If it’s time for a new roof, you may be overwhelmed with the decisions involved. Among the choices of materials, scheduling, contractor selection, etc., you may be debating about whether to leave the existing roof on and install a new roof system over top. What follows is information about why you might want to do this and how to know if it’s even possible for your next roofing project.
There are many benefits to installing a new roof over the existing one.
Cost
Because of less labor involved in your roofing project (because demolition is minimized), the project will probably be less expensive. Landfill fees will be smaller and less new insulation will be needed because you’re still able to reap the benefit of the R-value from the old roof system’s existing insulation.
Interior Protection
Because you’re not removing the old roof, there is less risk to the building interior. There are fewer chances of leaks or debris entry during construction .
Shorter Project Duration
With minimal demolition involved, the crew can get right to work with the installation of the new roof system. The faster it is installed, the less time required to supervise the project and the less obstruction to plant operations or surroundings.
Better for the Environment
There is environmental benefit to recovering, as it results in less landfill waste. And because the old roof assembly probably still has some R-value, it may improve the energy efficiency of your facility. Additionally, less new insulation material needs to be manufactured.
How do I know if my roof can be recovered?
Unfortunately, a recover is not always an option. There are three criteria that determine whether installing a new roof over the existing one is possible: the condition of the substrates, applicable building codes, and structural load.
To check the condition of the substrates, a visual inspection of the underside of the deck, core samples, and/or infrared thermography may be used. An experienced roofing contractor will ask you about the roof’s history of leaks and repairs, as well as check for deterioration and moisture. If the roof system components are saturated, it’s unlikely you’ll be able to recover. Likewise, if the steel deck is corroded or the wood deck is deteriorated, a partial or complete tear-off of the roof system for repair or deck replacement is necessary. And if the insulation has been damaged beyond reuse (either because it was crushed from repeated foot traffic or has deteriorated from long-term moisture exposure even if it’s currently dry), recover is not advised.
Building code may also dictate a roof’s recoverability. Most building codes only allow you to have two insulated roof assemblies on a facility. Depending on how the code is interpreted, you might be able to add another layer of membrane (with no insulation) or more plies of felts and asphalt to an asphaltic roof; this is sometimes considered a repair.
Lastly, structural load must be considered. Your roofing contractor can determine the weight of the existing roof components and the proposed roof system, but an engineer will have to determine what the structure is capable of holding. If you don’t have an engineer on your team capable of determining that, your roofing contractor can oversee this. A structural analysis may not always be necessary.
Many times a recover involves the removal of gravel or pavers. In that case it’s not likely your roofing contractor will be putting back as much weight as was removed.
