The patented Easy Slate is a ‘side lap strip’ that works by sealing the perp join on the slate and prevents the water from entering the layers of the slates.
Easy Slate has the effect of extending the head lap from the tail of the upper slate to the head of the slate below; for example, a roof using 500x250mm slates with a 100mm lap, will now have a sealed perp join and an effective head lap of 300mm.
On a regular slate roof there is often less than 0.5mm gap between the layers of the slates. Little or no gap between the slates means that air pressure will draw the water between the slates via capillary action, and this is one of the reasons that slates leak.
When the Easy Slate is used the slates are raised by 1mm and this increased gap allows the free movement of air below the slates, this releases the air pressure thus eliminating the capillary action.
In addition this also eliminates wind slate rattle.