How do you find a leak on a flat asphalt roof covered with gravel when the water just courses around under the gravel until it finds a hole?

Answer: A reliable and permanent fix for residential or commercial flat roofs is single-ply membrane roofing. A single-ply membrane can be installed directly over the gravel covered asphalt roof with the proper decking and bonding adhesive. Depending on the application, you can specify 45 mil, 60 mil, or 90 mil membrane. Each membrane sheet has internal reinforcing that makes it puncture-resistant — externally or from below. Also, it comes with a 20 year to lifetime warranty.

According to the National Roofing Construction Association (NRCA), the three most popular membrane roofing materials are:

• Ethylene propylene diene monomer (EPDM)
• Polyvinyl chloride (PVC)
• Thermoplastic olefin (TPO)

For new flat or gentle slope roofs, membrane roofing is also the roofing of choice. Let’s look at a membrane roof from the inside out. Attached to the decking we usually have one or two layers of rigid insulation. Next comes the membrane roofing. The membrane can be held in place with ballast, strips of metal fastened to the roof deck, or adhesive.

What if we turn the system upside down? This is a protected membrane roof (PRM) system. Rigid insulation such as Styrofoam is placed on top of the membrane roofing. The Styrofoam is highly moisture resistant and protects the membrane from physical damage but, more importantly, it protects the membrane from severe temperature changes, freeze-thaw cycling, and UV and ozone damage. On top of the rigid insulation, ballast is installed to hold everything down.

Quick Costs
Costs for the EPDM roofing are published quarterly in the Means Change Notice. The current material cost for: 45 mil, 28 PSF EPDM Roofing is $34.00 per square (100 square feet).

Plazas and roof terraces can be constructed on top of the roof membrane by using ballast that doubles as pavers. Hydrotech is just one company that offers a system of roofing, insulation, and pavers for this purpose. Open jointed concrete or stone pavers are each supported on four corners by metal pedestals resting on the insulation. Under the insulation is the membrane roofing. The open joints prevent water from collecting and puddling on the wearing surface.

To go one step further, let’s check out the garden roof, or living roof. This will enhance the appearance, give us an area for recreation, absorb heat, manage storm water, saved energy, and clean the environment. On top of the membrane roofing, we would place insulation, and a mixture soil becomes the ballast. Depending on our specific requirements and weight limitations, we can have as little as 3" and as much soil as the structure is designed to hold.