Waterproofing front porch that goes over crawlspace? - GreenBuildingAdvisor

Waterproofing front porch that goes over crawlspace? morgannewman | Posted in General Questions on March 31, 2026 04:19pm My newly-purchased home has a weird construction detail: the front porch goes over the crawlspace.    Before purchase, we were made aware that the previous waterproofing under the concrete had failed, so I:   1. Hired a concrete contractor to tear up the walkway and porch 2. Hired a GC with roofing/waterproofing experience to replace the rotten framing and add a new waterproofing membrane   The waterproofing contractor did the following:   1. Rebuild the framing under the porch 2. laid new plywood over the framing 3. used galvanized steel flashing around the entire perimeter 4. covered the entire thing with torch-down granulating roof material   This work was from a licensed GC and permitted with my city. It ended up costing ~$12K; however, for an unrelated improvement project, I had a pretty renowned (in the building science community) architect and GC/builder over to evaluate some unrelated improvements to my home while the front porch work was underway.   Both of them expressed concerns about the waterproofing solution implemented. They said:   1. The torch-down material they used is outdated and won’t last very long 2. The sloping is inadequate to allow any water that gets under the concrete to effectively drain 3. The effective lifespan of this fix before it leaks again could be as short as 10 years   These two didn’t really seem to be trying to bi...