They replaced my tar and gravel roof (100% flat) on my 1200 sq ft house with a TPO roof. The work didn't start the day that it was supposed to, they sited rain, but the forecasts only had a 5% chance for the entire week- it is rarely 0%. A couple of days after that they showed up to do the work. The initially failed to cover everything in my house- our roof is T&G post and beam, so there is no sheetrock or attic to protect the inside from dirt, but later caught it and tried to correct for it, but there was still a lot of dirt that they missed. Also, they cut power lines on my roof that I had to fix myself (they were going to have the roofers do electrical work- that's a no-no) and my phone line. After that, they started installing my new roof. The system is screwed down and then welded together at the seams. I had to have them come out no fewer than 5 times to correct areas taht they didn't fully weld and that were leaking. They always came out, but it would be my expectation that a new roof would never leak. Since then (now 2 yrs later), I have had no troubles with the roof, so I guess it is OK, but only time will tell.