Mule-Hide Blog

What’s That SMELL?

Posted: 4/1/2021

Strong Odors from Solvent-Based Adhesives

A crew finishes installing a fully adhered TPO roofing system on a residential garage. As they pack up, the smell of the solvent-based adhesive lingers in the air. They assure the homeowner that this is normal, and it will dissipate soon.

But it doesn’t.

Two weeks pass, and there is still a strong odor in the garage. It goes away when the space is vented but returns as soon as the garage door is closed. The homeowner calls, frustrated … “Why does it still stink? Will the smell go away?”

Yes, the odor will dissipate. How quickly the air clears will depend on a variety of factors.

The cause of the persistent smell? The TPO membrane was installed in cold weather using a solvent-based adhesive, and the adhesive was not given sufficient time to flash off.

Solvent-based adhesives can be applied in cooler temperatures than their water-based cousins can, making them popular choices for jobs completed during the fall, winter and spring. But with lower temperatures come longer flash-off times. Crews must be patient, precisely during times of the year when they feel greater pressure to quickly make a roof watertight. But rushing – not taking a breath to let the adhesive “breathe” – often leads to a lingering solvent odor.

If the roofing membrane is installed before the adhesive has flashed off, wet adhesive can become trapped between the substrate and the membrane. The solvents still need to escape, however, and now have two options. The vapors can go up through the roofing membrane, which will happen slowly over time. Or they can go down into the building. This is the more common occurrence, and when the solvent odor will be observed.

How long will the smell last? That depends. Solvent-based adhesives thicken in cooler weather, making them easy to over-apply; the thicker the coat, the longer the flash-off time. Mother Nature also has a lot to say in the matter; if temperatures rise, the process will speed up, but if they remain cool, it will take longer.

In the meantime, increasing air turnover by opening a window or running fans will help mitigate the odor inside the building.

And while the odor is unpleasant, the air inside the building usually remains safe to breathe. It is even rare for roofing crews to experience the effects of over-exposure, and they work directly with the adhesives in their liquid form.

Patience is the best practice when installing TPO roofing systems in cold weather; give the adhesive adequate time to flash off properly. But if there is a lingering solvent odor, it will go away; it, too, will just take time and patience.

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