Welted Drip dilema and PVC Facia

[frank999]

I am about to finish the edges on a flat roof on a loft conversion, on the sides of the roof I will have arris rail fixed to 18mm ply, beneath this will be 18mm PVC Facia board

I'm unsure whether to create a proper welted drip here, or as I have seen on some builds the Mineral cap sheet is simply draped/overlapped down the facia and then tacked using galv nails.

My concern is if I try torching any of this (rather than tack it) as I pull it over and down the arris rail, the lovely white PVC facia might melt.

On the same build where I saw it tacked, this was also the case at the gutter edge, (ie tacked) the underlay and mineral cap were draped into the middle of the gutter, I can see the logic - that up that high winds would blow water dripping off a welted drip back into the building and not let it drip down into the gutter, draped coverings as below would stop that, but being tacked I am worrried its a point of entry for water:

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• frank999
• 24 Jun 2013
• 1

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• frank999
• 24 Jun 2013
• 1

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• frank999
• 24 Jun 2013
• 1

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• frank999
• 24 Jun 2013
• 1

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• frank999
• 24 Jun 2013
• 1

 

[Alastairreid]

The rainwater does not get past a welted drip if done properly.

Tacking the edges is not adequate.

Use a smaller torch when heating the felt for the drip and verge detail and keep it lifted clear of the upvc when heating.

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• Alastairreid
• 8 Dec 2011
• 2

 

[frank999]

Thanks, yes that is how I think it should be done as per your diagram.
I guess I need to make the fall of the gutter minimal so the drip protrudes into the gutter sufficiently at both ends.

A small torch sounds easier to handle ... why didn't I think of that.

I also read the tacked method is used to avoid the ponding that occurs where the flap for the drip creates a ridge.

Once the scaffolding is down its up there for a long time, and I feel tacking though could let water penetrate.

 

[Alastairreid]

The lip created by the welted drip can be negated by butting then running another layer of 4mm capsheet...then run your final layer. Bit of overkill though as the amount of water is negligible and quickly evaporates.