Round clay tile roof leaks, needs repair

First, I am not a builder so cut me some slack if I use the wrong terminology.
Here is the situation: We are interested in buying a house that the owner is now deceased and the son lives in another state. The house has some existing water damage that had (sort of) been previously repaired. The drywall on the ceiling has been cut away to reveal the damage. They previously fixed the damaged rafter (? the beam that slopes upward to the peek of the roof) by smearing some white plaster looking stuff on it but did not fix the source of the leak. It appears the wood has the beginnings of dry rot -- slightly soft for the first 1/8" of depth in an area about one foot long. We are in the desert so there is not much rain here.
The damage and the plaster stuff is where the rafter meets the eave which would indicate that the leak is somewhere higher up on the roof -- the water gets in somewhere and runs down under the round cement shingles (made to look like clay) until it finds its way under the fabric and the plywood, near the bottom edge of the roof, and then exits about 2 feet from the bottom edge of the roof and soaks the rafter.
The son wants us to make an offer on the house "as is" so we do not have a way to determine the extent of the repair costs. The house is 15 years old, on a prime location and the interior has been extremely well maintained which means that after fixing the roof, this would be a very nice little home.
I am going to make a few assumptions and would like someone to correct me if I am wrong:
1. The only way to find the leak is to remove all the round cement tiles and the fabric upwards from the leak to find where the water is getting in. There do not appear to be any broken tiles. I did notice on another part of the roof that the flashing does not extend out far enough to reach the tile so the water runs off the flashing and under the tile. Many of the tiles on the side of the house have their corners chipped away from the roofer missing the nail and hitting the tile instead. It appears to be a poor roofing job.
2. There would be a lot of tile breakage meaning that new tiles would have to be purchased.
3. There could be additional water damage discovered including more dry rot and possibly mold (none observed).
4. The house is 55' x 45'. It would be very expensive to remove the tile, find the leak, fix it and any damage. The cost could vary from $5,000 up to $25,000 if the entire roof needed to be done over.
Do my assumptions sound about right? How much should it cost to have a professional roofer assess the situation?
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Ike wrote:

I'm not sure what you mean by "fabric". Tiles - whether clay or concrete - are basically pretty-pretties, not meant to make a structure watertight. That is done by what is *under* the tiles - in my case, 90# roofing hot mopped on. The type of membrane and the skill with which it was applied are crucial to the water tightness of the roof..
If that is what you mean then yes, tiles and it would have to be removed. As far a cost of totally re-roofing, you don't *have* to have a tile roof, sure cheaper without.
-- dadiOH ____________________________
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:

There are CC&R's in this development so, yes, the tiles are required. And, I have no idea what is under the tiles to make the roof waterproof. I only know that 'something' is under the tiles besides plywood. I have never seen them hot mop a roof prior to tiling in this area (Las Vegas).
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We have a concrete tile roof - house built in 1983. The roof developed a leak where the valley is. One of my neighbors was in the roofing business...he explained it is common for this to happen after about 15 yrs., but that once it's fixed there should be no further problem. They removed the tiles - at least set them aside - and fixed the problem underneath. Then they replaced the tiles and repainted. Perhaps you can do the same. Or, may be cheaper for you to just get new roof. Don't know about repairs in attic.
Mine is okay so far.
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Ike wrote:

As other posters have said, the tiles only provide UV protection for the underlayment, which is usually 90lb organic felt that is hot mopped or cold adhesive attached over a base sheet of 15lb or 30lb organic felt. The life expectancy of this roofing system is about 20 years in a hot climate. The underlayment provides the water tightness. The most common failure mode is when the top (cap) sheet is inadequately fastened to the base sheet, either because of a lack of adhesive, wrong adhesive, or poor installation where overlapping layers of the cap sheet aren't 'back nailed'. Eventually the underlayment either slips down or cracks, and the water comes in. You are correct that the leak is likely above where the water is coming in. Usually you will see blacked sheating where the water has been present.
Since it sounds like the leak has been long existing, at a minimum you should plan on having a roofer remove tiles above the affected area up to the ridge. If you find water damage to the plywood / OSB sheathing the damaged sheating should be replaced and a new underlayment system patched in, overlapping at least 6" in each direction over the old underlayment. Then the tiles can be reinstalled.
If it were my home, I would just install a new tile roof rather than put money into a roof that is near end of life anyway. Here in Florida a good quality tile roof costs about $400 / square (100 square feet). If you do reroof, I would recommend using a non-organic underlayment system such as GAF's Ultima 80 base sheet with a modified bitumen cap sheet hotmopped (or cold applied) on top of it. Use galvalume in the valleys and for all other flashings. That underlayment system should last 40 years when covered with tile. Attach the tile using a foam system such as Polyfoam or Dow TileBond, thus avoiding the penetrations of the underlayment that are caused by nails or screws.
Hope this helps.
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I am going to TELL you, To get it inspected, By several PROS,-- Roofing and Bldg or do not buy it... Or be a sucker............Sucker
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On Sat, 27 Nov 2004 17:58:50 -0600 snipped-for-privacy@webtv.net (m Ransley) wrote :

Spoken with all the wisdom and eloquence a true WebTV'er.
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If you're not sure of what needs to be done or how to do it, get several bids from reputable roofers.

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wrote :

I know that is the obvious answer, but here in Vegas there is so much construction work that it is very difficult to get someone to show up for a paying job. My assumption is I'll have to pay just to get a repair estimate. The problem is the real cost of repair will likely not be known until the tiles are pulled up.
I think I will need to make my offer based on a complete roof repair.
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You most certainly do. Call up a local roofer/contractor, tell them you are looking at the house to purchase and need an estimate.
Jeff
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