How to introduce more run into roof


I have a 16'x20' deck roof that is attached to my garage on one side and (3) 4"x4" posts on the other side.

The rise over the 16 feet is about 2 inches which is not enough for the water to get off the roof. It's pooling in certain spots. Probably because the 16 foot run is unsupported in the middle and it sags.

A friend is recommending that I jack up the roof, saw off 4 inches off the bottom of the posts to get the water to run off.

My concern is that this would rip the roof off the garage wall. Is this a practical way of introducing more pitch? Or is it better to just rip down the current structure and redo it with the appropriate pitch?

Best Answer

You've got a flat roof that isn't "true" (straight - you don't want it level). Your pitch isn't the problem so much as the dips allowing water to pool.

Ideally the best fix here is:

  1. Remove the existing surface material (tar and rubber)
  2. Remove the existing sheeting
  3. Shore up the roof structure with extra beams, and shim it as needed to make it true and consistent from high point to low point.
  4. Install a double layer of sheeting with perfectly flat plywood
  5. Resurface the roof with ice shield, tar and rubber