Hi apachediyman, The mortar you can see is the bedding for the tiles and valley gutters, it is unlikely to leak. You could replace the tile but this will be fiddly since you will have to cut a new tile and get it to bed properly. You also need to consider access and any damage that may result and stripping the roof above the broken tile. The easiest solution is to mix some sharp sand with cement and a brown colourant and cover the mortar area once you have damped it. Regards S
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!