When do you need to tear off your existing commercial roof and start fresh — and when can you just roof right on top of the one that’s already there?
Often, roofing contractors can install a new roof on top of an old one without a problem but if your roof falls under any of these three categories, it’s time to tear off. Plus there are some economic reasons to tear off a roof even if you’re not required to do so. Here’s what you need to know.
What is a roof tear off?
The term “roof tear off” refers to the process of tearing away an existing roof. A tear off always involves removing the exterior layer. In some cases, tearing away and replacing this layer is all that’s needed. However, usually the sublayers (for example, insulation) must be replaced as well, especially if they aren’t compatible with the new materials that will be used for the new roof.
Generally, the underlying structure that supports the roof — for example, roof deck, wood joists or steel beams — can remain with only damaged pieces being torn off and replaced.
Inspections and tests
Your roofing professional will determine whether sublayers should be replaced by performing a careful inspection of each type of underlayment. If the roof membrane has evidence of damage, the insulation under the membrane will be checked for damage as well. The same applies to the vapor barrier under the insulation, if applicable, and the deck under the vapor barrier.
When it comes to checking for damage, it’s not necessary to remove an entire layer to check the layers below. Instead, your roofing contractor roofers can bore a small hole (a core cut) in a damaged layer to see if the next layer is damaged, too. The process is similar to probing the ground to collect a soil sample. The hole can be sealed easily to prevent damage where it hasn’t yet occurred. Infrared testing — a nondestructive technique to detect water damage — can also be used.
3 situations that require a roof tear off
1. If there’s ponding or water damage
If your roofing contractor finds standing water or signs of water damage in all layers of the roofing system, it’s a sure sign that the roof should be completely removed and replaced. The same goes if your roof has areas that are sunken. These problems are too big to repair and roofing over them usually don’t solve them because they telegraph through to the new roof. Plus there could be water damage you can’t see yet so if leaks develop later, it will be much more difficult to determine their source and your building could get water damage in the meantime.
2. If there’s insufficient or incompatible substrate
To install a new roof on top of an old one, the old one needs to be able to provide a suitable base for new one. The old sublayers need to be compatible with the new materials and allow for proper attachment of new to old. For example, some roof decks are made of metal — you can install another roof on top of this type of roof deck if the existing insulation is still in good condition, and fasten it cheaply, easily and effectively. If your current roof is gravel in bitumen, you can remove the excess gravel and inspect the layers underneath. Wet insulation can be spot replaced when isolated. Large river rock gravel (ballast) must be removed prior to reroofing. As an option, ballast is sometimes reused and placed over the new roof membrane. Your roofing contractor will be able to tell you your options.
3. If there are two roofs on your building already
Adding a third roof is against most building codes if you already have two roofs on the building. But will you need to tear off both roofs? In some situations you might be able to tear off just the top roof. Sometimes the bottom roof is in much better condition than the top roof and may actually be the roof that’s been keeping the building from flooding!
In most cases, a complete roof tear off is performed when one of the three reasons above is met. Yet there’s a fourth reason to tear off a roof…
Roof tear off for economic value
Sometimes it makes better business sense to tear off your roof and start fresh. You may want to have the building in optimal condition for insurance purposes, for example, or you may be getting the building ready to sell. You may get enough added value from a roof with more longevity or a longer warranty period that it offsets some tear-off and installation costs.
Depending on your current roof, you may also be able to benefit financially from a roof made of newer materials or from a solar or vegetative roof. All of which mean a tear-off may be the way to go even if your roofing contractor can manage to squeeze another few years out of your existing roof.
Considering your options
If your roof is just starting to fail, only has a few problem areas, and is still pretty sound, it’s probably a good candidate for a second roof or maybe even just a roof restoration — no roof tear off needed. To find out for sure, get a roofing specialist like ours at Sentry to come do a professional evaluation. If you’re a Sentry Roof Care customer, you already have a three-year capital budget that comes with your annual maintenance program. We’re happy to talk with you any time about your unique set of options based on your goals for the building.