Mechanically Fastened TPO in Winter -Need Advice



First post on a roofing forum. Quick background I’m 27, have been installing since 18, started my own company my junior year of college, has been on the upward swing ever since.

I’m finally at a point this year in which I was not able to finish all my scheduled projects before the snow hit. I have personally never laid TPO with snow on the roof. I’m looking for some insight/tips in regards to running this system under winter weather conditions. 

We start 150sq layover (1 layer EPDM on roof now, running 1” iso 60 mill). Pretty wide open project, minor protrusions for the size. 

Our first thought is to build a set of “hot box’s” (12x6x8, heaters attached inside) on casters for the welders to be in to help heat the materials that are fastened prior to welding?

Our second thought is instead of just having materials stacked on pallets and tarped, to build an additional hotbox (using an old military tent and a salamander) to heat the materials up in advance every morning. 

Mainly curious as to weather this would improve weld time, but more importantly quality of the weld in cold weather?

Any other tips would be greatly appreciated!


#1, I hope you are slicing the existing EPDM before you install the iso and TPO. If not, you will have moisture problems down the road.
Your idea of keeping the material warm is a good one as far as application goes. The welds will be a problem if done in freezing weather or on moist seams. It is critical to test weld in the morning (when the temperature is usually lower), and then test weld again after lunch. Test welds should also be performed if any changes in substrate or weather conditions occur. This will lead to fewer cold welds, false welds, and/or overheated welds.
Make sure that the weather will be “warm” for several days before beginning the job and during the job. All the snow removed and existing deck dry. Better yet, take a vacation to Florida until the snow melts.


Here is a GFA guide for cool weather applications. Hope it helps you in making your plans for that FL trip!!!


Get carpet heat guns and use those to dry and warm the laps. Make sure you let the membrane relax before fastening. Welding will take longer and any moisture will cause cold welds. If you are running a robot welder it will need the speed reduced from what you are used to.