Butterfly Roof – torchon

Lift motor room in central Wellington.
The rubber membrane has lifted off and there are some rips in the rubber, the edge cap flashing has been half replaced on the inside, but rusty on the outside. At this point the only thing stopping the rubber blowing away altogether is the mechanical attachment of the edge flashings.
Quite an old roof, the rubber was laid on building paper nailed to the timber boards, this practise is no longer acceptable as the building paper is does not have the strength to resist wind uplift on its own.
The system we installed comprised;
Index Rollbase fleece backed base sheet mechanically fixed with LH stainless nails at 300mm centres, with heat welded laps.
Viking Bituclad 3mm torchon underlay dressed around the edges and over the waterchecks.
Same underlay torched to the rollbase, at right angles for increased cross laminated strength.
Viking Bituclad 4mm Grey Mineral Cap sheet torched to underlay.
Welted drip edges formed over the waterchecks and back onto the roof,
You may see some ropes in the images, these are safety lines for attachment of a full body safety harness worn by the applicator during the work.
hover cursor over image for text, click on them for larger version

location of the lift roof the lift motor room from the building roof level the lift roof ponds water the rubber membrane has lifted off and been re-stuck by others another view of the puddle there are some rips in the rubber membrane the edge cap flashing has been half replaced, on the inside rubber pulled off, was laid on building paper, drain is re-fixed down flush with the deck one side of the roof with the rubber removed reverse view of previous image Index Rollbase is laid and mechanically fixed with LH stainless nails at 300mm centres same through the flat base of the roof reverse view of previous image and the other sloping side rollbase completed rollbase completed rollbase completed the edge watercheck has 3mm torchon dressed over 2nd layer, 3mm torchon sanded finish at opposite angle 3mm 2nd layer, with reinforcing strip at level change another view of 2nd layer reinforcing strip extra attachment with plates and screws for added wind uplift protection another view of mechanical fixings 3rd layer, Bituclad 4mm Grey Mineral torched to 2nd layer horizontal 3rd layer Grey Mineral another view of 3rd layer Grey Mineral another view of 3rd layer Grey Mineral view of the lift room with 3mm underlay dressed over face of fascia welted drip edge being installed finished look from below of welted drip edge welted drip edge part done at roof level completed welted drip edge at roof level looking along the completed welted drip edge face completed roof another view of completed roof another view of completed roof
There was still some ponding on the roof, about half the depth once the drain had been refixed, but without a total rebuild of the deck……
With 3 layers of membrane with a total thickness of 9mm, this roof should see out another 15+years.

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