Moisture Management: A Lost Art?
You can answer this question yourself. Or even better, pose it to one of your low-slope roofing installers: What is the purpose of the plastic wrapping around pallets of polyiso, gypsum board and other roof insulations and coverboards?
You can answer this question yourself. Or even better, pose it to one of your low-slope roofing installers: What is the purpose of the plastic wrapping around pallets of polyiso, gypsum board and other roof insulations and coverboards?
A. To protect the roof boards from the elements.
B. To keep the boards steady on the pallet until they arrive on the jobsite.
C. To give the boards some extra impact resistance until they are delivered to the roof.
D. All of the above.
I admit that I shot from the hip and chose “A” as the answer. My guess is that more than a few roofers did the same. Despite the fact that there are warning labels on most insulation pallets, although not all of them are written in Spanish quite yet.
The correct answer is “B.” The wrapping should be cut and the insulation protected with a tarp. In fact, keeping the boards wrapped in plastic in high-humidity conditions will result in wet insulation. If coverboards like gypsum are immediately installed in hot asphalt, blistering may result. And it’s not the fault of the gypsum board; it’s the roofing contractor’s mistake for not recognized the excessive bubbling or frothing of asphalt during application. Depending on the application method, it’s also not a good idea to install wet polyiso.
Fortunately, some gypsum products feature a special facer and moisture-resistant core that protects the board from excessive moisture. If these boards get wet on the roof, all the contractor has to do is stand them up on end and the water will run off. Water does not wick into these coverboards. This is good, as the last thing the roofer wants to do these days is throw wet roofing materials into a landfill.
The roofing industry has also experienced moisture problems over new concrete decks and existing concrete decks during tear-offs.
By now, it should be obvious that new concrete decking needs to dry out. But existing concrete decks - especially those under leaky roofing systems - contain moisture as well. In the old days, the hot asphalt used as an adhesive directly over the concrete served as a moisture barrier.
Today, ribbons or beads of foam adhesive are more commonly used when adhering roofing materials to the concrete. The moisture retained in the concrete is then free to travel up through the roof system and condense on the top (cold side) of the roof system directly over the coverboard.
When designed properly, foam adhesives can work wonders over concrete. But the concrete must be allowed to dry, or a venting base sheet like Stratavent Eliminator can be used. The reality of roofing is that moisture will almost always play a part during or after the roofing installation. There are also many other sources of moisture within the building envelope that need to be understood and controlled. Often, moisture-resistant coverboards become the victims during litigation. Blaming design and installation mistakes on these products doesn’t solve the problems.
You can answer this question yourself. Or even better, pose it to one of your low-slope roofing installers: What is the purpose of the plastic wrapping around pallets of polyiso, gypsum board and other roof insulations and coverboards?
A. To protect the roof boards from the elements.
B. To keep the boards steady on the pallet until they arrive on the jobsite.
C. To give the boards some extra impact resistance until they are delivered to the roof.
D. All of the above.
I admit that I shot from the hip and chose “A” as the answer. My guess is that more than a few roofers did the same. Despite the fact that there are warning labels on most insulation pallets, although not all of them are written in Spanish quite yet.
The correct answer is “B.” The wrapping should be cut and the insulation protected with a tarp. In fact, keeping the boards wrapped in plastic in high-humidity conditions will result in wet insulation. If coverboards like gypsum are immediately installed in hot asphalt, blistering may result. And it’s not the fault of the gypsum board; it’s the roofing contractor’s mistake for not recognized the excessive bubbling or frothing of asphalt during application. Depending on the application method, it’s also not a good idea to install wet polyiso.
Fortunately, some gypsum products feature a special facer and moisture-resistant core that protects the board from excessive moisture. If these boards get wet on the roof, all the contractor has to do is stand them up on end and the water will run off. Water does not wick into these coverboards. This is good, as the last thing the roofer wants to do these days is throw wet roofing materials into a landfill.
The roofing industry has also experienced moisture problems over new concrete decks and existing concrete decks during tear-offs.
By now, it should be obvious that new concrete decking needs to dry out. But existing concrete decks - especially those under leaky roofing systems - contain moisture as well. In the old days, the hot asphalt used as an adhesive directly over the concrete served as a moisture barrier.
Today, ribbons or beads of foam adhesive are more commonly used when adhering roofing materials to the concrete. The moisture retained in the concrete is then free to travel up through the roof system and condense on the top (cold side) of the roof system directly over the coverboard.
When designed properly, foam adhesives can work wonders over concrete. But the concrete must be allowed to dry, or a venting base sheet like Stratavent Eliminator can be used. The reality of roofing is that moisture will almost always play a part during or after the roofing installation. There are also many other sources of moisture within the building envelope that need to be understood and controlled. Often, moisture-resistant coverboards become the victims during litigation. Blaming design and installation mistakes on these products doesn’t solve the problems.
