By: Ron Williams / Roof Doctor
Tile Roofing Maintenance, Part 2
I would like to address the myth and popular contention that on a tile roof, it is the felt or underlayment that protects your home from moisture and not the actual tile. The underlayment is one or two layers of #30 asphalt saturated felt that is applied directly over the wood roof sheathing and then the roof tiles are installed over it.
I have personally repaired thousands of tile roofs and at least 90% of them were leaking because of a failed flashing or tile. Once water gets under the tile the roof is going to leak, the felt is actually more of a vapor barrier than a waterproofing and there are thousands of nail penetrations in the felt as well as unsealed corners etc.
I have literally hundreds of photos of tile roof leaks caused 100% by either debris build up, failing flashings or tile with debris build up the major cause.
So with debris build up being the most prevalent cause of leaks to tile roofs, let's take a look at what actually happens.
First debris accumulates in a valley, chimney, or pipe flashing. Since the part of the flashing that carries the water is under the tile, like a dam the debris diverts water over the flashing that is under the tile and onto the felt.
I could literally show you a hundred pictures like this.
This will cause the roof to leak every single time because the felt is not a watertight system.
So let's quit telling homeowners that it's the felt that keeps the water out ok? It just isn't true. In almost every case, 30 lb. Felt is intended as a vapor barrier and nothing more.
