Friday, May 25, 2012


There are a few different types of roofing one can use for a flat-roofed house. I considered the following:
  • Torchdown - this is a classic method for waterproofing a flat roof. it involves applying heat to a bitumen-backed membrane (tar-like substance) and sealing it to the roof. This is relatively inexpensive and is expected to last 10-20 years depending on the thickness of the membrane. 
  • TPO (thermoplastic olefin) membrane - this is a relatively new kind of roofing membrane that's mid-priced. It is expected to last around 10-15 years. Since this is a newer, less proven material, some older TPO membranes have been known to break down faster than expected. I believe any new formulation doesn't have this problem. One nice thing about TPO is that it is white and allows for creating a cool roof
  • PVC (polyvinyl chloride) membrane - this is similar in design to TPO but has been in use for a much longer time. It comes in white, is a little easier to work with as far as sealing seams, and is expected to last 30-50 years. The downside is that it is the most expensive of the three options. 
Since I plan on living here for a while, I don't want to take any shortcuts with the roofing or siding of the house. I'd hate to get a leak, especially if it's underneath a layer of concrete. I chose to go with the PVC roofing. This roofing comes in several different thicknesses. I chose the thickest, 80 mil, since the price difference was only about 10% compared to 60 mil. It isn't very significant compared to installation costs and gives me some extra confidence that it will last. 

Here is what it looks like on the roll:

80 mil PVC roofing membrane
Installation is relatively straightforward. The roofers first lay down a thin sheet of foam insulation, mostly to prevent condensation from building up underneath the membrane during frosty nights. 

Roofers laying down foam insulation
 The PVC membrane is then rolled out on top of the foam, and is either heat welded or chemically bonded together. It looks like this when it is done:

Roof with PVC membrane
 The deck was finished in the same way.

View of deck from the master bedroom

Soon there will be 3" of concrete sitting on top of that. I really hope it never leaks.