Repairing Sloped Roof Leaks with Epoxy Mastic

Where Magelstick is suitable on a pitched roof

Magelstick is formulated for repairing stone, cement and metal roof details rather than acting as a full roof covering. It is commonly used around hairline cracks in cement verges, small gaps in stone coping, and metal flashing joints where water can track beneath the surface.

Its thixotropic, putty-like consistency is particularly useful on sloped or vertical areas, because it resists sagging while it cures. For localised leaks on a structurally sound pitched roof, Magelstick epoxy mastic can provide a durable exterior repair point.

Preparation and application basics

Getting a lasting seal depends on surface preparation. The area should be dry, sound and free from loose material, dust, moss or old sealant. Magelstick is designed to be mixed as a two-part putty and applied in small batches, which helps with precise work on roof details.

• Work when the surface temperature is at least 10°C.
• Rake out loose debris and key the repair edges where possible.
• Press the mixed mastic firmly into the crack or joint so it makes full contact.
• Shape the surface neatly before the material begins to set.

When this matters

This type of repair matters most when a sloped roof is otherwise sound, but water is getting in through a small, identifiable defect. It is a targeted fix rather than a replacement for failed flashing, damaged membranes or widespread roof covering breakdown.

If the roof structure is moving, or the leak covers a large area, the mastic alone is unlikely to solve the underlying problem. In those cases, it should be used as part of a wider waterproofing approach rather than a single-step cure.