Proper Slope is polycarb. sheet crucial. See what can happen to multiwall polycarbonate on roof pitch of less than 5 degrees. Do not install poly sheet on flat roof or pergola.
Base & Cap Install System
– Proper Slope or Condensation will not effectively drain out of the sheet.
– Leaks at lower edge much more likely.
– Capillary action will suck water up the channels.
– Mold & mildew will gather, turn black and never go away.
Worst case photo, heavy pollen, virtually no slope, never washed.