Can You Reroof Your Commercial Flat Roof?

Posted on: 30 June 2022

When it's time to replace a flat commercial roof, you have two options. You can either have the old roof torn off and a new one installed, or you can have the old roof restored with the application of a new membrane.

1. What is the state of the insulation?  

The insulation layer of a flat commercial roof sits below the main membrane surface and in some roofing systems, it is integrated into the membrane panels themselves. Minor damage that has led to water incursion can completely compromise this insulation layer. If only a few areas are wet, then removal of these areas before proceeding with the restoration may be possible. If the damage to the insulation is extensive, then a teardown and full re-roofing is needed.

2. How many times has the roof been restored?

When a flat roof is restored the new membrane system is typically installed over the old. This means an older membrane can be covered with multiple membranes and these membranes could be from two or more roofing styles. For example, you may have rubber EPDM roofing installed over the top of an old asphalt or bitumen roof. The main concern with restoring a roof with multiple restoration layers is weight. Eventually, there will be too much weight from the layers of membranes for the building to support. In this case, tearing down before installing the new roof is a necessity.

3. Is there extensive fastener failure?

The fasteners and seam seal type will determine on the specific flat roof system, but for restoration to be a viable option there should not be an extensive failure. A few failed seams can be resealed before the new membrane is placed upon the roof, and the same goes for a few backed-out fasteners. Extensive fastener failure, though, can mean that water has gotten into the ceiling through the membrane or that something is wrong with the roof base that is leading to failure. 

4. Has water ponding been an issue?

Excessive standing water on the roof, known as ponding, is a sign of major issues. Water may collect due to an insufficient slope or too few drains on the roof. If this is the case, then the roof must be rebuilt from the bottom up so that it slopes properly to the edges or to interior drainage. In some cases, though, ponding is simply the result of a failing roof membrane that has developed low areas. If there are only a few low areas such as these, then restoration with a new membrane layer may be possible.

For more info, contact a commercial roof contractor.