Thread: Question On Cement Roof Tile Valley Construction

On a recent inspection, I observed an area that was not coverd by concrete tile on this 17 year old roof. It is to the left of the front entry where three areas of the roof meet at the bottom of each of the valleys. Underlayment appears in excellent condition and was wondering if it needs to be covered by tile. Any thoughts?

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Looks like a low slope valley. Or as some would say, a water retention pond above grade.
Tile would probably be inappropriate and not helpful. The 'underlayment' should be roofing membrane, could be of various types. Flashing and verifying how far up the roofing goes up below the tile would be important.

It's a fairly common detail with roofs like that, especially with tile roofs - the various roof slope would otherwise meet into a non-drainable valley, the solution is to install a cricket as you see there.

The two most common problems with that are:
- 1) Insufficient roof slope for the material used in the valley, typically requiring a 4/12 slope but there is usually less that a 2/12, sometimes not even a 1/12 slope.
- 2) The incorrect material is frequently installed in that area, material which is not intended to be left exposed to daylight. At 17 years, that material was either the correct material or it was replaced within the first 5-6 years, or it may have been the correct material and replaced after 10-15 years.

Typically, the tile underlayment is the material with the shortest life of the installation. The tile is going to last a very long time as the tile will either be clay or concrete. It is not uncommon for archeologists to find clay tiles and pottery in digs over 5,000 years old - so the clay tile is not the problem; concrete also has a very long life, so concrete tiles are also not the problem.

The tile underlayment, though, is typically chosen by the roofer or builder based on its cheapest installed cost (who would have thunk that?), and tile underlayment may have a life of as little as 10-15 years or 15-20 years, rarely longer.

Guess what has to be ripped off in order to replace the tile underlayment? Yep - the tile. A tile roof would last a lot longer if modified was installed under the tile, and the installed cost is really not that much greater than what it typically use for tile underlayment.

Brian,

What type of material was in that valley? It looks like mod bit (torch down) but the photo is a little dark.

Thanks so much for the replies! Dom, it is mod bit torch down.

Originally Posted by Brian Harwood

Thanks so much for the replies! Dom, it is mod bit torch down.

That is what we see around here all the time in those dead valleys, and it typically holds up well (given the limitations of the product).

Just make sure to examine that low slope roof and valley for defects, leaks, errors, etc especially from the attic.

Dom.