproofing membraneA waterproofing product applied as a liquid by roller, brush or spray. Once dry it forms one continuous, flexible membrane with no seams., bridging smoothly from the 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. surface all the way up the vertical sides of each skylight curb.