Weighing in on Ballasted Roof Systems: Costly Issues You Need to Understand

Ballasted roof systems are simultaneously a roofer’s best friend and arch nemesis. Simply put, a ballasted roof is easy to install and basically guaranteed maintenance work for a roofer. Somebody walking on the roof will undoubtedly step on the ballast and put a hole in the membrane. Holes mean roof leaks and roof leaks mean call the roofer. Thanks best friend!

Enter arch nemesis. Roof leak investigation on a ballasted roof can be a bit of a nightmare. Ballasted roof systems hold dirt and dust in between the stone which makes finding small punctures very difficult. Plus, the only way you’re able to see the membrane is to move the ballast. That means somebody (Mr. Roofer) is shoveling stone out of the way.

This all takes time and costs the building owner more money.

When you are considering a new roof system ballast can be a good way to save money on the install but there are costly disadvantages to this sort of system.

Ballasted roof system
Ballasted roof system

Repairs to Ballast Roof Systems

As I mentioned earlier ballasted roofs can present certain challenges for a roofing contractor when attempting a repair. In order to locate the roof leak source the ballast stone needs to be moved to access the membrane below.

One of the biggest issues we see with repairs to ballasted roof systems is contractors who do not replace the ballast to the area after removal for repairs.

So what happens when the ballast isn’t put back in place? In order to understand why this is such a big problem let’s go over how a ballasted roof system works.

Area of missing ballast
Ballast removed from area of roof for repair and not replaced

Anatomy of a Ballast Roof System

Typical ballast roof assembly
Typical ballast roof assembly | Image Courtesy of Carlisle SynTec

The stone ballast on a ballasted roof system is the only thing holding the roof system in place.

The insulation is loose laid onto the decking. There are no fasteners installed at all (3 and 4).

Next the membrane is rolled over the insulation (2). This again is loose so there are no fasteners or glues used to hold it down.

Stone is then distributed over the entire system to weigh everything down (1).

When the stone is removed for leak investigations or penetration installs, that area becomes susceptible to wind uplift. The insulation can then be shuffled and stacked under the membrane.

Check out the below video to see what happens to a roof when ballast is removed and not replaced.

Play

Once the roof has gotten to this point you’ll be contacting Mr. Roofer once again to come out and repair the problems caused by the repair. The roof membrane has to be removed, the insulation re-positioned or replaced, new membrane installed and tied into the existing membrane. Now you are paying twice for one repair.

ALWAYS make sure your roofing contractor redistributes the ballast after repairs are made.

Roof Damage from Foot Traffic

Another costly issue with ballast roof systems is that people accessing the roof tend to walk directly where they need to go and ignore walkways.

Stepping directly on the stone ballast can result in excessive pressure pushing the stone into the membrane and creating a slice or hole.

While they may not always be convenient, walkways are definitely there for a reason. This expense is one that is easily avoidable. Make sure that anyone accessing your roof is directed to stay on the walkways to protect the membrane underneath.

Walkway on a ballasted roof system
Walkway on a ballasted roof system

Ballast Stone Breakdown

The last way ballasted systems can create higher repair bills is from stone degradation. After years of weathering and being walked on the stone will start to breakdown and actually split.

What started out as nice, smooth, round stone ends up sharp and jagged. These sharp edges are perfect for slicing the membrane the next time someone steps on them.

These sharp edges are perfect for slicing the membrane the next time someone steps on them.

Roof ballast sharding
Close up of ballast breaking down, also referred to as sharding

Conclusion

As you can see, cheap to install doesn’t necessarily mean cheap to own. Sometimes spending a little more up front can actually save you more money in the long run. There’s a lot more that should go into a roof system design decision than just a lower price point. There are better methods to help you save money on your roof installation cost.

After all, less issues and less roof leaks means less repairs which means less money spent and probably a lot less headaches.

Is your ballasted roof system in need of repairs or replacement?

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