Velux flashing: EDZ vs EDW for 16 degree pitch

[Tweedledee]

I've bought EDZ flashings to be used with Velux windows as instructed by my builder, roof to be fitted with Marley Mendip tiles.

The roof has a pitch just over 16 degrees, and I now see that EDZ is intended for 20 degrees plus, whilst EDW is for 15 degrees plus.

The builder is insistent that he and his roofer have used EDZ with no problem on low pitch roofs before.

What problems might we encounter if we go ahead with the EDZ flashings? Are problems likely? Will we have leaking windows in five years or so?

It's a nuisance as I've got to post the flashings back, but I'd rather get it right.

Are the EDW flashings uglier? Do they create a bigger rise in the tile as it approaches the window?

Dave

 

[Tweedledee]

Outcome: I swapped the flashings for EDW type. I think I've got to believe Velux over my builder.

 

[freddiemercurystwin]

Your builder is not a roofer. They are rarely the same.