Patent ID: 8389109

Claim:
An algae-resistant building element selected from a roofing tile or siding element, the algae-resistant building element comprising: a base layer comprising a first cured cementitious mixture, wherein the base layer has a thickness of 2 to 3 centimeters; an algae-resistant layer disposed on the base layer, the algae-resistant layer comprising a photocatalytic material dispersed within a second cured cementitious mixture wherein the algae-resistant layer has a thickness of 2 to 3 millimeters; and an interface formed between the base layer and the algae-resistant layer; wherein the interface has a cohesive strength that is at least as high as a fracture strength of the base layer and/or the algae-resistant layer, and wherein the algae-resistant layer includes 10 to 30 volume percent photocatalytic material.