Flat Roof

Old 10-27-08, 05:08 AM
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Flat Roof

I have a house with a flat roof that has a membrane on it. The membrane is 18+ years old, black not smooth, looks like paint when it alligators. The roof is not leaking, yet.
Does anyone know what material this membrane could possibly be made of?
What it's life expectancy is?
Is there anything I can apply to it to shore it up so that it does not leak?
And when it comes time to replace it, do I need to tear it off or can I lay another membrane on top of this one?
Old 10-27-08, 08:03 AM
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Sounds to me like you have a wet mopped roof. The alligatoring is the tar drying out and shrinking. Typical make up is a felt layer is applied and then tar is mopped onto it to waterproof it. Depending on the requirements and maintenence of it there may be serveral layers.
Life expectancy would be 15 to 20 years with no maintence. More if it is resealed every so often. I am not sure when they recommend it be resealed. Some roofers say it needs coated every year.
You can use the type of sealer they use on mobile homes for their roofs. I would use the type that has fiber in it. Mop or brush it on heavy so it seals the cracking.
You might get by for a while doing this every year or two for quite a while. But remember anything you add also adds weight and the plywood and rafters will only hold so much weight. Also keep in mind I cannot see your roof and can only guess at the condition by your description. Roofers give free estimates. Call a couple to look at your roof and make their suggestions. You should be able to determine from their recommendations if the sealing will work.
Those type roofs are generally torn off down to the plywood and everything is replaced. Depends on the cost it might be cheaper to go with rubber membrane roofing when you do replace it.
Old 10-28-08, 04:54 PM
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A flat asphalt roof left unmaintained usually lasts 10-15 years depending on the quality of material and installation. Without seeing the extent of the alligatoring I don't know if you have 1 or 5 years left in it. But since its 18 already id say its almost time that's for sure.
If its not leaking and its the only layer of roofing a layover with epdm or a modified bitumen system may be a fine option.

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