Lightweight insulating concrete and structural roof concrete are not interchangeable descriptions. A roof may include insulating material above a separate load-carrying deck. Owners should identify both before deciding what to retain, remove or repair during reroofing. A familiar product name or surface appearance cannot establish the supporting structure's capacity.
Read the roof as separate layers
Ask for a section drawing showing the supporting deck, any insulating fill, attachment layers and waterproofing. GAF distinguishes structural concrete deck types from lightweight insulating concrete placed over designed supporting systems. That basic separation helps explain why one roof can involve more than one material casually called “concrete.”
Gather building drawings and prior reroofing records before requesting final alternatives. If documents conflict with observed conditions, ask how the discrepancy will be investigated. The final proposal should name what the contractor expects to find and what information supports that expectation.
Do not turn a material label into a load decision
An owner considering new equipment may hear that the roof is “concrete” and assume the addition is straightforward. Instead, give the relevant designer the equipment information and supporting-system records. Roof attachment, structural support and waterproofing around a new installation are related tasks, but they do not answer the same question.
Similarly, removing an insulating layer is not automatically equivalent to removing part of the structural deck. Ask the contractor to explain the proposed demolition boundary. If the condition or role of a layer is uncertain, resolve that uncertainty before pricing extensive removal as routine work.
Compare replacement options on the same basis
Have bidders identify retained layers, required preparation, the proposed attachment method and the transition details at drains and curbs. One option may assume existing insulating material remains suitable while another includes removal. Those are different scopes even when both end with the same membrane.
Request separate descriptions for known work and work dependent on investigation. At closeout, keep photographs of exposed layers and a final section drawing. Future owners should not have to repeat the same uncertainty because the record says only “new concrete roof.”
Perkins' commercial inspection checklist can help organize existing-condition information. Its repair and replacement guide helps frame the broader investment decision. The next useful step is accurate assembly identification, followed by a proposal that connects the chosen roof covering to the substrate and structure actually present.
Manufacturer references: GAF: Concrete roof deck types.