I have recently bought a 30 year old house with over 2400 square ft of flat roof. The roof is leaking in few places and I am looking for ideas on getting it repaired. The ply under the roof top has rotted in several places. There are several segments that sag during a rainfall where the water gets collected.
I have received several estimates from contractors who have provided me with different ways to repair the roof. Ofcourse each and everyone of them is saying that their method is the best one to pursue. I am planning on staying in this house for next 15 years. So, please suggest the most appropriate method to get it repaired. Thanks in advance.

Need more precise info...what kind of material covers it now?

A roof CAN be your friend

Current coating on the roof is cracked and it is peeling. It is blackish/grey in color. At this point, it is being recommended by all the contractors to get rid of current material and start all over again. So, I am interested in finding out the best material to use to re-finish the roofing top. Also, they are planning on changing some of the ply that has rotted.

There are several types of roof coverings
that can work.

One of the most commonly used materials on residential properties is the "modified" bitumen. It comes in either smooth surface or granulated. Variations of this type of product can be applied with a torch, hot mopped, or glued down with a special adhesive. They come with a 10-12 year warranty.

One thing I've encountered frequently with these roofs is bad, or nonexistent flashing work. These roofs are most prone to leaking at the seams if not fully adhered, and at the flashings such as edge flashings, pipes, and other protrutions.

Rubber is another possibility, used widely on commercial buildings, used far less often on homes.

Tar and gravel, while having a bad rep, can be an excellent roof if installed correctly...or a can of worms if not.

Assuming your potential contractors are all offering good products, your main concern should be their competency and "thoroughness of installation". Roofing as a whole is bad these days, in my opinion, but flat roofs are the worst. They are more likely to leak if not installed correctly, than pitched roofs. I would concentrate on checking out your roofers. Check references thoroughly. If you have time, educate yourself on how the roof systems proposed are installed...including the flashing details, then slyly ask each one questions meant to reveal either their knowledge or ignorance.

But the most important thing you can do to protect yourself is to KNOW your roofer.

A roof CAN be your friend

Thanks for your insights and it would be great if you can recommend anyone in northern Virginia.

Sorry, not from there.

Start out with the BBB list of members, then call them. Don't be afraid to call numerous roofers. Some won't show. And be sure to ask for references, then make sure you call THEM. Many folks ask for references, but never call them.

A roof CAN be your friend