Can I Re-Roof Over an Existing Roof?

I’m getting different opinions about whether I should take the old roof off before I put a new roof on. Is it necessary? Important?

A: Good question. When businesses ask if they can have a new roof placed over the old roof, we answer with three simple words: yes, no… maybe. It all depends on the condition of the old roof.

It’s not often that a business can come up with the money to replace an entire roof, so we can replace the roof just where it’s needed, and service other portions of the roof, repairing or replacing as need be. We work hard to help our clients get the most out of their existing roofs and to break the costs into manageable chunks.

To assess the situation, we take infrared pictures of your roof to understand where the water is and what damage has been done. We find the natural transitions in the roof and then find a way to keep you dry by re-roofing only the sections that are critical.

We do core cuts, where we bore into the roof at regular intervals, to determine damage and wetness. We also use a capacitor and other sophisticated pieces of infrared and thermal equipment, which measure moisture content. Dry insulation warms up much more quickly than wet insulation because water has a greater thermal capacity. When we use this equipment, we can see the wet sections glowing.

When the answer is “Yes”

We leave the existing roof in place, which can be big cost savings, and we won’t have to put the old material in a landfill. It’s also beneficial because we don’t have to put the building at risk by exposing it to the elements while we’re reroofing.

When the answer is “No”

A serious moisture problem was found, so we remove the roof and replace it.

When the answer is “Maybe”

During our testing, we may find that moisture is an issue in only a very small portion of the roof. Then we can remove this portion of the roof only, and then reroof the entire building, if necessary. In Michigan, if there are already two layers of roofing, we are restricted from adding a third layer, no matter how dry the existing roof is.

In other instances, when we discover that a previous roofer has used wood fiberboard between layers of asphalt, we always remove it. It can become extremely acidic and harbors biological problems. If it’s trapped between two waterproof layers, it can destroy a building. We never use wood fiberboard, but use a closed-cell plastic urethane-based product because it’s much safer and has a much higher R-value for insulation. It costs more initially, but it’s worth the difference.

Ask Us Directly

Have your own question? Would you like to learn more about your specific roofing issue, options, and approaches? Please consider us a resource, and reach out to speak with our management. We’ve been doing commercial roofing and helping business owners and northern Michigan facility managers improve and protect their operations for three decades. Call us directly at 231.263.5300 or contact us for a timely response.