Don't break the balloon or the party will be over!

 
Don't break the balloon or the party will be over!
The same goes for any blisters on a membrane roof.

One reason for the blisters, water vapor trapped between the plies of modified or organic felt mat, or water vapor trapped in wooden deck substrate/s, when the new BUR roof is applied.

There are several causes for blistering or bubbles. Just don't pop the balloon or the party is over.

Here is a page from the national research council by by K.K.Y. Liu, R.M. Paroli and T.L. Smith. http://www.nrc-cnrc.gc.ca/ctu-sc/ctu_sc_n38
This Update, based on an IRC, or IRC Building Sciences Group Inc. study, describes causes of blistering in styrene-butadiene-styrene (SBS) modified bituminous roofs, suggests ways to prevent it and recommends methods to deal with it.

Blisters / balloons form in a hot-applied modified bituminous membrane 

Blisters form in a hot-applied modified bituminous membrane for the same reason as in a BUR: voids built into the roof. Voids can result from skips in bitumen mopping, entrapped debris, uneven substrates, unrelaxed membranes, or entrapped gases resulting from moisture in the materials. During the heat of the day, air and moisture trapped in the void expand. The pressure developed in the void stretches the warm flexible membranes and displaces them to form a blister. During the night, the membranes cool, become stiff, and resist returning to their original shape. This process creates a partial vacuum within the blister, and more air is drawn into the blister through micro-cracks in the membranes. The blister is now slightly bigger and ready to start another cycle the next day. As in BUR, the blisters grow when the volume of air drawn into them during the night is higher than that forced out of them during the day, and when the increased pressure overcomes the strength of the peripheral bond of the blister. The presence of water vapour accelerates blister growth according to this same cyclic pumping action.
So remember, don't break the balloon or the party will be over. you will be going home in the rain.

 


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