sheet closures should be on the bottom of the polycarb. using a step ladder peer over the gutter and you should see them. they will be the same colour as your conny i.e. white or brown.
prior to installation of the sheets a bead of silicone should be run along the top edge of the closure and then fitted over the sheet. once on, both sides should be sealed inbetween the sheet and the closure foming a water seal. as an extra precaution i would also run a bead of clear silicone along the edge of the closure and sheet joint once the sheet is on.
on the underneath of the closure there should be hollows to allow an air-flow into the cells.
it is true that the pitch does sound too shallow for a normal poly sheet roof but nowadays that has been solved. when first erected a thick sheeted roof system should of been used (ultra-light to name just one).
as a 16mm sheet has been used it sounds like only the sheets have been replaced and not the whole roof system. the standard thickness is 25mm and more recently 35mm.
and as i mentioned low pitch roofing systems have vastly improved.
levi lewy
September 2009
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